Line-Level Spring Reverb Unit...anyone built one?

[lonote]

I had a query from someone about what it would take to use a spring reverb pan in a DAW effects loop &/or an amp with a loop. I have a 6G15 that I built, but that is really tailored to instrument-level in/out.

I have never really though about it, but it seemed line-level unit could be not much more than the internal Fender amp 2-tube reverb circuit, with a dwell control & it's own PSU added.


Anyone built something like this or experimented along these lines?

[TUBEDUDE]

If you use a 6AW8 for the reverb send/return, your second tube can add the extra gain

[lonote]

If you use a 6AW8 for the reverb send/return, your second tube can add the extra gain

I will have to try to work out output levels required. I think that most of the equipment being patched together has boost/attenuation for input & output levels.

It may be that a 12AX7 would not have to drive the subsequent channel input, but really have no idea. Also not familiar with the 6AW8, but see it is a triode/pentode combo.

For topography I am seeing ; dwell/input control>the typical paralleled 12AT7 driver> trans >tank> 6G15 recovery circuit, which includes a dry signal cathode follower using the 2nd half of the recovery tube, facilitating a "MIx" control to the output.

A typical mutli-node power rail should work OK & have adequate filtering to keep things quiet.

[maxkracht]

If I were building this for myself mainly for studio use, I would make the input side a "reamp" to add some extra functionality. Balanced line in to instrument out, normalled to another instrument in, then treat the spring reverb however you usually would. Maybe even a DI out. Couple edcor or similar reamp and DI transformers would only add $20-30 to the BOM and you get a way to reamp, fx loop for pedals, and can go back into a nice mic pre or other studio gear with balanced I/O.

[B Ingram]

Anyone built something like this or experimented along these lines?

Ever heard of Hammond Organ Company? The ones who invented spring reverb?

The AO-44 Reverb does what you're asking, but it is speaker-level. The speaker of the existing organ is attached at the point towards the lower-left of the schematic labeled "Sig Input" and the resistor/lamp bridge circuit both reduces the voltage/power and compresses the signal. The pair of "Driver" terminals are then attached to Hot and Ground of a reverb tank input.

The output of the reverb tank is attached to the input jack drawn at the top-left of the schematic. The rest of the schematic is just a simple push-pull power amp, which winds up feeding its own speaker. The net result is an original Organ with dry speaker(s), and a separate "reverb speaker."



Reverb tanks often require around 1 watt to fully drive, so any "line level reverb circuit" is all about figuring out a no-kidding about of signal available, and how much additional power-amplification will be need to drive the tank-input hard enough. The output side of the tank gets the same voltage-(or power-)amplification needed to do whatever job is required (if pushing a DAW instead of a speaker, then much less amplification is required).

[Stevem]

Since it sounds like your going this route for sound quality then get a Accutronics / Belton digital reverb PAC.
They are simple as hell to hook up and only need 5 volts .

I've got two of them in a few of my fenders and I love them.

No more surprises with busted springs and no reverb at a gig.

[lonote]

Thank you all for the replies & brain fodder.

The initial query was really coming from a mostly non-tech perspective (how can I hook up a real spring tank here?) & that questions gave rise to my thinking about a minimalist real-world implementation.

I had drawn up (& built a while back) a little add-on reverb driver/recovery module (AB763-style) that worked well, so I was starting from there in my head.

Yesterday, we played around with several reverb tanks I have; new Mojotone, MOD, new Accutronics, vintage Accutronics, Folded Line, 2-spring, 3-spring, ..running them into a reverb Champ I built & they are all very different sounding, which makes a universal reverb "driver" unit sort of interesting.

Has me wondering about small DIY plate units now...

[nuke]

Were I going to build a device, I'd go with solid state. There are many choices of reverb spring units of suitable impedance, and it is fairly simple to use an opamp like a 4560 to drive it. Pretty simple matter of setting up the filtering on the drive side, and setup the recovery side gain structure to get to the output level you're looking for. Should be quite easy for single-ended, a little more work if you want balanced audio IO.

[lonote]

As a follow-up, in case anyone else is looking for something similar, I happened on this TAG thread from 2007 that is just about exactly what I was initially posting about, but with some extras.

Pretty much a Fender 2-tube reverb circuit, but also a Dumbleator circuit, with a shared power supply & in one chassis.

https://ampgarage.com/forum/viewtopic.php?f=5&t=3031

Seems like it would be a useful little box. Apparently a few were built, but sadly, no follow-up on how they worked out functionally.

[Hartwell]

Anyone built something like this or experimented along these lines?

The AO-44 Reverb does what you're asking, but it is speaker-level. The speaker of the existing organ is attached at the point towards the lower-left of the schematic labeled "Driver" and the resistor/lamp bridge circuit both reduces the voltage/power and compresses the signal. The pair of "Sig Input" terminals are then attached to Hot and Ground of a reverb

I think you’ve got this backwards - the speaker signal is the “Sig Input” and the “Driver” is the reverb tank input.

[Astronomicum]

Take a look at the the Pioneer SR-101 (attached) for some ideas. Nice sounding circuit.

[lonote]

Take a look at the the Pioneer SR-101 (attached) for some ideas. Nice sounding circuit.

Thanks for that. Is that is the same hifi Pioneer? Google pics have a different looking logo than I am familiar with.

After my initial query at the top of this thread, I drew up a 2-tube reverb schematic based partially on a Hook amp schematic I saw on the Rift amps YT channel, but I used a pentode/triode for the driver, borrowed for this current thread on TAG: https://ampgarage.com/forum/viewtopic.php?f=6&t=37925

It looks very, very similar to the SR-101 schematic. Good to know I am on the right track.

[nuke]

If you just want to buy one, there are Shure reverb units on eBay and reverb, pretty much what you want. Solid state, model PE70-RM.

I have been contemplating a stand-alone reverb for a while, to use with some vintage amps that don't have reverb built in. The cost of buying or building a tube reverb unit is just a bit out of hand.

On the other hand, this is a side-chain processing job that could be done very nicely with a simple solid state circuit, the entirety of the circuitry BOM is a fraction of the price of a single vacuum tube.

I plan to do it, the most expensive part of my plan is the enclosure. I would like to build one with a full-size pan, so the enclosure needs to be large enough for that. The second most expensive part is the pan, third most is the power transformer. The entire PCB stuffed with parts, is less than a decent 12AX7A.

[Astronomicum]

Is that is the same hifi Pioneer?

[/quote]

[B Ingram]

I think you’ve got this backwards - the speaker signal is the “Sig Input” and the “Driver” is the reverb tank input.

Thanks!

Checking the M-100 Manual where the AO44 is shown connected to the organ's speakers confirms what you're saying.