Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Foreplay III => Topic started by: Jim R. on July 01, 2012, 05:43:11 AM
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As I generally don't like dual volume controls (and believe me, this comes from a whole lot of experience with all kinds, including stepped) I've been looking through the posts here and have not really seen anything other than a custom dual attenuator based on the original 15k pot -- which seems fine, though the variable loading of the source seems to be a concern (although only a theoretical one at the moment and may not be anything at all to be worried about.)
However, I wonder about a stepped system that uses two 6-position rotary switches for a total of 36 steps -- one coarse and one fine) and wonder if anybody has done this and what type of attenuator you built -- series, ladder, or hybrid?
This seems like it could be a somewhat more economical way to a high quality attenuator for the FP III.
Thoughts?
-- Jim
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Jim,
I'm in the midst of defining a path for improving the volume controls in my EFP3. I'm curious why you find dual mono controls a detriment? I'm currently using a Goldpoint selector with sweetest whispers shunt attenuators. The padding resistors are Audio Note and Shinkoh Tantalum's. I'm trying to explore the audible effects of several different types of resistors. I've not begun testing yet as my speakers remain unfinished. If you please, I would like to know more about resistors you have used and your evaluation of their sonic effect. Would you agree that any, high quality passive volume control is essentially 90% due to the resistors used? I also would like to build an economical high quality volume control as I think this is an area where real sonic improvements can be achieved. I will continue reading with interest.
Thanks,
John
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Funny you mention that. PB just bought the parts to build a coarse/fine stereo attenuator as a test for the 300B preamp.
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Wow, that is exactly what I was wondering about! The idea came from the days when I owned a tuner that has fine and coarse tuning. This would be the same idea. Like I have said before, there is an EXACT volume that I am trying to reach in some recordings.
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How about something like this,
http://glass-ware.stores.yahoo.net/netcjstat.html
I have one in one of my projects, works pretty well...John
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John R. -- really just me and my preferences -- far easier to turn one knob than it is to count clicks on two stepped attenuators, and two linear pots always ends up with me going back and forth to the listening chair typically several times before I get it right, then when the mix strays to one side I feel as if I should get up and tweak it -- none of these is really conducive to deep listening IMO. I'd much rather set it and forget it.
Yes, the resistor, and even the solder play a significant role in the sonics. I've not tried all the ones out there certainly, and as well none of the real boutique ones in a stepped attenuaator, but inddividually the vishay rn-55 is a good all-around metal film resistor, the CMF-55 a step up, and then the Texas components (nude vishay's) but you can also use the super expensive tantalums, nudes, and others in more critical places -- such as shunt and padding resistors in the foreplay and probably take the whole thing up a notch. Night and day difference? Doubt it, but noticeable for sure and worth it is strictly up to the individual. My main complaint with the smd resistors is that typically the resistive element is nichrome and I just don't think nickel or chromium sounds very good in an electrical circuit.
Dan, great -- perhaps PJ will tell us more when he gets back.
John, I'll have to look again, but I recall the tubecad attenuator being a bit too large for the BH chassis, and at least for me with my new rack, widening the BH chassis is not an option. But yes, that's the idea that got me thinking about a similar approach for the FP III.
-- Jim
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John, that ad really knock me over! Soooo, it's not just me. Now, if I could just verify the quality of this product. This is EXACTLY what I would want, in theory. Thanks for the post.
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Greg,
the TCJ hardware is of top quality -- very substantial pcboards and he only uses the swiss made, hard gold contact, Elma rotary switches, plus you always have the option of buying your own resistors if you don't like his options.
-- Jim
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I finally found the reference to using "boutique" resistors in the most used positions, VoltSecond!
So build and find which positions are used most. Then, after listening for a while, you have determined where you listen most often. At that point you can put a $17 Nude Vishay in the series position and a $6 boutique in the shunt to ground positions.
This appeals to the cheapskate in me.
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Hey Grainger,
There's some cheapskate in all DIY, right? Besides we are value conscience.... Of course I usually don't get it right the first several times but that's another story!
John
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Greg,
the TCJ hardware is of top quality -- very substantial pcboards and he only uses the swiss made, hard gold contact, Elma rotary switches, plus you always have the option of buying your own resistors if you don't like his options.
