Introducing the "Cream Pie" !

[JHS]

There are 3 common designs for a 1-trannie preamp, w voltage FB, current FB or voltage+current FB, that's why nearly every tranniestage look the same. A stable bias is good for a smooth sounding trannie, a looser bias for a stiff sounding trannie, all in all a matter of taste. 

JHS

[Dragonfly]

.....all in all a matter of taste. 

JHS

absolutely....if it sounds good, thats all that matters !

AC

[mac]

any chance you've tried 2 Cream Pies in series, one driving the other ?

Not exactly the Creamy but I'm working on a 3 stage design Rc=10k, Re=5K-A pot, Rb-gnd=100k, Rfeedback=47K+47K, 1nF and a parallel LED from the junction of the 47K to gnd in the second stage, only a 0.1uF between stages, in & out. Transistors are 2sd352 npn hfe: 65 leakage: 200uA. They are very very low freq power trannies that's why the second stage trick. But can try with 2n388 or 2sd72k.
It is on the breadboard now so I could quickly adapt it to 3 Creamy stages. I guess that 0.1uf and maybe a 10k between stages can work.


mac

[dosmun]

I built it today using HairyAndy's Vero layout.  The tranny needs to be reversed in the Vero layout.  I didn't get a chance to actually play it into my amp yet to give it a good run but the vero layout does work.

[Dragonfly]

I built it today using HairyAndy's Vero layout.  The tranny needs to be reversed in the Vero layout.  I didn't get a chance to actually play it into my amp yet to give it a good run but the vero layout does work.

i mentioned to him about the tranny the other day, so i'd imagine he'll get it changed when he has a chance....

theres also a vero layout in my gallery..

AC

[Dragonfly]

**********UPDATED VERO LAYOUT**********

This layout has the "gain pot" mod, as well as power supply filtering and reverse polarity protection...

Enjoy !

      AC

[Barcode80]

is there any rebiasing to be done if you use a Si tranny instead?

[Dragonfly]

is there any rebiasing to be done if you use a Si tranny instead?

i would imagine that you'll still be able to dial it in just fine with the trimmer...

[PNG123]

:s,
I was going to test  out the PNP version yesterday.

Could you do a PCB layout of the PCB of the Cream Pie VERSION 2 please ?

[hairyandy]

I built it today using HairyAndy's Vero layout.  The tranny needs to be reversed in the Vero layout.  I didn't get a chance to actually play it into my amp yet to give it a good run but the vero layout does work.

i mentioned to him about the tranny the other day, so i'd imagine he'll get it changed when he has a chance....

theres also a vero layout in my gallery..

AC

Yeah, sorry about that.  So much for attention to detail!  I normally label the trannys just so there's no confusion but I forgot this time.  I'll get to it eventually...

Andy

[markm]

This looks like it's developed into a heck of a little circuit 

[Dragonfly]

Here's a PCB layout for the "Cream Pie V2" !

CREAM PIE V2

have fun !

AC

[mac]

I just bradboarded the CP. Sounds nice from the start, the mids are just fine. Love it. I used 2sd352, ac187, 2sd72, 2n388 and neg gnd 2sb172 PNP. They all sound terrific.
Well done Dragonfly.

BTW, make place on the PCB layout for a 1k-A pot and a 22uF resistor to control gain and a spdt switch to connect a back to back pair of Ge diodes to gnd at the output   


mac

[Dragonfly]

I just bradboarded the CP. Sounds nice from the start, the mids are just fine. Love it. I used 2sd352, ac187, 2sd72, 2n388 and neg gnd 2sb172 PNP. They all sound terrific.
Well done Dragonfly.

glad ya like it !

BTW, make place on the PCB layout for a 1k-A pot and a 22uF resistor to control gain and a spdt switch to connect a back to back pair of Ge diodes to gnd at the output   


mac

the "Cream Pie V2" layout uses a 5k pot to ground ...i could possibly "add" a place for a cap as well....

as for the Ge diodes....could be interesting...you got soundclips ?

AC

[cab42]

I breadboarded the CB last night, and it sounds very good. I used a OC140/CV7112 It biased to app 4.5V at around 29K.

I havent measured my transistors so I have no idea of the hfe, so I'm planning to try a few. Does anyone have an idea how big the variation is?

Writing this I came to think of this post by Aron about the fact that OC140's are symmetrical. The red dot can be emitter or collector but with different gain. Another thing to play with. I also think I will try a 100K pot on the output.

http://www.diystompboxes.com/smfforum/index.php?topic=45124.msg329454#msg329454

Dragonfly, thanks for all your work.

Regards

Carsten

[MartyMart]

Carsten, I remember that thread, I've had great results using the OC140's with red dot as "emitter"
only to find that the dot means "collector" !!
Just shows you that the "symetrical" idea is true, mil spec and all

MM

[mac]

as for the Ge diodes....could be interesting...you got soundclips ?

I recorded with the built in mic of the computer... add mp3 conversion and just crap.
But I have something better... For those who want 2 slices of cream pies just out of the oven:

http://geocities.com/guitarfxs/images/cream_pies_1.gif

Just a demo but can be easily modded. Hope you like it.


mac

[markm]

My head is spinning!
There are so many designs coming out from this idea it's incredible.
I think Andy has created a Monster here!! 

[Dragonfly]

as for the Ge diodes....could be interesting...you got soundclips ?

I recorded with the built in mic of the computer... add mp3 conversion and just crap.
But I have something better... For those who want 2 slices of cream pies just out of the oven:

http://geocities.com/guitarfxs/images/cream_pies_1.gif

Just a demo but can be easily modded. Hope you like it.


mac

got the schemo...what about putting the SWTC in between stages ?

didnt get the demo yet... 

AC

[Dragonfly]

My head is spinning!
There are so many designs coming out from this idea it's incredible.
I think Andy has created a Monster here!! 

you''re right....i think i may have created a monster !  might be because, so far, it seems like this basic circuit works great with such a wide variety of transistors, is easily biased, works PNP or NPN, and sounds great with a  wide variety of amps/guitars....plus it seems like a great "building block" ....

hmmm..cream pie driving a mosfet stage anyone?

AC