preamp for aksa 55

[mb]

Kenji, you seem to vascillate between a complete refusal to accept suggestions and a strong sense of inquisitiveness.

There are a only a handful of persons on this board who are more knowledgeable and patient than Hugh, and yet you largely disregard (by way of questioning most of his points without prerequisite effort to find out more on your own). When in doubt, given that the AKSA is Hugh's design, Hugh's recommendation is correct, as he has the insight into his design. Sometimes alternatives like Gaetan's are also correct.

Some preamps are prone to hum on a badly grounded amp. Otherwise, by virtue of their design may be much less, even "immune" to hum. In any case, your guarantee is a soundly grounded amp.

When putting together my AKSA, I thoroughly read up whatever resources I could find. in particular, as Samuel has pointed out, Doug Self's articles were invaluable to me. Please have a read. Ground Loops

After much pondering, I had to relate the theory to the AKSA's ground scheme. It wasn't too difficult. Hugh has implemented a very sound ground . In the process, I slowly drew out the ground paths to convince myself why speaker ground and input ground needed to connect to different points, etc, etc.

By the time you start addressing the grounding again, there should be a very clear picture in your mind which ground path your input signal, output signal, power supply and chassis take. If you see more than one, that's where problems may occur.

Regarding logarithmic attenuators, again Google is your Friend. Google "audio taper" and there's really enough in the first six websites to answer just about everything you seem to expect us to spoonfeed you with. In reality the people here are being really nice because Hugh deserves the support.

[gaetan8888]

Hello Kenji

Another detail, even a very low ground loop noise would reduce a lot the sound qualities of your Aksa amp, so even wen you don't ear hum and buzz noises, there is a loss of sound qualities wen there is a ground loop.

Bye

Gaetan

[Professor smith]

Hugh (or indeed anyone else), you mentioned that the Benchmark was a good DAC. Have you tried this device with the AKSA to see how it sounds? I am slightly sceptical given my pervious bad experiences with other dac/preamps. I am convinced there is a matching issue here but nobody seems to be able to tell me why there should be any mismatch.

[AKSA]

Hi Kenji,

No, unfortunately I haven't tried the Benchmark.

The AKSA uses a floating earth with back to back diodes and a 10R resistor. Only fb shunt cap, input bias resistor and input ground are floated, the remaining grounds are taken to Star Earth.

This is a conventional, widely used earthing schema with proven credentials.

I cannot understand why there should be a mismatch between the AKSA and the Benchmark, particularly if the Star Earth on the AKSA is correctly floated to mains earth via more back to back diodes and a 10R resistor, as supplied.

Cheers,

Hugh

[Professor smith]

hi Hugh,

Is it possible to banish the slight hum coming from the bass drivers which if I recall correctly adds 2nd harmonics, by rearranging the transformers?

It can only be heard within a few inches away but not from where I'm sitting.

[AKSA]

Very likely, yes, but also dress of the wires, particularly input wires and power supply wires to the modules is important.

Be sure to check the hum is from the drivers, not from the trafos themselves.

Do you have a wire from Star earth to mains ground via back to back diodes and the 10R resistor (I believe I supplied it with the modules).

Cheers,

Hugh

[gaetan8888]

Hello Professor smith

If you still have hum problem, you really should do that important modification that I've described in this #43 post;

preamp for aksa 55

You will alway have hum problems if you don't correct that ground loop problem in your input wires.

Bye

Gaetan

[Professor smith]

Yes, the back to back diodes are connected. What about hiss, again it's only very slight and audible from close up. Can this be reduced further or not?

cheers.

[Professor smith]

Professor Hugh,

Some time ago, I asked if you could test your headphone amp, as a preamp with the AKSA amp. Have you managed to do this and can you inform me of your results?

thankyou.

[andyr]

Originally Posted by Professor smith

hi Hugh,

Is it possible to banish the slight hum coming from the bass drivers which if I recall correctly adds 2nd harmonics, by rearranging the transformers?

It can only be heard within a few inches away but not from where I'm sitting.

This truly is a fascinating thread. Prof, WTF won't you take the good advice given to you by Gaetan and others? (You seem to have an extremely short-term focus, as in "Oh, it's no longer humming, so I'll stop", rather than "Yes, I had better sort out the wire routing and earthing once and for all, since people have spent their time to give me all this good advice".)

Just as a matter of record, I have 3-way active speakers driven by AKSA Lifeforce amps. And I happen to have a GK-1 preamp. My amplifier setup is conducive to hum and noise in the sense that I have 3 x LF modules plus an active XO (and 4 PSes) in the one box. (With a box behind each speaker.)

I get absolutely zero hum when listening to CD or tuner - even if you hold your ear 10cm away from each driver. So if you have hum or noise, it's because you built it wrong (or can't understand instructions) - not because Hugh's designs are defective.

If you live in or near Melbourne, by all means drop in and listen for yourself.

Regards,

Andy