-- Jim
The ELMA switchs at parts conneXion are $60 each, and the TCJ kit with three switches is $30. I think I'm missing something!
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Hmmm, maybe he's changed switches since I last looked. Or, pcx is marking them way up :-)
-- Jim
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Oops, does indeed look like he has changed switches:
"The kit includes instructions and three high-quality, open-frame, rotary switches... "
Those are definitely not the sealed, hard gold Elmas he used to sell with the kit -- which also used to be something like $170. Ah, looks like he still offers that kit too, but at $160:
http://glass-ware.stores.yahoo.net/tcj-stepped-attenuator.html
Also, the A5 kit (possibly subbing elma 6 position switches) looks like it may be just the ticket for the FP III -- and it will fit, but probably not in the stock top plate. Might even work as-is as far as the configuration too:
http://glass-ware.stores.yahoo.net/a5stat.html
-- Jim
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Now, I did dig a little further to find he offered another kit for $160, probably the one you remember. It was obviously 'hi-fi' as the bodies of the switches looked exactly like the Elna(I'm sure that they were because they were out of stock, waiting for more switch bodies from Switzerland:). Anyway, you know where this is headed, with me talking all about the exact volume,etc. Time to start deigning a switchbox with a volume control(passive preamp?)
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I just found that Khozmo makes a shunt-type attenuator -- would this work suitably well in the FP III+ and would the recommendation be for 25 or 50 k and would you still put the 33k resistor under it? Or, would it be better to get a custom 15k or 20k version from them and wire as described in the manual?
I'm not worried about the fit as I'm machining new top plates for my fp III, eros, and SR-45s out of copper plates.
Thanks,
Jim
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To try all this stuff out for 'comfort', a Quckie kit has been ordered with the optional upgrade. Along with that thinking, I believe that I will try the cheaper ($30) volume control first. If this all works as I think it should, who knows what will happen next? (Not even my entire team of psychiatrists are willing to bet on that one)
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Greg,
Just for yucks try the 100k Alps Stereo Volume control from Radio Shack first. It costs over $3 now, damn near $4, it used to be $2.
http://www.radioshack.com/product/index.jsp?productId=2062359
Many say that the low level tracking is off but I have used them for over 20 years with no problems.
I mean, if you are going to do a survey of this stuff, start at the bottom.
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I still have one of those Alps pots on a half kit I built. I bought a Blue Velvet to replace it but never got around to it. Mine actually tracks fairly well but listening level on that amp is usually 11 O'clock or higher. Actually I think those little S5 kits had/have a version of the same control. I have one of the older/original S5 kits with the 11BM8 tubes that sounds better than any amp under 100 bucks has any right to. A pair of full rangers with Fostex drivers crank on that little amp. That little kit with it's cheap transformers, run of the mill PCB and cheap passives along with an old Scott 299B is what started me back with tube audio gear a dozen years ago. Those cheap wirewound Alps pots sound fine to my ears but with 2 disclaimers. First, I havent compared them to anything else in those amps. And second, MY EARS being the operative words. They probably arent quite tin but they are closer to tin than gold ;D
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Well, I do have an ALPS that has been orphaned by the PEC.
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How about a remote control?
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Hey, now, I don't need that...I'm married.
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hi again, here is a small demonstration of my ongoing ignorance. my components are placed on a big ol' sturdy coffee table at arms length directly in front of me. an efp 3, a sex 2.1, a decware cd 200i and an old carver fm tuner. my speakers are audio nirvana 12 inch and are flanking the components at around 70 inches from my ears. this idea was stolen from pierre at mapleshade audio. i have been set up this way for over six months now and will most likely NEVER return to the "rule of thirds"..........no remote control, no tedious walks back and forth to change sources, or discs, or volume adjustments. walking back and forth to a set of controls is not my idea of a good listening experience. no room treatments seem to be required. other sorts of things that will not come to mind right now.............i'm hoping that some out there will have comments that i may learn from. are any of you experienced with this method and know stuff i am missing?? don
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Hey Don,
If it works for you, that's all that really matters, right? I have to admit to being a past skeptic, now turned believer in Pierre's often whacky methods. Some of it is really, really hard to get your head (and eyes) around, but he and Ron are eccentric geniuses with impeccable engineering credentials.
