Hi,
I have a cheap pratice amp i sometimes use as a pre, I am going to try re voice it and chuck a few quality parts i have laying around in the signal path before i decide wether to get rid of it.
Just wondering if a basic tube fender twin passive treb/bass/mid tone would work on a ss amp that uses op's for pre gain and passive tone treb/bass/mid, or if the audio signal strengths in valve and ss differ to much?
also would the pot values have to be changed as well?
Ps. I plan on changing the 22 coupling caps as well, its just something to muck around with realy,
Ta
I have a cheap pratice amp i sometimes use as a pre, I am going to try re voice it and chuck a few quality parts i have laying around in the signal path before i decide wether to get rid of it.
Just wondering if a basic tube fender twin passive treb/bass/mid tone would work on a ss amp that uses op's for pre gain and passive tone treb/bass/mid, or if the audio signal strengths in valve and ss differ to much?
also would the pot values have to be changed as well?
Ps. I plan on changing the 22 coupling caps as well, its just something to muck around with realy,
Ta
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It would help to see the plan of the amp it is going into.
However.... just try it. It will probably work.
However.... just try it. It will probably work.
I'd use a high input impedance fet op amp buffer stage between the tone stack and ss amp.
Then there should be no issues.
https://upload.wikimedia.org/wikipe...r.svg/2000px-Op-Amp_Unity-Gain_Buffer.svg.png
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Hi Paul,
a cheap SS amp like this can be a ton of fun for DIY.
But you can get more bang for your soldering than replacing coupling caps value for value.
First you have to "de-nastify" it. Read the tube emulation & eq thread that is current on this site. That is one approach.
I have had several successes with small SS amps.
1st step: Reduce the band pass of the first opamp stage.
LT Spice shows the mg15 is (3dB) flat from 850 Hz to 100kHz. Nasty.
Make C4 a 1n cap and your -3dB band pass becomes 800Hz to only 12kHz. Still plenty for guitar work - could be reduced a lot more. Tune by ear.
a cheap SS amp like this can be a ton of fun for DIY.
But you can get more bang for your soldering than replacing coupling caps value for value.
First you have to "de-nastify" it. Read the tube emulation & eq thread that is current on this site. That is one approach.
I have had several successes with small SS amps.
1st step: Reduce the band pass of the first opamp stage.
LT Spice shows the mg15 is (3dB) flat from 850 Hz to 100kHz. Nasty.
Make C4 a 1n cap and your -3dB band pass becomes 800Hz to only 12kHz. Still plenty for guitar work - could be reduced a lot more. Tune by ear.
Is that really 850 Hz, or is it perhaps 85 Hz?
Guitar low "E" is between 82 and 83 Hz.
850 Hz is between 16th-fret G# and 17th fret "A" on the thinnest string, i.e., the vast majority of all notes playable on the guitar have fundamental frequencies below 850 Hz.
If bass cut off is really 850 Hz, the sound will be thin in the extreme, severely lacking all bass and body.
It is possible, though: I believe the Roland micro-cube is equally bad, with a lower cutoff frequency somewhere up around 1 kHz (!), higher than virtually every playable note on a normal 21 or 22 fret guitar in standard tuning!
I agree. Somewhat to my shock, I am having a hard time finding any good musical reason for more than 6 kHz bandwidth from any electric guitar, including electro-acoustics. Only unpleasantly harsh sounds seem to live up there.
-Gnobuddy
That is 850Hz according to LT Spice. 80Hz is 13dB down from 850Hz. Yes...nasty. Maybe ok for the OD part of the circuit but no bass or body when clean. Currently putting the rest of the circuit into the model.
Hope you are still with us Paul.
Here are some more caps to play with.
Increase C7 to 1uF for a 6dB increase on your Clean Channel bottom E.
Decrease C5 to 0.47uF so the extra bass is kept out of your OD channel.
C4 could be between 1n and 10n.
I suspect that these mods will also make the existing tone stack sound more responsive. (All suggested values came from LT spice sims.)
Here are some more caps to play with.
Increase C7 to 1uF for a 6dB increase on your Clean Channel bottom E.
Decrease C5 to 0.47uF so the extra bass is kept out of your OD channel.
C4 could be between 1n and 10n.
I suspect that these mods will also make the existing tone stack sound more responsive. (All suggested values came from LT spice sims.)
That amp HAS a "Fender Twin tonestack" IN it.
Except all the values are different, and not all the same ratio. (If it was same-ratio the response would be unchanged.) And a minor difference in how the MID pot comes in, which only matters at extreme. The result does not look "wrong".
I'm not sure if djgibson's 850Hz is a mis-reading of those cap values, or may be real. Some of those caps do seem awful shy, but I hate that notation and the sloppy labeling. 13dB down at 85Hz is heavy bass-shave but *may* be appropriate for a small g-amp working with a bass player. (Don't compete for boom; sing higher than the bass.) It won't be impressive playing alone.
Except all the values are different, and not all the same ratio. (If it was same-ratio the response would be unchanged.) And a minor difference in how the MID pot comes in, which only matters at extreme. The result does not look "wrong".
I'm not sure if djgibson's 850Hz is a mis-reading of those cap values, or may be real. Some of those caps do seem awful shy, but I hate that notation and the sloppy labeling. 13dB down at 85Hz is heavy bass-shave but *may* be appropriate for a small g-amp working with a bass player. (Don't compete for boom; sing higher than the bass.) It won't be impressive playing alone.
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