Supro Dual Tone 1624T/6424 (sans trem)

[Loomer]

Having recently resurrected the thread about my AC15/Dual Lite/Matchless hybrid project, I decided that one is still open to some tinkering and, since I already own and AC4 and an AC30, building something simple, verbatim to a tried and tested layout and with a different sound signature to a Vox would make a better first build project. The Dual Tone has been on my radar for some time and I have gathered the parts to put one together, so why not?

I will be using Steve's layout here:https://sluckeyamps.com/supro/supro.htm

I'd like to keep things simple and, since I don't tend to use tremolo much, I might skip that, simplifying the project further. I've gone through the schematic and layout and it looks like I can keep to the layout 1:1 simply removing everything between the two 10uF filter caps, the pots and connections (ie to pin 3 of V1), though confirmation would be most welcome for this newbie budding amp builder here...!

Secondly (I know I said I'd stick to the plan, but...) I'm not keen to go down the juke box power tubes path, but instead of EL84 I'm looking to go 6V6 as the PT I have for this only supplies 2A for the heaters - see attached. I'd probably look to add a Fender-style 1.5k grid stopped on the socket. Speaking of the PT, while it's got 280 on tap rather than the full 320 I'll be going with a SS rectifier (+sag resistor, maybe) so voltages should remains close enough.

Old Supros that used two 6V6s in PP tended to go straight to ground from the cathodes, but I'm thinking that might be a bit much, and going 250R/25u effectively replicating the setup on the Tweed Deluxe should play nicer with the tubes while keeping wattage in check for the OT I'm planning to use, which is a Marshall 18w OT.

Supros seem to be known for having slightly undersized/small transformers which are said to contribute to the sound, something that's said of the 18 watters, so that should work well. Additionally, those OTs are often used with 6V6s in Plexi 6V6 builds.

Anything I'm overlooking or does it all look set and ready? 🤔

[bmccowan]

Did you intend to post a circuit schematic?
Should be a good project. I have built that amp without tremolo, both for 6973s (your jukebox tube - a great tube with a viable alternative tube; 6CZ5) and for 6V6s. Both sound good.

Old Supros that used two 6V6s in PP tended to go straight to ground from the cathodes, but I'm thinking that might be a bit much, and going 250R/25u effectively replicating the setup on the Tweed Deluxe

I'm not sure what you meant by this. Old 6V6 Supros and their other Valco variants were all cathode biased using either a 200R or 250R resister to ground. Some included bypass capacitors, typically 35uf, and some did not. It's interesting to try it both ways.
Search for Leon C on YouTube if you would like to hear several Valcos. And Leon is a great player.

[Loomer]

Did you intend to post a circuit schematic?
Should be a good project. I have built that amp without tremolo, both for 6973s (your jukebox tube - a great tube with a viable alternative tube; 6CZ5) and for 6V6s. Both sound good.

Schems and layout are over Steve’s website - didn’t want to repost here without his blessing not to draw away from his good work, but will put together a screenshot highlighting the elements I’m looking to take off the board for review 👍

Also, great to hear the 6V6 version has been done! I’m a bit skeptic about the “mojo” of vintage tubes and figured in a reasonably clean power amp another beam tetrode should do a pretty good job in replacing the 6973, especially since the EL84s which Steve has planned for in his project files would take filament draw over the 2A mark.

Out of curiosity, did you use a grid leak R at all out and what OT did you use?

I'm not sure what you meant by this. Old 6V6 Supros and their other Valco variants were all cathode biased using either a 200R or 250R resister to ground. Some included bypass capacitors, typically 35uf, and some did not. It's interesting to try it both ways.
Search for Leon C on YouTube if you would like to hear several Valcos. And Leon is a great player.

My bad, I’d trawled through some of those Supro/Valco schems and onky found one PP 6V6 with that setup, but might have gotten a bit lost there - those names are very confusing so I find myself going back and forth a lot!

Great to hear they biased pretty much as I’d planned to and using the unused pins on the sockets means no tweaking the layout.

I’d seen some of Leon’s demos, he sure seems to be the Valco scholar and his Valclones seem well loved by those who plugged into one.

These amps seem well love for their lovey cutting dimed tone and the Page connections is a big part of it but I’m actually really excited about the cleans/low gain tones, seems a slightly ragged and squished/hairy version of a Fender-ish clean halfway up the volume control. A new colour to my Vox only palette and one I can definitely see myself using!

[bmccowan]

No better schematics, layouts, and guidance than Sluckey's. He may not chime in as he has stepped away after many years of helping builders here - me included. His documentation is included in Doug's collection of schematics, so no issues with posting here.
I agree with your assessment of tone - and I think the circuit sounds fine with 6V6s. 6973s seem to need more volume to reach a sweet spot IMO.
Attached are a couple of Valco schematics that you might find helpful - you may already have them.

[Loomer]

No better schematics, layouts, and guidance than Sluckey's. He may not chime in as he has stepped away after many years of helping builders here - me included. His documentation is included in Doug's collection of schematics, so no issues with posting here.
I agree with your assessment of tone - and I think the circuit sounds fine with 6V6s. 6973s seem to need more volume to reach a sweet spot IMO.
Attached are a couple of Valco schematics that you might find helpful - you may already have them.