I was completely skeptical of their power strip but got to demo one in my place a few weekks ago (one of the "Stratum AC conditioners -- power strip mounteed on a maple block) and was stunned, literally, at the difference. Unfortunately I can't use the speaker wires or interconnects as my cat loves to chew on bright shiny things and plastic films, and it doesn't take much to get that insulation off -- which is bad for the electrical gear, and worse for the cat.
Anyway, back to the subject at hand, I see I had misinterpreted how the FP III+ volume control hooks up, and not that I've got it figured out, I've gone ahead and ordered a 25k 48-step khozmo ladder attenuator and will play with the padding resistor until I find the right balance of adjustability and overall gain. I'm also going to put the resistors between the selector and the pot to keep things simple and reduce the possibility of noise pickup. I don't really need each input to be level maatched as I will have somewhat more than 11 steps to work with. I'm also using a single stereo control and will place it on the opposite side from the power switch.
Problem solved, case closed. :-)
-- Jim
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hi again, here is a small demonstration of my ongoing ignorance. my components are placed on a big ol' sturdy coffee table at arms length directly in front of me. an efp 3, a sex 2.1, a decware cd 200i and an old carver fm tuner. my speakers are audio nirvana 12 inch and are flanking the components at around 70 inches from my ears. this idea was stolen from pierre at mapleshade audio. i have been set up this way for over six months now and will most likely NEVER return to the "rule of thirds"..........no remote control, no tedious walks back and forth to change sources, or discs, or volume adjustments. walking back and forth to a set of controls is not my idea of a good listening experience. no room treatments seem to be required. other sorts of things that will not come to mind right now.............i'm hoping that some out there will have comments that i may learn from. are any of you experienced with this method and know stuff i am missing?? don
don - I kind of like that idea! I worry about people (like me) and their coffee in close proximity to my gear! I guess in a dedicated listening room - for sure.
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to jim's topic: recently asked a fellow bottlehead to install a goldpoint mini-v unit into my sex 2.1. that improved it so much i am almost speechless. along with some other upgrades this li'l guy is better performing that my wife tells me i deserve! grateful!....so now he is receiving my efp 3 in order to do similar upgrades. and then i happen upon mention of khozmo. look it up and behold! machinery heaven! and then i read that quite knowledgeable people are turning to khozmo instead other stuff. i am just about to make a purchase. any ideas? don pettit
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Don, I just looked at the Khozmo, and again, I couldn't be more impressed with the build quality. Simply amazing, but about the sound? I can't answer that. I can tell you that the cheap Chinese stepped attenuator that I tried out on my amp was taken out and replaced with a PEC control.I really like it, BUT it doesn't have any more control that the ALPS I started with(of course, being the same value and taper I didn't expect it to). Anyway, the Khozmo has 41 steps. That is quite a bit of control if the taper is right, and the pad resistors are chosen well. We can try using that one in your EFP III if you want, and like I said the last time, I will buy it if you aren't amazed by it.
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Greg and Don,
I got the ladder type -- meaning the one with 48 steps and non-SMD resistors. That said, I have no idea if it will fit in a stock foreplay III, but as I'm making my own top plate, I will be able to adjust the positions of some things a bit, though the basic layout and spacing will be retained. Mainly I'm getting the IEC inlet off the top and will put one on the rear or use a PowerCon. If there's room I'll probably also put the power switch somewhere in that rear corner where the iec inlet was.
