Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: xcortes on March 08, 2010, 07:27:22 AM
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What voltage must the caps be rated for?
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200VDC should be fine if you are considering film caps. They are 100uF.
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Xavier,
you beat me to it :D.
Thanks for the response, Doc.
-- Jim
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Parts Express has a Dayton brand metallized polypropylene rated 100uF at 250V for about $24 each. PN 027-447.
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This is an interesting option....
http://www.tedss.com/item.asp?id=2020005894 (http://www.tedss.com/item.asp?id=2020005894)
Somewhere I have seen 100uf Auricaps, but a pair of those would be about as much as the cost of the kit...
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And here's another option:
AXON-73679
100uF / 250VDC, True Cap, (D: 48.2mm x L: 65mm)
$32.28 $16.14 pcX USD Price
AXON True Cap Metalized Polypropylene Capacitors
axon.jpg
These are the capacitors chosen by some of the most highly regarded speaker manufactures
around the world. The sound quality is very neutral and open. AXON True Capacitors
are made from the finest grade European metalized polypropylene, by the same OEM
company in France (SCR), that makes the SOLEN Metalized polypropylene caps. In fact,
these are functionally and materially identical to the PA series SOLEN caps, with
one advantage - typically, the "actual/measured" AXON values are more closely wound
to the nominal printed value.
AXON True Caps are manufactured on high precision Swiss machines with high winding
tension to suppress microphonics. They use a multi-wrap encapsulation (white epoxy
ends) for protection and oven annealing to improve internal damping. Tolerance is
5% precision, centered on the nominal value. The leads are solid copper, coated with
pure tin to prevent oxidation.
Personal note:
I've used these and like them better than the higher voltage Solens. They seem to be somewhat smoother overall, but even more pronounced i n the mids.
$16 each, you probably can't go too far wrong, but could also be bypassed for changing the flavor to your liking.
-- Jim
Of course you can also find some of those huge Sprague 100 uF motor run caps, typically for even less than these Axons, and they too sound fantastic.
-- Jim
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Is it OK to go to 150uF?
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150uf should work just fine. In a similar circuit I built some years ago, I ended up using 220uf.
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Just curious how much room will there be inside the chassis for these beer can size caps?
Thanks,
Jim
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I ordered some of the Axons yesterday, and I'll let you guys know how we end up fitting them in. We also put C4Ss with BIG heatsinks on the 6080, so it may be a bit of a tight fit in our prototype.
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For the truly enthusiastic, are you aware of the CDE military-quality caps? Electrolytic caps, 125 degrees C, stainless steel cases, 100 year lifetime, flat pack 0.5" by 1.5" by 1.75" for example. "Not your fathers's electrolytic."
Spec sheet at
http://www.cde.com/catalogs/MLS.pdf
OK, so a pair costs more than the Crack. So? Mouser has 25 of them (330uF, 200v) in stock, only $120 each! :^)
No, I've never heard them or even seen one.
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PJ, you are the master of sourcing obscure parts! By the way, I have eight of those giant CDE film caps that you recommend for our little high voltage project, they are HUGE!!!!
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PJ, you are the master of sourcing obscure parts! By the way, I have eight of those giant CDE film caps that you recommend for our little high voltage project, they are HUGE!!!!
Haha! Yeah, they lookd like beer cans for alcoholics ... :^)
I have the bleeder resistors, give me a buzz...
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. . . By the way, I have eight of those giant CDE film caps that you recommend for our little high voltage project, they are HUGE!!!!
Since we don't have a bunch of smiley faces available:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.audiokarma.org%2Fforums%2Fimages%2Fsmilies%2Fttiwwp.gif&hash=fc52f72b7a9b6744f96ea252a7ba643df8c75ded)
Hey, I got it to work! But it should read "that post."
How about posting a picture?
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How about a pair of Black Gates NH. Mike Percy has 150uFs for about $50.
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I was toying with the idea of using these when I order mine:
http://www.diyhifisupply.com/catalog/34
Obbligato PSU caps.
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Dueland CAST-PIO, 40uF. You would probably want two in parallel for each channel. At $2,581.00 each, they seem like a total bargain.
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Isn't that at, or beyond the point that we can call it Gilding the Lilly?
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How about we just call it obscene :-)
Sure, I'm guilty of buying some boutique parts, cables, etc., but this just seems a bit too far out there. Then again, I guess it's all relative to your situation.
-- Jim
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Jim,
Obscene is good! Seems that PIO caps like these are priced like Teflon caps. Although Teflon caps are not available in 100uF. Not any thing close that I have seen.
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@Doc, gotta love it! $5k for caps..... I have read much about the Duelunds, and I am sure they are the best you can buy, but....really???!!$5k? I gotta start winding my own!
Love the new kit, almost ready to pull the trigger on one!
Here are some vintage Mallory 100uF 250V, it takes a bit for the page to load then scroll a ways down:
http://www.vt4c.com/shop/program/main.php?cat_id=2&group_id=1&hit_cat=
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Although that link says, "Paper Tube Electrolysis Capacitor," I feel sure they meant to say Electrolytic. Most old electrolytic capacitors are leaky. And I don't mean physically. The electrolyte is drying up and they are not as good as they were when made.
Maybe these Mallory caps are different?
