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In Reply to: RE: Volume vs Gain posted by Tre' on August 11, 2015 at 13:03:49
Isn't it true that an AMP is generally FIXED gain while the VC simply acts to attenuate the INPUT signal to the amp? A VC acts as a simple voltage divider, right? So the amp simply adds its 'gain' to whatever the input voltage happens to be.
Too much is never enough
Follow Ups:
Exactly....generally.
In the end there are many ways to skin a cat.
I believe there are circuits where the "volume/gain" control changes circuit components around a stage that actually changes the gain of that stage vs. just simply attenuating the signal directly.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
My PSAudio integrated was billed as 'Variable Gain' and used proprietary input circuitry called 'Gain Cell'.
However, I believe this to be HYPE (No relation to HYPEX) since the amp used essentially unmodified B&O ICE Modules.
I know the INPUT section of my PARASOUND amps (A23) use an attenuator (100k, per Richard Schramm) which I'm DYING to replace with a 6 position Stepped Attenuator using 1% (or better) 1/4 watt film resistors. I believe the improvement will be small, but real over the carbon film pot used.
Too much is never enough
Let me know if the stepped attenuator improves sound quality from your Parasound Halo A23. I've got the Halo A21 and my attenuators are set about half way. If you get a noticeable improvement, I might just make a simple voltage divider from a couple of precision resistors. I don't really need a stepped attenuator.
Thanks,
John Elison
YOUR suggestion was my FIRST idea. But, no reason to sacrifice the feature.And from our FWIW department, Richard Schramm thought it was a decent idea and would result in a slight help. I'd say that YOU are in a better position to judge given that in my case the pot is OUT of the circuit since it is at 'max gain' position. However, I DO want to turn it down a few db so I'm up in the 'sweet spot' of the preamps gain range.
Since I don't have a schematic, I do NOT know if the controls is a single gang applied between the balanced/ single ended input AND the amp OR somehow they use a stereo version and use one section of the 'stereo' pot for balanced and the other for the single ended.
DO YOU KNOW?
I'd bet that both the '21 and '23 use the same system / circuit at that point.
PM me if you would like to SHARE? I could use some help should I decide to go with the 6 position GoldPoint switch. I think THAT would be where I'd like to 'land'..
I'd need help in resistor selection since I have no idea how to relate DB to resistance. All I know is that it should sum to the total of the current pot which I think is 100k if I remember correctly from my post to Richard……..
Now that I think about it, I don't need more than 9 db of TOTAL attenuation. That means I can turn it down 3db and have space on either side in just the switch I specified.
Too much is never enough
Edits: 08/12/15
I don't know what type of potentiometer is used. You would have to open it up and take a look -- possibly make some measurements. I guess you will need to figure that out before you buy a stepped attenuator. My system sounds real good with the stock potentiometers so I probably won't take my amp apart anytime soon. However, if you modify yours, I'll be interested to know what you discover.
Thanks,
John Elison
I won't do much of anything without 2 things.
First: a Schematic would be nice
Second: Figure What resistor net would give -1.5 db per step for 6 stepsI just had an Idea! I'm going to look at and download some interior photos. Maybe, if the pics are of sufficient resolution I can SEE the pot and at least see what Type it is.
A quick look at BOTH the '23 and the '21 shows a single gang, 3 wire 'pot' on each channel.
It is wired into a sub board with what LOOKS to be a few additional resistors. I can't tell.The next issue, due to the sub-board below each pot would be one of SPACE for which accomodations may need to be made.
As it turns out, the GOLDPOINT 24 step 'mono' attenuator is less expensive than the 6 position switch would be after adding resistors. the Stepper comes with 0.5% resistors and at the top to middle of the range features 2db steps. Perfectly fine. The KNOBS are expensive, though at 15$ to 19$ EACH. It is a non-standard (1/4"= standard) shaft size, so watch out.
If there is enough space, this would be the obvious way to go. At about 200$ per amp!
Too much is never enough
Edits: 08/13/15 08/13/15
I sent a note to Richard S requesting a schematic or just that part which shows the input circuitry.
Next step would be to open the case top and take a few measurements. See IF what I propose will FIT.
After that? If all goes well, I've got to RATIONALIZE about 200$ per amp in 'upgrades'.
Too much is never enough
That's a lot of money for a modification that might not sound any different than the stock potentiometer. Before I spent that kind of money, I would set the pots to the volume level you require. Then remove them and measure with an ohmmeter. Buy some quality resistors and install a cheap voltage divider. Leave one of your amplifiers stock and compare the sound quality.
My gut says it isn't worth $400 to modify two amplifiers but it might be worth installing simple voltage dividers. In other words, you might hear a slight difference but you might not be able to tell if it's better or worse, or just different. Moreover, even if you determine it to sound better, it might not sound enough better to justify spending $400. Of course, if it sounds significantly better and you want to install the stepped attenuators, then you've spend only a few extra dollars on the simple voltage dividers.
Good luck,
John Elison
But…….But……But…..
It's ONLY money!
I might add, in all honesty, that the divider was the recommended 'fix' IF I could decide on a single setting. I was also told to expect 'some' improvement.
Too much is never enough
Edits: 08/14/15
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