[tangent]

Quote:

STACKING the buffers eg. 2 per socket, total 24. is this possible?

Yes, but due to the low output resistance, you should match the offset of your buffers so they don't get warm fighting against each other. Put them in a socket, measure the voltage drop from IN to OUT on each buffer and sort them by that drop. Then pair them up so that each pair is close to each other.

Quote:

how does one change the GAIN on the PPA?

R4.

 

[jtfoo]

I find the Bass boost on my PPA too overwhelming.. I'm using 68nF // 15nF for total 83nF for C7 and R7 is 100K..

I'm thinking of reducing R7 to 50K, how many dB boost will this give?

 

[PeterR]

about 15dB, 5dB less than now.

 

[tangent]

You might also consider increasing the value of C7. Even 220nF isn't unreasonable.

 

[jtfoo]

Quote:

Originally posted by PeterR about 15dB, 5dB less than now.

Thanks, I guess 5dB I should hear a significant reduction in bass boost?

Quote:

Originally posted by tangent You might also consider increasing the value of C7. Even 220nF isn't unreasonable.

Hi tangent,
Wouldn't increasing the value of C7 also increase the range of frequency to be boosted? How does this help?

 

[tangent]

Quote:

I guess 5dB I should hear a significant reduction in bass boost?

Yes.

Quote:

Wouldn't increasing the value of C7 also increase the range of frequency to be boosted?

My docs said that up until recently, but they were wrong. The higher the value of C7, the lower the corner frequency of the filter.

 

[jtfoo]

Quote:

Originally posted by tangent Yes. My docs said that up until recently, but they were wrong. The higher the value of C7, the lower the corner frequency of the filter.

Thanks for clarification, the last I read your tweak doc was sometime ago.. I'll try changing C7 first to maybe 0.1uF as I have plenty of these.

 

[ablaze]

hmm..is it normal for the amp to hum with no source connected, but for the hum to go away once a source is plugged in?

 

[Chipko]

Ablaze, yes, your input can act as an antenna when unconnected.

 

[eric343]

Quote:

Originally posted by ablaze hmm..is it normal for the amp to hum with no source connected, but for the hum to go away once a source is plugged in?

No. No properly working amp I've ever had has done this... Even my KGSS with its gain of 1000 doesn't do this.

 

[ppl]

if your amp is at min Volume no Hum should be present regardless of wether or not any input is connected. If the Volume is set at any higher than min. yes hum can get in via the input on poorly shieled input cables or twisted pair.

 

[ablaze]

the hum kicks in at about 50% of the max volume. I've already taken pains to twist the input cables. I think I"ll try to shorten it, its about 3cm long now.

 

[Voodoochile]

I don't see that effect at all, ablaze... not even with the bare PPA on the workbench. And that is saying something because there is a fluorescent fixture 3' above, and a computer monitor about 10" away. Nothing like hum to report.

My inputs are connected with some mini starquad.

 

[jtfoo]

Ablaze, a possibility could be your PSU. Try using a better one then the one from SLT. Or better use batteries.

 

[tangent]

Have you attached a ground strap to your pot, ablaze?