Adding effects loop into brownface vibrolux

[matoni]

Hey all, I am doing a brownface vibrolux amp build and I want to add an effects loop after the preamp and before the tremolo. Where do I do so? I am assuming after the 220K resistors as seen on this schematic, but I'm not sure if there's anything special I need to do. Please let me know if there's anything I need to do, or if I am good just to jump wires off of this point and add the effects loop. I don't need it to be buffered, as I plan to just run a tube reverb unit through it.

Thanks for your help!

[Ten Over]

Tell us about this tube reverb unit.

[sluckey]

You need a coupling cap to block that 180V plate voltage from reaching the loop jacks (and whatever is externally connected).

[matoni]

Tell us about this tube reverb unit.

I was planning on designing and building a Dumble style 3 tube reverb external tube reverb unit. I decided to do this instead of making the amp a vibroverb because I recently talked with Andy Marshall of THD amps, and he told me that an amp with no reverb sounds completely different than an amp with reverb because there is less sag on the power transformer.

You need a coupling cap to block that 180V plate voltage from reaching the loop jacks (and whatever is externally connected).

Ok. what value cap do I need and where should I put it? In between the input for the output of those 220K resistors and the input of the phase inverter? also, how do I wire it so that it works with nothing in the loop as well? is there anything special I have to do there, or can I just do this (see attached schematic) I don't think that this is right, however, I know very little about this kind of stuff. If one of you more experienced people could, please send me an annotated schematic with an added effects loop. sorry for bring such a pain, and thanks for your reply.

[sluckey]

Look at this... http://sluckeyamps.com/november/november.pdf

[Ten Over]

I was planning on designing and building a Dumble style 3 tube reverb external tube reverb unit.

I don't know what this is. Do you have a schematic?

[matoni]

Look at this... http://sluckeyamps.com/november/november.pdf

I don't see the coupling cap that you mentioned to keep the voltage from reaching the jacks. Is this a problem? and I think I get it a little more. I need to use stereo jacks. Link the sleeves to each other and ground that, link the rings together, and have the tips go their own separate ways. this makes more sense now. Thanks so much for the input. I think I get how to do this now, minus the coupling cap that I don't seem to see..

I was planning on designing and building a Dumble style 3 tube reverb external tube reverb unit.

I don't know what this is. Do you have a schematic?

I was planning on using the tube reverb from ODR 60, as can be seen in this schematic. I may do a deep dive and find the differences in values between this and SSS#4 and see what values I will choose. Either way, this is the type of reverb I plan to do, as I love the lush-sounding reverb that comes from these amps (I have a TR JM sig clone that I made, and it has the same sort of 3-tube reverb setup) Am I overlooking anything? My plan was just to use it like the fender reverb unit or victoria reverberate, without having to shell out 1-2 thousand bucks for one of these tube reverb units. Plus, I'd get to customize it to my liking and have Guitar Cabs direct build me a cab with matching tolex to my brownface amp.

Thanks for your help and questions guys I really appreciate it.

[LOUDthud]

... I recently talked with Andy Marshall of THD amps, and he told me that an amp with no reverb sounds completely different than an amp with reverb because there is less sag on the power transformer.

Either you misunderstood what Andy was saying, or he's completely clueless. The 6G11 Vibrolux uses the bias wiggle tremolo and didn't have reverb until the Blackface era. To get the Tremolo to sound it's best, you have to bias the tubes a little on the cold side. Although you could insert a loop between the channel mix resistors and the PI input, you may have to install some kind of buffer if you want to drive a long cable.

[sluckey]

I don't see the coupling cap that you mentioned to keep the voltage from reaching the jacks. Is this a problem? and I think I get it a little more. I need to use stereo jacks. Link the sleeves to each other and ground that, link the rings together, and have the tips go their own separate ways. this makes more sense now. Thanks so much for the input. I think I get how to do this now, minus the coupling cap that I don't seem to see..

The coupling cap is not needed on the schematic I posted, but it is required on your schematic.

The jacks are Switchcraft 12A, one circuit with switch. They are not stereo jacks!

[matoni]

I don't see the coupling cap that you mentioned to keep the voltage from reaching the jacks. Is this a problem? and I think I get it a little more. I need to use stereo jacks. Link the sleeves to each other and ground that, link the rings together, and have the tips go their own separate ways. this makes more sense now. Thanks so much for the input. I think I get how to do this now, minus the coupling cap that I don't seem to see..

The coupling cap is not needed on the schematic I posted, but it is required on your schematic.

The jacks are Switchcraft 12A, one circuit with switch. They are not stereo jacks!

what size capacitor do I need? and does it just go between the end of the mix resistors and the preamp output jack? thanks for your help. Ill look for the Switchcraft 12A jacks.

Thanks!

[sluckey]

like this...

6g11a.png

[matoni]

thanks so much that's exactly what I needed.

[Reeltarded]

Have you ever actually played through a Vibroverb?

Don't miss the chance to play the best amp Fender ever made, reverb included. It's 109% surreal.

[Stevem]

To the OP, please note this empirical lesson that I learned in regards to a mod as you have inquired about doing many moons ago.
Any time based effects like reverb, delay or chorus introduced into a amps signal chain will sound like crap if any of the amp's gain or output stages after that get driven into clipping/distortion, and especially if any 2 or more are used at the same time!

A lot of guys who put the time into doing this to there amp will not talk about it and have a jumper cable in there effects loop to bypass it.

[matoni]

Hello again; I am currently in the process of designing the power stage for the reverb unit.

I was planning on using a Hammond 270X PT, and I was wondering what kind of conditioning (caps) I need to run to keep it quiet. I want to use a diode rectifier, so I assume i can just use the 2 red taps on the transformer secondary and feed them into a typical diode rectifier. Please let me know if there is anything wrong with my thoughts on this. To power the amp though, I was just thinking of using a cap can like the one used on vintage Princeton Reverbs: a 4x20 UF with appropriate stepdown resistors to make it so the tubes run at the correct voltages, and so the reverb transformer gets powered properly. Let me know if there are any problems I am overlooking, as i am still a relatively new amp builder.

To the OP, please note this empirical lesson that I learned in regards to a mod as you have inquired about doing many moons ago.
Any time based effects like reverb, delay or chorus introduced into a amps signal chain will sound like crap if any of the amp's gain or output stages after that get driven into clipping/distortion, and especially if any 2 or more are used at the same time!

A lot of guys who put the time into doing this to there amp will not talk about it and have a jumper cable in there effects loop to bypass it.

I was planning on putting this after the gain stage in this amp but before the power amp. The power amp doesn't really clip though (as far as I know) it just compresses. Let me know if I am wrong though, as I would hate for this amp to sound like crap.

I also need a relay recommendation. I need a DPDT relay that runs off of the 5-volt AC tap of the power transformer. If anyone has any ideas, please let me know, it would be much appreciated.