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

[frequencycentral]

Hey Berger, the clips sounds really meaty and chunky, glad you got it built! I'd be interested to see your full schematic.

[Berger]

the funny deal is that I had my attenuator on so that was only half of the volume. I played it again this morning and it's even more meaty and chunky. BTW no tone control on it.
I'll try to get a schematic up for it. I made a diy layout for it as well.

I combined your charge pump on the board with the amp design. I believe I have the charge pump at ~90vdc with it being in the 80's while under load.

Glad you like it. I'm really glad I built it

I'll try to get you guys more info soon.

-Berger

[jacobyjd]

I dig the sound of that--I'll be looking forward to your schematic.

For anyone: where do you guys pick up those hefty power resistors? I generally get my stock from Futurlec/Pedalpartsplus/Smallbear, and I'd really only need to get the high-wattage resistors from a different vendor--I don't have any close-by electronics stores to go to, either--any ideas? Ebay maybe?

[Berger]

For the big power resistors, If I only need 1-10 I'll usually pick them up on ebay. I did that with the big resistors for the small pentodes that frequency central uses.

Otherwise I've always gotten them from mouser. When I built the Firefly amp I ordered extra 1/2watt 1watt resistors to same on costs...so I have some from there...but I need more

So...whats a good piece of software to draw up the schematic? like I said I have a layout, but I think it'd be easier to understand with a schematic..

-Berger

[jacobyjd]

ahh--ok, I refined my search terms a bit and found what I need on Ebay--yeah, 10 or so items is all I'd need-this would be a one-off thing for me

[Berger]

Ok I did this quick in ExpressSCH I believe it is correct. Let me know if you see anything.

The pentode is a 6ba5 it would also work with the 5639 but that has more current draw on the heaters. But they both sound good.

Keep the questions coming if you got them

-Berger



link to full size
http://farm3.static.flickr.com/2463/3620347202_71b0a9583c_b_d.jpg

[Berger]

I'm not getting much from the pots in terms of them changing much. it kinda goes from quiet to full on 
Any ideas on how to get more range from it?

-Berger

[Berger]

Actually I played with it again last night and the knobs work well, so I'd say use those values if you build it.
Oh and the b+ I'm using is between 80 and 90 vdc

-Berger

[MikeH]

Where have you guys found an 18ohm 2 watt resistor?  Mouser doesn't even carry them.

[Berger]

I used ebay
http://shop.ebay.com/items/?_nkw=18+ohm+2w&_sacat=0&_trksid=p3286.m270.l1313&_odkw=18ohm+2w&_osacat=0

that search turned up some. If you want I can lookup the seller I bought them from, I got 10 and it was pretty reasonable.

[frequencycentral]

Got mine from Banzai (Germany): http://www.banzaieffects.com/Royal-Ohm-2W-c-1129.html

[MikeH]

Any US suppliers that anyone knows of?

[frequencycentral]

Any US suppliers that anyone knows of?

You could use a 7806 voltage regulator instead.

[MikeH]

Yeah, I didn't know if that had been brought up in this long thread (which I have not completely read) but I was thinking regulation might be a better way to go anyway, especially if I was using a compact layout, and a smallish enclosure with the tubes inside.  I thought heat might become a problem.

[frequencycentral]

If you check my layout, the two voltage drop resistors sit between the two tubes, so if you have the tubes protruding from the enclosure like mine are, there's good ventilation to dissipate the heat.........and hot resistors do smell so good don't they!

[Berger]

I used the regulators in mine


I'm painting my enclosure at moment   

[bbmonster]

...


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?!

If you don't mind me asking, what are the dimensions to the pnp (lenght & width)? My image software is saying the print size is 16 inches by 9 inches, seems a bit too big.

Thanks.
-Bernard

[frequencycentral]

If you don't mind me asking, what are the dimensions to the pnp (lenght & width)? My image software is saying the print size is 16 inches by 9 inches, seems a bit too big.

Thanks.
-Bernard

John Lyons made me up some boards from the same files I posted here, their dimensions are 68mm x 35mm (2.677" x 1.378").

[bbmonster]

A few more questions if you don't mind again. What size enclosure did you use (metal one)? And in the previous posts looked like there was a build with a plastic enclosure, is there a difference in performance from the plastic to your metal enclosed one (noise wise)? Or enclosure material doesn't matter much for this small amp?

Thanks.
-Bernard

[frequencycentral]

A few more questions if you don't mind again. What size enclosure did you use (metal one)? And in the previous posts looked like there was a build with a plastic enclosure, is there a difference in performance from the plastic to your metal enclosed one (noise wise)? Or enclosure material doesn't matter much for this small amp?

Thanks.
-Bernard

The metal enclosure I used is an Eddystone (subsiduary of Hammond) 110mm x 60mm x 30mm. Is that a 1590B? There's no difference in performance with the plastic cased ones I made versus the metal cased ones. I'm much happier with the mateal case ones though - they look so cool, though it is a tight fit to squeeze everything in!