Is a long time I'm looking for documentation of commercial amps that uses a Tone Control after preamp pentodes (usually only a rotary switch with caps is used)
Recently I've find the Ampeg Duette Preamp schematic that uses a Treble + a Bass control after a 6SJ7
[img:5607:3967]http://i.imgur.com/nb1ShUd.jpg[/img]
here a description of the amp
http://www.ggjaguar.com/duette.htm
This configuration is indicated as an optional, but at the end I've find a commercial amp with such a configuration
I'm not able to find the schematic of the whole amp in which this preamp was used (as optional), someone has a link to the schematic ?
Many thanks for any info
Franco
Ampeg Duette Preamp ... which is the whole amp schematic ?
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Kagliostro
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Re: Ampeg Duette Preamp ... which is the whole amp schematic ?
I think that the key benefit in using a pentode pre-amp is for its high gain.
Unfortunately they have high output impedance, such that when trying to drive a medium impedance load such as tone controls, the gain would be reduced, perhaps to the point at which a regular triode may as well have been used.
Other Ampegs of that era all seem to have a very similar design of power amp, so it may be reasonable to assume that the Duette / Dolphin power amp and supply was also similar.
http://bmamps.com/Schematics/ampeg/Ampe ... ematic.pdf
http://bmamps.com/Schematics/ampeg/Ampe ... matics.pdf
http://bmamps.com/Schematics/ampeg/Ampe ... ematic.pdf
http://bmamps.com/Schematics/ampeg/Ampe ... ematic.pdf
Those with EL37 power tubes all seem to use an OC3 dropper for the screen grid supply, perhaps to ensure that their 400V limit is not breached.
Unfortunately they have high output impedance, such that when trying to drive a medium impedance load such as tone controls, the gain would be reduced, perhaps to the point at which a regular triode may as well have been used.
Other Ampegs of that era all seem to have a very similar design of power amp, so it may be reasonable to assume that the Duette / Dolphin power amp and supply was also similar.
http://bmamps.com/Schematics/ampeg/Ampe ... ematic.pdf
http://bmamps.com/Schematics/ampeg/Ampe ... matics.pdf
http://bmamps.com/Schematics/ampeg/Ampe ... ematic.pdf
http://bmamps.com/Schematics/ampeg/Ampe ... ematic.pdf
Those with EL37 power tubes all seem to use an OC3 dropper for the screen grid supply, perhaps to ensure that their 400V limit is not breached.
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Stevem
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M
A pentode preamp can be set up to add compression / sustane without clipping to a much larger degree then a triode which is a nice trate to work with!
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Kagliostro
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Re: Ampeg Duette Preamp ... which is the whole amp schematic ?
Many thanks for answering and for the link of the schematics
Franco
Franco