HTH,
Jim
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Informative thread, thanks. I'm curious though, I recently removed a pair of Goldpoint Mini-V's (with Nichrome thin film resistors) because I heard a distinct change in tone. I'm not sure exactly how to describe it except to say the tone became somewhat veiled, less musical. I disliked it so much I reinstalled the sweetest whispers attenuators. I haven't had a chance to listen since as my speakers are in a state of change. The Khozmo attenuator looks as though it uses similar surface mount resistors, Resistors: 1% 100ppm , 1/10W, low noise, non-inductive. The surface mounted resistors used on the standard Goldpoint Mini-Vs are 0.1% Nichrome THIN film with a thermal noise specification (TCR) of 25 PPM or 50 PPM. Thin film as opposed to metal film. A small difference perhaps but "we" DIY to chase the grail in a more value conscience way. Frustrating though. But then again I've learned more about resistors this morning, now if I can only remember it all :)
Best regards,
John
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hi john, to my ears, in my sex 2.1, i heard a vast improvement when the mini-v was installed to replace the stock unit. greg seems to have heard the same thing. so far so good.........now, turning to my efp 3 i am thinking why not the same improvement here? but i do recognize the ballgame may well be entirely different. since i am not a diy person and the preamp is in the hands of greg i have this decision to make. drat, i don't really know what to do. $180 or khozmo or $150 for goldpoint or $4 at rat shack? myohmy!!!!!!!!!!! don
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You are replacing completely different attenuators in S.E.X. and FPIII. S.E.X. has an inexpensive Alpha pot and FPIII uses a stepped attenuator with thru hole metal film resistors. IMO the Mini V sounds quite a bit better than the Alpha, but not quite as good as an attenuator made with thru hole resistors. This is why I recommend buying the Goldpoint Mini V Custom that uses thru hole resistors for the S.E.X. amp. Arn is a great guy to deal with.
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thank you sir doc!! greg, my email is hosed up again. let's do what the good doctor advocates!! moving on to the channel attenuators. i do not like such largely spaced units and wonder about goldpoint units. the way to go or not? i do apologize for hijacking jim's topic and would like to wrap this up and to get out of the way. please, put me out of my misery and get rid of me!!!! don
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John,
You wrote:
"The
Khozmo attenuator looks as though it uses similar surface mount resistors, Resistors:
1% 100ppm , 1/10W, low noise, non-inductive. The surface mounted resistors used on
the standard Goldpoint Mini-Vs are 0.1% Nichrome THIN film with a thermal noise specification
(TCR) of 25 PPM or 50 PPM. Thin film as opposed to metal film."
That's only one kind of Khozmo attenuator. Look at the Khozmo web site and look at the "ladder" attenuator link. This type uses through-hole dale vishay rn55 and caddocks as standard -- though there are other choices at higher prices. They also have 48 steps instead of 41. Should be easy to replace the caddocks with nude vishays.
I ordered mine directly from Khozmo as PCX did not have the 25k stocked in this ladder configuration.
Don, I've purchased my attenuator and after figuring out my wrong assumption on how the attenuator was wired, I'm all set, have my attenuator ordered and have a plan, so I'm done with this thread.
-- Jim
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You guys have tempted me with these things long enough, but I found a surprise in the basement from years ago. A Shalco stepped attenuator project that, at the time, I didn't have the skills to deal with(and besides, seems to me, it was a balanced config). It'a real mess, as I wasn't able to neatly cut the leads the way that would work best. Anyway, it does offer yet another possibility for the new project I will starting in the near future(no Don, not yours, these things are giant).
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That is an interesting idea:
However, I wonder about a stepped system that uses two 6-position rotary switches for a total of 36 steps -- one coarse and one fine) and wonder if anybody has done this and what type of attenuator you built -- series, ladder, or hybrid?
With two - 2 pole 6 position switches we could consider for the second switch an "inverse" "Single Series, Single Shunt, Stepped attenuator" to generate a "fine" control. An inverse S5 attenuator keeps one resistor in the ground leg and switches a resistor to he input. The inverse attenuator has the benefit of not "popping" when switching volumes even if a non-shorting switch is used. The inverse attenuator has the disadvantage of wide input resistance swings, but for 6 steps, it can be made controllable.
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fwww.siteswithstyle.com%2FVoltSecond%2F12_posistion_shunt%2FSHUNT_MODE_POT_CONFIG_B.gif&hash=be09b45456c58fc2ee86cda6dbdc97e67a0dbef8)
The question would be what would be best for the first stage? I'm thinking a standard stepped attenuator would work.
What is to be considered is if an "impedance leveling" resistor between the first and second stage is needed.
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I'm thinking 2 db steps for fine control and 10 dB for coarse as a goal. One step of fine would over lap with the coarse settings giving about a 60 dB adjust range.
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Another thought:
A single pole single throw center off switch could be also be added for a 1 dB balance adjust. The center off would be used for a "mute" switch.
