Grateful Dead Music Forum

A place to talk about the music of the Grateful Dead 

 #105394  by modz
 Fri Nov 18, 2011 10:35 am
I know this subject has been covered here but I am looking to send a full signal to a Mcintosh without any alterations to my stock 1974 Deluxe reverb. I want the power tubes too so a preamp out isn't the answer. I came across this schematic and it looks interesting. I have already talked to a few of my guru friends and they thought it looked good. I would put it in a pedal enclosure and plug a jumper speaker cord from amp speaker jack > DI enclosure back to speaker and then line out > a volume pedal for stage volume control > a small mixer > Mcintosh > K120 1x12 box. I can keep my Deluxe at the sweet spot (on 5 for me) and control my stage volume via volume pedal. The Deluxe with D120 will be on also but I don't want to change the volume on it at all. Any more than 5 it starts getting mushy and any less it doesn't compress or break up.
Any thoughts would be appreciated. I will let ya know how it turns out. I don't know what the capacitor does in there??? Seems like the best of both worlds to me. I would be hearing the Deluxe and the "boink" from the Mcintosh.
 #105396  by ugly rumor
 Fri Nov 18, 2011 10:46 am
Rube Goldberg-esque is my impression. KISS
 #105442  by SarnoMusicSolutions
 Sat Nov 19, 2011 11:15 pm
Yet another very cool way to tap the output of a Fender amp and send it to a more powerful power amp. The great advantage here is that you can drive the Fender's power tubes into any degree of clipping you'd like, and then use the external power amp to deliver whatever volume you need into a speaker cab. Pretty cool. Modz posted a pretty clever adjustable version. There can be fixed versions of that as well using a simple pair of resistors. But this adjustable version gives a handy line level control right there on the device itself.

I was thinking that the external speaker jack on a Fender amp would be the ideal place to wire in a pair of resistors to offer this type of post-power-tube line output.

Keep in mind that it's important for the Fender amp to still drive a real speaker for this to deliver the ideal signal.

Thanks Modz, cool stuff.

 #105453  by NeebruM
 Sun Nov 20, 2011 11:54 am
It would be interesting to hear the result.
Seems like a good idea to me...

I see what you are trying to accomplish, just take the sum results of the Deluxe's total (amped) sound and boost it through the Mac.

I don't know how well it would work though, choking that signal down to a line level, but it's sure worth a try. (I have to wonder why Jerry didn't do this!)

He would have sold 500 more tickets to me alone! I loved the multi Twin sound era. :)
(though I have to admit, I had many a fine evening listening to Budman and his friends as well)
 #105489  by modz
 Mon Nov 21, 2011 3:14 pm
I'm no engineer at all but as I understand, Jerry's out was tapped after the power tubes. I have talked to others who say Jerry's power tubes were removed. I'm swamped right now but hopefully I will try it out within a couple days. I will try it on my reissue deluxe before my 74.
 #105511  by NeebruM
 Tue Nov 22, 2011 7:23 am
I always thought it was pre amp only...
Sounded a bit too clean to me. (and yea, I've heard that too about the power tubes, and wondered about those big power transformers in the twins)

Maybe I have kidded myself, but I swear I can hear the difference in the "amalgamated" mis-mash of ALLLLL the tubes into a distortion that no digital combination can match. NOT that there isn't room for effects and pedals and racks, etc. Just that it's a different sound and should be treated that way, IMO.

Another thing that crossed my mind (briefly :)) when I saw you playing through that 2300 was why not use a blues Jr. or some 3-5 watt (choked) as a pre amp into the Mac? I don't know what would happen lol but it would have hair on it. I'd think.

May your sweet spot shine brother, at great heights.... :peas:
 #105515  by waldo041
 Tue Nov 22, 2011 9:07 am
modz wrote:I'm no engineer at all but as I understand, Jerry's out was tapped after the power tubes.
nope, preamp tapped just before the 220k mix node resistor after the coupling cap. NO power tubes installed, this raises voltages so bigger filter capacitors are needed. at least 500v ratings or as healy stated "the biggest you can fit in the can"!




and this picture appears to show only the 3 essential preamp tubes. V2, V3 and the Reverb tube shields are the only ones visible. is it just irony that those are the only tubes needed for a jerry preamp?
V1, Vibrato and the PI tubes appear to be gone but are NOT needed and would only cause trouble if one were to go faulty within the circuit. removing these also slightly raises plate voltages, which is a plus!

 #105524  by modz
 Tue Nov 22, 2011 10:47 am
Thanks Mike. I remember discussing that with Brad and seeing the pics with no power tubes. I remember a few people thinking the tap was after the power tubes for a while but I guess healy cleared that up. Thanks for the info.