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Old 7th November 2008, 02:19 PM   #1
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Question Modding a tonebone to switch to pentode triode operation?Can this be done??

Hello guys,

Recently ive modded a fender hot rod deluxe to that: [URL=http://s392.photobucket.com/albums/pp3/Nicko_lps/My%20hand%20made%20cab%20and%20modded%20amp/[/URL]

I changed the tubes and transformers locations,added 1 resistor to the volume and 1 to the gain pot and now im preparing to change the filter caps add some orange drops,and a switchable on/off resistor that will allow me to use JJ 6V6.

I saw 3 days ago a VOX amp that had a triode/pentode switch,my question is can i make those TAD tonebones switching from triode to pentode operation?I saw 1-2 schematics in the forum but i dont know if theres a differance to that im asking about.Could i add a switch that will allow me to choose operation with the proper schematic and whatever it might needs?

I know that this amp might not worth all that,but after all im not planing to spend the cash for a new one since im not a pro musician.

Thank you,
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Old 8th November 2008, 12:29 PM   #2
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hey-Hey!!!,
Going from triode to pentode is not something I'd do while powered. It isn't impossible of course...some things to consider, have the switching done close by( as with a relay) so the B+ and signal isn't running all over the place.
cheers,
Douglas
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Old 8th November 2008, 04:01 PM   #3
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Nice job!

Reminds me of an old vintage "Deluxe" I had in high school that
I did the exact same thing with. Took the amp chassis out and
built a "head" with it (also added a gain stage, mid tone, and
master volume...) and a separate cab. I kept the old box and
later put it all back in there for portability...

I have a Hot Rod Deluxe now and my biggest issue is the ridiculous
gain, opamp based signal path. I think the output stage actually
sounds like a 6L6 PP Fender, despite all the bells & whistles. I
made the amp usable by building a -20db pad with 1/4" phone
ends and plug it between the pre out and main in jacks. That
way a gust of wind won't change the volume setting ;-)

I thought about heavily modding mine, like lose all that gain and
opamps, etc. and go to a signal path like the good old AB-763/
Twin Reverb which I also had at one time and liked a lot.

I thought about making the second channel a pentode channel
using an EF86 (gain structure provided for) so it could have a
really different flavor. I'd also put in a tube reverb driver instead
of the chipamp or whatever they're using.

Anyway, that's my idea on pentode, to have a 12Ax7 channel and
an EF86 (E80F maybe?) channel.

Maybe triode outputs would be interesting, but probably not so
much in class AB...

Cheers,

Michael
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Old 8th November 2008, 04:35 PM   #4
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hey-Hey!!!,
I really like the pentode input stage. Gain and output Z are going to be totally adjustable with the plate resistor value. You also get the nearly capacitance-free g1 of the pentode...which can do much for sonics effected by the pickup/coil loading.
cheers,
Douglas
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Old 9th November 2008, 02:43 PM   #5
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Quote:
Originally posted by Michael Koster
Nice job!

Maybe triode outputs would be interesting, but probably not so
much in class AB...

Cheers,

Michael
It runs in triode right now i like the sound but to be honest i liked that vox that is switching while active the triode pentode operation.
Its crunchy and that EL84 in triode is an awsome update for that amp lets say it fits well,but as i know triode is smooth the pentode would be more less smooth.:P

Any ideas of how could i do that?
Is it a bad idea after all and not possible to happen?

Thank you for your good words all
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Old 9th November 2008, 03:25 PM   #6
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Hmm, I missed the point of your question. You want to install a switch
between triode tonebone and pentode tonebone on the fly. The
triode and pentode both work in class A. Presumably everything
outside the socket is the same, so why can't you just switch?

Apparently the Vox AC30 and AC15 heritage amps allow switching
both the EF86 and the EL84s from triode to pentode separately.

If you don't want to switch "on the fly" it could be done by wiring
a second set of sockets for pentode tonebones and just switch all
the signals. I'd be inclined to use a relay to keep the wiring short,
even if not switching live.

I don't know if the VOX allows switching on the fly, but it would take
some engineering to make it work cleanly. If you do want to switch,
say, in the middle of a song, that will be a much more difficult mod.

Hmm, now I want to try tonebones in my amp. It might help with the
gain issue also.

Cheers,

Michael
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Old 9th November 2008, 11:30 PM   #7
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Quote:
Originally posted by Michael Koster
Hmm, I missed the point of your question. You want to install a switch
between triode tonebone and pentode tonebone on the fly. The
triode and pentode both work in class A. Presumably everything
outside the socket is the same, so why can't you just switch?

Apparently the Vox AC30 and AC15 heritage amps allow switching
both the EF86 and the EL84s from triode to pentode separately.

If you don't want to switch "on the fly" it could be done by wiring
a second set of sockets for pentode tonebones and just switch all
the signals. I'd be inclined to use a relay to keep the wiring short,
even if not switching live.

I don't know if the VOX allows switching on the fly, but it would take
some engineering to make it work cleanly. If you do want to switch,
say, in the middle of a song, that will be a much more difficult mod.

Hmm, now I want to try tonebones in my amp. It might help with the
gain issue also.

Cheers,

Michael
I ment to add some circuit on the tone bone so it will switch to pentode not have another set of sockets in there just waiting.that can be done?

Also if you install those tonebones triode youll get an awsome deal of gain at 7-8 watts.But if you think that istalling them you will be able to crank up the amp in a room,the aswer is definately NOP!I use that amp with 2 celestion alnico gold and is so loud even at the 8 watts or whatever.
They claim 7-8 watts for a 50 watt amp,mine was originaly 40 so im less than 7 i guess,still loud but excelent gain chan in low vols.

Peace


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Old 9th November 2008, 11:30 PM   #8
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Join Date: Nov 2008
Quote:
Originally posted by Michael Koster
Hmm, I missed the point of your question. You want to install a switch
between triode tonebone and pentode tonebone on the fly. The
triode and pentode both work in class A. Presumably everything
outside the socket is the same, so why can't you just switch?

Apparently the Vox AC30 and AC15 heritage amps allow switching
both the EF86 and the EL84s from triode to pentode separately.

If you don't want to switch "on the fly" it could be done by wiring
a second set of sockets for pentode tonebones and just switch all
the signals. I'd be inclined to use a relay to keep the wiring short,
even if not switching live.

I don't know if the VOX allows switching on the fly, but it would take
some engineering to make it work cleanly. If you do want to switch,
say, in the middle of a song, that will be a much more difficult mod.

Hmm, now I want to try tonebones in my amp. It might help with the
gain issue also.

Cheers,

Michael
I ment to add some circuit on the tone bone so it will switch to pentode not have another set of sockets in there just waiting.that can be done?

Also if you install those tonebones triode youll get an awsome deal of gain at 7-8 watts.But if you think that istalling them you will be able to crank up the amp in a room,the aswer is definately NOP!I use that amp with 2 celestion alnico gold and is so loud even at the 8 watts or whatever.
They claim 7-8 watts for a 50 watt amp,mine was originaly 40 so im less than 7 i guess,still loud but excelent gain chan in low vols.

Peace


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