[morsel]

A volume control spans from maximum gain to zero volume. A gain control spans from maximum gain to unity gain. Most of the range of a volume control is below unity gain, so a gain control is no substitute.

 

[Super-Gonzo]

Quote:

Originally Posted by morsel A volume control spans from maximum gain to zero volume. A gain control spans from maximum gain to unity gain. Most of the range of a volume control is below unity gain, so a gain control is no substitute.

This being the case, what is it exactly that psAudio is doing with their "Gain control" amplifiers?

 

[Super-Gonzo]

Quote:

Originally Posted by amb Super-Gonzo, the variable-gain method as described on my site does not allow you to completely mute the audio...

AMB, given a variable gain with a wide range, say 2-17 as mentioned on your site, what capacity caps would you reccomend for C1L and C1R (given the default ad8610 opamp)?

 

[z2trillion]

Quote:

Originally Posted by Super-Gonzo This being the case, what is it exactly that psAudio is doing with their "Gain control" amplifiers?

Might they be using the opamp in an inverting mode, this would allow them to acheive below unity gains. Just a guess.

 

[amb]

Quote:

Originally Posted by Super-Gonzo AMB, given a variable gain with a wide range, say 2-17 as mentioned on your site, what capacity caps would you reccomend for C1L and C1R (given the default ad8610 opamp)?

You can use the default of 33pF, or to be extra conservative, go to 47pF. The latter will ensure that the square wave response to be ring-free, at the expense of slightly reduced bandwidth (but will still be far beyond the audio spectrum).

Quote:

This being the case, what is it exactly that psAudio is doing with their "Gain control" amplifiers?

Without seeing a schematic diagram I don't know. Their marketing blurb on the "Gain Cell" is pure hogwash, because there is no way to program the gain of an amplifier without varying some sort of resistance.

 

[Super-Gonzo]

Thanks for the advice!

 

[skyskraper]

gotten most of my M³ done. a minor pita was the fact that i could only get 3w resistors locally (didnt want to risk 1w), theyre bigger then the board gives space for and the ceramic caps i got were a bit bigger then the board has space for. a minor annoyance forsaking only neatness

you can see here

but here's where my M³ is up to atm:

just waiting on some self tapping screws, panduit crimper, and pcb jumpers, all to be brought home by housemate from work, before i get stuck in to setting the thing up

 

[morsel]

Don't use electrolytic caps instead of metallized film for C2 & C8.

Why not mail order the correct parts instead? At least use the same yellow films as C6.

 

[individual6891]

Would 1W be ok in that position morsel?

 

[morsel]

P = IV = I²R = V²/R

for R=1, P = I² = V²

That makes it easy to calculate power dissipated by the output resistor.

You can get away with 1W output resistors if you are using high impedance or high efficiency headphones, but I would not want to limit my amp that way.

edit: 1W is OK for most headphones, but it is nice to have some headroom. To keep the resistor at a reasonable temperature it should be running at no more than 1/2 rated power.

 

[skyskraper]

morsel: theyre bipolars and theyre temporary until the proper caps arrive in a week or so

for 20c each its no skin off my noce

 

[MisterX]

New case plus a condor Power-One PSU.
Needless to say the hammond case (with the fan) went right in the trash.

 

[phobus]

WOW!!! More pics!!

 

[pabbi1]

Nice... where did you get the case?

 

[MisterX]

lol.... That case was a adventure to say the least.
It came from Ebay.
It was like $50 and shipping from Thailand was also $50.

(the same case retails for like $170 here in the US)
But there was a major catch.
It was 16" long when I got it so I busted out the Dremel and cut the top in half.

I think the results were worth the effort.