Details of the Jon Bessent Reverb Mod for Twin?

Bill Terry · Post by **Bill Terry** » 11 Mar 2015 8:10 am

I bought a '69 Twin recently that was blackfaced by Jon Bessent at Tonecraft in Austin before his untimely passing. As part of that mod the previous owner also had him do some sort of Reverb mod that he liked. It involved unhooking the drive stages of the non-reverb channel and using them in the reverb drive (or recovery?) path instead.

While the mod really does sound good, it renders the first channel useless, and I've started a gig where I'm doubling guitar/dobro and could use the second channel, so I'd like to put it back stock.

I haven't had the amp apart to look at it yet, and maybe it's an obvious mod, but rather than try to reverse engineer what he did which by tracing wires and comparing to a schematic, I wondered if anybody is familiar with this mod?

Thanks in advance.

Steve Lipsey · Post by **Steve Lipsey** » 11 Mar 2015 8:41 am

Another option that I use is to front end the single channel with a channel switch, with a good EQ pedal on one input...set up the amp for steel, plug your steel into channel one of the switch, plug your dobro into the EQ pedal and then into channel 2, plug the switch into your amp. Set up the EQ to compensate for the steel settings, that's how I do my dobro...it actually is nicer in some ways, fewer long cables going to the amp...

Bill Terry · Post by **Bill Terry** » 11 Mar 2015 9:32 am

Thanks Steve, I considered that, but I'd still like to have that normal channel available.

I've got a good A-B switch and a Baggs Para DI, so that may be the short term solution until I've had time to take the amp apart and reverse engineer.

Steve Schmidt · Post by **Steve Schmidt** » 11 Mar 2015 10:04 am

Hi Bill
A popular thing to do with fender reverbs is to disconnect the return wire coming from the reverb pan and plug it into channel one. I've never done it but apparently you can then run you returned reverb signal thru the first channels EQ abilities. Without looking, my guess is it was modified internally to accomplish the same thing.

Bill Hatcher · Post by **Bill Hatcher** » 11 Mar 2015 11:19 am

i used to do a lot of fender amp repair for my own stuff and some of my buds. during the 80s i spent most of my time UNDOING mods. i refused to mod an amp for anyone....its ok if you want to do that, just get someone else...so to your issue. its easy to find online a copy of the LAYOUT of the amp. this is the pic of all the components as they are and the wiring. take that and open your amp up and just make sure that all the components are there and correctly wired. follow all rules of safety...there are some lethal voltages there for sure and you can be killed also...disclaimer.

i can tell you this....i "blueprinted" (car guys will know this word) many many fender amps. i was continually amazed at the sound when all the components were with specs and the voltages were too. mods are so worthless in my estimation....thats whats wrong with the silverface amps anyway....they are a mod of the original design of leo fender. duh!

anyway. just look at the pics and use your meter to read ALL the voltages listed. good luck

John Billings · Post by **John Billings** » 11 Mar 2015 11:29 am

Could it be as simple as a wire from the Reverb Return RCA Jack, to the Input Jack of Channel 1?

Bill Terry · Post by **Bill Terry** » 11 Mar 2015 11:44 am

Thanks for all the responses guys.

John, I dunno, I think it's a bit more than that but I'm not sure. I guess I'll take it apart and find out. It could be very simple.

John Billings · Post by **John Billings** » 11 Mar 2015 11:49 am

Well Bill,
I believe I got the same result by making a cord RCA on one end and 1/4" jack on the other. I just unplugged the Reverb return cable, plugged in my RCA jack cord, and plugged the other end into Channel 1. Sounds like yours has just been done internally?

Bill Terry · Post by **Bill Terry** » 11 Mar 2015 11:53 am

It could be John, but I don't believe the tone controls on the normal channel work either.. which could be something a bit different.

Ideally, it would be nice if it's that simple.

