hammond tube reverb as effect

[puls]

Howdy
I've been researching an analog spring reverb (not a digital recreation of a spring reverb) to put in front of my princeton reverb. Unfortunately, it seems the more highly reguarded units are out of my price range at the moment. However, I've noticed there seems to be a lot of tube reverb units that have been removed from hammond organs. Does anyone have any experience using these units as an outboard effect for guitar or studio work? If so, are there any/ many modifications that have to be made, input/ output level adjustments, etc.? I haven't done any work on tube devices before, but it seems like it might be a good first project.

thanx

jwp

p.s. brian, I finally got the pinouts for an Audix 35101, & as I expected, they're the same as a 35102. Our conversation got interupted by the board going down & I haven't been able to get on until recently.

[RustyBrooks]

I don't have any experience with tube reverbs from organs but I did build a solid state reverb. It's fairl cheap. I used the springs out of a busted old princeton I found, but they are not that expensive to buy. Typically the circuit you make is a amplifier that goes into the reverb and one that comes out. I used the project at http://www.generalguitargadgets.com/ind ... Itemid=142
I have a little "virtual kit" for it here: http://www.rustybrooks.com/electronics/ ... nterreverb

Note: I built the project before I compiled this virtual kit, there may be mistakes in my parts list. Check it out before you buy.

I think the quality is pretty decent, comparable to most amp's internal spring reverb units. I've used it in the effects loop of an amp, mostly, but I've also used it between a mic preamp and the recording interface. I have not really experimented with whether it would work before the amp (note that reverb before distortion is bad. The ideal place is post-amp)

[ckeene]

I want to make one of these, thanks for posting this.

Also, what would it take to get this to run at balanced line levels so I can put it in a rack and use it on mixes? Is a 1:1 transformer good or would I need to step up or down to adjust for impedence?

Also, what's the general rule for using stompboxes on line level stuff?

-chris

I don't have any experience with tube reverbs from organs but I did build a solid state reverb. It's fairl cheap. I used the springs out of a busted old princeton I found, but they are not that expensive to buy. Typically the circuit you make is a amplifier that goes into the reverb and one that comes out. I used the project at http://www.generalguitargadgets.com/ind ... Itemid=142
I have a little "virtual kit" for it here: http://www.rustybrooks.com/electronics/ ... nterreverb

Note: I built the project before I compiled this virtual kit, there may be mistakes in my parts list. Check it out before you buy.

I think the quality is pretty decent, comparable to most amp's internal spring reverb units. I've used it in the effects loop of an amp, mostly, but I've also used it between a mic preamp and the recording interface. I have not really experimented with whether it would work before the amp (note that reverb before distortion is bad. The ideal place is post-amp)

[RustyBrooks]

Honestly, I have no idea to the "right" answer to most of your questions.

You could either build in balanced in/outs or use little things you can buy for the purpose. There are simple circuits for balanced I/O out there, hunt around. I'll see if I can find one later. I think the circuit I linked to would probably work OK as an effect in an insert channel.

Using effects pedals in line level settings is largely going to be useful if the pedal can handle larger voltage swings and still perform OK. Guitars put out 100-200mV or so. +4dbU is a nominal signal of about 1.2V and -10dbV is about .35V. -10dbV is closer but this is also the "consumer" line level, most pro stuff is +4dbU. I imagine that 1.2V is going to clip a lot of effects pedals pretty badly, make distortions unusable, etc. Some stuff will probably work OK.

I have never checked to see what kind of voltage comes out of an effects loop in an amp. Now that I think about it, it's probably well over a few volts since it's after the preamp stage. Maybe it's ramped down and then back up again when it comes back? Because I think most people use the same effects in effects loops that they might use before the amp.

Honestly I'm kind of clueless on this stuff, I sort of bumble around, so take it all with a grain of salt.

Anyway, you can build the reverb for $20 or $30 if you have all the tools you need (soldering iron, wire cutters, etc) or a LOT less if you have an enclosure sitting around. I used a wooden tea box, which was the perfect size to put the springs and electronics into. I have been thinking about re-mounting it in a 1U rack box that I have around.

