Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: hylaphone on September 14, 2025, 08:40:45 am
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Hiya, I once had a schematic (which has since grown legs) of an amp from the 70's with an inductor based EQ along the lines of the SVT, but perhaps a few more bands?Does this ring a bell with anyone?
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Not a valve amp but some old Peavey solid state amps use inductors in the EQ section.
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Not a valve amp but some old Peavey solid state amps use inductors in the EQ section.
Thanks, but IIRC this was happening between a couple triodes. Pretty sure it was one of the big 70's amps (400PS, SVT, etc.) just can't remember for the life of me
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i spent hours look'n through Doug's porn collection, maybe you'll find that special TS :icon_biggrin:
https://el34world.com/charts/TubeAmpSchematics.htm
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It's not the 400PS.
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... Pretty sure it was one of the big 70's amps (400PS, SVT, etc.) just can't remember for the life of me
Ampeg SVT (https://el34world.com/charts/Schematics/files/Ampeg/Ampeg_SVT%20(1969-71,%206146%20tube).pdf)
Careful if you copy: coils like to pick up hum.
(EDIT: Sorry, this is wrong because it's not multi-frequency as requested.)
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Ah, I found it.Fender 300PSThanks
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Which is your interest on the equalizer ?
Years ago at DIYItalia a forumer developed an equalizer borrowed from SVT but without inductors, instead of inductors it used gyrators
If you have interest I can search the resulting schematic
Franco
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Which is your interest on the equalizer ?
Years ago at DIYItalia a forumer developed an equalizer borrowed from SVT but without inductors, instead of inductors it used gyrators
If you have interest I can search the resulting schematic
Franco
Thanks for the offer, got a fellow who wants inductor mid control for bass guitar. I remembered this Fender design as a simpler approach than the SVT, figured it was worth experimenting with.
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... got a fellow who wants inductor mid control for bass guitar. ...
Gibson had a Varitone (https://www.youtube.com/watch?v=bAKvmnDqz9k) that use inductors and caps, but it's worth seeing that like a Wah pedal: you can get a lot of Treble or a lot of Bass, though a lot of Mids is also sort of a lack of Treble/Bass. You also don't have control of "How Much."
If you use inductors, you need to fit them in a shielding box of some kind, tied to cable-shields for the internal wiring. Because that inductor will pick up hum & noise out of the air to add to the signal (which is the basis of hum-cancelling dummy-coils).
Of course, there are also pedals that do this: WahFul (https://www.fulltoneusa.com/products/wahfull) (where you also get to adjust the amount of mid-boost), graphic EQs (https://www.boss.info/us/products/ge-7/), parametric EQs (https://empresseffects.com/products/paraeq-mkii).
I'm sure the player believes he needs finger-tip control of the Mid. However, I bet after 1 gig he will pretty much know what sound he will want to kick on, and the need to have this mid-boost in the Bass itself will vanish.
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... got a fellow who wants inductor mid control for bass guitar. ...
I'm sure the player believes he needs finger-tip control of the Mid. However, I bet after 1 gig he will pretty much know what sound he will want to kick on, and the need to have this mid-boost in the Bass itself will vanish.
Sorry, I should have clarified - this is for a bass guitar preamp. I tacked it together today with parts I had on hand, it works really well.