Tube Preamp for Apox Volume Control

[fdegrove]

Hi,

It just takes a lot more resisitors.

No technical reason it should though...

Cheers,

[Rarkov]

Hi Variac,
I had seen this board, but not considered it, since I wanted balanced inputs / outputs and two of these boards wit the resistor pack is $280 (£162.39) !!! If I use single ended (as I always have in the past) it brings it down to a much more managable $140 (£81.19).

However, since this is only attenuation, I feel that I need some kind of gain stage, which brings us back to the original question...

What is a good small gain stage (read cheap yet audiophile ) for this system?

Thanks,
Gaz

[Cobra2]

Have you searched...for e.x: Simple Fet-Buffer or something similar?

BoSoZ (Balanced Line Stage) is also a cheaper/simpler option to Aleph P

Arne K

[Peter Daniel]

With P 1.7 the Apox is recommended to be used after the preamp stage (at the output) and this is mainly what it was (Apox) designed for.

You might consider maybe trying this High-end preamp for my GC

It's as simple as chip preamp comes and supposedly sounds good (although I don't really believe it)

[Variac]

two of these boards wit the resistor pack is $280 (£162.39)

Yeah, that's why I don't have them!

I second the BoSoZ, that's what most people around here use.(well maybe not in the Tubes forum but certainly over in the Pass forum )

[f.k.l.chan]

hi rarkov,

if you need a buffer with low voltage, the circuit of figure 16a in http://www.borbelyaudio.com/ae699bor.pdf should be a good choice for you, when you connect your GC in inverting mode, you will need 2 of this buffer, one before APOX 2 and one after.

DAC-->buffer-->APOX 2-->buffer-->GC

leo

[Rarkov]

Hi,
I was reading through my AudioXpress mags to try and get some inspiration. It suddenly dawned on me that I had wanted to try the "Line Stage Odyssey" described in the feb and march 2003 issues. It is a transformer output line stage "with parafeed taking it to the ultimate".

It does look very compact yet appealing design. The author (as expected) raves about the quality of the line stage module.

Has anyone any thoughts on the compatability of these? It does say in the article that a volume pot / attenuator should go before the module, which is a direct conflict with what Peter has been saying. Peter?

Thanks,
Gaz

[Peter Daniel]

It is not in conflict with anything. I've built BOZ and was using pot at the input, but it is recommended to use it at the output as it attenuates the noise coming from that preamp.

It is dependant on the design and pot can be placed both before and after an active module. It's just in some cases it works better one way than the other.

But I also like to use pot directly at the input of the active stage.

[Rarkov]

OK, sorry, got my wires crossed then. So in this case, would you suggest putting the tube module before or after the apox attenuator? I assume you have seen the article I'm referring to?

Thanks,
Gaz

[Peter Daniel]

I'm not familiar with the article and maybe some tube guys can suggest better.

The Apox SHM doesn't provide constant input impedance, so using it at the input might be questionable. However, when high resistor values are used it might be possible. Using it at the output (providing resistance is low) whould probably be a better solution anyway. But my experience with Apox is too limited to provide satisfying enough info. Try to contact Dale and ask him. The rumor is they work on a budget version of a system, so maybe this would be something more suitable for you.