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Maya gain

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#2
Hi PK,
Thanks for the post - answer is a partial yes.
You increase the feedback shunt 120R resistor to 180R.
The gain drops from (3300+120)/120 to (3300+180)/180 which is 17.66,
or 24.94dB, a bit lower than normal gain of 29.1dB.
To reduce it further you need to re-compensate the amp with is doable but tricky.
Cheers
Hugh
 
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#4
It sits directly above the 100uF shunt cap C17 at the bottom center of the PCB. It is designated R17. On V4.23 fb shunt is written above the resistor.
Yes changing gain does effect feedback and feedback affects amp stability you want to avoid at any cost! It should minimally affect the sound quality.
Hugh
 
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#5
Wouldn't it be more simple to add a voltage divider using 2 resistors before the power amp input. The values would need consideration not to effect the Zin too much. That way the amp is left stock as designed.

I had to do this a couple of times. Bi-amping with power amps with different gains. A pre amp with a stupidly high gain which meant the volume pot gave very little control with 9 o'clock being at very loud volume so fine adjustment was impossible.

I don't know what the OP problem is with high SPL speakers but I suspect it could be control of the volume pot operating over a small range.
 
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#7
rabbitz said:
Wouldn't it be more simple to add a voltage divider using 2 resistors before the power amp input. The values would need consideration not to effect the Zin too much. That way the amp is left stock as designed.

I had to do this a couple of times. Bi-amping with power amps with different gains. A pre amp with a stupidly high gain which meant the volume pot gave very little control with 9 o'clock being at very loud volume so fine adjustment was impossible.

I don't know what the OP problem is with high SPL speakers but I suspect it could be control of the volume pot operating over a small range.
Click to expand...

My dac has a low output signal, so the problem is not really the volume range, but rather the gain mismatch between preamp, Maya and speakers. The slight hiss from the pre is amplified too much by the Maya into the speakers. On a normal speaker I wouldn't have had any issues.

I tried with Rothwell plugs. It removes the hiss, but somehow I find that they make the sound flatter 🤔
 
#8
AKSA said:
It sits directly above the 100uF shunt cap C17 at the bottom center of the PCB. It is designated R17. On V4.23 fb shunt is written above the resistor.
Yes changing gain does effect feedback and feedback affects amp stability you want to avoid at any cost! It should minimally affect the sound quality.
Hugh
Click to expand...

Thanks. I'm leaning towards keeping the Maya intact instead of trying to modify it.
 
#9
Painkiller said:
I tried with Rothwell plugs. It removes the hiss, but somehow I find that they make the sound flatter 🤔
Click to expand...
Yes that can certainly happen and I've experienced that with some (impedance mismatch?). I had a pre with a fixed and variable output via a 1K pot which was detrimental the sound but OK for sub duty. Ended up building a pre with no gain and problem solved. These days I use a commercial integrated amp with 0dB gain in the pre section and 31dB in the power amp so no noise but my speakers are only 86dB.

Now I understand your problem and hope you find a solution.
 
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#10
With 86 dB speakers I would certainly have no issues. Things start getting scary at 110 dB/W. Any hum or noise from the preamp can get really really loud. Even the warmup crackling noises from the tubes can be mind numbingly loud.

I am thinking a cathode follower pre with 0 gain could work pretty good. But a power amp with less gain would be preferable. Then, if something malfunctions further up the chain it wouldn't be amplified 30x into the speakers.
 
#11
Yes Jørgen, high efficiency speakers, over 105dB/watt/metre, are a pain to work with because of issues with gain and hum.
I have never much appreciated them; they tend to be peaky, often use horns which I find a bit honky, and can also be bandwidth limited.
But for small power tube amplifiers they are common but sound pretty good on tube amps. On a SS amp I like my speakers around 90dB/watt/metre and design them for this sensitivity.

You can put in a resistive divider at the input, but you have to use very good resistors. A couple of 5k resistors in series would give the source 10k impedance and cut your 'gain' by 6dB. Add the 4dB from changing the shunt resistor, and you have a 10dB reduction, worthwhile in fact!

Hugh
 
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#12
When you say a couple 5k resistors, do you mean a voltage divider with 5k series plus 5k to ground? Or just 10k series resistance?

I understand that the Maya is not really designed for my speakers. But it's always been sounding so sweet. Still sounds better to me than my friend's 10k USD integrated amp. I have never had any problems with hum, but my new tube preamp gives some hiss. White noise. I do have horn speakers, but they are short horns so they are not honky. The drivers are very sensitive tho. Crossovers are tuned to perfectly flat response to 22kHz.
 
#17
Here it is, R14, a smd resistor of 120R.
1738550908090.png
Just above C4, which is to the right of C8 and directly on top of R13.
Ignore the arrow, that is the nested feedback resistor!
Cheers,
Hugh
 
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