Aside from the: 'That sounds great test' What are the suggested steps in confirming the proper operation of a modified design tube amp? I'm not talking about a new concept design or the start up procedures., rather the completion of a modified existing circuit?
In short, to know the amp is properly designed as the concept established.
Testing the:
Pre amp section?
Power amp section?
Parameters such as:
Actual power output
The correct ratios of signal levels input to audio power out
Correct matching of the circuits
Suggestions greatly appreciated,
Ccat.
In short, to know the amp is properly designed as the concept established.
Testing the:
Pre amp section?
Power amp section?
Parameters such as:
Actual power output
The correct ratios of signal levels input to audio power out
Correct matching of the circuits
Suggestions greatly appreciated,
Ccat.
knowing what mods have been made and why would help determine what testing would be required.
unless this is something ultra secret or revolutionary that can't shared for reasons that can't be disclosed...
unless this is something ultra secret or revolutionary that can't shared for reasons that can't be disclosed...
What is the question? You want someone here to tell you if a modification to an amplifier was implemented correctly without A) giving us a schematic of the original design B) giving us a schematic with the proposed modifications.
I know there are some brilliant people on here but I don't know of any mind readers lol 😉
I know there are some brilliant people on here but I don't know of any mind readers lol 😉
I'll rephrase the question
Let me try it this way:
What standard practices, (tests) are employed to determine if an amplifier design is functioning properly?
Are there ultrasonic or RF frequencies present?
Is the harmonic distortion good or bad? ( I know some bad distortion will be obvious to the ear but is it distortion or some other design failure)
Perhaps it is only a matter of Sonics? Maybe there are no standards besides harmonic distortion determination. It's working and sounds good. Ship it!
There is nothing secrete about the amp. At this point I wanted to post a general question rather than a specific application example. That way I wouldn't have to ask the question each time I build an amp and want to know if it is working properly even though it may sound okay.
I also wonder if this should be moved to the tube amplifier section?
Ccat.
Let me try it this way:
What standard practices, (tests) are employed to determine if an amplifier design is functioning properly?
Are there ultrasonic or RF frequencies present?
Is the harmonic distortion good or bad? ( I know some bad distortion will be obvious to the ear but is it distortion or some other design failure)
Perhaps it is only a matter of Sonics? Maybe there are no standards besides harmonic distortion determination. It's working and sounds good. Ship it!
There is nothing secrete about the amp. At this point I wanted to post a general question rather than a specific application example. That way I wouldn't have to ask the question each time I build an amp and want to know if it is working properly even though it may sound okay.
I also wonder if this should be moved to the tube amplifier section?
Ccat.
Check that it delivers the expected output power without 'unusual behaviour', especially oscillation (audible or otherwise) and excessive crossover distortion. Plus a check for redplating, and there ain't much left where guitar amps are concerned. Thrash it for a while, and if it survives, presumably its OK.
Regarding Oscillations
I have a 20 mhz B&K dual channel as well as a 60 mhz Tek. I don't really use the Tek but could.
Where should I check for oscillations and what sort of settings regarding V/cm and Sweep times?
I saw a couple screen shots from another post, of waveforms with the hf on top of the wave so I believe I know what to look for.
This is all for future, perhaps tonight testing so I don't have anything under the knife yet.
Ccat.
I have a 20 mhz B&K dual channel as well as a 60 mhz Tek. I don't really use the Tek but could.
Where should I check for oscillations and what sort of settings regarding V/cm and Sweep times?
I saw a couple screen shots from another post, of waveforms with the hf on top of the wave so I believe I know what to look for.
This is all for future, perhaps tonight testing so I don't have anything under the knife yet.
Ccat.
I have just built up an amplifier that had oscillation on the output.
I tried changing the VAS capacitor and a feedback capacitor to get rid of it but it didn't.
I found I had to use base stopper resistors to slow down the waveform.
I tried changing the VAS capacitor and a feedback capacitor to get rid of it but it didn't.
I found I had to use base stopper resistors to slow down the waveform.
in checking for oscillations pump a 0.25 vpp square wave into it and monitor supply lines (b+ power) for any sign of signal appearing on what should be steady stable DC(like across the main supply filter caps) if nothing funny is happening at low frequencies increase the horizontal sweep to detect higher frequency "abnormalities".
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You put in a signal of known dimensions, load the amplifier and see what comes out.
What are you going to use for a load? I suggest a resistor. 8 ohms, must be capable of tolerating the expected output power. You can use the speaker, but I suggest a resistor.
You need something to examine the output. A scope, a computer with sound, at minimum a DMM.
You want to verify the clean output, not clipping, but turned up full. Now you know the gain, because you know the input level. An input signal is easy to make these days, using Audacity and a motherboard sound output.
Set the tone controls flat. Depending on your exact intent you should probably perform the measurement of power without either pre- or power-amp clipping.
Now you want to check that you can drive the preamp into distortion, and also, depending on intent, the power amp.
You should have some idea of the boost and/or cut of any tone controls at any given frequency, you can observe their operation on the scope too, but you might find it preferable to view the output on a computer screen using e.g. ARTA in spectrum analyser mode with white noise input or frequency sweep. You have to be careful not to blow up the sound input with too much voltage.
What are you going to use for a load? I suggest a resistor. 8 ohms, must be capable of tolerating the expected output power. You can use the speaker, but I suggest a resistor.
You need something to examine the output. A scope, a computer with sound, at minimum a DMM.
You want to verify the clean output, not clipping, but turned up full. Now you know the gain, because you know the input level. An input signal is easy to make these days, using Audacity and a motherboard sound output.
Set the tone controls flat. Depending on your exact intent you should probably perform the measurement of power without either pre- or power-amp clipping.
Now you want to check that you can drive the preamp into distortion, and also, depending on intent, the power amp.
You should have some idea of the boost and/or cut of any tone controls at any given frequency, you can observe their operation on the scope too, but you might find it preferable to view the output on a computer screen using e.g. ARTA in spectrum analyser mode with white noise input or frequency sweep. You have to be careful not to blow up the sound input with too much voltage.
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Very Timely
I just finished my build tonight and will have an opportunity to try some of these tests.
As it is I'm experiencing some problems and will post them on the topic already started here: http://www.diyaudio.com/forums/instruments-amps/265261-sunn-sceptre-style-build.html
Thanks for the schoolin so far...
Ccat.
I just finished my build tonight and will have an opportunity to try some of these tests.
As it is I'm experiencing some problems and will post them on the topic already started here: http://www.diyaudio.com/forums/instruments-amps/265261-sunn-sceptre-style-build.html
Thanks for the schoolin so far...
Ccat.
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