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AS-USA K2003 S.E. amp kit. Mods, alternatives?

63.10.164.74
Posted on March 30, 1999 at 08:33:25
St-Ides


 
I'm looking for an inexpensive kit to experiment with. Any suggestions? Thanks!

 

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Re: AS-USA K2003 S.E. amp kit. Mods, alternatives?, posted on March 30, 1999 at 09:18:50
bp


 
Take a look at http://www.bottlehead.com. The parasex kit is not too much and allows extensive mods. I've found that the sound with the stock OPTs is fairly good, but is excellent with with better OPTs like the TFA204s.

 

Thanks! I'll take a look. (nt), posted on March 30, 1999 at 10:17:26
St-Ides


 
nt

 

Get better caps and resistors for the signal path., posted on March 30, 1999 at 15:16:42
Dave VH


 
The supplied ones are cheapo electronics store stuff, not a good grade for top-notch audio. You'll need:

2 - 10K Ohm - 1/2w resistors (R23 & R24)
2 - .22/250v capacitors (C1 & C6) Hovland is good.

Call Ron Welborne at Welborne Labs (303-470-6585) and he can get you these caps and resistors for about $25. I just ordered mine. You can also get these parts from Sonic Frontiers Assemblage Kit Division, Angela Electronics, or Cary's Audio Engineering Division, Antique Electronics and many other places. Tomorrow, I'll order NOS tubes a 5751 and EL84's.

(I assume that you're building the kit? If so be careful and atake your time. There's no picture to show you how the wiring should look when finished, and you can end up with parts too close together if you're not careful. I found one resistor that wasn't in the instructions and had to track it down on the schematic to figure out where it went.)

Good luck, and have fun.

Dave Van Harn

 

Try the AS-USA A2 Kit!, posted on April 1, 1999 at 10:19:11
Chris Fagas


 
You won't believe it, but the A2 is around the same price as the one you mentioned, but it has twice the power output and uses a tube rectifier. The A2 is a pair of EL84s in push-pull on each channel, so it includes twice as many of the same EL84 output tubes plus a tube rectifier for the same price because it isn't single-ended (which happens to be currently trendy). The funny thing is that single-ended circuits were the way tube audio started, before it graduated to the higher power output and improved efficiency of push-pull circuits at its pinnacle. In my opinion, how you bias and run the tubes in the circuit, and the characteristics of the output transformers, have a lot more to do with the "sound" than whether the amp is single-ended, parallel single-ended, or push-pull...

My A2 sounds really good on my second system with my really old CJ preamp. I did substitute PTFE (Teflon) insulated wiring which will better tolerate the fairly high operating temperature of a tube amp, and also higher quality REL Multicaps for the inexpensive polyester caps which were included and shown on the schematic to be directly in the signal path.

I bought the basic black chassis with the full black cage. The black finish is a nice heavy textured paint. The A2 looks great perched atop the old CJ preamp. This whole kit only cost around $450 delivered to my door, plus a little extra for the few upgraded parts...

Keep in mind that the ASUSA kits are for more experienced builders and that there are no exploded diagrams and really detailed pointers (like Heathkit used to be so good at providing). You get a step-by-step suggested wiring order, which in the case of the A2 is about 95% optimized, and a schematic diagram. The A2 is point-to-point wired with no circuit boards.

Have fun building!

Kind Regards, Chris

 

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