Problem with Aksa Gk-1 preamp driving a Gainclone (LM3875)

vsr123 · « **on:** 13 Apr 2004, 06:31 am »

Folks,
Can anyone tell me what is going on?
I put the Gainclone kit (http://www.diyaudio.com/forums/showthread.php?s=&postid=370452#post370452)
together with a 25+25 Toroid, tested all the voltages, etc and -
went from A Marantz 63se (with in built volume control) to the Gainclone amp to speakers. Sounds very good, but extremely loud to the point that I cannot go above 3 levels on the Marantz....way too loud.
I then went from the CD player to an Aksa GK-1 preamp and then to the Gainclone, the aksa at almost full volume and the CD player at half volume, I can barely hear anything

I then went from the CD -> GK-1-> Aleph 3 and it sounds just fine, so I know that there is nothing wrong with the GK-1.

Is this something to do with input/output impedance matching? what is wrong here? I initially thought of using the GK-1 as a volume control/pre-amp, but I am wondering if it is useable now?

thanks
vsr

andyr · « **Reply #1 on:** 13 Apr 2004, 08:27 am »

Hi vsr123,

You have dropped a few names in your post but haven't explicitly said, for instance, what a Gainclone is ... so we may not be able to help you much. However:

A. You said " ... then went from the CD --> GK-1--> Aleph 3 and it sounds just fine, so I know that there is nothing wrong with the GK-1."

B. You also said "I initially thought of using the GK-1 as a volume control/pre-amp, but I am wondering if it is useable now?"

With A, above, you've just proved to yourself that you have a fine system: source --> source selection & vol control (ie. pre-amp) --> power amp --> speakers.

The GK-1 *IS* the pre-amp ... just as you surmised in B.

Regards,

Andy

AKSA · « **Reply #2 on:** 13 Apr 2004, 12:22 pm »

I'm pretty sure the Gainclone is only 10K input impedance. The GK-1 should drive this OK, but not brilliantly, it really prefers driving around 20K input impedance, which is just about any hifi amp in the market.

I will have a gander at the GC and get back to you.

Cheers,

Hugh

AKSA · « **Reply #3 on:** 13 Apr 2004, 12:31 pm »

I've looked at the design, and as far as I can tell Zin is around 20K, a shade under 22K.

It's a conventional power opamp design with the LM3875, and I can't see any reason why the GK1 can't drive it.

Have you checked signal ground connects between the GK1 and the GC? With everything switched off, check continuity from ground GK1 output to ground GC input; the DMM should buzz.

Sometimes these things can be a faulty RCA, or connector socket. Check them for continuity. This should work, and work well.

Hope this is helpful,

Cheers,

Hugh

vsr123 · « **Reply #4 on:** 13 Apr 2004, 03:43 pm »

...loose connection from the CD player out...i feel silly.

Greg Erskine · « **Reply #5 on:** 14 Apr 2004, 04:01 am »

Just adding my two cents worth.

I've recently built a BrianGT GC using premimum components and it was supplied with a 22.1k resistor across the input.

I been using my Aspen TLP for the pre-amp and it works like a charm.

BTW: Although this GC sounds pretty good, it still not as good as my AKSA 55.

Malcolm Fear · « **Reply #6 on:** 14 Apr 2004, 01:30 pm »

Hi Greg

Toni and I are roaming USA.
If your problem is not solved in a couple of weeks, why not bring the GK-1 and Gainclone over to my place. Perhaps there is something silly in your GK-1.

regards