BAF 2015 Coverage

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The one and only
Joined 2001
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Is there any stability issues due to phase shift with the transformer in the feedback loop? Maybe I should rephrase my question. If there was no stability issues with the current Jensen transformer used and if another was used in it's place could there be stability issues due to the resonance placed differently by the manufacturer? Will there be a need for possible compensation components?

I had that discussion yesterday with 6L6, as he's ready to start laying out
pcb's, and I noted that I need to check for the possibility of low frequency
motor-boating if the signal source has a capacitor in series. This could be
addressed by using a buffer with a DC output value, but possibly as easily by
adjustment of feedback impedance. No high frequency issues are anticipated.

Anyway, I'll report back after I fire one up and check.

:cool:
 
The one and only
Joined 2001
Paid Member
Regulated is nice, but not particularly essential. The PSRR is on the order of
40 dB, so if you want 100 uV of noise at the output, the supply needs less
than about 10 mV ripple. A quick sim shows that two 47000 uF separated
by .5 ohms for the RC filter will get you about 7 mV rms.

You can do more capacitance or resistance if you want.

:cool:
 
Regulated is nice, but not particularly essential. The PSRR is on the order of
40 dB, so if you want 100 uV of noise at the output, the supply needs less
than about 10 mV ripple. A quick sim shows that two 47000 uF separated
by .5 ohms for the RC filter will get you about 7 mV rms.

You can do more capacitance or resistance if you want.

:cool:

Thanks, papa. Exactly what I needed. The other parts are on the UPS truck today...;-)
 
I had that discussion yesterday with 6L6, as he's ready to start laying out
pcb's, and I noted that I need to check for the possibility of low frequency
motor-boating if the signal source has a capacitor in series. This could be
addressed by using a buffer with a DC output value, but possibly as easily by
adjustment of feedback impedance. No high frequency issues are anticipated.

Anyway, I'll report back after I fire one up and check.

:cool:

Ahhh yes LFO.........the chance of a capacitor in series with the input is probably pretty high since most sources and preamps will have an output capacitor.

The talk of PCB's being laid out is exciting!!

Thank you for all your work, there are some exciting things in the near future :)
 
I need to check for the possibility of low frequency
motor-boating if the signal source has a capacitor in series. This could be
addressed by using a buffer with a DC output value, but possibly as easily by
adjustment of feedback impedance. No high frequency issues are anticipated.

Anyway, I'll report back after I fire one up and check.

:cool:

Quite a few of us do not have source equipment with the output impedance you mentioned (eg B1 is 1k output impedance), will there be the option for a cascoded jfet buffer at the input on this amp for us poor souls (sought of like F6)?
 
Last edited:
Member
Joined 2009
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