On second thought these caps might have been used for electrolysis after all.
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My Axons arrived today. Not very scientific but I downloaded the jpg of the underside view and zoomed it up via Preview. Best I could do was about 5.75"; close enough. Holding one of the caps to my monitor it appears that they'll fit just fine. They'll fit better without that terminal strip adjacent to the 6AS7.
I ordered some of the Axons yesterday, and I'll let you guys know how we end up fitting them in. We also put C4Ss with BIG heatsinks on the 6080, so it may be a bit of a tight fit in our prototype.
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You could hop on over to Radio Shack and buy an extra 5 lug terminal strip, then add it to the 2nd bolt on the 6080. Then the big honkin caps can fit between those two strips, with the caps tied between the outside terminals on the two strips. I would jumper from the cathode pins of the 6080 (3 and 6) to the outside terminals of your added T-strip, then the wiring for the headphone outputs can be retained.
You will, undoubtedly, have to bend the leads of the caps around their bodies a bit to get them to fit, but it should work fine.
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Quick note here - the last power supply capacitor is equally important to the sound IMHO.
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And what would be the value/rating of that? Will you be including a TSHA with the kit?
Also, can I ask how many terminal strips will be in this amp -- not including the extra one PB just mentioned?
-- Jim
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The power supply capacitors in the kit are the 220uf 250v caps found in the extended Foreplay III. These are TSUP series Panasonics.
There will be four terminal strips included with the kit: two 5-lug strips, and two 6-lug strips.
Although the quality of the last cap in the supply is quite important as PJ mentions, the value is also quite critical. If it gets sized down much at all, the ripple becomes audible. Of course, the ESR of film caps tends to be nice and low, so some experimentation will probably be needed to find a comfortable balance.
Incidentally, there is probably just enough room to squeeze a giant Solen cap between the 6-lug terminal strips that flank the power transformer. I may need to trade in my ugly prototype for a fresh kit when the plates arrive...
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Thanks, Paul. I forgot to ask if there will be one or two of these PSU caps. I'm assuming you're using dual supplies so as to balance the transformer secondaries on the PT-3, so I'm therefore assuming two big psu caps.
-- Jim
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I may need to trade in my ugly prototype for a fresh kit when the plates arrive...
You may have to take a number. We doubled the initial chassis plate order and just ten days after introducing the kit we have only ten kits left from the first run.
We got the Dayton film caps in yesterday and gave them an initial listen. While they sound clearer and cleaner it makes me realize that the stock lytics are pretty good. I think the C4S upgrade makes a bigger improvement than the cap upgrade. We will be figuring out an upgrade for the final cap next. The chassis is getting very crowded with all this upgrade experimentation...
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Oops, make that only seven kits left from the first run. At this rate those will probably all sell this weekend. We will start a second run as soon as those sell, which probably means a lag of at least a couple weeks between runs. So if you're thinking about ordering a kit, today would be a good day to do it.
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That has to be some sort of record! Congrats.
-- Jim
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I like your idea. I've been toying with various ideas for securing those caps to the top plate; the glue gun idea didn't last long. Strictly based on that photo I've been toying with not using either of those two terminal strips and going point-to-point but using strips as supports for those caps makes for a pretty elegant solution.
You could hop on over to Radio Shack and buy an extra 5 lug terminal strip, then add it to the 2nd bolt on the 6080. Then the big honkin caps can fit between those two strips, with the caps tied between the outside terminals on the two strips. I would jumper from the cathode pins of the 6080 (3 and 6) to the outside terminals of your added T-strip, then the wiring for the headphone outputs can be retained.
You will, undoubtedly, have to bend the leads of the caps around their bodies a bit to get them to fit, but it should work fine.
Here are some rough dimensions if anyone's considering these caps:
Each lead is 2 3/8" long. The body's 2 5/8" long and 1 3/4" tall.
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Thanks, Paul. I forgot to ask if there will be one or two of these PSU caps. I'm assuming you're using dual supplies so as to balance the transformer secondaries on the PT-3, so I'm therefore assuming two big psu caps.
-- Jim
Jim, I looked at the picture of the Crack belly and there are 3 caps in the power supply. One has to be for the heaters, the other two are for the high voltage.
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The three caps are all power supply caps for the B+. It took a CRCRC to really get the Crack nice and quiet.
On the layout, I would suggest sticking pretty close to what is there in stock form, as the upgrades that are coming down the pipeline will be somewhat harder to install without some terminals on the T-strips available.
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The newest:
http://www.cde.com/catalogs/944U.pdf
The littlest one is 100uF and less than 2" tall. For about $300 you can replace the last PSU and the output caps. Plus the cost of a second chassis box to mount them...
Here's the big guys:
http://www.cde.com/catalogs/947C.pdf
CDE makes more kinds; these are just what's at Mouser.
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Thanks, Grainger and PB. I'm really looking forward to this kit.
-- Jim
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Ok, I goofed big time when I asked:
Thanks, Paul. I forgot to ask if there will be one or two of these PSU caps. I'm
assuming you're using dual supplies so as to balance the transformer secondaries...
Afterreading this again I realized how stupid that was. Of course you're not using dual supplies as there is only one output tube ;-)
Ok, putting on my dunce cap and going to sit in the corner for a while :-).
