Submini Tube Amp Project (Edited w/ more questions)

[Kevin Mitchell]

I know it's not a stompbox so I'm sorry if this is irrelevant to the forum or if no one can relate to such a project.

I've edited this post after a night of long research. I've also noticed I've started a similar topic about a year ago that went absolutely nowhere. So if you've decided to check this one out I'm very grateful!

I was trying to figure out what tubes (from smallbear) would be good for a Superfly build. I eventually found an answer and have decided to make a few ebay purchases in the daze of midnight  -last night

So I have 2 packages coming in by the end of the month. A 10 pack of each - 6n16b and 6n17b which has been used in at least one successful Superfly Special build and are also a good choice according to information on THIS SITE ON SUBMINI TUBE SIMULATIONS Plus they're so much cheaper than tubes closer to home. I've also ordered a couple 6111W tubes if a higher voltage tube becomes ideal at the power section.

I'm still a noob... So I'm asking anyone reading who may have ideas to please review the link above and explain how one would connect a reverb tank and also explain the second (reverb) transformer in the schematics. Is it still part of the main transformer? (125A will be the case) I'd like to start by breadboarding the Superfly and then adding reverb. From there I'll mold it into a submini fender amp.

Here's the Superfly Special page if you've been missing out!
LINK

[Kevin Mitchell]

I've updated the above post. I hope someone is interested enough to comment or explain.

Rock on, guys. 

[Kipper4]

Way way way above my paygrade but good luck Kevin.

[Ripthorn]

Typically your reverb transformer is going to be an additional unit, not part of your output transformer.  You cannot isolate windings for two different purposes in your output tranny; the signals would interfere with each other and do bad things.  Also, I don't think the impedances would match well anyway.

[Kevin Mitchell]

Typically your reverb transformer is going to be an additional unit, not part of your output transformer.  You cannot isolate windings for two different purposes in your output tranny; the signals would interfere with each other and do bad things.  Also, I don't think the impedances would match well anyway.

Thank you for replying and clearing that up! Here's a quote on the power input of these transformers

The 230V B+ of the output stage can be combined with the 190V B+ of the reverb stage; on my prototypes these were fed from separate PS units and the two show up on the schematics

This is where I thought it was one of the same transformer. Though it is getting less power... I'm still confused. Any suggestions on a reverb transformer? Man... the bill only gets bigger... I wish the author of that page noted ideal transformer specs...

I was also confused on the power supplies for some of the schematics on that page. But now as I understand - there's 4-5 individual  power supplies (rather, 4-5 appropriate voltages) in two of the push-pull circuits.

I'm going to be buried in research for a while. Keep the info coming!

[Ripthorn]

As I recall, the 125A is an output transformer.  The voltage needed by both the OT and RT can indeed be supplied by the PT, but you will need to make sure you get the appropriate B+ on each. 

[Kevin Mitchell]

As I recall, the 125A is an output transformer.  The voltage needed by both the OT and RT can indeed be supplied by the PT, but you will need to make sure you get the appropriate B+ on each.

Of course! So if they can share the transformer could you or anyone who understands mark the pins of the trasformer in junction to the 125A schematic? It will certainly help me wrap my head around the schematic and some of it's workings.


I've only worked with small transformers for octave-fuzz effects.

If you look at the first three schematics you'll notice a "AC voltage source, (~)" symbol. I've never seen one before. My guess would be a fuse but I know nothing about this. Could someone elaborate on what this is? For what reason is it not in the last schematic with the Russian tubes?

[Ripthorn]

Your question is still a little vague, but here is an answer based on what I understand of your question:

After you rectify your AC and filter it, you have B+1, B+2, etc.  B+1 goes to the center tap of the primary side of your 125A.  You would need a separate B+, let's call it B+R for your reverb, that will be further filtered and will be lower voltage than B+1.  B+R will be fed to the one side of your reverb transformers primary, while the other primary is connected to the reverb tube's plate.  There is no direct connection between the 125A and the reverb transformer. Your amp will have a total of 3 transformers: power, reverb, and output.

The little squiggly symbol is usually a fuse.

[tonyharker]

The reverb transformer is used as the output transformer!  It happens to be a convenient transformer for this design. There is NO reverb tank in the design.

[Kevin Mitchell]

My apologies. I misunderstood. So I would indeed need a second transformer (one that isn't center tapped) for the reverb. The main power would be via SMPS as the Superfly is setup on.

If you could, please suggest a transformer that would be appropriate so I'm on the right track. Obviously it would have to take up to 190 volts on it's top primary connection (pin1?). I believe that another 125A would work just as well. But I'd rather find something better on my wallet for this one if possible...