Thanks a lot for chiming in again! Steve/sluckey will certainly be missed, but you have to really credit his commitment and passion for helping others on here, a man of huge expertise and I have benefitted enormously from his suggestions, correction and replies both to mine and anyone else's interventions!

This is his layout along with the schematic while attached is my crudely highlighted plan of what to remove in order to make the amp without the trem - does everything check out?

I had made the assumption grid leak resistors might have been in order for the 6V6, mostly as they seem usually ubiquitous, but the schematics you attached seem to forgo them. The fact the 6973s need a bit more to shine could be an argument in favour of them, but if your build was without and all was well I might leave them out, knowing I can always install them on the socket base if need be.

I also see Steve used a post soldered to the back of a pot to tie up some connections but I might resort to a small tag strip like the one by V1 - not that it would make any difference.

This reasonably compact chassis from Modulus should lend itself very well to the cause, as will their blank 18w hole board (I count 24 rows needed for a very comfortable fit and that has 27, so some nice room to spare).

[SpeedTrip]

Any updates on the build. I've been thinking about using Steve/Sluckey's schematic with 6v6s so interested on your progress

[Loomer]

Any updates on the build. I've been thinking about using Steve/Sluckey's schematic with 6v6s so interested on your progress

Apologies, only just checked back here after the thread had gone quiet.

Will be ordering the extra parts in the coming couple of weeks or so after getting a lovely voucher for Modulus for christmas!

So this is not yet built, I will be checking and double checking that the tremolo part I'm omitting is correct, though the link to Steve's documentation and my image highlighting the section I would be removing are there for community-checking and commenting on should anyone see anything out of place. I will be having another look as mentioned and will be posting a layout hoping to get further feedback at that point!

[Loomer]

No better schematics, layouts, and guidance than Sluckey's.

And since we all agree on that I figured I'd reach for those to clarify my above post.

The way I'm looking at it is that by omitting the section which I've highlighted in Steve's schematic in the attached image I will have a perfectly working but trem-less version of this amp. I do not believe I'm mistaken there and Steve's drawing seems to support this, but I certainly would love some feedback on this and confirmation that I'm not going down the wrong path here!

I take it when you built your two trem-less versions that was how you went about it?

[SEL49]

The way I'm looking at it is that by omitting the section which I've highlighted in Steve's schematic in the attached image I will have a perfectly working but trem-less version of this amp.

That is correct.

[Loomer]

The way I'm looking at it is that by omitting the section which I've highlighted in Steve's schematic in the attached image I will have a perfectly working but trem-less version of this amp.

That is correct.

Thank you for chiming in! It seemed perfectly obvious, but as a newbie you can't have enough pairs of more experienced eyes going over your plans!

Off to work I go to get that layout drawn...!

[bmccowan]

Yup - looks good. Keep us posted on your build.
Speed Trip - It will be easy to amend for 6v6s using the schematic posted on 9/30. I think I have a .sch file for that amp with 6v6s if so, I'll attach.

[Loomer]

Yup - looks good. Keep us posted on your build.
Speed Trip - It will be easy to amend for 6v6s using the schematic posted on 9/30. I think I have a .sch file for that amp with 6v6s if so, I'll attach.

Thank you so much for chiming in!
Any chance of an exported version of the .sch file? I have no way of opening it and the Altium online viewer returns an error if I try using that.

[bmccowan]

Here you go - I posted the sch file in case someone wanted to load it into ExpressSCH

[SEL49]

Off to work I go to get that layout drawn...!

Did you see this...

     https://sluckeyamps.com/supro/Supro_no_trem.pdf

[Loomer]

Off to work I go to get that layout drawn...!

Did you see this...

     https://sluckeyamps.com/supro/Supro_no_trem.pdf

Ha wait when was that added? I feel like I've visited that page so many times and I never noticed it?!

Well now I know exactly what it is that I'm going to build...!

[SpeedTrip]

Many thanks for the 6v6 circuit with two stage tremolo circuit. I'm going to go down this route building the amp into an old CRATE vintage 30 combo unit.  Ill need to make a slight change as I fancy the dual tone version. Ill start a new post as when Ive got my thoughts together on how to use the crate transformer. 

[passaloutre]

I’m curious why you keep asking about grid leak resistors and omitting them. I’m not sure of any circuit which can omit the ground reference for the grid. If you mean grid stoppers, they are a cheap preventative measure against oscillation which has no effect on the sound of your amp.

[Willabe]

If you mean grid stoppers, they are a cheap preventative measure against oscillation which has no effect on the sound of your amp.

For the most part true.

But it can depend on the value and the tube.

[SpeedTrip]

I've started the post on my 6v6 possible build and it looks like Ill be going down the same road as Loomer with a transformer that sound as though its a very similar output. Ill be a bit behind but looks as the Modulus Amps will be getting some business from both of us!!