I got a 6080 the other day and just love the look of it as it resembles a giant 6sn7. Just never saw a tube quite with a form-factor like this. I was expecting a big ST type like the 6AS7s I had a while ago.
-- Jim
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Dude, you were right the first time. The output tube is a dual power triode, and a dual-mono power supply would be perfectly reasonable. Just not at the $199 price point ...
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Ok, that's true too :-). Point taken. Thanks for making me feel not quite as stupid :-)
-- Jim
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From the Crack "belly Shot" the PSU looks to be C-R-C-R-C, amd AC filaments for the two valves. I'll SWAG those WW power resistors are around 270 ohms @ 5W ?
Would bypassing the two 100 uF output caps with something like 2.2uF @ 250V film, or "Green Kommie Kaps" be a useful upgrade?
Looks like I got the next to the next to last one of the first run! yahoux!!!!
/ed B in NC
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You are spot on with all your conjectures.
I would vote for removing the last Panasonic Electrolytic and substitute a 200uf @250v Solen in its place ;)
Bypassing should be fine, you will get diminishing returns adding bypasses before the last cap in the supply.
I am out of town and on a computer without modeling software, but I'd imagine substituting Triad C-7X chokes for the 270 ohm resistors will drastically reduce the required capacitor size for sufficiently low ripple. Finding space for all that could be pretty rough...
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PB, which software do you use?
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I use good old PSUD-II. You can simulate the stock power supply, jot down the ripple, then start messing around adding chokes and different caps to see if you can stay under the stock level.
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I will probably get shot for asking this on this forum, but....
Is there a sonic advantage to using tubes for power supply regulation, or could
you more tightly control it with semiconductors, and just use the tubes for the signal path?
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Bottlehead uses tubes for voltage regulation in the Foreplay III, Paramount and Eros. So it is easy to say that they like it. The regulator circuits use solid state devices and tubes. So if PJ, Doc, and the rest thought that an all SS circuit was best they would design it that way.
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We use both solid state and tube regulators. The stock Foreplay III is the only kit using a strictly tube regulator. In the rest of the kits with a shunt regulator use a tube as a voltage source for the solid state regulator, and the tube burns off excess current at the same time.
If you wanted to try a purely solid state voltage regulator, one could modify any of the circuits to use a zener string instead of the triode, or possibly make a voltage source with something besides the extra triode.
(We have listened to this and prefer our regulator)
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We did build a test buffer, which used 12AT7s or 12AU7s as cathode followers. I chose the cathode follower because that is the circuit most audibly sensitive to power supply performance. The test vehicle had six different shunt regulation schemes - a gas regulator tube, a string of Zeners (bypassed), and four different triode-based regulators, augmented with various bits of silicon. The two best sounding were very similar hybrid regulators using the TL431 or TL1431 chip with a triode in cascode to handle the voltage (the chip is limited to 30v maximum). We chose the simpler of the two.
We did not follow up with optimizations of each candidate - for example, a high-voltage transistor or FET could be used as the cascode device, with a suitable heat sink. We had at that time been working for many years with John Tucker and the late John "Buddha" Camille, and they had done more extensive experiments - this must have been back in the late nineties. They had concluded that FETs just didn't sound as good, though they worked very well on paper and in measurements.
Here's an interesting historical note. Some 15 years ago (before I began designing for Bottlehead) Bottlehead was using paralleled triodes for drivers, 5965s and 6N1Ps mostly. Eventually Bottlehead switched to single sections, finding a bit of smearing (for want of a precise technical term!) in the sound of paralleled triodes. That left a spare triode in each monoblock. As I recall it, I made an idle suggestion to use that triode for a shunt regulator and John Tucker immediately built one. I really did not expect it to be audible, since the driver was already isolated from the power supply by a C4S plate load. I was so astounded when I heard it, I insisted on switching amps (only on channel was regulated) and then turned the amps over on the floor to trace the circuits for the next 15 minutes. I really suspected Tucker of pulling a fast one!
Anyhow, that's how we came to use the triode as the heat- and voltage-dissipating element. There has never seemed to be sufficient reason to try to develop a different approach, beyond that initial test device to confirm we weren't missing something obvious.
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I messed around a bit with fets and the current Bottlehead regulator scheme. I have found that keeping the fets cool is far more difficult than letting a triode cool itself. Heck, when you want to burn off 5-8 watts or so at high voltage, you end up spending quite a bit of money and space on heatsinks where a little 9 pin tube would suffice.
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PJ,
Thanks for the background info. I love hearing these historical anecdotes laden with great and useful technical findings and ideas!
-- Jim
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For the truly enthusiastic, are you aware of the CDE military-quality caps? Electrolytic caps, 125 degrees C, stainless steel cases, 100 year lifetime, flat pack 0.5" by 1.5" by 1.75" for example. "Not your fathers's electrolytic."
Spec sheet at
http://www.cde.com/catalogs/MLS.pdf
I guy I worked with along time ago used CDE flat packs told me "don't use those flatpack capacitors. . ." I wonder if it has anything to do with the "lasagna battery" effect.
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Any guesses on how a pair of electrolytics in series (to increase voltage rating) would sound? I' ve never done this for a coupling capacitor and wonder if it would have a detrimental effect on the sound?
