New Amplifier Design - "Murder One" - Submini Pentode, Low Voltage

[Ice-9]

Congrats, thats a really nice looking build. Now that its finished any chance of a few sound clips please.

[frequencycentral]

Thanks for the kind comments. 

The hum I mentioned - dodgy guitar lead - would you believe it?? I just was getting ready for a serious debug too! Darn it.

I'll get some clips together over the next week - got no microphone here at the moment.

[svstee]

So I', assuming you used perfboard? How did that work out?

[Renegadrian]

Rick you're the man...God what a nice enclosure and a good amp you made...

[frequencycentral]

Murder in the dark:

[Darkness, Darkness]

Nice creation !! Congratulations !

[Ripthorn]

What kind of transformer did you use?  If you already mentioned it, then I must have missed it, but I don't think I saw it.

[frequencycentral]

What kind of transformer did you use?  If you already mentioned it, then I must have missed it, but I don't think I saw it.

Its on the schematic - fender reverb transformer #22921, 22500ohm/8ohm. Mine is a clone, not fender, but same spec.

[Ripthorn]

Ha! I totally missed it.  Sorry for the dumb question.

[DiamondDog]

Though it has some hum that isn't there on the version on my breadboard - strange, I would expect the breadboard version to be noisier.

The trafo position and angle look sub-optimal to me. There's a reason valve amps have a lot of space in them. 

[~arph]

Where are all the diodes 

[frequencycentral]

Though it has some hum that isn't there on the version on my breadboard - strange, I would expect the breadboard version to be noisier.

The trafo position and angle look sub-optimal to me. There's a reason valve amps have a lot of space in them. 

The hum was a dodgy guitar lead - is quiet as a mouse now. 

Where are all the diodes 

They are on the underside of the perf, 'surface mounted' between the legs of the caps. 1n4148 are so small, it was the logical thing to do - and saved some space. 

[jacobyjd]

Rick (or anyone),

This amp design has caught my interest, but I'm a noob to the amp-building scene--where are the speaker connections located in the schematic?

My best guess would be that it goes on the leads of the transformer, but I'd want to be sure before building

[frequencycentral]

Rick (or anyone),

This amp design has caught my interest, but I'm a noob to the amp-building scene--where are the speaker connections located in the schematic?

My best guess would be that it goes on the leads of the transformer, but I'd want to be sure before building

Oh yeah sorry. The fender reverb transformer has four wires coming out of it:

Two are for the primary winding - these go to the 5672's plate and B+, as shown in the schematic. I connected the 0 ohm to the plate and the 22500 ohm to B+

Two are the for the secondary winding - these go to the speaker. I connected the 0 ohm to ground and the 8 ohm to the speaker.

This was my first tube amp build too - first time I've used an output transformer too, so I'm assuming I got the poliarity of the transformer correct. Hey, it works!

[jacobyjd]

Ok, thanks--I figured that's how it would go--but transformers are a little confusing to me sometimes, with all their taps and whatnot.

I have a larger trans from an old Bose powered speaker amp lying around...I may see if the specs are anywhere close to that. If not, I might put a Fender reverb trans on order

Have you thought about posting some clips?

[frequencycentral]

Have you thought about posting some clips?

Yes, I will post some clips, I just haven't got access to a mic until the end of the week. What I can tell you is:

- the clean sound is pretty quiet (as stated in an earlier post)

- with gain all the way up it's loud and raunchy.

- with a high gain pedal before it (I use my Valvecaster) it feeds back and sustains forever.

[jacobyjd]

cool, thanks

[frequencycentral]

cool, thanks

No problem. I should say that my design concept was to make a 12 volt tube amp where I could turn everything up full to get that sound that I would get if I dared to turn my 60 watt tube amp up full. Massive crunch, but reasonably eardrum and neighbour friendly. Hopefully I'll be able to plug it into a 4x12, mic it up, and it will sound like a huge stack going at full pelt. Good for home recording.

I'm planning another submini tube amp which should be much louder, so the clean sound will be more meaningful. Two 7327 submini dual triodes, 12 volt supply using a 555 switch mode to get 100's of volts, push/pull, Hammond 125a O/T. But that's a while away yet.......

[jacobyjd]

Yeah, cranked-amp at suitable recording levels is what I'm after as well--I can get plenty of clean headroom elsewhere 

[Ripthorn]

So Rick, are you using the switching supply schem from the JJS place?