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For what it's worth, none of the current products were laid out with the Khozmo, Shallco, or other large attenuator in mind. I don't know what will fit in which product, (The Goldpoints are mostly similar in size to the stock and should fit.) I did a layout for an upcoming version of the Crack which does fit the large attenuators but I don't know if that aspect made it into the latest production design. I'll certainly push for it in the 300B preamp though!
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Paul,
Well, if it's of any help, I certainly believe BH gear to be totally worthy of these boutique parts for those who want to make that choice. The stock kits are a superb value as they come -- and the engineering and sonics are there for sure, and will satisfy a large percentage of listeners, but with a couple upgrades in intelligent places, a lot of the products can hang with the big boys for sure. Does it make any sense to put Duelund silver foil CAST caps in a Quickie? Perhaps not, but a good attaenuator in just about any product that uses one is definitely going to be a nice upgrade for a lot of people. You can't undo the damage to the signal done in a pot but you can minimize it with a higher quality one.
-- Jim
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Well said indeed.
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Paul,
Well, if it's of any help, I certainly believe BH gear to be totally worthy of these boutique parts for those who want to make that choice. The stock kits are a superb value as they come -- and the engineering and sonics are there for sure, and will satisfy a large percentage of listeners, but with a couple upgrades in intelligent places, a lot of the products can hang with the big boys for sure. Does it make any sense to put Duelund silver foil CAST caps in a Quickie? Perhaps not, but a good attaenuator in just about any product that uses one is definitely going to be a nice upgrade for a lot of people. You can't undo the damage to the signal done in a pot but you can minimize it with a higher quality one.
-- Jim
Hey Jim - cant agree more! Duelund CAST is a bit over the top, not sure where they would be 'worth it' to tell you the truth. Not that I dont think that they are worth the money. Just not sure where you would justify it. You could easily say 'not in a Quickie' but then where? I guess you could spending $2-3K on caps is in a component that costs upwards of $20K. But then you are forced to deal with the issue of why did a $20K component not have them already? I would feel pretty ripped off if my $20K component didn't have the pinnacle of boutique part already on board, and here I was hacking out some $2 parts. The sad thing is that most of them dont have the good stuff. You are paying for someones supposed 'genius'. I personally think that is idiotic. There are many smart folks out there. Many of them involved with Bottlehead. For those that are too lazy to put some personal sweat and toil into their kit, and have money they dont know what to do with, there are the big bucks vendor. For the other 99% there is Bottlehead and others. My personal opinion is that China has had a good effect on this industry. They have made due with common electronics and produced great sounding kit for practically nothing. We (the USA) can, and we are doing the same. It has taken an awakening. In the past we have defined this industry. We will continue to. Use the KISS principle.
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I shouldn't but I will say it anyway, fitting a khozmo in yor Crack is a lot like, well fitting a khozmo in your crack. It can be done but you gotta dremel out the base.
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Randall,
How did you keep from going through the outside of the base? Those notches look deep!
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I shouldn't but I will say it anyway, fitting a khozmo in yor Crack is a lot like, well fitting a khozmo in your crack. It can be done but you gotta dremel out the base.
I shouldnt say it either but, since you provided the mental graphic ... I probably wouldnt mind Dremeling out my Crack base if I wanted a Khozmo bad enough but I wouldnt want to Dremel out my Crack ;D
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Desmond,
Maybe you've just discovered a whole new, untapped market for dremel accessories :D.
Sorry, couldn't resist.
-- Jim
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Desmond,
Maybe you've just discovered a whole new, untapped market for dremel accessories :D.
Sorry, couldn't resist.
-- Jim
I don't know, I think Randall would have to get the credit for those accessories. He kinda started it.
That said, it's a strange world and I dont think I'd be surprised to read about folks who have found "creative" uses for the Dremel tool somewhere other than the work bench. :o
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Dremel tools a great for DIY. I've pretty much worn mine out using it on all manner of things. Pressing it beyond it's design limits for sure. Time for a new one or just replace the bearings.
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Though I own two dremels, the 'multi-saw' can be handy as well. But for the brave hearted, the die grinder tops them all.
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I didn't have to cut quite as deep as it looks. A rounded pocket on two adjacent sides that I guess to be just shy of half the thickness of the wood at the deepest.
I think the 45 degree brace makes it look more dramatic.
No visible marks from the top so it is only as deep as the routed inset.
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Got'cha! Thanks, it worried me.