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

[Br4d13y]

do you think we could take this thing a step further and add multiple power amp stages too output more volume, but keep a smaller preamp section "ala" an orange?? just throwing some ideas out there

[frequencycentral]

Sounds like fun, it's something I've been meaning to try.

[Berger]

A lot of the designs I see are using pentodes for the power amp section. The firefly amp I have(ax84.com) uses a 12au7 for the power amp section. I'm thinking of breadboarding that up as well, to see how it sounds.

[frequencycentral]

I've had a number of requests for the layout I used. TBH, I was holding off as I planned to retire to the Bahamas on the strength of Murder One sales, but it looks as if i'll be luck to retire to S@#$%horpe. So here's the perf layout I used for the first few, and the PCB layout I'm now using. Both are obviously tailored to the enclosure layout I use, and also the size of the caps and the two voltage drop resistors, R4 and R5.





Here's the direct links to the files, as I think Photbucket might resize the PNP

http://dl.getdropbox.com/u/967492/MOperf.gif

http://dl.getdropbox.com/u/967492/MOpcb.gif

http://dl.getdropbox.com/u/967492/MOpnp.gif

Enjoy! It's good to share isn't it?!

[frequencycentral]

For anyone who wants a ready made PCB, I've passed the files to John Lyons, his work is very high quality, he can be contacted here:

Email: basicaudiowv@earthlink.net

PM: http://www.diystompboxes.com/smfforum/index.php?action=profile;u=1334

[Berger]

Thanks for making these available 

I'm working on perf now...just waiting for the transformer to show up, so I can finally test this thing!

-Berger

[Berger]

I tried hooking up my 5639 and I got a farty/slubby sound out of it.

Hi, you got it running with a 5672 first? How did it sound? The only info I have on the transformer is it's ratios. Did your 5639 amplify but sound farty? I would experiment with with grid 2 resistor (100 ohm in the schematic), try a 33K maybe. Also, you know the cathode resistor/cap you used in Pentaboost, are you doing the same with the amp with the 5639? try playing with those values too. I've tried many different amp ideas on the breadboard with the same transformer, impedence mismatch doesn't seem so crucial to me. Maybe we should discuss this in public on the thread for the benefit of others too......!

It sounds great with the 5672 in place. since its only 5 pins I've been keeping it in the breadboard, so I can go back and hook up to it to make sure things work ok, while trying to work with the 5639.

I'm using the same cathode resistor/cap as before. I've played with the resistor and it helps clena things up a bit, but at a big volume loss. I also changed the grid 2 resistor to a potentiometer and I experience the same deal, of cleanup but volume loss.
I did some reading after I posted and it suggested what you suggested above, of course it was bed time so I haven't gotten to play around with it any more.


Also did you ever experiment with a triode or a twin triode running parallel as the power section?

-Berger

[frequencycentral]

All I can suggest with the 5639 is just to play about with the cathode resistor/cap values, and the grid 2 value. It might be a trade off between good sound and volume. You might even try directly connecting grid 2 to B+ (is that called triode mode?), though generally it is desirable for the grid to be neagtive to the plate, ie, have a lower voltage presented to it. You could also try directly grounding the cathode. It's hard to harm these subminis, they were designed to stand up to massive abuse!

During Murder One's design I experimented with a parallel triode output section (google the Heavy Watter), and also a single ended arrangement using two 6111 similar to a Pepper Shredder ( http://www.tube-town.net/diy/lov/lov02-peppershredder-eng.html ), but using the final stage as a power amp. The parallel triodes didn't seem to add anything, and I found the sound sweeter and brighter using the 5672. Still worth experimenting with though, your experiences may vary from mine.

[Berger]

Thanks! From what I read last night, thats about all I can try at the moment. I'll see if I can play with it tonight, otherwise I won't till next monday(I'll be out of town) if anything that'll give me a lot of time to read up on the subjects.

I'll looked at both of those designs, i'll have to print them out so I can study them over the weekend.

I'll keep this thread posted with what I find out.

Thanks Again!

-Berger

[frequencycentral]

Cool. You probably already know Valve Wizard, but here it is anyway - a great resource for all things tube, and Merlin is such a nice guy too: http://www.freewebs.com/valvewizard/

[Berger]

I've been printing out the pages and reading them before bed. I've also been using aiken amps tech info pages http://aikenamps.com/TechInfo_2.htm
The combo of the two have really helped me understand whats going on.

Slowly but surely I'll get this stuff figured out.

Thanks!

-Berger


Edit: Just pulled up the heavy watter scheme, and it looks like something I really want to try. I'll have to play with the 12au7 "power amp" sometime. i've been looking for a schematic of a parallel single ended power amp stage and that is it! Thanks!

[frequencycentral]

Murder one featured in Guitar Buyer Magazine!

Well, not exactly featured, Murder One owner stereovoid says..........

...i did write a letter to Guitar Buyer about the interesting people i've met that are making interesting stuff...and they printed it!! its in this months mag, and there is a picture of it!

[Berger]

nice! Congrats!
I'm hopefully going to get time tonight, or next week to work on this some more.

-Aaron

[Berger]

Ok, got to play tonight!
I got it working with the 5639 tube. Normal connections but 1uf to 10uf cap on pin8 and a 1k resistor on pin 8. Changing the cap value changed some of the hum I was getting, and it seemed to affect the tone.
I was running the plate voltage at 60v, I'm sure I can push it farther, just need to make another power charger circuit.

I also change the preamp section to a pentaboost, I like it! I also tried some different triode tubes for the "power" section, Not so great sounds, I'm sure I need to do some biasing there.

I think I'll play with the preamp section, maybe throw a tonestack in there, and then mess with the tridoes for power.

Thanks for all your help!

[frequencycentral]

That's cool! One of my early versions of Murder One used a 5672 (ie Pentaboost) as the pre and another 5672 at the power amp, I found a daul triode preamp worked better for me. But you've got a 5639 as the power amp right? I have some 5840 which should be similar enough to the 5639 for me to try this.

If you have any 6112 in stock you can use that in place of the 6111 and add a tonestack without losing gain/volume. The 6112 has a gain of 70 compared to the 6111 gain of 20, so the tonestack losses will be made up for by the extra gain of the 6112.

[Berger]

I got to play around today.
I traded out the 5639 for a 6BA5 and I like it! It sounds the same but have a lot less current draw on the heaters.

I redid the preamp section as the heavywatter into the 6ba5. I like it! I used 6112s for the 12ax7s.
I tried a bmp tonestack and I was amazed how much of the volume, and thus distortion, was pulled out of the circuit...and it didn't make a good tone control either...I'll have to make something else up.

I'm going to see if I can read up on the heavywatter and see what changes I can make to it tone wise as well.

-Berger

[John Lyons]

Rick gave me the ok to make some boards for sale.
These are .06 thick, 2oz heavy copper.



$15 worldwide, postage included.
Just email me at: basicaudiowv AT earthlink.net
Paypal is best for me but a Money Order is fine.

John

[MicFarlow77]

Rick gave me the ok to make some boards for sale.
These are .06 thick, 2oz heavy copper.



$15 worldwide, postage included.
Just email me at: basicaudiowv AT earthlink.net
Paypal is best for me but a Money Order is fine.

John

John, your work is just plain awesome!!!!!!!

[John Lyons]

"I didn't ask for this gift, it was forced upon me..." 

Well maybe plain but I don't know about awesome.

Too kind!

john

[Berger]

I ended up going with the heavy watter with a pentode power amp section



here is a little clip of it too
http://www.youtube.com/watch?v=RBrWUla-QWM