Thank you for taking the time to answer my questions, Ripthorn. I really appreciate it.

The reverb transformer is used as the output transformer!  It happens to be a convenient transformer for this design. There is NO reverb tank in the design.

Wait, what? I thought that's what the E1 tank in the schematics were... Please explain.

How many transformers do I actually need w/ use of reverb? 

[Kevin Mitchell]

I see you viewing, thomasha!

Come on in! Help me understand if you could 

Your work on the Russian Superfly has fueled my ambitions!

[thomasha]

Hehe,
I was going to start posting my videos...

I think there is some confusion about which schematic you're using!

let me post this here>

[Kevin Mitchell]

Yes that is the most relevant one. I think it's based off the Murder One with tremolo and reverb added (my guess). Sure does resemble the Superfly in parts.

[thomasha]

I made a layout for this one (kind of, was a layout that could be used both for the superfly as for this one).

The feedback to the grid of the second triode didn't impress me, so I built a modified superfly in the end. The problem with my layout was noise near the first stage, and after that one I decide that it is easier to build the SMPS in a separate board and move it to a position that produces less noise.

back to your schematic, with the currents its easy to calculate the resistor between the high voltage stages. So you only need one HV source.

You're right about the reverb, it's quite a small SE amp inside the amp, with the signal modified by the springs that goes back and is mixed with the rest of the signal. So you will need the Hammond 125A PP transformer, the 3W version is OK, for the output stage, that goes connected to the speaker and the fender reverb transformer with 22,5k also called 22921 for the reverb.

I saw that you're thnking about the SMPS thing, but with the small amplifier and the reverb, I would expect a lot of heat, and your 12V wall wart would be > (4 tubes with 400 mA heaters, in series& parallel would need 800mA, and the SMPS with 230V 20mA with an efficiency of 70% would require more 600mA, 1400mA total, I would use my 2A one).

I'm guessing the current here, I modified the cathode resistor in my build and it is higher. While my superfly has no problem with heating, my jcm combo has...

Cheers,
Thomas

[Kevin Mitchell]

the fender reverb transformer with 22,5k also called 22921 for the reverb.

Woah there we go! Thank you kindly. At about $20 that's not so bad. Perhaps I can find something similar for less on mouser.
EDIT: Just noticed; that reverb transformer "22921" is the main transformer in the Murder One project.

Great suggestions! Keeping everything in mind for sure.

When your $60 amp idea is tossed out the window... Can't wait to start!
Happy DIYing! 

[danielzink]

All this talk about reverb transformers...

We need a layout for a Sub Mini Tube Reverb amp.

Using one of those small reverb tanks...ie: https://www.tubesandmore.com/products/P-RAMC2BF3

Unfortunately I don't know enough about tubes etc. to do it myself.

But would be neat.

[thomasha]

this one is a good one too>
https://www.tubesandmore.com/products/P-TF22921 for 14 bucks

and for the output stage you could use a 5w 100v line transformer, it's really cheap when compared to the 125a.

[Kevin Mitchell]

this one is a good one too>
https://www.tubesandmore.com/products/P-TF22921 for 14 bucks

and for the output stage you could use a 5w 100v line transformer, it's really cheap when compared to the 125a.

Sweet deal! Any suggestions on a particular output transformer with those specs? Looking into it myself I keep looking at more Hammonds... I'm not sure what you mean "100v line" as you put it. I know I'll need something that can handle up to 200 volts but I'm not sure what specs I should be looking at.

I'm obviously misunderstanding something 

[thomasha]

This> http://www.altronics.com.au/p/m1112-8-ohm-to-0.33w-5w-pa-speaker-transformer/

It's also known as PA transformer or 100v line matching transformer, there is also the 70v version, more common in the US that also works.

some theory > http://www.ozvalveamps.org/optrans.htm

http://home.alphalink.com.au/~cambie/6AN8amp/6an8amp.htm

and here:
http://www.diystompboxes.com/smfforum/index.php?topic=52385.0

and almost forgot the right connections! http://www.diystompboxes.com/smfforum/index.php?topic=52385.0

It's cheaper, but only works for PP because there's no gap, in SE there would be saturation...
I think that it is a good when I can't find the 125A transformer at a good price.

[Kevin Mitchell]

Great links! I actually recognize a couple from when I was researching last year. It's all a fuzz 

Great info on transformers. I will not be tampering with them (seen some transformer mods/tweaks)

I can't believe I missed this one. It's half the price of the 125A, for a Fender power amp and in stock on mouser.
Hammond 1750A

EDIT: Oops. Just realized it's the reverb tank transformer...

They also have the 1750H which is the Fender Reverb Amp transformer though it's 20watts - for the same price as the 125A.
Must not give in...