Finally testing my F5T-Channels 
, everything looks good so far .
Setup: 33V rails, 3x IRFP9140 + 3x IRFP240, CLC with 141mF/1mH; 0,5 Ohms Resistors, 9,8mA Jfets, Bias 2 Amps.
When fed with a square wave, the output voltage does overshoot a bit, at least more than depicted in the F5T article. Could this be related to the use of IRF-devices instead of Fairchild ? I couldn´t get FQAs anywhere.
The overshoot could be trimmed a bit by changing P3, but this also changed the straightness of the rest of the positive/negative output signal.
If anyone has an idea on this, i would be grateful to hear.
Can´t wait to listen to the F5T - have to do the enclosure still - especially as to how it compares to my A75.
Greetings
norb
, everything looks good so far .Setup: 33V rails, 3x IRFP9140 + 3x IRFP240, CLC with 141mF/1mH; 0,5 Ohms Resistors, 9,8mA Jfets, Bias 2 Amps.
When fed with a square wave, the output voltage does overshoot a bit, at least more than depicted in the F5T article. Could this be related to the use of IRF-devices instead of Fairchild ? I couldn´t get FQAs anywhere.
The overshoot could be trimmed a bit by changing P3, but this also changed the straightness of the rest of the positive/negative output signal.
If anyone has an idea on this, i would be grateful to hear.
Can´t wait to listen to the F5T - have to do the enclosure still - especially as to how it compares to my A75.
Greetings
norb
Attachments
For the standard F5 Turbo V1 (no diodes or whatsoever, just higher rail voltage + 2 output pairs), is it ok to go for 0,5V voltage drop around the source resistors (as in standard F5T papers, 2 1R 3W Resistors, so 0,5R total) to go for a total of 2A bias per channel? Or should I exchange the source resistors to, lets say 0,68R and thus decrease the voltage drop?
Regards,
Fabian
Regards,
Fabian
Finally testing my F5T-Channels
Setup: 33V rails, 3x IRFP9140 + 3x IRFP240, CLC with 141mF/1mH; 0,5 Ohms Resistors, 9,8mA Jfets, Bias 2 Amps.
When fed with a square wave, the output voltage does overshoot a bit, at least more than depicted in the F5T article. Could this be related to the use of IRF-devices instead of Fairchild ? I couldn´t get FQAs anywhere.
The overshoot could be trimmed a bit by changing P3, but this also changed the straightness of the rest of the positive/negative output signal.
If anyone has an idea on this, i would be grateful to hear.
Can´t wait to listen to the F5T - have to do the enclosure still - especially as to how it compares to my A75.
Greetings
norb
Putting a 1000pF to 2000pF cap across the feedback resistors will fix the overshoot.
You can also change the value of the input resistor.
yes. 1A pr device is no problem with +/-32V rails. thats 32W dissipation pr fet.
Hi there.
Any ideas on how to implement a "leaving class A" indicator with a LED for example, for the F5 turbo?
As far as I know, the vumeter on the Pass Labs amplifiers are not really vumeters but act as indicators (when the niddle moves) that the amplifier is leaving class A operation and entering into class B.
Is there a relatively easy way to implement something like this but with a LED acting as this indicator? i.e. that the led starts to light when leaving class A operation?
Any ideas on how to implement a "leaving class A" indicator with a LED for example, for the F5 turbo?
As far as I know, the vumeter on the Pass Labs amplifiers are not really vumeters but act as indicators (when the niddle moves) that the amplifier is leaving class A operation and entering into class B.
Is there a relatively easy way to implement something like this but with a LED acting as this indicator? i.e. that the led starts to light when leaving class A operation?
You will probably only want one indicator.
Take a look at the original F5 circuit, delete R21 & R22, disconnect the collectors of Q5 & Q6 and add an LED and resistor in series with each, connect the other end of the LED/resistor string to 0V, adjust the attenuator (R17 R19 & R18 R20) to suit your bias level ie. Turbo values 1A & 0.5R, leave class A at 2A (x 0.5R = 1V), with R17 & R18 = 1K, R19 & R20 = 2K that should put you somewhere in the ball park.
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advice required
hello
I am at an early a f5t build, trying to see how the components will arrange internally. the heat sinks in use are quite deep, so width is a little limited (they were a donation so felt compelled to use them) however gained a bit on usual case height.
The photos depict the space available, also I have blue tacked some jar lids! to indicate were inductors may be placed .
I have a couple of concerns.
1, the co-location of the output devices to the transformers, currently a 30mm gap.
2, is this an acceptable location for the inductors.
Would really appreciate some opinions
regards
hello
I am at an early a f5t build, trying to see how the components will arrange internally. the heat sinks in use are quite deep, so width is a little limited (they were a donation so felt compelled to use them) however gained a bit on usual case height.
The photos depict the space available, also I have blue tacked some jar lids! to indicate were inductors may be placed .
I have a couple of concerns.
1, the co-location of the output devices to the transformers, currently a 30mm gap.
2, is this an acceptable location for the inductors.
Would really appreciate some opinions
regards
Thanks for your concerns.
Bourns manufacture a pot with side entry, this will allow vertical access to P1 & P2. P3 legs can extended and turned through 90deg for same access, not pretty but a fix. The bourns pot adjusting tool is plastic and the tool for the job, but will still take heed of your advice when dealing with live power supplies.