[Soymilk]

gonna build my amp this weekend, but i'm not sure what gain to use. i was thinking something like 4? just thought it'd be nice to have a point of reference to start from instead of just shooting in the dark and then adjusting for my needs.

 

[TzeYang]

your source?

Most of the time, you don't need that much voltage gain. If you prefer lower volumes, stick with feedback free, unity gain configuration for the PPA buffers with AD744/AD829 in ground channel with compensation pin as output.

Sounds better and most importantly, cheaper

 

[MisterX]

I would go higher.


How high depends on what op-amps you plan on using.

 

[kramer5150]

Quote:

Originally Posted by MisterX /img/forum/go_quote.gif I would go higher. How high depends on what op-amps you plan on using.

Listen to this man...!! carefully. I ran my PPA at gain of 5.5. It sent my OPA637(L/R) into oscillation and it cooked my Yuin PK1, in 2-3 minutes

I came back to my listening room and they were hot and smelling kind of funky.

So, while I like the sound of the 637 better at times than the 627, I cant recommend using them at gains as low as mine. So I'm using the 627 in L/R/G instead, which isn't all together a downgrade (IMHO) Given my bright Grados and A250.

Gain of 5.5 is PLENTY with my 1-2 Volt sources and all my cans

 

[Soymilk]

my source is my computer, and i'll be using the opa627 with a 637 in ground.

 

[MisterX]

Quote:

i'll be using the opa637 with a 627 in ground

7 or higher for guaranteed stability

 

[Soymilk]

i'm confused, you switched the 627 and 637 in your post. isn't the 627 the one that's usually in the L and R positions since you don't need high gain for them to be stable?

 

[MisterX]

the OPA637 is not unity gain stable.
You cannot use it in the ground channel.

 

[Soymilk]

ah, i must've been interpreting stuff wrong this whole time then lol. i guess i'll try out the 637 L/R and 627 G config then with a gain of 7 to start. thanks for the heads up.

 

[Tomo]

Hey,

Kinda dumb, but I gotta tell you [G = 21] is too big even for 600 ohmers. You gotta stay lower than that. Otherwise you will regret it when you got high-grade CDP. Those CDPs line outputs > +-1V!!

Tomo

 

[Fitz]

Go as low as your volume requirements and opamps will allow. My amp (not a PPA) runs at a gain of 6.1, and it's more than enough to reach high volume with inefficient phones like the K340 and K240DF.

 

[Soymilk]

confused by tomo's post, did he come in to tell me a gain of 21 is too high?

 

[Tomo]

Quote:

Originally Posted by Soymilk /img/forum/go_quote.gif confused by tomo's post, did he come in to tell me a gain of 21 is too high?

Yep,

And I am a fool.

... but kinda nice to know the upper bound, right?

Oh crap, I forgot to say. I use G = 11 now. But it's kinda high-ish. So I think I can confirm Fitz's result.

Tomo