Submini Tube Reverb request

[danielzink]

Sorry I've been putting this off for a million years But i finally started on it today, so I'll keep you posted as progress is made.

Patiently waiting

[danielzink]

Checking in

[vigilante397]

Crap, I kind of dropped the ball on this one I got the schematic imported in, but there was a weird pin discrepency between the 6V6 and the 6P30, so I started working on other projects and completely forgot to come back to this one I'll pull the schematic back up and today and see how doable it looks.

[Greenwichpaul]

Definitely interested in updates!

[danielzink]

Checking in again !

[tubegeek]

So - you're putting together a 6G15-style circuit, and that includes a transformer feeding the reverb tank. Seems like the submini tubes are the least of your worries as far as size & weight - although the ender reverb transformer is not particularly large, it's still a transformer.

Meanwhile the consensus I've seen - Rod Elliott, for example, and I think MerlinB is also of this opinion - is that the benefits of current drive to a reverb tank are pretty dramatic soundwise, getting you over and above the Fender Reverb Unit's sound in a fairly dramatic way.

I'm not one to discourage the building of tube equipment by any means, I just wonder if this is a bit of a crazy idea.

And again, nothing against crazy ideas, either.

[vigilante397]

I never completely forget about this, but it's never on the top of my list until it gets brought up again

So the big snag I've hit is with the pentode. In doing some digging I don't really like the differences between the 6P30 and 6V6, to the point I'm not sure the 6P30 would work.

That being said I looked around at other tube-driven spring reverb units, are you familiar with The Wave? It's said to be based on the 6G15 tonally, but it uses 3x 12AX7 and 1x 12AT7 for tubes, which would make it easier to just drop in a quartet of 6N21B. Still uses the same reverb transformer so the same tank should work, but would be way easier to design. Thoughts?

[tubegeek]

It's said to be based on the 6G15 tonally, but it uses 3x 12AX7 and 1x 12AT7 for tubes, which would make it easier to just drop in a quartet of 6N21B. Still uses the same reverb transformer so the same tank should work, but would be way easier to design. Thoughts?

I was wondering what your choice would be for the reverb driver if you were using a Rooskie subminiature tube.

12AT7 (both halves paralleled) is typical for driving the reverb transformer in many Fender amps. I don't ...think... the 6G15 used any different transformer with the pentode but I could be wrong for sure. The 12AT7 circuit always uses a little single-ended 8-ohm-out output transformer such as would be used in a small radio set, I've used it to make a little single-ended power amp. It's not nearly as good for speaker service as the Hammond SE125 series, even the smallest one ("C" I think?), but it'd probably be actually BETTER as a reverb driver with the limited bandwidth.

I might have one of those transformers kicking around here somewhere....

[vigilante397]

I'm planning to use a 6N21B as a reverb driver as well. It's gain factor is closer to a 12AX7, but plate current is spot on with 12AT7, which in my understanding is more important.

I think you're right, I think they use the same transformer with 12AT7 and 6V6.

[PRR]

> I don't ...think... the 6G15 used any different transformer with the pentode but I could be wrong for sure. The 12AT7 circuit always uses a little single-ended 8-ohm-out output transformer

The 6G15 uses a 6F6-market ~~3W ~~7k home radio transformer. A Champ OT is "too much" but is a common alternative since all the radio-spares got dumped decades ago.

The onboard 12AT7 plan uses a ~~1W 15k-22k communication radio transformer. (Low power in a high performance 250+V radio getting nasty speech+static sounds you don't want as loud as good music.)

[vigilante397]

Brief update:

I've got the schematic done and I'm starting on the board layout. My plan is to have the circuit in a 1590BB with RCA jacks on the top that will run out to the tank. I like to mount tubes flat against the board so they can be protected inside the enclosure, but they could also be mounted vertically and stick out the top of the box. I'm planning to run the whole thing off a 12V power supply, and it should draw a little less than 1A I think.

