N&P channel mismatch
Hi Mr. Pass,
This was on the J2 thread but thought I'd ask here for the sake of relevance. Were you referring to trimming R11/R12? As for the 2nd part is my sketch correct? Not that I have anything to analyze with but perhaps I'll look for something on eBay if it seems worthwhile.
Hi Mr. Pass,
This was on the J2 thread but thought I'd ask here for the sake of relevance. Were you referring to trimming R11/R12? As for the 2nd part is my sketch correct? Not that I have anything to analyze with but perhaps I'll look for something on eBay if it seems worthwhile.
Attachments
Ok, though it was aimed at the humming speaker. Did you check that? No I didin't. But good tip.
? and Nothing wrong there What I mean here is I raised the offset since, if set to zero, it would cycle between +4mv and -4mv. Raise it to 8 or 10 and it stays zero or above. As a novice, I take things literal.
Maybe not. Did you check your signal wires, and ensured that they are away from supply lines.Yes. And shielded.
RubbersDidn't have any. Used speaker dampening stuff. And loosened it. Did reduce the amplification of the buzzing but it still buzzed.
Have all the resistors in a new board. Add the rest of the parts tonight. Test tomorrow to see if I had one problem. Thanks for all your input.
Q: Is transformer buzzing alright if I can isolate it and make it inaudible?
? and Nothing wrong there What I mean here is I raised the offset since, if set to zero, it would cycle between +4mv and -4mv. Raise it to 8 or 10 and it stays zero or above. As a novice, I take things literal.
Maybe not. Did you check your signal wires, and ensured that they are away from supply lines.Yes. And shielded.
RubbersDidn't have any.
Used speaker dampening stuff. And loosened it. Did reduce the amplification of the buzzing but it still buzzed. Have all the resistors in a new board. Add the rest of the parts tonight. Test tomorrow to see if I had one problem. Thanks for all your input.
Q: Is transformer buzzing alright if I can isolate it and make it inaudible?
Ok, though it was aimed at the humming speaker. Did you check that? No I didin't. But good tip.
? and Nothing wrong there What I mean here is I raised the offset since, if set to zero, it would cycle between +4mv and -4mv. Raise it to 8 or 10 and it stays zero or above. As a novice, I take things literal.
Maybe not. Did you check your signal wires, and ensured that they are away from supply lines.Yes. And shielded.
RubbersDidn't have any.
Have all the resistors in a new board. Add the rest of the parts tonight. Test tomorrow to see if I had one problem. Thanks for all your input.
Q: Is transformer buzzing alright if I can isolate it and make it inaudible?
Scranton, My F5 trannies have a tiny buzz to them, but it's not audible through the speakers, only if your standing a foot or so away from it.
adjustments
Hi Mr. Pass,
Thanks for the reply.
Just to confirm, you are referring to R11&R12=0.47ohm 3watt source resistors, right? It does seem that it would be difficult to adjust this value.
While on this subject, on the last page of the F5 manual it says:
"If you have the equipment to see it, you may find that different gain devices will give you a small peak somewhere just below 1MHz. I have found that you can trim this by playing with the values of R13 and R14, but as both values approach 0 ohms, you are likely to see parasitic oscillations."
Is this also doing the same thing as the afore mentioned adjustments? It continues:
"You can additionally limit frequency response with an input capacitor across R10, and also in the feedback loop with capacitance across R5 and/or R8."
Approximately what value caps are we talking here? I've read this whole thread and I don't recall anyone mentioning that they did this. If anyone has, please comment. The only thing said about adjustments was Than1971 in a post about fiddling with R1 & R2 to increase/decrease 2nd/3rd harmonic.
Garrett
I meant the 3 watt resistors on the Sources of the power
Mosfets going to the supply rails.
And yes, your drawing would be correct.
Either approach works - the pot is more convenient.
Hi Mr. Pass,
Thanks for the reply.
Just to confirm, you are referring to R11&R12=0.47ohm 3watt source resistors, right? It does seem that it would be difficult to adjust this value.
While on this subject, on the last page of the F5 manual it says:
"If you have the equipment to see it, you may find that different gain devices will give you a small peak somewhere just below 1MHz. I have found that you can trim this by playing with the values of R13 and R14, but as both values approach 0 ohms, you are likely to see parasitic oscillations."
Is this also doing the same thing as the afore mentioned adjustments? It continues:
"You can additionally limit frequency response with an input capacitor across R10, and also in the feedback loop with capacitance across R5 and/or R8."
Approximately what value caps are we talking here? I've read this whole thread and I don't recall anyone mentioning that they did this. If anyone has, please comment. The only thing said about adjustments was Than1971 in a post about fiddling with R1 & R2 to increase/decrease 2nd/3rd harmonic.
Garrett
my Naim amps did this quite frequently.
i placed an order for a 18+18 500VA TX from SumR. the other TX i have from Richard is dead quiet. not terribly expensive at $98 either. the PS will be in a separate chassis a la Naim for possible future Pass recipes. i've opted not to go down the bridged amp route for now - it's time i started playing around with FR drivers.
heatsinks arrived today too!
no. $130 total for an encapsulated/shielded, plus shipping is $26 to MN. i had Richard pot my other TX for a B22 headphone amp/preamp that some builders have had noise problems with. although the non-potted version does have a "banded shielded core" to help absorb some EMI. lead time is 1 wk or so.
I'm still debating with myself about getting another 300VA Plitron to make mono blocks or getting 500-600VA transformer for a stereo amp. I noticed the SUMR transformers don't regulate quite the same as Plitron. Not sure if this would affect anything. Just want to be sure to get proper secondary voltages so everything is running in the sweet spot.
build two completely separate monoblock power amplifiers.
Locate each immediately behind the speaker terminals with very short speaker cable.
P1/r3
Thanks for the reply.
One other thing that I have been wondering about is the P1/R3 portion of the circuit (the 2.2K paralleled with the 5K trim pot). Why not just use a 1.5K trim pot and save the resistor?
Garrett
If you have a scope and/or distortion analyzer, then you
can play with this. Try different values, starting with values
close to the stock values and see what you get.
Thanks for the reply.
One other thing that I have been wondering about is the P1/R3 portion of the circuit (the 2.2K paralleled with the 5K trim pot). Why not just use a 1.5K trim pot and save the resistor?
Garrett
I don't know for sure, but one benefit might be to prevent mass destruction if the pot goes open for some reason.
Yes, but also it allows you to fine tune it so you can adjust by tiny amounts to get your DC offfset to almost zero
Fran
Banned
Joined 2002
switchmod on a class a ? are you crazy ? way to much work way to much noise. Not worth it at all. Toroidial transformer caps etc etc