-- Jim
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Any guesses on how a pair of electrolytics in series (to increase voltage rating) would sound? I' ve never done this for a coupling capacitor and wonder if it would have a detrimental effect on the sound?
-- Jim
Well, ideally you would want resistors in series with these caps to keep the voltage across each of them balanced. This, of course, defeats the purpose of DC blocking unless you use very, very high values (to create a voltage divider that puts a few mV of DC out at the output). Putting the caps in series also halves the capacitance, which isn't super helpful in this case. Did you have a specific cap in mind?
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PB,
Yes, I guess the series resistors would defeat the DC blocking, and hence why I've never used them this way :-). Ron Welborne has a bunch of surplus 220 uF 100v Elna Cerafines, and that's the only reason I asked, in case I could put them to use somehow in this amp.
-- Jim
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You will, undoubtedly, have to bend the leads of the caps around their bodies a bit to get them to fit, but it should work fine.
Incidentally, there is probably just enough room to squeeze a giant Solen cap between the 6-lug terminal strips that flank the power transformer. I may need to trade in my ugly prototype for a fresh kit when the plates arrive...
Makes me wonder why "crack" wasn't built on the new standard 8 X 10 chassis plate instead of reverting back to the old 6 X 10 format. The experimental aspect of the amp tend to become narrowed when you have to shoehorn components into the box.
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You will, undoubtedly, have to bend the leads of the caps around their bodies a bit to get them to fit, but it should work fine.
Incidentally, there is probably just enough room to squeeze a giant Solen cap between the 6-lug terminal strips that flank the power transformer. I may need to trade in my ugly prototype for a fresh kit when the plates arrive...
Makes me wonder why "crack" wasn't built on the new standard 8 X 10 chassis plate instead of reverting back to the old 6 X 10 format. The experimental aspect of the amp tend to become narrowed when you have to shoehorn components into the box.
I would imagine, among other things, that the larger chassis plate and wooden enclosure would have required a little higher price point than $199, which is amazing for this type of amp.
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Makes me wonder why "crack" wasn't built on the new standard 8 X 10 chassis plate instead of reverting back to the old 6 X 10 format. The experimental aspect of the amp tend to become narrowed when you have to shoehorn components into the box.
The same question could be asked about the SEX amp and the new Stereomour chassis, which is quite a bit bigger than the 8x10. Ultimately it boils down to costs and practicality of upgrades in combination with what must fit. Ultimately the fun part of DIY is figuring out how to fit all the desired mods in the space provided.
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. . . Makes me wonder why "crack" wasn't built on the new standard 8 X 10 chassis plate instead of reverting back to the old 6 X 10 format. The experimental aspect of the amp tend to become narrowed when you have to shoehorn components into the box.
Edited in Red:
There is an alternate way to get more room. Custom make a deeper base, simple enough Paully and I have done it.
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I did a search on caps and came up with this.
http://www.newark.com/jsp/search/productdetail.jsp?SKU=13M4422&CMP=AFC-GB100000001 (http://www.newark.com/jsp/search/productdetail.jsp?SKU=13M4422&CMP=AFC-GB100000001)
I don't know if these would be OK. I'm sure someone else can comment on the specs. I like my crack the way it is for now.
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I would try those. From the belly picture on the products page the stock output caps look tiny. You might lift one of the leads on both caps and clip the "Oilers" in just to see if they are a good flavor. That way you are not too far from the stock configuration if they don't suit you.
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Metalized Polypropelene. According to the datasheet 2.75in by 4.75in.
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I saw them and assumed they were just like the almost identical 100uF that I have. I see now, reading, that they are not the standard oil motor start/run caps. But they look a lot like them, just a lot more expensive and a better dielectric.
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I just bought 2 for the heck of it. There's only 8 left in stock if you're interested
Rich
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I just bought 2 for the heck of it. There's only 8 left in stock if you're interested
Rich
Let us know how they sound.
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Bought these to try. Nubie question: Do they need to be installed with a specific orientation?
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IIRC, for power supply applications the outer wrap should be at, or closest to ground than the other lead. For a coupling cap application the outer wrap goes to the input, or toward the tube.
You will most likely have to contact the manufacturer to find out which lead is which. But post back when you get an answer.
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I just don't have any restraint anymore!
I ordered a pair of those new(ish) Obbligato film caps that they're marketing as power supply caps. If you haven't seen them, they come in two sizes, 47uF 500V and 100uF 400V.
I got the 100uF caps the other day but I figured I'd stick to my guns and wait to install them after getting the Speedball .
Well, I guess if they're in the house, they're fair game right? Well, at least that's what I'm trying to convince myself.
I'm listening to Esperanza Spalding right now. She's kind of a hot bass player vocalist I saw at Monterey last year and her album kicks some pretty serious butt.
It's been in pretty heavy rotation around here and with the change in caps, I'm hearing some pretty nice changes so far. Pretty lively sounding, fast, open and doesn't take anything away from the stock sound but just improves on it. Unless they take a turn for the worse, I'm thinking they'll be taking up permanent residence in my Crack (ouch!). Just like the film caps other folks here have tried, these are big suckers but I think there's going to be plenty of room with the Speedball's heat sinks and all.
Not crazy money either ($39 each).
