Crack;Bottlehead OTL
May 21, 2010 at 3:37 PM Post #137 of 11,047

ironbut

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Thanks nikongod.
That's a great description of the amps sound.
I'm kinda shocked how good those humble Panasonic caps sound but I'll probably get around to trying some bypass caps in the weeks leading up to CanJam (I'll be bringing my Crack).
I might even try some boutique resistors on the 12au7 Rp if I have the right value laying around here.
I'm holding off on buying the Speedball upgrade until after Chicago. I know from experience that if it's in the house, I won't be able to resist installing it. I want to let folks who're interested in getting a Crack, get a listen to it in essentially stock form.
 
See you there!
 
May 25, 2010 at 12:43 AM Post #139 of 11,047

nikongod

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I made this transformer box some time ago as a "prroof of concept" for the SP extreme I had at the time, but it works quite nicely on the Crack too.
 

 

 
It is a pair of inexpensive Speeco transformers set up as auto-formers with the knob on the front to select between the bunches of various step-down ratios they allow. They sound great with the crack and low impedance headphones.
 
May 25, 2010 at 12:45 AM Post #140 of 11,047

Ypoknons

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You should commercialize that thing and sell it to the legions of OTL tube amp users out there you know. 
tongue.gif

 
May 28, 2010 at 1:32 PM Post #141 of 11,047

ironbut

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I'd love to hear those Speeco's. Could you bring them to CanJam?
 
Speaking of which, I'll have my AD2000's which isn't a great match for this amp, so you'll be welcome to come by and plug in any headphone you want. Except for signal wire and a TKD pot, it's dead stock.
I'm dying to try a pair of HD800's and the T1 with it myself. I think the punchy bass and the nice midrange body of this amp could be just what these phones need (for my tastes of course).
I sent my amp to the Hyatt so it should be there the day I arrive. I have 2 tube sets that seem to be pretty nice that will be there too.
Tung-sol 6080WB graphite plate/ Tungsram E80cc
Sylvania 6080WB/CBS-Hytron 5814a
 
Both sets have their pluses and minuses and which one will spend the most time in the Crack will just come with time. I'm still waiting for a 5998 to arrive so the whole thing could change when that happens.
 
I'm planning on ordering the Speedball upgrade when I get home from Chicago so we'll see where that puts the sound too.
 
May 30, 2010 at 8:44 PM Post #142 of 11,047

HiGHFLYiN9

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Well I just bit the bullet, this amp looks like too much fun to pass up, and I have a nice 100K stepped attenuator laying around that would be perfect to swap in.
 
I saw that the price is going up $20 in the next week, that was the straw that broke my relatively weak camel's back :wink:
 
Jun 3, 2010 at 7:12 PM Post #146 of 11,047

HiGHFLYiN9

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Years ago I rolled a Blue Velvet ($25), a Chinese stepped attenuator with soldered in Vishay resistors ($70), and the DACT ($150). The DACT was the clearest and best sounding of the bunch, and the Chinese stepped attenuator wasn't too far off. There was a marked difference between the Blue Velvet and the Chinese SA. Goldpoint runs about $150 as well, but I haven't tried one myself. I don't know if the DACT would be worth purchasing for a $200 amp, I just have one laying around that I'd figured I'd use. If you go searching for a Chinese SA, be sure to pay close attention to the number of steps. 24 is pretty typical, and a minimum imho.
 
Potentiometers and Stepped attenuators just have six pins that you solder to, it shouldn't pose a problem.
 
Jun 7, 2010 at 9:57 PM Post #147 of 11,047

ironbut

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Ya know, I put in a pretty decent TKD pot in my Crack amp. I've used them in a couple of projects and I've found to be a fairly good performer. They are kind of expensive for what you get (around $70) but to get a much better pot you have to spend a lot more. I've also tried some of the "made in china" DACT  copies but I don't really like the sound of those SMD resistors. I think you'll find a pretty small gain in performance for the money spent on fancy pots. To me, it's kind of the icing on the cake.
After spending some time with the Speedball upgrade, I have no problem sticking my neck out and saying that there isn't going to be anything you can replace in this amp that's going to equal what this does.
The sound is more detailed, , the noise level is reduced (which may be revealing the improved details), the bass seems to go lower and is tighter, and there's a few dB more gain. Without doing any A/B testing with my stock Crack amp, I found that all vocals sounded more true to life and instrumental separation is better. Best of all, the amp remains very musical and doesn't become clinical which can happen with many well intentioned upgrades.
It's still just as hard to rip yourself away from the music. That's always the "acid test" for me. When I change something then listen to some music to see how the change effected the sound, and all of the sudden I realize that I've listened to a whole album, I know I'm on the right track.
Bottom line is, the improvements aren't subtle.
 
Jun 10, 2010 at 2:19 AM Post #148 of 11,047

tdogzthmn

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My amp is assembled but I have voltage problems on a few of the terminals and pins.  Both of the tubes have power and have a nice glow.  I want to listen soo badly!
 
Anyone know if both LEDs should be light?  Right now only the one between A3 and the center pin is lit up.
 
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Jun 10, 2010 at 8:53 AM Post #149 of 11,047

Todd R

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Quote:
My amp is assembled but I have voltage problems on a few of the terminals and pins.  Both of the tubes have power and have a nice glow.  I want to listen soo badly!
 
Anyone know if both LEDs should be light?  Right now only the one between A3 and the center pin is lit up.


Have you posted this at the Bottlehead Forum?  Someone there probably has the answer.
 

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