"Dongbiter" 30 pics online

[andrew]

Thanks Mark. My Hammond OT has the older style tap hookup where you have to rewire the all of the taps to get 16,8 or 4 ohms. If it is wired for the 8 ohms what NFB resistor value should be on the 8 ohm tap? Thanks for any help.

[M Fowler]

What Mark said.
Heres a secret, bass pot is 3M.......

Yeah that one throw me for a loop and now I have to find a 3M audio pot or is it a reverse audio pot?

Andrew you could use a 220k.

Mark

[Reeltarded]

3MRA?!!

OMG! Put a 1MA in backwards, and fly a 1M resistor off both ends!

[M Fowler]

I think I'm going to try a 1MA pot and get a 3MA ready to fly.

The only reason I was thinking 3MRA is because they are readily available and maybe this weird circuit was crazy enough to go in reverse.

Mark

[kwijabo]

because i was curious i simulated the filter in pspice. attached is a document with some screen shots.

EDIT: the first page shows 7 different values for the value of the bass pot that is in the circuit from 0-3Meg, keeping all other components the same.

EDIT: on the page that deals with C1, i have the red/blue curve values reversed. blue = 0.047uF, red = 0.022uF
the next pages show the bass pot set to 100k, then changing other values. the reason i set it there is because i found out as the pot value goes up, the effect the other components have on the filter becomes less. though now i'm saying that i think i didn't try changing the 33k/500p filter when the pot was 0 and 3Meg to see. something to try.

thoughts about the pot:
- as randalp3000 noted, i'd agree this is a larger value pot to give you more range. 3meg log pot would work nice.
- the way it is drawn up on the layout, if you were to turn the bass pot clockwise on the face of it (i would think that means you're turning up the bass = adding bass), the R value that is actually in the filter decreases. my plots show as the R value that is in the circuit goes up bass goes down. that would make me suspect it is not a reverse pot.

[kwijabo]

i don't see any 3Meg audio PEC pots? their website says they only have linear tapers above 1meg.

[Clyde]

But how does it sound?

[randalp3000]

I don't think the bass pot is a PEC

[passfan]

I am cobbing together a prototype for this circuit here. Iron is vintage Hammond from an E100 series. I am going to use a 6SL7 for the PI and a pair of 7591's for the power. B+ probably in the neighborhood of 400 volts or so. It should be interesting and I'll probably have it barking here within a week or so. Thanks to all here who have gone before me.

[randalp3000]

But how does it sound?

The first time I used it at a gig my impression was eh. My #1 amp is an original RX on the edge of breakup with a Cusack Screamer for dirt through a Gold in a custom Thiele 1x12 cab. The SW comes stock with sovtec 12ax7lp's which I think are ok for a PI if you can find a good one but I don't care for them in a v1 position. I threw a Eh in v1 that tested at 80-90% of spec of all tests on a Amplitrex which seems to have helped.

Last night at a gig I swapped to the SW for the last set and was quite surprised. The amp is ridiculously responsive where it's almost weird. I could get the volume up to 12:00 where it just started to breakup with a Dimarzio PAF. If you've played an amp without a tone stack that's what it sounds like eq wise. The difference between the two bright settings on the bright switch are very subtle, I think they're 200 + 250pf. The cleans sounded very nice, pretty flat without too much mid scoop with nice bottom and a bit of sparkle on top but not harsh. With the screamer it gets pretty gnarly, very fat with tons of harmonics and feeds back very easily. You can really hear the power section breaking up and for my taste I would have liked it to be a bit tighter on the bottom end. I would think with a SS recto it would stay tighter but the OP trans and choke seem a bit on the small size so maybe that could play a part in it.

It's an interesting amp, not sure yet if it will get my #1 spot. Sometimes I'm blown away by it and other times I wish I was using the RX or Zwreck. I'm ok with the ridiculous purchase because it only cost me 2 guitars and now it's out of my system. The build quality is very impressive but that shrink wrap is an annoyance.

hope this helps
rp

[Gaz]

The shrink wrap sure is annoying, isn't it? If I were you, I'd cut it all off

But seriously, randal, have you ever played an AC30 normal channel? I just wonder how it compares since they are so similar.

[M Fowler]

The bass pot must be 3m linear I do not see a regular audio pot beyond 1m.

Linear pots go up to 5m.

[randalp3000]

The shrink wrap sure is annoying, isn't it? If I were you, I'd cut it all off

But seriously, randal, have you ever played an AC30 normal channel? I just wonder how it compares since they are so similar.

no I have not, I would love to compare however.

[DocJames]

this pot looks about right.

http://www.intertexelectronics.com/Clar ... P9786.aspx

[andrew]

I must be doing something wrong because my SW build while smooth and feels good it is rather dull sounding. Even with the bass turned to less bass and the cut on full treble it has no clarity ( treble?) at all. I have a 2 meg bass pot in there now and any bass is too much. The cathode cap on V1 is 40uf. I am using a Dynaco 470 from Triode and a Moose PT. Would removing the NFB wake it up.
I built this from an existing Rocket build.
Any help please.
http://www.smcelectronics.com/pot.htm Here is a source for Allen Bradley 3 MEG linear pots for $2