I did some searching around but didn't find word one about these caps. I can't wait to try them in a power supply. I've got some other caps I'll try bypassing these just for fun but these are sounding pretty nice ala carte.
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Hmmmm interesting use of these. I have used the PP Film in Oil Obbligatos in my Paramours. I only needed a 10uF.
Very imaginative!
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Waiting eagerly for my Crack kit to arrive. Won a pair of HD800s and can't wait to hear them with the Crack.
For anyone looking for coupling caps in the UK, I found these 50uF/250V polyprop caps at Farnell (the price is super cheap):
http://uk.farnell.com/parmar/r1008hp500p25/capacitor-50uf-250v/dp/3851850
You'll need two in parallel for each channel, but even then the price is great. No idea how they sound, but can't be worse that an electrolytic.
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That Parmar cap is nearly 10 cm long [4"]. It has a 5 cm diameter [2"]. Four of those will be hard to fit.
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For those of you who have not seen it, grufti made a very nice chart showing the low frequency cutoff you can attain with different output cap values and different headphone impedance ratings. Depending upon the cans you choose 50 uF could be a reasonable value, and it should work just fine with HD800s, getting down to around -3dB@11Hz:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fimg808.imageshack.us%2Fimg808%2F6843%2Fcouplingcap.jpg&hash=76ad0b3ab4e7303f822fd7592a3e0234b50abd76)
I would be interested in hearing feedback from folks using lower impedance cans in the 32-70 ohm range who have compared the stock 100uF caps with higher values like 300uF-500uF.
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For those of you who have not seen it, grufti made a very nice chart showing the low frequency cutoff you can attain with different output cap values and different headphone impedance ratings. Depending upon the cans you choose 50 uF could be a reasonable value, and it should work just fine with HD800s, getting down to around -3dB@11Hz:
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fimg808.imageshack.us%2Fimg808%2F6843%2Fcouplingcap.jpg&hash=76ad0b3ab4e7303f822fd7592a3e0234b50abd76)
I would be interested in hearing feedback from folks using lower impedance cans in the 32-70 ohm range who have compared the stock 100uF caps with higher values like 300uF-500uF.
Just curious - with a 5998 instead of the 6080/6AS7, and a 500 or 600uF output cap, it seems like one could possibly drive a small 8 ohm speaker, no? How much power would you be able to put into something like a dinky desktop monitor? I have the Crack next to my computer and have wondered about this - little desktop speakers probably would need no more than 250mW or so and certainly wouldn't even come close to the -3dB cutoff in the bass frequencies. (Another idea I've had is to make a sort of "FrankenCrack" - OTL as usual for headphones, and add a MOSFET chip output stage from the 12AU7 for small speakers).
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The chart is for a voltage source/cap/load but the Crack has a 120 ohm output impedance. The cutoff in the bass goes with the total of 120 ohms plus the headphone impedance, so the 160-ohm line shows about what you can get with any low-impedance phone. You do not need a huge capacitor unless you do something (different tube, feedback, etc) to lower the output impedance.
For speakers, the output is limited to about 20mARMS, which would be about 3mW into 8 ohms. The damping factor would be about 0.07, so the bass design would be quite different from the usual. Being current-limited, you get power proportional to speaker impedance so a whole bunch of drivers in series might be workable. Or get a 600:8 ohm transformer; you should see around 250mW then. A 25-v line transformer would do the job and be quite cheap.
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Sounds like the MOSEFT hybrid idea might be more promising if I want to squeeze in occasional speaker duty. But I may put bigger caps in there anyway if I end up getting AKG's (K-702; 62 ohm impedance), and will post any observations at that point.
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Very true.
I have continued to work on the chart in the meantime and I'll post two new versions of it later on today. One for the original tube configuration with the 6080/6AS7G and its 120 Ohm output impedance. And then a second chart for the 5998/7236 output impedance around 75 Ohm.
It may even be possible to combine the two into a single table. I'll give it a try.
The chart is for a voltage source/cap/load but the Crack has a 120 ohm output impedance. The cutoff in the bass goes with the total of 120 ohms plus the headphone impedance, so the 160-ohm line shows about what you can get with any low-impedance phone. You do not need a huge capacitor unless you do something (different tube, feedback, etc) to lower the output impedance.
For speakers, the output is limited to about 20mARMS, which would be about 3mW into 8 ohms. The damping factor would be about 0.07, so the bass design would be quite different from the usual. Being current-limited, you get power proportional to speaker impedance so a whole bunch of drivers in series might be workable. Or get a 600:8 ohm transformer; you should see around 250mW then. A 25-v line transformer would do the job and be quite cheap.
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Or get a 600:8 ohm transformer;
Better yet, get a S.E.X. amp. That's what we designed that amp to do - headphones or speakers. You'll see a lot more power output into 8 ohms. On another forum someone was asking about comparisons of Crack with a $1200 headphone amp that a competitor makes. If that is a reasonable budget and one is willing to build their own gear one could buy a Crack, a Speedball, a S.E.X. amp and the MQ iron upgrade for S.E.X. for less than the price of the competitor's amp, and have all sorts of fun.
