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PS - just like Uncle charlie is scared of EF3's , I'm scared of CFP's
But why be scared of CFP - the MOSFET likes to oscillate almost as much as the CFP does.
Hi BV,
Yes, the last one looks like it just adds too much to do with the boards I have. I will take a closer look later.
I have an issue with the boards right now. I have just been testing the IPS and with 475R load resistors installed and tied to the NFB, at +-70V rails I cannot get the VAS below 5.7mA, even with the 200R pots dialed all the way up. Which resistor(s) can I change to bring that down some? Measuring across the two 475R resistors I see 5.37Vdc. I need to be down around 4.7vdc I think.
Thanks, Terry
Yes, the last one looks like it just adds too much to do with the boards I have. I will take a closer look later.
I have an issue with the boards right now. I have just been testing the IPS and with 475R load resistors installed and tied to the NFB, at +-70V rails I cannot get the VAS below 5.7mA, even with the 200R pots dialed all the way up. Which resistor(s) can I change to bring that down some? Measuring across the two 475R resistors I see 5.37Vdc. I need to be down around 4.7vdc I think.
Thanks, Terry
Attachments
Increase R16 and R21 a little, say 160Ω or 180Ω any you could increase R6 and R11 if you need to, but that will affect the input pair current as well. The slightly higher current through the VAS shouldn't cause any real issue so long as you can adjust the OPS bias.
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I guess my concern with that is that I believe the CCS controls both VAS and the IP so if I max out the pots to reduce the VAS don't I take a chance of getting the IP too low?
Anyway, I hooked it up as is and was easily able to adjust output bias. I ran some square wave through it and it doesn't look good. I'm attaching screen shots. I did hook up both board and they look the same.
Anyway, I hooked it up as is and was easily able to adjust output bias. I ran some square wave through it and it doesn't look good. I'm attaching screen shots. I did hook up both board and they look the same.
Attachments
spooky
Ι haven't made any modification yet.
Instead of this ι decided to repeat listening tests.The same music track was repeated again and again.
Now i have clear image.
Spooky is so clear as Vssa but very-very powerful .
Two pairs musical ears have the same opinion about this.
Test at 28VRMS out Att 1:28
Ι haven't made any modification yet.
Instead of this ι decided to repeat listening tests.The same music track was repeated again and again.
Now i have clear image.
Spooky is so clear as Vssa but very-very powerful .
Two pairs musical ears have the same opinion about this.
Test at 28VRMS out Att 1:28
Attachments
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Square waves pictures looks simply like well damped overshoot (the same duration in all pictures), at inductive load and/or output inductor, or inductance (parasitic -e.g. wires between IPS and OPS) somewhere in circuit, SR is quite high (dU/dT). Try to place paralel to output inductor second resistor, 5-10ohm. If peak will decrese, it is clear. Amp wit lower SR will not show this behavior. Or increase input filter capacity.
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Not really that bad. No sustained oscillation ... raise Cdom(s) to 47p.
Bonsai's NX needed 47p to quench the "ring" (his nx pdf explains).
PS -The nx has the same ...but a "mono" MIC comp.
OS
Hi BV,
No idea what SR, dU/dT means. I took some more readings. I used both channels of the scope. Input is on the bottom, output on top. I took reading on the CFA-XH while I was at it. Both amps had an 8R 300w dummy load attached. Output was set at 10vac/1kHz.
One note, the Mod1 is way higher gain. I had to increase sensitivity on the scope two clicks the volts knob.
No idea what SR, dU/dT means. I took some more readings. I used both channels of the scope. Input is on the bottom, output on top. I took reading on the CFA-XH while I was at it. Both amps had an 8R 300w dummy load attached. Output was set at 10vac/1kHz.
One note, the Mod1 is way higher gain. I had to increase sensitivity on the scope two clicks the volts knob.
Attachments
Google always give me too much information. I'm dizzy before I get to what I need to know. My mind works in pictures. Until there is a picture in my mind, they are just words on a page.
So SR stands for slewrate?
To be honest, I don't understand what slew rate is or why it's important. Look at the screen shots above. If thats what Higher slew rate does. I'll pass.
So SR stands for slewrate?
To be honest, I don't understand what slew rate is or why it's important. Look at the screen shots above. If thats what Higher slew rate does. I'll pass.
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Terry,
One thing that is confusing me are the lower posted scope shots. Aren't they both of the same signal generator? If this is just the signal generator output why don't they look the same in both sets of measurements? I can see even without zooming in that the traces are different at the leading edge with what looks like a slight peak on the first set of traces.
Dv/Dt what this is saying Terry if I am no idiot is the rate of voltage rise over time. How fast the amplifier can produce a voltage rise vs the time to do it. Really a simple division problem. Voltage over time.
One thing that is confusing me are the lower posted scope shots. Aren't they both of the same signal generator? If this is just the signal generator output why don't they look the same in both sets of measurements? I can see even without zooming in that the traces are different at the leading edge with what looks like a slight peak on the first set of traces.
Dv/Dt what this is saying Terry if I am no idiot is the rate of voltage rise over time. How fast the amplifier can produce a voltage rise vs the time to do it. Really a simple division problem. Voltage over time.
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Terry,
dV/dt or more correctly ΔV/Δt, where the d refers the the Greek letter 'Delta' Δ, means 'a change in' or a 'difference in'. In this context, where we speak of Slew Rate (SR) we are talking about a given change in output voltage for a given change in time - x Volts change in y Seconds.
A high slew rate just means the amplifier can accurately follow the input signal and faithfully reproduce it. Generally an amplifier with a high slew rate tends to also have very little 'phase shift', the difference in time of arrival of the signal from input to output if you will, over not only the audio band but well beyond too. Some feel these things help improve / preserve the breadth and depth of the music's illusion of 'soundstage'.
Hey, this is the SlewMaster project, right?
dV/dt or more correctly ΔV/Δt, where the d refers the the Greek letter 'Delta' Δ, means 'a change in' or a 'difference in'. In this context, where we speak of Slew Rate (SR) we are talking about a given change in output voltage for a given change in time - x Volts change in y Seconds.
A high slew rate just means the amplifier can accurately follow the input signal and faithfully reproduce it. Generally an amplifier with a high slew rate tends to also have very little 'phase shift', the difference in time of arrival of the signal from input to output if you will, over not only the audio band but well beyond too. Some feel these things help improve / preserve the breadth and depth of the music's illusion of 'soundstage'.
Hey, this is the SlewMaster project, right?