Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Nathan on May 28, 2014, 05:22:12 PM
-
I ordered my Crack in April- took about 3 weeks to arrive. The day it arrived I assembled the base. The following day I did the mechanical work - ie, mounting the switches, transformer, etc. the only issue I had their was that I wasn't sent enough small nuts. Easy enough trip to the hardware store fixed that. I spent two evenings soldering. My years being an avid modeler when I was younger paid off as you need to be patient and meticulous.
The base was machine sanded, stained with 2 coats of Sedonna red, then 3 coats of semi gloss polyurethane ( sanded between coats).
All resistance checks were spot on, as we're all voltage checks. I used a Hakko soldering station and Cardas solder. All solder joints look shiny.
The moment of truth- plugged it is and give it a listen. First tried an inexpensive pair of cans and I got sound. Next came the HD600's. Perfect! At any sane listening levels there's zero noise. Sure if I have no music paying and the volume is jacked way up, there's hum but that's not realistic.
Color me very impressed.
Only one issue- with my HD600's, the total rotation of the volume knob from silent to loudest I can bear is 1/6 rotation of the volume knob at best. Time to solder in some resistors. I see the FAQ section covers this and suggests either 270k or 470k resistors. Though I have both value resistors, I'm curious if other with HD600's have encountered the same thing and if so what value they have used
-
You'll generally have better luck if you spend the big bucks and get 4 resistors. I would put a 33K across the outer pair of lugs on each level, and a 75K in series between each center post on the RCA jacks and the wire connected to them. This will give you some serious padding, as well as maintaining a reasonable input impedance.
-
thanks for the suggestion-
if you could, as I am very good at following directions but am not well versed in building electronics, if somehow you could provide some sort of wiring diagram for the 75k ohm and 33k ohm resistors, that would be greatly appreciated
Thanks- Nate
-
Nathan,
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi244.photobucket.com%2Falbums%2Fgg7%2FGrainger49%2FSmiles%2Fttiwwp.gif&hash=e7ff13cc08d6091a1bf54867d2dfd1da75ce755a)
I want to see the base!
Let's see if I can give you different instructions.
At the input RCA jacks remove the wires going to the center of the jack, insert one end of a 75k Ohm resistor and solder the wires back to the other end of the 75k Ohm resistor. That puts the resistors in series with the signal "hot."
Then at the volume control, you have three lugs one set on top, one set closer to the plate. If I have this right, Paul is saying to go from the input lug (from the RCA jacks) to the ground connection of each set of three. Those are the outer lugs, the center lug of each trio goes to the 12AT7.
-
There is a pretty good diagram on this webpage that you can look over:
http://www.goldpt.com/mods.html (http://www.goldpt.com/mods.html)
-
If you understand what I wrote that is exactly what is on the link.
-
Ok, I get it- 75k on series with the hot RCA pins, then the 33k across the outer lugs on both levels of the volume pot.
-
Nathan,
(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi244.photobucket.com%2Falbums%2Fgg7%2FGrainger49%2FSmiles%2Fttiwwp.gif&hash=e7ff13cc08d6091a1bf54867d2dfd1da75ce755a)
+1 -- take a pic! I want to see this Sedona base!
-
I'll do the picture- hopefully later today- it came our real purty
Nathan
-
The forum's FAQ suggests thus to pad down the volume -
"3. I can barely turn my Crack up at all before it's far too loud, what do I do?
Remove the white wire from the left RCA jack at the rear of the chassis. Solder in a 270K resistor to the solder cup on that jack, solder the white wire to the other end. Repeat this for the red wire with another 270K resistor. This will give you about a -10dB pad at the input. If you still have the issue, try 470K instead. The wattage of these resistors isn't all that important, anything between 1/16 Watt and 1/2 Watt is reasonable, with metal film and carbon film types being most recommended."
Why is the suggestion here of 2 33k ohm resistors across the outer lugs of the volume control and a 75k ohm resistor in series with each of the hot pins of the RCA's a better solution?
-
Why is the suggestion here of 2 33k ohm resistors across the outer lugs of the volume control and a 75k ohm resistor in series with each of the hot pins of the RCA's a better solution?
This will give you some serious padding, as well as maintaining a reasonable input impedance.
-
Seems like it would be appropriate, but I must ask:
Will this 2-33K and 1-75K per channel resistor combination be a good way to "pad" the volume on the S.E.X. 2.1?
-
Seems like it would be appropriate, but I must ask:
Will this 2-33K and 1-75K per channel resistor combination be a good way to "pad" the volume on the S.E.X. 2.1?
Yes, the same logic applies, though I believe you would be the first person to pad down the level control the SEX.
-
Ok, installed the pair of 75k resistors in line with the hot pins and the 33k resistors as instructed- not the neatest job as the volume control area was already crowded. Wondering if I wanted a little less padding down what value resistors I should use? Really don't want to change the 33k ones as they were pain.
-
Try 50K in place of the 75K.
-PB
-
It would be easier to parallel in some 150K ohm resistors. Same net effect and if I prefered it at 75K ohm, I could just snip them out
-
http://bottlehead.com/smf/index.php/topic,3.0.html
Please read the fourth rule.
-
Ok-
Anyone know where I can get just 2 resistors without paying more in shipping than the cost of the resistors?
-
Ok-
Anyone know where I can get just 2 resistors without paying more in shipping than the cost of the resistors?
At you local electronics shop.
-
RS? Only have carbon in stock-
-
RS? Only have carbon in stock-
Carbon will work.
-
Here's my built Crack
Tube compliment is a Tung Sol 5998 and Mullard 12AU7, both NOS
I've padded down the volume control using 2 33k Ohm resistors on the outer legs of the volume control and 75K ohm resistors on the hot pins at the RCA's. Next step is to reduce the resistance at the hot pins to 50K ohms. I'm inclined to trying some paralleled 150K ohm resistors and if that's 'just right' then just putting in some 50K ohm resistiors. Once that's done I'm going to put a few spots of hot melt glue between the base and top plate so the top plate doesn't move around every time I pull the headphone plug. I can't imagine how much better a Speedball could be!
-
Larger image
-
Is that stained Nathan? if so its came out really nice and even. It reminded me of your native Jarrah wood when I first saw the pic.
-
Thank You!
It's stained. With this sort of wood, you have to use a pre-stain otherwise you run a real risk of the stain being blotchy.
Here's what I did to finish the base. After assembly I used a power sander to get it nice and smooth. Some compressed air and then tack cloth to get rid of the dust. Then pre-stain. After the pre-stain, I did multiple coats of stain. Then I used a semi gloss polyurathane, sanding between coats and once again, using compressed air and tack cloth. Were I to do this again, the only thing I would do different would be to use steel wool between coats of polyurathane (did 3 coats). I used steel wool between poly coats on another wood project and like the results better but someone talked me out of using the steel wool, saying I run the risk of tiny bits of the steel breaking off and embedding into the wood. That had never been my experience and I don't know why I listened.
Came out quite nice anyway . . . .
PS- this is my first BH kit. Must be another Nathan lurking around as well.
-
The alder takes stain quite nicely without a sealer. IME the best approach is to use water base aniline dye.
-
Could be the analine is the best approach. Note that Minwax specifically recommends their prestain on alder. I suppose there is more than one road to the same destination