26 posts
Updates as the project comes together... I'm building a self-contained spring reverb using an Epiphone Valve Jr. head as the reverb circuit and chassis. A 9-1/4" reverb tank a la MOD or Accutronics will fit right inside the chassis, a 16-3/4" (Twin style) will not. I'm probably going to mount the 9-1/4 inside, and buy a spare 16" for when I need more reverb... the reverb tank connects via RCAs. Should be a fairly easy build and at around $120 much, much cheaper than any tube-driven spring reverb on the market. I've got the Epi coming via ebay ($100 shipped), and I purchased my pots and jacks. My buddy Joe actually has three of each tank (9-1/4 3-spring and 16-3/4 2-spring and 3-spring) from Accutronics and MOD... is building a switch into his to swap between them, so I can test them all and figure out which one to buy.
I'll post pics in this thread as it starts to come together.
Noice! Let us know how it goes, I gotta VJr chillin here.
Thats awesome Charger. Can't wait to see and hear it.
ok, this is such a cool idea, I had to try something similar.
I have an old Crate amp (old 80's model, when they actually looked like wooden crates) with a reverb tank in it - once I got it out of the amp, it's an older (USA made) accutronics type (9-1/4 size) -- a relevant spring reverb to test out!
I ran a line out from my 400f to a blue tube preamp -> input on the reverb -> output back to the other channel on the blue tube -> 400f.
in retrospect, I could probably go straight to the reverb input from the mackie but I didn't know if I'd need gain or not.
I sent the source via a bus with a high pass eq on it since my initial impression was: "low freq content sounds like crap" - high pass at 310 Hz for this test.
after reverb, it needed about +50 dB of gain or so (max gain from the blue tube and some extra from the onyx's pre).
it sounds kinda decent now - needs more adjustment - it's promising.
clip! (using most recent fnj take, so reference to digital echo/reverb sound is on there)
starts with just the reverb, then just the source.
then both together with mix of the reverb starting high and going lower, adding stereo spread and chorus to the reverb while mix level continues down.
outro is this final sound in the mix.
don't know if I'll use this ever again but it was a fun experiment! heh.
Sheep, that's essentially the idea of the spring reverb circuit, unrefined.
I never thought about it before - neat thing to test out.
Although it's a little more sophisticated when you get the full circuit involved... with dwell (how hard the first tube stage hits the front of the spring), tone, and mix you can really refine the reverb... also remember every tank is specifically designed for the circuit it is going to be built in, so it's got a specific input and output resistance.
My cohort Joe posted his listening notes on facebook for the 6 reverb tanks he has...
Reverb-zilla! I just did a listening test between 6 different tanks (accutronics vs. MOD, types 4, 8 & 9), and the results are interesting. The MOD type-9 is the best overall, the Accutronics type-4 is the most Fendery, the Accutronics type-9 has the longest decay, and the MOD type-8 the best short tank. I think I need to build a cab to hold all these with the selector switch...
so you're saying... there's lots more to it than a mic preamp!? pft! ;)
very cool project you guys are into with this - looking forward to clippage of what it's like when done correctly!
So far so good, my Valve Jr, is coming, $100 on ebay (there was one for $75 on Craigslist but I missed it), I had to buy a couple of nicer pots ($20) and a cheap one ($4), flat-mount 1/4" jack was $2, depending on the reverb tank I decide on it's another $15-25. Total will be around $140-150 all in...
plus, selling the guts of a valve junior on ebay can recoup a GOOD part of that.
Uh, I need the guts. The point is to get the loaded chassis--it's perfect for a tube reverb driver, it's got a power tube, a preamp tube, a choke, and an output transformer. I'll use the entire circuit minus the output transformer to build the reverb circuit.
parts are arriving... a couple of very pricey pots ($20), the valve junior head, and a 1/4" jack. I played through the Valve Jr at our weekly jam last night in what was probably its first and last appearance as an actual amp... a couple more parts and then it will be converted.
Waiting on a very hard to find pot and some new knobs...
What kind of pot?
...and no I didn't mean what strain! heh heh
50k audio taper. Actually not super hard to find, but I was looking for a nice one... I'm going with a $2 Alpha instead, I wanted something nicer and never found it.
what do you mean by nicer? a brand in particular?
Precision Electronics 50k audio taper pot... around $10. Never found it. I found lots of other values though. Alpha is the $2 alternative...
did you look for a Bourns? That's what I put in my Hafler pre-amp when I modded it years ago.
My electronics guru specifically recommended against Bourns... PE was his bottom-line recommendation, Alpha his second choice...
Yep. $12 though... I was looking to spend $10... instead I went with Alpha and spent 2...
curious as to why he recommended against Bourns, but, certainly for different applications different things work better. For home stereo, they make some seriously good stuff. Or at least used too... When I did my pre-amp, the best volume pot they had was over $100, but the mod company said "if you can afford it, it's worth the difference." The one I got before he said that was about $40.
The thing with pots is (your guy will confer) they are NOT close tolerance devices when you get the "affordable" ones. One guitar tech at The Gear Page told me that he buys Alpha and CTS pots 100 at a time, tests them all, and labels them, because unlike caps where you can easily get 1% tolerance, the pots are usually sold with 20% tolerance! So a 500K pot may actually test out at from 400K to 600k.
I didn't check specs on what you bought. But if this is the standard type alpha that we all use for pedals, amps etc. it's 20% tolerance.
Yep, that's the difference between the precision electronics and the alpha. 10% vs. 20%.
Bourns, btw, is 20%, and 1/2 watt. I think the reason my guy didn't recommend it is I needed a 1 watt or 2 watt, the alpha is 1 watt, the PE are 2 watt.
yeah, that's what I figured. Bourns higher end stereo pots are 1% plus the dual ganged volume controls are laser trimmed and gar-own-teed to be less than .1dB difference between left and right channels. I hadn't really looked at these type pots with them. I'll keep the precision ones in mind for this stuff.
Given that it's a reverb, I don't think it's the tolerance that matters, but I do think the wattage rating was important.