 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
84.66.73.106
In Reply to: Re: 0.001 caps posted by dickmc on April 17, 2005 at 10:26:41:
I would try option 1 first - if what the Mfg'r say is correct then no problem, but it might need option 2, but if thats the case im guessing you could get away with a lower value say 20-50pf. A good rule of thumb is to keep the bypass cap 1/100 or more of the value of the main C.The effect of .001uf caps would not be that much on your amp in terms of audio spectrum per se but it would start to roll off the higher freq >20kHz which would have an effect on the rise and fall times (slew rate) of the transient response. (But testing is the only real way to know for sure) -something not that heavly though about in those days, - it was also easier to sell an amp that had a gentle top treble roll off - as it sounded sweeter, bit like valve ones.
godd luck Chris.
Follow Ups:
do you even know what that circuit does?
I do have a good appreciation of what the circuit does.
however i assumed that the .001 caps would still be in the signal path when the drive limit transistors were off as the diodes were biased on asuming the voltages stated were at quesent levels, this would give a 3db/octave roll off -Was I wrong in this repect ?Arn't polystyrine caps inductive at high frequencies ?
"Was I wrong in this repect ?"The caps feed the speaker output through a 1K resistor, if they went to ground they would represent a load (but they don't).
The slew rate is determined largely by the current in the differential pair being able to charge and discharge the 15pF cap around TR05.
"do you even know what that circuit does?"Not in detail beyond TR01 other than driving the bases of output power transistors TR701 and TR705 in what I presume is some kind of following and error detection circuit. That's why I asked the question hoping for enlightenment (which Chris was quite helpful in capacitor type selection).
If someone knows "how" the middle works from TR03 through TR13, I would be most interested.
Chris doesn't even know what that circuit does, how can he recommend changing it?TR15, 17 are the foldback current limiter. Protects output stage from short circuits.
TR1, 03 are the differential pair and provide voltage gain, TR05 is the second voltage amplifier (also called the VAS) and provides most of the voltage gain for the amplifier.
TR07 is a current source, allows the voltage to swing negative.
TR09 bias transistor.
TR11, 13 are the driver transistors.
TR701, 705 are the outputs.
The drivers and outputs provide the current gain to drive the speakers.
The schematic has an error. R17 does not hook to ground, it hooks to the junction of R37 and ZD01.
and the type we need more of around here. Far too many people are offering advice without understanding. Are into the tubes too by any chance?
Russ
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
