[OBF]

This may be a dumb question, but is there any easy way to increase the gain in the AKSA design if a person is using a passive pre and a low output CD player?  By "easy" I mean like changing a resistor or single part and not, of course, messing with the circuit design.

Thanks.

[gonefishin]

Hi OBF,

   While Hugh and others should be able to set you straight on the right path.

     Is this passive preamp a transformer based preamp?  If it is...do you have the 6db tap on the transformer attenuators?  It may be more desirable (if this extra db isn't needed all the time) to make use of the 6db increase from the transformers (via a switch) on those rare occasions that you need the extra db.  I'd look into this option as well...before making the amplifier circuit changes.

   something to think about until Hugh and others come along...

   dan

[AKSA]

You need to be careful here, OBF, because the gain settings of the AKSA have some influence on the sonics.

AKSA gain, both amps, is 38.3, or 31.6dB.  This is quite high for a power amplifier, around 50% higher than most amps in their category.  This was done deliberately to enable use with CD/DVD players and passive preamps, like the TLP.  You can vary gain down to around 28 and up to around 46 by changing the value of the feedback node resistor, presently 2K2.  3K gives a gain of 28.3, while 1K8 gives a gain of 46.5.  Within these limits, gain adjustment is acceptable, but much outside this and you threaten the sonics.

That must be a VERY low output CDP!!

Cheers,

Hugh

[OBF]

Dan and Hugh, thanks for the responses.

Yes, it is a TVC (Bent) and that's a good idea on using a switch because I'm guessing it would only be certain recording where I wouldn't have quite enough.  I had thought about the 6db boost but it's my understanding many people think it hurts the purity of the Bent and I wouldn't want that, but having the option to use it on occasion is another story.  The only downside is one more switch in the path but I don't imagine that's too big a deal.

Hugh, it's a .7v player I'm thinking of.  I know that's not outrageously low, but my current setup is approx 2v RMS, basically the standard, and with my inneficient speakers (84db) I think I would have problems dropping down to like 40% of my current gain.

At least I'm glad to know I have some options.  Possibly either the switchable transformer gain or bumping the AKSA up to 46 or a combo of both might solve the issue with little downside.

Thanks,

Mark

[gonefishin]

Hi OBF...I've also got the Bent NOH passive (which I do love...but will be replaced with a DEQX).  I've also wired in the 6db tap on a switch.  This way I can choose to use the "extra boost" or leave the transformer untouched.  Well, relatively untouched  As you mention there will be one additional switch in the pathway.
 
   While it  may be true that using the 6db of "free" gain does run the chance of degrading the sound.  You won't be using this option very often.  So it comes down to having one additional switch in the signal path during most regular play.  

    While minimizing your connections is always a good idea...this is one that may fit into your system.  Just remember to make good solder joints.  If the additional switch in the signal path is still bothering you...hardwire your interconnects directly to the AKSA board instead of using the extra rca connectors.  This way you will eliminate an additional two solder joints (per channel) and one mechanical connection (per channel) thru the female to male connection at the amp to interconnect.

    seems like a nice trade off

    hope you find something that works for ya....

     dan

[andyr]

Just to confirm Dan's comment that "removing a switch in the signal path" will deliver you a sonic benefit ... I recently introduced a switch into my Phantom Audio phono stage, as part of a "polarity-reversal" circuit.

When the polarity-reversal circuit was NOT in play, the output from the phono stage merely went through a switch.  Of course, when the switch was set the other way, the circuit was live and the signal polarity was reversed.

Comparing the sound from my phono stage with another identical one which didn't have the polarity-reversal circuit, revealed that this switch - even though it was the "highest quality" I could get hold of (a Nais relay, as used for selector switches in the GK-1R) - narrowed the sound stage significantly.  (The polarity-reversal circuit was not in play!)

After this test, I removed the polarity-reversal circuit (and the switch) from my phono stage!

Regards,

Andy