Project: Low Watt With Reverb

For me the added stuff wasnt worth the hassle on such a small amp when there are so many good verb pedals out there.
Cabinet finish options are endless. Heres a tweed princeton with no tweed....

 

That's what I concluded too. I was going to put reverb & trem into the empty area in my Plexi-6V6 chassis but since I didn't originally plan for that the extra wiring next to the power section would have been a noisy nightmare. I bought a Strymon Flint instead and I'm very happy with it. The faceplate covered the extra holes.

 

A good number of people have put a 1-tube reverb into a Princeton and it probably costs good amount less than a Strymon Flint.

My next project is a Deluxe Micro with 1-tube reverb. I have a backup in the form of tube-town's LND reverb too. Most of the cost, obviously, is in the reverb spring, so it doesn't hurt the wallet too much to find a few bits and experiment

I haven't tried this, but this is Tubenit, from the el34 forum, with a suggestion for a 1-tube reverb in that circuit.

 

The one-tube circuit as a drop-in reverb is limited in that you can only do so much wet/dry mixing without going the Fender route -- which is to attenuate a majority of the dry signal in the mixing stage, then recover the losses in a following stage.

To this effect I now consider the Fender reverb a 2-tube reverb because it won't work without the recovery stage. Also FYI you don't really need parallel 12AT7 driver, a single triode is fine. The 12DW7 is probably the ideal tube for the 1-tube reverb.

Sorry for the unsolicited brain dump on that but I recently got done with several iterations of revision to the 1-tube reverb trying to achieve Fender-style amounts of reverb and I wish the info out there had a better disclaimer as to its inherent limitations and how it actually performs. It's still a nice reverb but even on 10 I could never say it's too much and probably not enough for many folks.

 

You'd be switching between a lossy and non-lossy tone control, therefore there is a big gain boost in the tweed/champ style mode. Just something to think about, it would be cool but know it's way more than an frequency response adjustment.

 

Awww sorry to hear the little 1 tube reverb with a 12DW7 doesn't add much reverb to the sound... I was thinking of trying it in a PP6V6 build. Might have to go the traditional transformer style.

The single tube 12DW7 reverb I was thinking of trying doesn't use a transformer.. similar to an old Ampeg style.

 

Ah, good info, do you have a thread on that?

 

The 1-tube reverb still uses a transformer. It's very similar to the Fender circuit in many ways. But the mixing/recovery is where things get different. You could say it's more about the implementation of the reverb circuit than the circuit itself.

 

No but if you started one I would surely jump in to add my 2 cents, and would be super curious to hear other folk's take on the matter as well.

 

@jchabalk,

Here is a one-tube reverb that I designed and use with success on several of my compact amps :



The reverb transformer can indeed be a regular 022921 Fender one. IIRC the reverb unit is a 8AB3C1B from Belton-Accutronics, fully damped in a bag and shielded. But as you can see, the following gain stage must offer a recovery gain of 5.05/0.651 = 7.75 to retrieve the initial input voltage.

The amp below is an example of implementation of that single tube reverb circuit :



It's a compact amp but not a low watt though : 23WRMS clean tone on a 8" 100W Eminence speaker. Size comparison with a SF PR :



That said, the reverb circuit is of course convenient for a low watt amp, just assuming you can provide the recovery gain of circa 7.8 .

-tbln

 

I‘ve built a parallel SE 6V6 amp with full Fender style reverb and TMB where the middle pot also acts as a raw control where you can gradually take out the tonestack and get less gain loss and more tweed style tones which I really like. It makes it a very flexible amp and I think it could be more useful and less complicated than a switch and two seperate tonestacks.

For home volumes you could also use only one 6V6...nice cabinet by the way!

 

I’ve built 4 amps with the Tubenit 1-tube reverb. Not quite capable of Dick Dale but generally more than you ever really need (usually sitting at 3 or 4 on the reverb dial).

 

Which 4 preamps were in play?

It may have much to do with how much signal is passed to the reverb circuit, less dry signal means higher wet mix potential.

I had better luck with it on an 18W circuit for example, than D-style circuits.

 

How do you find the tube-town reverb?

I am in hurry-up-and-get-stuff-done-outside-before-the-white-stuff-arrives mode so I have not tried this yet. I want to make an add-on for a normal Champ with a single preamp tube. I have mid impedance tanks so low voltage seems to be the way to go with them. That can be high voltage for others if need be. The way out there part is taking the reverb signal from the grid of the second triode and the return signal from the tank sent to the cathode of the triode. I figure if temolo or NFB can be sent to the cathode circuit why not the reverb? It may require a cathode follower, or a mosfet source follower instead for less power requirements.

The upside would be people being able to add reverb to their BF or Tweed amps with no modification other than soldering in a send line and a return. A SS circuit with adapter and tank might be a way to go with a reverb control on the back of the cab rather than drilling a hole in the amp. Anyway that is the concept. Will it give enough reverb? I do not see why not, but until I get around to doing it I can't say for sure.

 

It's a back up for my Deluxe Micro, which I'm not near to starting yet (unless there's another lockdown) ; I'm going to build the board with space and power supply for a 1-tube and might well try with both that and the tube-town.

Reports on the tube-town are very limited; compared to the Surfy-verb, though, you can use it at line level and it only cost $15 or so - transformer and tank will work with either, hopefully.

 

there is a tube-town forum with some posts about the LND reverb. Posts are mostly in German, but nothing google translate couldn't fix ...

Edit: typos...