[brianroth]

Paia still sells the "Hot Springs" unit that can be easily modded for most any aplication:

http://www.paia.com/proddetail.asp?prod=6740K

The OEM springs are also still available:

http://www.accutronicsreverb.com/history.htm

Bri

[RustyBrooks]

Very cool idea and a very reasonable price, especially if it comes with the tanks (looks like it does...?) The tanks I've seen are usually $25-ish.

[puls]

Thank everyone for the replies.
I've been at work & periodically checking replies, and now I'm able to reply.
The main reason for wanting this is to use w/ my '69 Fender Princeton. The amp was cheap (got lucky), & w/ a recap & new weber vst speaker it sounds awesome. If I'm able to use it for something besides the amp also, that's a plus.
I was hoping for a tube spring reverb because guitars & tubes just seem to go together. Don't get me wrong, I've got plenty of non-tube devices between the guitar & the amp, but the reverb's going to be the last in that chain & when the overdrive kicks in a solidstate reverb will react differently then a tube reverb. There's also the fact that the built in Fender reverbs are some of the best for guitar amps, & that's sound I'm striving for. Buying a Princeton reverb would cost me significantly more then I've already got into this non-reverb princeton, and there's no guarentee it will sound as good. I'm not married to the idea of a tube driven reverb though, so these ideas are all good.
The PAIA looks promising, however, if you read the print, it's got an effect output & a dry output, so to use it w/ a guitar amp, you need a two channel amp to regulate the amount of reverb; the Princeton is only one channel. In order to use it, it would need some sort of blend control. It would seem like an easy mod - any ideas on this?
One other question about the PAIA unit, how long is the spring? I got a Little Lanillie (sp?) from Songworks. It has a 6" spring, and it's just not long enough to get a good slapback w/ it. So I think a 8-9" spring would be the minimum length that would work.
The Hammond units I mentioned are selling on ebay for 'complete' for $35-$70 depending on the auction. 'Complete' means the entire drive/ reamp assembly w/ tubes and spring tank, but I suspect no power supply and, of course, no organ to mount them in. Usually described as 'working when removed from organ.' I would think these are high quality units, coming from a hammond organ, and would make a good reverb w/ just a little work. I may consult w/ the local hammond/ leslie guru & see if he's got any thoughts on this. Heck, he's probably got several of these reverb units lying around as we speak.
Please throw out any other ideas anyone may have, & I'll get back on what I decide (whenever that might be).
One last thing, just got a spring tank for a Vox amp from Accutronics, new, $45 w/ shipping.

thanx

jwp

[puls]

Oops
After looking at the PAIA unit again, it only has an effect output. If I read it correctly, wet only w/ no dry signal at all. So I would have to build a circuit that taps the original signal pre reverb, & then mixes it w/ the effect output from the reverb. Is that correct? Any ideas on how this could be done?

thanx

jwp

[ashcat_lt]

(note that reverb before distortion is bad. The ideal place is post-amp)

not bad, just different. maybe not what the op is looking for, but there are valid reasons to put a reverb before the distortion. Keep in mind that in a smaller amp with built in reverb, the springs will be before the power amp and will be affected by any pa distortion.

To the question of pedals connected to line level signals I can tell you I've never had a problem in umpteen years. Interestingly, most pieces of gear with line level outputs have "volume controls" which allow you to regulate the voltage output.

[RustyBrooks]

(note that reverb before distortion is bad. The ideal place is post-amp)

not bad, just different. maybe not what the op is looking for, but there are valid reasons to put a reverb before the distortion. Keep in mind that in a smaller amp with built in reverb, the springs will be before the power amp and will be affected by any pa distortion.

That's a pretty good point actually. A lot of the tone that modern professionals try to emulate is something bad from the past, that became part of rock or pop sound through constant use (generally, the inability for old equipment to avoid whatever it is). Most in-amp reverbs ARE pre-power-amp so I guess we've gotten used to the sound. Still, for anyone who's never tried it, moving time-based effects to post-amp can be revelatory. When I meet someone who is trying to get better tone this is always the second thing I suggest (the first is using EQ stages to control distortion voicing - including post-power-amp eq).