Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dude on May 30, 2014, 04:40:45 pm

Title: Might be the stupidest question on Neg Feedback
Post by: dude on May 30, 2014, 04:40:45 pm
Can you have a presence control on a cathode bias amp? 

Just that all the presence controls I ever seen were "fixed bias", I can' t imagine why not.

I have an extra face plate hole and since I'm converting this chassis to an 18 watt, 6V6 plexi style amp, I thought I'd put in a presence control.

Thanks as always,
al 
Title: Re: Might be the stupidest question on Neg Feedback
Post by: navdave on May 30, 2014, 04:51:44 pm
Yessir everyday and twice on Sunday

Quote from: dude on May 30, 2014, 04:40:45 pm
Can you have a presence control on a cathode bias amp? 

Just that all the presence controls I ever seen were "fixed bias", I can' t imagine why not.

I have an extra face plate hole and since I'm converting this chassis to an 18 watt, 6V6 plexi style amp, I thought I'd put in a presence control.

Thanks as always,
al
Title: Re: Might be the stupidest question on Neg Feedback
Post by: PRR on June 01, 2014, 10:36:36 pm
> all the presence controls I ever seen were "fixed bias", I can' t imagine why not.

You only get an extra knob on the highest price amps.

Cathode-bias is usually a low price amp.

Yes, you can add multiple input channels, tremolo, reverb, Mid, Master, and Presence to a 1-Watt KAY/Kent amp. But then it won't be $19.95.

As a general thing, jacks and knobs are $10 each on the final amp. (Not that a knob costs $10, but counting all the stuff the buyer can't directly see or understand, $10/knob is a good reference retail price for a box.)

Such an over-knobbed under-Watted thing may be very useful in bedroom or studio.
Title: Re: Might be the stupidest question on Neg Feedback
Post by: Gainzilla on June 04, 2014, 09:33:22 pm
Quote from: dude on May 30, 2014, 04:40:45 pm
Can you have a presence control on a cathode bias amp? 


Did you mean single-ended? If so, I think there are a couple examples of that. Fender Champ comes to mind. [size=78%]http://el34world.com/charts/Schematics/files/fender/Fender_champ_aa764_schem.pdf (http://el34world.com/charts/Schematics/files/fender/Fender_champ_aa764_schem.pdf)[/size]
Title: Re: Might be the stupidest question on Neg Feedback
Post by: dude on June 06, 2014, 04:07:38 pm
Quote from: Gainzilla on June 04, 2014, 09:33:22 pm
Quote from: dude on May 30, 2014, 04:40:45 pm
Can you have a presence control on a cathode bias amp? 


Did you mean single-ended? If so, I think there are a couple examples of that. Fender Champ comes to mind. [size=78%]http://el34world.com/charts/Schematics/files/fender/Fender_champ_aa764_schem.pdf (http://el34world.com/charts/Schematics/files/fender/Fender_champ_aa764_schem.pdf)[/size]

No, PP 18 watt 6V6 cathode bias. Only reason I put neg feedback in this conversion is the faceplate had an extra hole and since I was making a cathode bias plexi style amp, I though I'd put it in.

al