Anyone have a good schematic for gain stage for a jcm800?

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Kapo_Polenton

Kapo_Polenton

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I think i am done tinkering with my Traynor.. it isn't a high gain beast, more of a hiwatt on steroids and i am fine with it because the big huge chords are orgasmic enough for their use on recordings or AC DC ish stuff. I have another project PTP 800 style amp about to take a turn on my work bench. I know there is more than enough gain you can coax out of a 2204 preamp circuit. I already tweaked my 82' 800 and it sounds great. No point in having two the same and this thing already had the extra preamp tube (old laney AOR) drilled so I want to use half an extra tube. Anyone have any good starting point schematics or layouts? I found the Bainzy mod here: http://www.pleximods.com/bainzymod.html but it is based more from a plexi circuit layout and less from an 800. (I know they are close anyway) but I am looking for something that is built off an 800 preamp platform. Tone wise, I was listening to some Blue Murder the other day and holy $hit Syke's tone is off the charts. I love that grind. Thought I would try going for it without use of an OD.
 
Kapo_Polenton":12apeoti said:
I think i am done tinkering with my Traynor.. it isn't a high gain beast, more of a hiwatt on steroids and i am fine with it because the big huge chords are orgasmic enough for their use on recordings or AC DC ish stuff. I have another project PTP 800 style amp about to take a turn on my work bench. I know there is more than enough gain you can coax out of a 2204 preamp circuit. I already tweaked my 82' 800 and it sounds great. No point in having two the same and this thing already had the extra preamp tube (old laney AOR) drilled so I want to use half an extra tube. Anyone have any good starting point schematics or layouts? I found the Bainzy mod here: http://www.pleximods.com/bainzymod.html but it is based more from a plexi circuit layout and less from an 800. (I know they are close anyway) but I am looking for something that is built off an 800 preamp platform. Tone wise, I was listening to some Blue Murder the other day and holy $hit Syke's tone is off the charts. I love that grind. Thought I would try going for it without use of an OD.
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Change V1 to 300K grid resistor and cathode to 2.7K/.68uF, change 10K in V2 cathode to 2.7K/.68uF. Adjust to taste. Thank me later...

Steve
 
Thanks for the quick reply! After hearing your amp clips I am thinking this might be just what i needed..
 
i've been referring to this one, it was posted here i think a while ago.
 

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Thanks Yeti, but if not mistaken that is just squeaking more gain out of 3 peramp tubes vs adding a fourth is it not?
 
lol so true.. he has "sykes-friedman-Jose_Cameron-aLDRiCh all done did rolled inta one dang awesomeampnobodybetter than cuz i ain't rip y'all off HA they overprice such good amp mine is the shit..you'llsee if you just listen"
 
Just reviving this thread as I came by this layout and wondered if the general idea (values may have to be different) or wiring is accurate to add an extra half tube on a DPDT to my 2204? http://forum.metroamp.com/download/file.php?id=5371 I think I am confused as to the wiring of the DPDT switch. The goal would be to retain the core tone of the 2204 circuit when this is not switched into the circuit. If anyone would like to provide suggested values or alternate wiring, I'm also all ears as my understanding is that the ones in this layout might be a little bass heavy or might cause blocking distortion from too much too soon in the circuit.

I have other stock circuits i can do the "just add pedals to" before people make that suggestion and i have another lightly modded jcm800 without the tube that has more gain. I just want to play with something different and i find myself moving away from pedals lately. I'm really enjoying the tone of the circuits themselves and forcing my hands to do more work.

thanks
 
Kapo_Polenton":2okjdpc5 said:
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I have other stock circuits i can do the "just add pedals to" before people make that suggestion and i have another lightly modded jcm800 without the tube that has more gain. I just want to play with something different and i find myself moving away from pedals lately. I'm really enjoying the tone of the circuits themselves and forcing my hands to do more work.

thanks
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im SO with you there!!
 
bump for more insight/info on the DPDT siwtching layout i linked to.. really interested in making this switchable! arigato.
 
Bumpskie again.. i am really confused as to how to wire a DPDT into a 2204 circuit. If anyone can hook me up, pm me please. I see a lot of stages added to 1959 type circuits but not switchable with jcm800.. we really need an amp tech section here!
 
Kapo_Polenton":hnx0yoce said:
Bumpskie again.. i am really confused as to how to wire a DPDT into a 2204 circuit. If anyone can hook me up, pm me please. I see a lot of stages added to 1959 type circuits but not switchable with jcm800.. we really need an amp tech section here!
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I asked Brad for that a few times and he just blew me off....go figure.
 
Tried SDM as well.. nothing so far. if anyone has the time, look at this diagram below and let me know!
 

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What do you want to know about it? I might change the cathode bypass cap and/or resistor adjust the response of the stage. Perhaps a .67uf bypass cap to keep the input stage from being too bassy, and you might want to just experiment with the value of the resistor. Being the first stage, I'm not sure, but I'd think you'd want to bias the stage in such a way to work with the 3rd stage (second stage of the 2203 stock)....meaning allowing the clipping to happen on the same part of the waveform. I don't think I'd go with the 820....at least the 2.7k so that it and the first stage are biased the same. But no sense in not trying other values and see what happens.
 
Rogue":2wzmpxqn said:
What do you want to know about it? I might change the cathode bypass cap and/or resistor adjust the response of the stage. Perhaps a .67uf bypass cap to keep the input stage from being too bassy, and you might want to just experiment with the value of the resistor. Being the first stage, I'm not sure, but I'd think you'd want to bias the stage in such a way to work with the 3rd stage (second stage of the 2203 stock)....meaning allowing the clipping to happen on the same part of the waveform. I don't think I'd go with the 820....at least the 2.7k so that it and the first stage are biased the same. But no sense in not trying other values and see what happens.
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Thanks for the reply..even simpler than that, I want to know in the image I attached, is the DPDT switch wired correctly? I'm questioning the signal flow and trying to wrap my head around whether or not it would work or if maybe it was drawn incorrectly. I agree though, i will be going with more traditional values..
 
It would take too long to explain, but here is how you want to wire in an extra gain stage. Just consider the added stage in the picture your extra triode and have it come in after the first stage. Depending on how hot your first stage is you are going to need to attenuate the new stage down with a voltage divider.

http://www.triodeamplification.com/Hoffman.html

-Brian
 
Kapo_Polenton":y9fpsgvv said:
Thanks for the reply..even simpler than that, I want to know in the image I attached, is the DPDT switch wired correctly? I'm questioning the signal flow and trying to wrap my head around whether or not it would work or if maybe it was drawn incorrectly. I agree though, i will be going with more traditional values..
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Start at the jack, with the DPDT switched to the upper lugs, the signal just goes to through the switch and to the 68k resistor of V1. This would be your normal circuit.

Switch the DPDT switched to the lower lugs, the signal now goes to the 68k resistor of the extra tube, out of the that to the pot (which I assume is an added pot), from there back to the DPDT (we're at the middle lug left now). Since it is switched down, that signal goes the lower left lug but that is bridged via a wire to the upper right lug which goes back to the 68k of V1.

I'm with brian, though, I'd do it in such a way you're not making the first stage switchable. It may work fine, idk, but I don't think that is standard. You also wouldn't have to fool with added an extra gain knob....you'd just use your existing one.
 
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