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FDP Forum / Amp Mods, Repairs, and Projects / Is there a "best" way to add reverb to normal channel of DRRI?

Tinkerer
Contributing Member
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San Diego, CA USA

Apr 15th, 2019 09:44 AM   Edit   Profile  

I have a Deluxe Reverb reissue that I purchased new in 1999, and I would like mod it so that I have reverb on both channels. I have seen different ways of doing this online, and am wondering if there is a best/easiest way to do this, and if so, can someone provide a link to their preferred instructions?

Thanks!!

Peegoo
Contributing Member
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Just beyond Mars

there's a world of fools
Apr 15th, 2019 10:14 AM   Edit   Profile  

Go here (link) and scroll down to the "65 DRRI Reverb Channel Mod."

Allows reverb and trem on both channels

Tinkerer
Contributing Member
*****

San Diego, CA USA

Apr 15th, 2019 12:10 PM   Edit   Profile  

Thanks so much Peegoo.

This is a very basic question- this mod allows both channel inputs to be jumped and used together- how do you jump them though- what gets connected to what?

Thanks so much!! You are so generous with your expertise- I feel like we are all receiving a full, free ride to Peegoo University, and the education is phenomenal and very useful!!!

Leftee
Contributing Member
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VA

Knuckleheading
Apr 15th, 2019 12:14 PM   Edit   Profile  

The frat-house initiation is hell, tho.

Peegoo
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Just beyond Mars

there's a world of fools
Apr 15th, 2019 12:54 PM   Edit   Profile  

Oh no...I'm an idiot. Don't give me too much credit!

One simple way to jump the channels is to use a short cable to go from one input jack to the other. This joins both channels, BUT now you have the problem of the channels being out of phase. An easy way to get around this is to place an AB/Y switch in that short jumper chain and flip the phase on the signal.

Many two-channel Fender amps are like this (channels out of phase). Marshalls are not like this.



Tinkerer
Contributing Member
*****

San Diego, CA USA

Apr 15th, 2019 05:06 PM   Edit   Profile  

Thanks Peegoo,

I did the Robrob mod from the link you posted, and the instructions say that that particular mod puts the channels in phase- So if that is the case, does this mean that if I wanted to use both channels, I would plug into the normal channel's #1 jack with my guitar, and then use a short 1/4" mono cable to go from the normal channel's #2 jack into the vibrato channel's #1 jack?

Thanks again!! And may I say that if you are an idiot, I'm very much hoping that your idiocy is contagious.

Doc Sarvis
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USA/Salt Lake City

Tuned Strings and Tight Lines
Apr 15th, 2019 05:50 PM   Edit   Profile  

My lazy butt would play through one of my Fender Reverb Units so I'm glad someone took the high road.

Peegoo
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Just beyond Mars

there's a world of fools
Apr 15th, 2019 06:01 PM   Edit   Profile  

"Does this mean that if I wanted to use both channels, I would plug into the normal channel's #1 jack with my guitar, and then use a short 1/4" mono cable to go from the normal channel's #2 jack into the vibrato channel's #1 jack?"

Yes, that is correct!

Tinkerer
Contributing Member
*****

San Diego, CA USA

Apr 15th, 2019 06:08 PM   Edit   Profile  

Thank you!!!!

Roly
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Whitehorse Canada

I don't get out much
Apr 17th, 2019 09:32 PM   Edit   Profile  

I use Peter Farington's method. (pdf64)
A few years ago Peter described his method and backed it up with math that is out of my league.
One jumper wire is needed...jump pin 6 of V1 to pin 6 of V2 and disconnect the line from the .047 cap connected to V1 pin 6 feeding the 220K summing resistors in front of the phase inverter.
Very simple even for a bass player.
Please correct any errors in my post Peter if I have not described things correctly.
cheers
Roly

pdf64

UK

Apr 19th, 2019 04:57 AM   Edit   Profile  

Hey Roly, yes, I think you described the mod perfectly :-)
Though it may be easier to put the link wire between the board eyelets (see link).
robrob has documented it as the 'Fender reverb' mod on his site (it's a link on the page Peegoo linked to).
His criticisms of that method seem nonsensical to me; perhaps something else was going on, or he made a mistake, when he tried it? robrob's site is great but he's not an EE, so there's some dodgy info up there.
The method he recommends (using mixing resistors) is fine too.
Apologies to Fritz but I'm not keen on his preferred method (also on robrob's site) of linking after the channels caps, as that creates a weird change to the freq response of each channel, boosting the bass on the vib channel whilst cutting it on the normal channel. It's due to the frequency dependant potential divider created by the 2 caps and the 'other' channel's plate impedance.

Channel link mod

(This message was last edited by pdf64 at 07:29 AM, Apr 19th, 2019)

Roly
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Whitehorse Canada

I don't get out much
Apr 21st, 2019 12:54 AM   Edit   Profile  

Hello Mr 64...:>)
My description is flawed
I was thinking eyelets, but I didn't state eyelets.
That was an error.
Eyelet to eyelet is what I meant.
cheers
Roly



DanL

Northern CT - USA

"We're not University material."
Oct 16th, 2019 07:09 PM   Edit   Profile  

Cant recall which mod I found online, printed out and brought to my amp tech about 15 years ago to do this mod to my 2000 DRRI amp. But I'm so glad I did it. I find the Normal channel to have a fuller sound and takes dirt pedals better than the Vibrato channel.

It's funny to think back and realize that back then I had to have a tech do this simple mod for me. I guess I've learned a lot over the years cuz I would definitely give this mod a shot myself if I were to do it today. Very worthwhile mod. Makes a big difference. My main gigging amp over the past 8 years. I always use the Normal channel. Nice to have verb and trem available.

FDP Forum / Amp Mods, Repairs, and Projects / Is there a "best" way to add reverb to normal channel of DRRI?




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