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Or get a 600:8 ohm transformer;
Better yet, get a S.E.X. amp. That's what we designed that amp to do - headphones or speakers. You'll see a lot more power output into 8 ohms. On another forum someone was asking about comparisons of Crack with a $1200 headphone amp that a competitor makes. If that is a reasonable budget and one is willing to build their own gear one could buy a Crack, a Speedball, a S.E.X. amp and the MQ iron upgrade for S.E.X. for less than the price of the competitor's amp, and have all sorts of fun.
Already have all of those! But the temptation to keep messing around with them is hard to resist. Maybe the Stereomour should be next....
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Please take a look at these new -3dB tables [... removed because they contained errors]. 100uF really sticks out as the best value to chose.
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The newer Sennheiser 595's are rated at 50 ohm impedance. I've enjoyed the cans for some time with the S.E.X. amp and other gear. The fact that the Crack amp was designed for high impedance cans did not hinder the desire to own one, not one little bit. If the amp didn't perform well with the 595's, there would simply be new cans in the collection.
There were no serious performance issues with the stock Crack amp and the 595's. This combo managed to slap a stupid grin on my face and actually brought tears of joy to my eyes, but the lower freqs did seem a little gentle.
I managed to salvage the 220uF PS filters from the rail that came off the FPIII upgrade and used them to replace the 100uF coupling caps on the Crack. Now all things are very much where I like them. New cans can wait until I burn the 595's up.
-Joe Sengl
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Thanks for those charts grufti! Excellent stuff.
Hmm,.. I have to guess that you have a pair of MB Quarts?
I aways wondered if MB Quart is part of the same company that makes the MBHO microphones?
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You guessed it. I do own a set of MB-Quart headphones and still like them roughly twenty years after I bought them. Too bad MB didn't survive intact.
MBHO was founded by Herbert Haun, who had been at MB from the start as a technical director. He went back to his microphone roots. There is a wiki article available at:
http://wiki.faust3d.com/wiki//index.php?title=PMB_/_MB_Quart
A company called GermanMAESTRO picked up some of the pieces and still produces headphones that are similar to the MB-Quarts.
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Would you be able to explain what is going on in the charts you posted? I dont have an engineering background but I am interested in your findings.
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Nice graphs, but I'm confused. The graph labeled as "6AS7" shows lower -3dB values for a given impedance, with the 5998 graph being opposite. For example, JH16 Pro (18 ohms) is listed as needing a coupling cap of 47uF to get a -3dB point of 25Hz with the 6AS7, yet the same value is listed as yielding a higher (36Hz) point with the lower resistance 5998. Since the 5998 has a lower Rp than the 6AS7, shouldn't the -3dB be lower for any given impedance/cap combo? Maybe the graph labels were reversed?
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There is nothing really special going in the charts/tables.
The coupling cap (100uF/160V in the kit) influences the low frequency roll-off in the frequency response of the amp. The formula for calculating the frequency at which the output is reduced by 3dB popped up somewhere way back in this thread. At first I computed the table based on that formula, but that is correct only for a voltage source.
The latest two charts/tables use what I hope is the correct way to calculate the bass roll-off frequency. Any value under 20Hz (better yet 10Hz) and greater than 2Hz is very good. All the values in the tables are frequencies in Hz by the way. The column for the 100uF capacitor has ideal values for just about any headphone on the market, between 12Hz and 2Hz for the 6080 output tube in the kit.
The Bottlehead crew fortunately takes care of this kind of design work before they sell their amps to you and me, so we usually don't have to worry. And it turns out that they got it right yet again. It's just for some very unusual headphones that a different capacitor might make a difference.
I hope this helps.
Would you be able to explain what is going on in the charts you posted? I dont have an engineering background but I am interested in your findings.
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Steve K.,
How large are those Obligato PS caps? I just checked out the diyhfs pages and they don't list the dimensions of most of the caps.
Has your impression of them changed any?
-- Jim
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It isn't that, but you're right.
Sloppy thinking on my part. I'll modify my post as soon as I have more than just a minute to do it. In the meantime ignore the two new tables.
Nice graphs, but I'm confused. The graph labeled as "6AS7" shows lower -3dB values for a given impedance, with the 5998 graph being opposite. For example, JH16 Pro (18 ohms) is listed as needing a coupling cap of 47uF to get a -3dB point of 25Hz with the 6AS7, yet the same value is listed as yielding a higher (36Hz) point with the lower resistance 5998. Since the 5998 has a lower Rp than the 6AS7, shouldn't the -3dB be lower for any given impedance/cap combo? Maybe the graph labels were reversed?
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Hi Jim,
They're pretty big. About 4x1.5 inches.
I'm still going to give them another day or two before I do any critical listening. I guess I have about 150 hours on them so far and they've gone through the regular film cap changes (I check them about once or twice a day) and they've seemed to settled down for the most part.
I'll post something in a day or two how they compare to the stock Panasonics.
This is with a stock unit and however they turn out, I'm sure it won't be as positive an improvement as the Speedball is (I seriously doubt that any component change will do that).
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Steve,
Ah, thought this was with the speedball installed.
With all the great things people said about the upgrade, I'm thinking the BGs as coupling caps would be quickly taking me into the territory of rapidly diminishing returns and might find themselves better used n something else. Stereomour?
Then again, maybe finding a nice bypass for the stock caps would be enough.
