Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on March 27, 2020, 08:39:56 am
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In my last build I would like to hook up a rotary
switch to act as a tone pot. It is a 6 position switch. I would leave the 6th one unconnected to have access to the original tone of the amp.
What would be the best way to achieve that ?
Thanx
Colas
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Without seeing a schematic it's hard to understand exactly what you want. But, take a look at page 2 of this pdf. Might give you some ideas...
http://sluckeyamps.com/VAC15/Vox_AC15.pdf
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There is also a different approach, option b instead of option a (Pot instead of Rotary Switch)
(https://i.imgur.com/1Kw5ibB.jpg)
Franco
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Very interesting indeed. No signal is sent to gnd in the vox nor in Kagliostro circuits.Now would this mod be more effective early in the circuit rather than late ? I have an idea in mind: since that rotary switch is stereo, placing it between the PI and the output tubes would improve or disminuish it s effectiveness ? The schem I don't have, but the preamp section is copied from the Marshall 2204 model, without the tone stack. It is my second 2204 since january. The first one is a bit less bright and more pleasant tonically, though the trannies are the same ( but the power tranny on this particular one which is a toroidal type from Avel Lindberg but with same voltages) this is why I d like to add a tone switch to adjust the brightness. I removed the 1000p cap accross the volume pot to give it a try but it changed the overall tone , though less bright. I put it back in place after. Same with the 470k bypass cap (470p).
Thanx buddies.
Colas
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The circuits below provide varying degrees of bass cut; sounds like your goal is variable treble cut?
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instead of PI to PA, might be better as part of your NFB, like a rotary presence control :dontknow:
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Yes, treble cut
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Shooter good idea, ( if there was a NFB :icon_biggrin: )
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You can implement one NFB with values that can affect tone and not the general function of the amp
(I think :icon_biggrin: )
Franco
p.s.: .... Treble Cut ...... :think1: ......
EDIT: I remembered !
(https://i.imgur.com/IgOsUvf.jpg)
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when I finally get to the point of building my own amp, I'm thinking of doing something similar with a pushbutton and rotary control.
Check out the schematic for the Selmer Zodiac tone control.
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..... with a pushbutton and rotary control
Or Rotary Switch + Rotary Control
(https://i.imgur.com/LNlh2Y1.png)
(https://i.imgur.com/64mDRKR.png)
other Selmer with Rotary Control
(https://i.imgur.com/w4LMHtP.jpg)
Franco
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just build this and be happy :icon_biggrin:
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Can't find it right now, but I could swear that Ted Weber's site had a schematic for a rotary SW for different tone caps, to match values for F, M & V tonestack values.
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ended up with the easiest one, 1m pot between the k and right after the first coupling cap. A bit more subtle that what I was expecting but it does the job right. Thanx Franco, you're my man ! :icon_biggrin:
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De Nada :icon_biggrin:
Franco
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Hey Shooter, I d sure be happy I am certain that EQ would be awesome , I might build it one of these days !
Thanx for sharing it
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:laugh:
I got it from Franco couple years back :icon_biggrin:
I'm not good enough to pull it off, but I keep lookin :laugh:
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Ciao Colas
I was talking with a friend of a different thing, and a council for you exit out
is a thing only to have a try, but may be you can be happy with it
instead of the 1M pot give a try to a 2.2M - 3M - 5M
reverse log, but you can try with a no reverse one and if happy, you can obtain the reverse log with the trick of the paralleled resistors, if you are not able to find a commercial one
http://www.geofex.com/article_folders/potsecrets/potscret.htm (http://www.geofex.com/article_folders/potsecrets/potscret.htm)
(https://i.imgur.com/74D5cym.gif)
Franco