Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TerryD on June 30, 2012, 09:27:45 pm
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I bought me a Stinger/Texas Tornado. Actually quite a good clone...with an added midrange controll. Has a ceramic speaker, point to point, great great parts all around. This is actually 001, the prototype.
Any normal mods to make an already good jazz amp (A.K.A. the Delux reverb) into a better one?
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The best thing I can think of is adjustable NFB. I haven't seen the amp, but it probably has less NFB than a stock (greater than 820Ω). What I gather from reading on the web, this amp has had most of the standard BF tricks done to it already. Depending on your taste you may want to change the NFB. Don't go lower than stock, and any value over about 6kΩ doesn't do very much. A 5kΩ pot in series with 820Ω should cover it. Most bluesy players like the looser sound of less NFB, some jazz players might like it a little tighter. On my 76 DR I've converted the ground switch to 6800Ω - 1500Ω - 820Ω NFB.
I usually use it at 6800Ω (less NFB), but for surf-type instrumentals I'll switch it for more NFB (tighter sound.)
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The best thing I can think of is adjustable NFB. I haven't seen the amp, but it probably has less NFB than a stock (greater than 820Ω). What I gather from reading on the web, this amp has had most of the standard BF tricks done to it already. Depending on your taste you may want to change the NFB. Don't go lower than stock, and any value over about 6kΩ doesn't do very much. A 5kΩ pot in series with 820Ω should cover it. Most bluesy players like the looser sound of less NFB, some jazz players might like it a little tighter. On my 76 DR I've converted the ground switch to 6800Ω - 1500Ω - 820Ω NFB.
I usually use it at 6800Ω (less NFB), but for surf-type instrumentals I'll switch it for more NFB (tighter sound.)
Could you illustrate how you wire up the switch for the NFB?
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You can try a 12AY7 in V1 and use 5uf cathode caps on the V1 tube. Should give a significantly cleaner tone.
with respect, Tubenit
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Here's what I did on my Deluxe reverb. You may have to make a hole for a switch, I used the already existing ground switch. You could use a push-pull switch on a pot, but then you'd only have a choice of two values:
(https://lh3.googleusercontent.com/-9HoiG1fR0iM/T_BwKhlArFI/AAAAAAAAJPs/Rf0TvjYYcYc/s800/ab763.)jpg
Check to see if your amp doesn't have some kind of NFB adjustment already- there should be a wire from the hot terminal of the speaker output going back to a resistor on the circuit board which would connect to the PI circuit.
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This link describes Jazz modes for the normal channel on a Deluxe Reverb. I plan to do these mods on my Fender Twin once I have a shop space again.
http://www.qrp.pops.net/jazzamp.asp (http://www.qrp.pops.net/jazzamp.asp)