-- Jim
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Well, after around 250 hours of 24/7 burn in, I can't really say the the Obbligatto caps are full burned in yet. Most of the warts that that sprung up during break in have receded so I think I can say where it'll eventually get to.
With the tube set that I enjoyed the most with the old caps was a Tungsram E80cc and a Sylvania 6080WB the differences with the new caps were pretty subtle. This is with my Audio Technica AD2000's and computer based rig.
Then I tried a Tung-sol 5998 with a CBS/Hytron 5814a which I found to be a nice pairing. Wow,.. I still need to re-install the Panasonics to double check but I'm listening to a 24/96 download of Raising Sand with the Pure Music player on my Mac/Metric Halo and this is the best depth and realistic soundstage I've heard with digital. I've used "Trampled Rose" for demo's of my headphone rig for more than a year and this is way-way better than it's ever sounded. I have to admit that I've heard a more analog sound with digital but you don't even want to know what that was done with! But for a "sane" system,.. not bad at all.
Tomorrow when I have time, I'll hook it up to my Tape Project rig and that should be pretty scary.
So, like I said, I'll roll the stock caps back in this weekend but right now, I'm just in hog heaven!
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I went ahead and switched back to the stock Panasonics and listened today. I still have to say that I'm amazed how good those things sound.
Then I switched back to the Obbligatto PS film caps. (BTW I used some solid copper 18AWG wire I get from Chris Venhaus for the leads)
Once again, these listening tests were done with a pair of ATH AD2000's my digital system and a Tung-sol 5998 CTL top getters (1958 I think) and a CBS 5814a.
Everything seems a touch more defined like a layer of fuzz has been eliminated. Not huge by itself in any particular frequency range.
The soundstage is much more 3D with these caps. Maybe better than I recall it was with the Speedball (It's been a while but I can't remember being blown away by stage depth. Maybe the combo of the 5998/5814 with the Speedball will, I'll have to wait and see).
I think the level of the perceived bass is a touch less but it's better defined just like with the Speedball. The Speedball did add a half octave or so to the lower extension and did a similar job of cleaning up the lower frequencies. The definition of the lows was also better with the Speedball.
So, I'm pretty certain that these caps will stay in the Crack for a while even after I get the Speedball.
They don't seem to add anything bad and seem to do a better job of getting out of the way than the stock caps. Pretty subtle stuff but it may be more pronounced with the Speedball (or less?). We'll see.
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I feel a little weird replying to my last reply to myself,.. on second though, no I'm not.
Just wanted to let you guys know that I got the Speedball yesterday and installed it. I burned it in overnight so it's probably got around 20 hours on it right now.
So, with the Obbligatto PS caps and the same signal chain as the two previous posts, all is wonderful and killerliciousness!
One of the great things about this combo (other than the price) is the sound seems improved on all genres of music. It doesn't improve a bad recording of course but it also doesn't call a lot attention to the worts either.
IMHO the improved soundstage and imaging is worth the cost alone.
Very engaging too,.. (I've been trying to write this post for about an hour now).
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Having had the pleasure of listening to a couple of your rigs Steve, color me impressed! Maybe it's time to get one myself :)
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Thanks for the compliments johnsonad.
IIRC you heard my Tape Project/electrostatic rig at the LA CanJam a little over a year ago. Like I said at the time, the amp is in a constant state of flux and the next time you hear it, it should be totally different (in a good way I hope!).
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Steve,
Somewhat OT, but do you think you'll be coming to the RMAF CanJam in mid-October?
-- Jim
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Steve I had a question for you, would you mind sending me an email please?
Regards,
Aaron
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Steve,
Somewhat OT, but do you think you'll be coming to the RMAF CanJam in mid-October?
-- Jim
It's penciled in on my calender. It always comes in on the heels of the Monterey Jazz Festival (a week or two after) so funds are always a question.
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Steve, sounds good. Wish I could make it to Monterey too -- I have a cousin and her family who live there. No money and travel is pretty difficult these days, but fortunately RMAF is just 40 minutes down the road from where I live.
-- Jim
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The chart is for a voltage source/cap/load but the Crack has a 120 ohm output impedance. The cutoff in the bass goes with the total of 120 ohms plus the headphone impedance, so the 160-ohm line shows about what you can get with any low-impedance phone. You do not need a huge capacitor unless you do something (different tube, feedback, etc) to lower the output impedance.
Pauls comments should be self explanatory, but, Im dumb, so I need to ask a dumb question for clarity:
Does this mean that the Headphone impedance should be added to the 120 ohm amplifier output impedance and then this total impedance should be used to reference the chart for the -3db point? So, with stock 100uf output cap, for 32 ohm phones you would reference the chart for the -3db point of 152 ohms (120 ohm Crack output imped. + 32 ohm headphones), not 32 ohms ... so theoretical - 3db would be a little above 10 hz with 32 ohm phones, not 50 hz?
Or, am I once again missing "it".
Thanks.
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The load and resistors are in parallel, so they don't add as they do when they are in series. In essence, to get the equivalent parallel resistance, you need to take the invere of the sum of reciprocal values, which essentially means that the total will always be less than the smallest resistance in the series. Simple example would be two 10 ohm resistors: 1/10 + 1/10 = 2/10, inverted is 10/2, or 5. This is the same basic formula for n number of resistors, just add up all the reciprocals and then invert that number to get the equivalent resistance.
