Re: BA output caps
Posted: Sun Nov 08, 2009 12:10 am
you are suggesting a 5k resistor in series with the BA output? I'll try it...
I'd be delighted to get away from large expensive polyprop valve hifi caps for low volt circuits like the BA but i just need to know what to try instead... I'll see what I can find in line with your suggestions.
the claritycap SA is not extreme high end, the 4.7uF only costs around £5, which is as much as I am willing to spend on a cap... but its generally regarded as very good sound for the price.. it is bulky though, and unnecessarily high voltage at 630V. it was certainly an big improvement on the polyesters and the small polyprops I had for guitar amps. I haven't compared it with its immediate competitors. I have some russian paper caps which are nearly as good. (and some other russian paper caps which are totally coloured!)
my valve pres should have an output Z in the low hundreds of ohms, my own design has a 12at7 or 12av7 parallel cathode follower for output, and that is inside a global nfb loop which should lower the output z further, the mila uses a parallel 12av7 plate loaded stage which is also low Z, the one bottle is higher z out, and that may be the cause of my reservations about it, I will probably convert those to two bottles.
yep we were misunderstanding each other about the -out cap, i was talking about the -out cap you thought i meant something else...
and another misunderstanding - i wasnt talking about the bandwidth cap either, but the main output cap, for which I am/was looking to substitute a film type
about keeping the rolloff point below 5hz, 4.7uF into 10k gives 3.4hz doesn't it?, unless the output impedance of the preceding stage is affecting it... how do I calculate that?
I'd be delighted to get away from large expensive polyprop valve hifi caps for low volt circuits like the BA but i just need to know what to try instead... I'll see what I can find in line with your suggestions.
the claritycap SA is not extreme high end, the 4.7uF only costs around £5, which is as much as I am willing to spend on a cap... but its generally regarded as very good sound for the price.. it is bulky though, and unnecessarily high voltage at 630V. it was certainly an big improvement on the polyesters and the small polyprops I had for guitar amps. I haven't compared it with its immediate competitors. I have some russian paper caps which are nearly as good. (and some other russian paper caps which are totally coloured!)
my valve pres should have an output Z in the low hundreds of ohms, my own design has a 12at7 or 12av7 parallel cathode follower for output, and that is inside a global nfb loop which should lower the output z further, the mila uses a parallel 12av7 plate loaded stage which is also low Z, the one bottle is higher z out, and that may be the cause of my reservations about it, I will probably convert those to two bottles.
yep we were misunderstanding each other about the -out cap, i was talking about the -out cap you thought i meant something else...
and another misunderstanding - i wasnt talking about the bandwidth cap either, but the main output cap, for which I am/was looking to substitute a film type
about keeping the rolloff point below 5hz, 4.7uF into 10k gives 3.4hz doesn't it?, unless the output impedance of the preceding stage is affecting it... how do I calculate that?