Curtis Alford · Post by **Curtis Alford** » 13 Mar 2015 7:29 pm

Bill,you have talked to the people that bought Jon's shop out? They are in the back of music exchange where Walter had his woodworking shop. I am told they got all info and tools and patents.
Just a thought
Curtis

Bill Terry · Post by **Bill Terry** » 14 Mar 2015 5:11 am

Thanks Curtis, I haven't. In fact I wasn't sure what became of Tonecraft. Thanks for the info.

Bobby Snell · Post by **Bobby Snell** » 14 Mar 2015 7:33 am

Last time I was over at that shop was summer...the new guy in the amp section is Ben Stevens, "Joe's Amps." (ben "at" joesamps "dot" com)

We chatted a bit, he gave me a good deal on a replacement speaker. Haven't had a chance to go back, but definitely different from whoever took over after Jon.

I don't have any of Jon's amps, but have played through a couple that were wonderful. His stomps are also sought after. Legendary guy who helped out lots of musicians with small repairs too.

John Billings · Post by **John Billings** » 14 Mar 2015 7:48 am

" but I don't believe the tone controls on the normal channel work either."

What would be the point of the mod if the tone controls don't work? That's the reason I made that adapter cord. Being able to adjust the sound of the reverb with the Tone controls, and then mixing it in with the Volume control makes sense. At least to me.

Bill Terry · Post by **Bill Terry** » 14 Mar 2015 7:54 am

Hi John,
I'm not sure what the point of the mod was to be honest, but the original owner said something about different gain in the Reverb path, and the tone controls don't do anything. That's all I know.

From a 'seat of the pants' perspective, the reverb sounds considerably smoother than a stock Fender spring reverb (which I'm VERY familiar with), a lot less clangy and the tail is cleaner. I'm actually hoping for time to get the amp open tomorrow and if I can figure it out I'll reply back to the thread.

Bill Terry · Post by **Bill Terry** » 14 Mar 2015 7:59 am

Bobby Snell wrote: Legendary guy who helped out lots of musicians with small repairs too.

Never met him, but I've heard that time and time again. Apparently a talented amp guru, but also a very nice guy.

John Billings · Post by **John Billings** » 14 Mar 2015 9:11 am

" different gain in the Reverb path"

Okay, that does make sense.

Brad Sarno · Post by **Brad Sarno** » 15 Mar 2015 1:28 pm

Bill Hatcher wrote:i used to do a lot of fender amp repair for my own stuff and some of my buds. during the 80s i spent most of my time UNDOING mods. i refused to mod an amp for anyone....its ok if you want to do that, just get someone else...so to your issue. its easy to find online a copy of the LAYOUT of the amp. this is the pic of all the components as they are and the wiring. take that and open your amp up and just make sure that all the components are there and correctly wired. follow all rules of safety...there are some lethal voltages there for sure and you can be killed also...disclaimer.

i can tell you this....i "blueprinted" (car guys will know this word) many many fender amps. i was continually amazed at the sound when all the components were with specs and the voltages were too. mods are so worthless in my estimation....thats whats wrong with the silverface amps anyway....they are a mod of the original design of leo fender. duh!

anyway. just look at the pics and use your meter to read ALL the voltages listed. good luck

Amen Brother Bill!

Bobby Snell · Post by **Bobby Snell** » 16 Mar 2015 6:03 am

Just my very humble opinion:

This is not really "black-faced," it's a unique creation. Mr. Terry in his original post opines it does sound good. And, of course, there's no new "Hippie Jon" amps being made. Just to point out to Mr. Sarno and Mr. Hatcher that its not just some hack mod job.

There's a boat-load of Twins out there for cheap that are good candidates for blue-printing, black-facing, or modding to whatever. CL Austin had one recently with JBL's for about $850; I've seen SFTR's go for $700 or less.

So the effort and cost of returning the amp to stock may not be the most efficient way of coming up with a dual-purpose Twin.

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Details of the Jon Bessent Reverb Mod for Twin?

Details of the Jon Bessent Reverb Mod for Twin?

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