From this you can also see that very high resistances in on the order of several k, will have very little effect on the lowest resistance in the series, so the 2.xk resistors across the headphone jacks are negligible.
Hope this helps, I'm no teacher so I apologize for any assumptions I've made on your background.
-- Jim
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Hi Jim
I should have stated my question differently. I do know that parallel resistors dont add the resistors values together. I used the wrong wording as I didnt mean "plus" in terms of resistors and the math of it. I was wanting clarifiction on Pauls comments reqarding not needing a higher uF cap for lower -3db cutoff with low impedance phones.
Paul stated ... "The chart is for a voltage source/cap/load but the Crack has a 120 ohm output impedance. The cutoff in the bass goes with the total of 120 ohms plus the headphone impedance, so the 160-ohm line shows about what you can get with any low-impedance phone. You do not need a huge capacitor unless you do something (different tube, feedback, etc) to lower the output impedance."
So what I was asking for was clarification on that. My understanding of Pauls comments are that, the cutoff for most low impedance phones would be what is shown in the 160 ohm line in the chart, NOT the line corresponding to the actual stated impedance of the phones themselves.
For a direct question .. would a 50 ohm headphone have a 32hz -3db cutoff as directly shown by the 50 ohm line on the chart? or would it have about a 10Hz -3db cutoff as corresponds to the 160 ohm line in that chart? From Pauls comments, I was assuming the latter and that's what I was looking for clarification on as to whether I was understanding that correctly or missing what he was saying.
Thanks
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Well, when it comes to charts, being blind as I am, I'm kind of useless at interpreting what I can't see :-). Which is all to say that I can't answer your question on impedance.
Sorry for the unnecessary lesson in parallel resistance :-).
-- Jim
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I appreciate the Reply. Eventhough I did know about the parallel resistance I still added the output impedance to the headphone impedance to use as, what was, a very bad example and would logically elicit a lesson in parallel resistance like you gave. So my fault all around for not thinking or explaining what I was getting at. Im not very good at being succinct when typing and it was a brain fart on my part to boot.
Thanks for the effort.
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Laudanum - in spite of the opioid implication :^) - has it correct. The source impedance (120 ohms resistive approximately) is in series with the load impedance (32 ohm headphones for instance) so the current loop consists of the output capacitor in series with the total impedance (152 ohms resistive in this case).
This analysis is based on a voltage source (zero impedance) in series with the source resistance, the output capacitance, and the load resistance.
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Thank you once again, Paul.
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Hope this discussion is still alive...
I just bought and built a Crack. LOVE it already. Same old, same old. Massdrop x Sennheiser HD-6XX and experimenting with coupling these with an OTL.
I have, but haven't installed, the Speedball upgrade. I'm acclimating myself to the stock Crack, and shaking it down. Sounds lovely like it is. Have ventured into some tube rolling. From previous tube lives, I have a cosmos of 12AU7s to select from, but the 6080 is a new one for me. (I really like the 6SN7 and 6CG7. I have a lot of them and reading through the Crack discussions it seems that the Crack can easily accommodate these tubes for the 12AU7 position.)
Pretty much two changes I'm considering. A different potentiometer and film output coupling caps. I see that Mouser has some Kemet film caps in the same value as the Lelon aluminum electrolytics my kit came with - 100mfd/160V. They're small, affordable. I'm considering giving these a try.
Question I have is that the three Nichicon power supply electrolytics and the two output coupling caps are all polarized. The film cap, AFAIK, isn't polarized. Does this matter? How? Why? Do I have to consider worry about polarized/non-polarized? Guidance here would be appreciated.
Thanks!
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I see that Mouser has some Kemet film caps in the same value as the Lelon aluminum electrolytics my kit came with - 100mfd/160V. They're small, affordable. I'm considering giving these a try.
I'm not sure which caps at on mouser (could you post a link) however, the caps that come with the crack are 100uF/160V. The only caps that size and brand that I could find on mouser are polyester film.
The film caps that others are installing are mostly polypropylene film, not small and not overly affordable, and should offer much better audio performance. I would double check that the caps you are considering are the correct value and would actually improve performance over the stock (A lot of people dislike polyester caps in the audio path).
Question I have is that the three Nichicon power supply electrolytics and the two output coupling caps are all polarized. The film cap, AFAIK, isn't polarized. Does this matter? How? Why? Do I have to consider worry about polarized/non-polarized? Guidance here would be appreciated.
Most electrolytic are polarized, most polymer caps are not (Some have a preferred direction). You can install either (in this application), however if the cap is polarised, pay attention to install direction.
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Can someone who has experience rolling different output capacitors on the Crack/Crackatwoa comment on the significance and audibility of these changes? On my Crackatwoa, I have a pair of Mundorf Evo Aluminum in Oil, basically bought the highest quality output caps I could fit without too much trouble, and admittedly, did not do a lengthy A-B comparison versus stock since I was strapped for time when building. I haven't attempted to swap them out since finishing the build a year ago, and probably never will, but just curious for those who have swapped several caps, what is the magnitude of the difference in sound?
For example, many people call the Mundorfs "warm" vs. other caps. Are we talking a slight warm tilt, or a night-and-day difference? Thanks.