I'm hoping to get the layout done tonight as I already have a large PCB order ready to go, so if I can throw this on it will only be another $2 for 5 boards and I can save on shipping. That would get me boards late next week or early the week after, and I can get them soldered up and tested and post results on here. It's finally happening!

This is a 3D view of how the larger components will sit on the board:

[vigilante397]

I went so long without giving any updates on this thread that I don't even feel bad doing multiple updates in one night

So I finished placing all the components on the board, all that's left is routing. Placement is always the hard part, because good placement makes routing easy, whereas careless placement makes routing difficult and sometimes impossible. So I'm getting ready to start routing, should be able to finish tonight. I moved things around a bunch while I was placing components, so now mounting the tubes vertical isn't really a convenient option, but it was worth it for placement's sake. So unless something goes wrong during routing this is basically what top and bottom of the board will look like:

[vigilante397]

Well that wasn't too bad. Just finished routing. I need to make a few tweaks on one of my other boards, but I expect to send the PCB order out tomorrow and get it back in a week or so. This is how it ended up:

[imJonWain]

Cool project!  I just sent off a bunch of stuff this morning and kept adding random boards because it saves so much on shipping lol...

off topic but I'm curious.  Do you do your own panels or do you just let them do it and who do you use for fab?

[danielzink]

This....

Is awesome.

Can't wait for the boards to get in and you start testing.

What tubes did you end up using ?

Count me in for a couple boards as soon as it's verified.


I've kept this tank in my bookmarks for a couple years now:

https://www.tubesandmore.com/products/reverb-tank-accutronics-amc2bf-2-spring

If the board will fit in a 1590BB...

We could truly have a tube spring reverb that would fit in a package smaller than a shoebox....

Thanks again !

Dan

[vigilante397]

Cool project!  I just sent off a bunch of stuff this morning and kept adding random boards because it saves so much on shipping lol...

off topic but I'm curious.  Do you do your own panels or do you just let them do it and who do you use for fab?

Yup, I usually don't order PCBs unless I need at least 4 designs. I use JLCPCB, and I let them do panelization for me. The exception being SMD stencils, which I "panelize" myself to save money.

I ended up using 6N21B for all 4 tubes. I only ordered 5 PCBs for now since this is a "version 0" untested design, but I only plan on building one so I can sell the other boards if this version works right away.

[danielzink]

Cool project!  I just sent off a bunch of stuff this morning and kept adding random boards because it saves so much on shipping lol...

off topic but I'm curious.  Do you do your own panels or do you just let them do it and who do you use for fab?

Yup, I usually don't order PCBs unless I need at least 4 designs. I use JLCPCB, and I let them do panelization for me. The exception being SMD stencils, which I "panelize" myself to save money.

I ended up using 6N21B for all 4 tubes. I only ordered 5 PCBs for now since this is a "version 0" untested design, but I only plan on building one so I can sell the other boards if this version works right away.

I'm in for (2) of whatever version works

[vigilante397]

Brief update: my PCB order that has this board has 9 PCB designs and 2 SMD stencils, so it took a bit to get everything done, but I've been informed that production is finished for everything, and it's now pending carrier pickup. I paid extra for DHL express shipping, so I'll probably have these boards early next week. My Tayda order showed up yesterday and my Smallbear order will be here saturday, so I should be ready to put everything together when it gets here.

[Ben N]

I wonder if 6N16b might not work for this. (God knows they aren't much good for anything else.)

[vigilante397]

I wonder if 6N16b might not work for this. (God knows they aren't much good for anything else.)

I'm afraid probably not, which is a shame because I still have a few dozen They're just not ballsy enough to drive a reverb tank, it would be like trying to use a 12AU7 in your amp.

That being said my digital tube reverb uses a 6N16B to drive a Belton brick, and that sounded pretty good. They're not a bad sounding tube for clean usage, but they're complete garbage if you overdrive them.