[CButterworth]

I have a great sounding DIY Meta42 which is biased into Class A and has selectable Linkwitz crossfeed. I have never heard such clean, revealing sound as this amp combined with Grados.

OK, I have since built the AKSA55 which resulted in the removal of my old HiFi amp. I love the sound and built a passive preamp using an Elma selector and Alps 50K pot.

Still, I am unsure if I can improve the sonics of the amp by using an active preamp for the CD and DVD line-level inputs to the AKSA. I suppose that I can simply begin by swapping out the DIY passive for the Meta42.

More importantly, if the gain is set TOO high, could I damage the AKSA? The sensible thing is to switch on using a portable CD-player with volume control set to zero, and the Meta42 set to zero and go from there.

Would my basic CMOY work and sound good as a passive preamp. I could easily place it within my passive preamp chassis. Although if I do this, should I wire the passive preamp's 50K pot (in shunt-mode) before, or after the CMOY? My guess is that the volume should go before the CMOY.

Questions, questions.
Regards,
Charlie

[AKSA]

Charlie,

The AKSA has a gain of almost 32dB, which is high by amplifier standards, but set deliberately high to enable use with just about any source.  Normally we would be concerned with keeping noise down, but on the AKSA this is never a problem, so I decided to go for utility, to permit use with lossy passive preamps.

I know neither the Meta42, nor the CMOY preamp.  However, if the gain of the AKSA is too high, it can be reduced with no cost to sonics by replacing R9 with say 3K3 or 4K7.  

As long as you have the volume turned low at the outset, there is little chance of damaging the AKSA with high inputs.

Cheers,

Hugh

[blizzard]

Hi Hugh,
  As stated, a stock AKSA 55 has about 32db of gain.  What gain does the AKSA have if R9 is dropped to 3K3?

           Thanks,
               Steve

[mb]

Hi Charlie,

Congratulations on the AKSA and the Meta42. IMO, you will find great benefit to adapting the buffer section of the Meta42, and using it (without the gain section) as a buffer for the AKSA input stage. A 50k attenuator feeding the 47k input section of the AKSA is not ideal, I think.

I use a similar scheme (10k attenuator -> battery powered buffer, a la Meta42 buffer -> AKSA input). Work's wonderfully for me. I would be interested to hear your opinion on the outcome. There is enough gain on the AKSA that the preceding opamp on the Meta42 won't be needed.

[CButterworth]

Mb,

Thank-you for the reply.  I tried the Meta42 as a simple preamp and did not notice any sonic differences.  I suppose that I could adapt the circuit to use just the buffer, although I'll need to go back and look at the circuit diagram to decide what needs doing, and I'll likely build my own on breadboard rather than pull apart my headphone amp.  If you used Tangent's part list, could you send me a list of the components that you used in your buffer, I'd be most grateful.

Thanks,
Charlie