Adding tube reverb to a SS amp?

[MadMax]

I have a little 6W SS amp from the 70's that has the sweetest clean tones you could ask for. It has tremolo and reverb built in, but the reverb leaves a lot to be desired. The tank is tiny (maybe 6" x 1.5") and is mounted right inside the chassis. I'd like to build the reverb section from a Princeton and put a real tank in there. I have searched for schematics for my amp and had no luck yet. Is there a way to figure out where to take the signal from and where to put it back in. I'm thinking I can disconnect the original return at the reverb pot and route the new signal back to it. But how to figure out where to get the dry signal from?

The amp is a Unicord, Stage 25. I swear I would buy another one if I got the chance. They made bigger ones, but I haven't had a chance to hear any of them yet.

[sluckey]

You will need a suitable power transformer and B+ supply to power that tube reverb circuit. Makes more sense to me to just build a 6G15 reverb unit. Then you can use it with any amp.

[MadMax]

Hmm. Good input. I guess 120 VAC isn't going to power a tube reverb section. And I do have my eye on building a 6G15 reverb some time soon. Still that little Stage 25 is a great, portable practice amp so I really want better reverb built in it. Maybe the tiny tank is the real problem and I can just upgrade that and move it down into the cabinet.
When I get a minute I'll measure the resistance of the IN/OUT of the original tank. All I need do is match those, right?

BTW, have you heard one of these amps before? I got mine for $7. at a second-hand shop, and I wouldn't sell it for $100.

[John]

http://www.ebay.com/itm/Vintage-Unicord-STAGE-25-amplifier-w-Reverb-/251692870242?pt=LH_DefaultDomain_0&hash=item3a9a106a62


Looking at that picture, seems you could try getting a new tank from Accutronics as long as the impedance is the same. Or maybe Doug even sells one that fit?


Seems that they are well though of little amps, from just a bit of reading I skimmed. :)

[MadMax]

Yeah, that's the one. Here are a couple of pics of mine. I recovered it and put oxblood grill cloth on it, a leather handle, and wired in an LED to replace the broken lamp bezel. Oh, and I replaced the cheap 8" speaker with a new Celestion.

One day, I might try to trace the circuit board and clone that thing. The heart of it is a Toshiba Chip: TA7202P.

As I understand it, Unicord became Univox, which became the Vox we know today.

[John]

Not to go too far off topic.... I love my tube amps, and some of the SS amps I've had have been ... not junk, but not good sounding. But I've got a little Roland Cube I bought for $99 new, and it sounds swweeeettttt. And like I said, that Univox seems to be well regarded. I know eleventeen on here loves his Peavey ... shit, Valveking? or something like that. Says you can "buy 'em all day" for about a buckfifty.

[MadMax]

John, I have a Roland Micro Cube, in fact I have two of them. I had one at home when I got deployed to Iraq. When my wife shipped one of guitars over she couldn't locate my Roland, so she had the music store ship me a new one. When I got home, I hacked one up to get it into a nice little cabinet I had. I read that they are made to play through a full-range speaker so I replaced the little 4" speaker with a  6" x 9" 2-way Infinity speaker. Lots of neat tones in that thing, But as is the case with most modeling amps, I can't get a perfectly clean tone out of it.

When I get home tonight, I'll try to post a pic of that thing.
Is yours a micro, or one of the bigger ones?

[John]

IIRC, it's the bigger one. Has 1 speaker, I think they say it's a 5 watt. My buddy has it at his house playing his bass through it just for practice, very low volume. The micro has a couple tiny speakers, doesn't it?

[MadMax]

Here are a couple of pics of my Micro Cube Frankenstein. I literally had to cut the 90 degree chassis in half to make it fit flat in the rear of this cabinet. What do you think?

[HotBluePlates]

As I understand it, Unicord became Univox, which became the Vox we know today.

Umm, no. At least not the "... which became the Vox we know today."

Jennings Musical Industries (JMI) started building tube guitar amps in the late 50's, using the Vox name. I'm sketchy on the story now, but I believe Jennings owned a retail store and was branching out into manufacturing the instruments sold. No need to go into the full story, but JMI was ultimately sold to Korg which was also a Marshall distributor until 2010.

I'm not super-familiar with Unicord and Univox, but every one I've seen has been a transistor amp. Guess I should have looked at Wikipedia (though that can have errors due to crowd-sourced info). Unicord's distribution of Marshall, which Korg eventually bought, and the current ownership of the "British Vox" name by the same company seems to be the root of the confusion.

[MadMax]

So then if I understand it now... Unicord was the parent company under which Univox amps and later Stage amps were carried, and these never were in the British Vox lineage? Thanks for weighing in with that. Univox definitely made tube amps (combos and heads), there are some for sale on eBay now. Don't know if the Stage brand was ever into tubes, but the tone on mine doesn't leave me wishing it was.

[John]

Max, just now checking back in there. I like that shoehorn job on the cabinet!

[jojokeo]

If it were me I'd either use the Belton Brick for the reverb circuit and build it inside the amp area using lower DC voltage already available or simply making and/or buying a pedal which uses a simple circuit such as this one below. There's a good number of reverb circuits out there using these and they sound pretty good.
 

[MadMax]

I think that Belton Brick is a great idea. Thanks for posting, you may have resurrected my hopes for this project.