freestompboxes.org

Any bought this? Sounds like a great pedal, check here:

The opening to that demo sounds really good! I would like to have heard the full gain range on the demo rather than just %50 and full.

I would definately be interested in trying to get this one breadboarded.

Great sounding demo. I have no idea what's inside, but I'd bet that if you broke out the hidden TMB tonestack of a BD-2, you'd get something very much like this.

In the YouTube video posed above at 47 seconds there is a gut shot of the pcb, transistors resistors and caps, no sign of any opamps, can't see if there are any components on the other side of the pcb. You may find the tone stack is more like a twin 'Blackface amp' . tempted to buy one but £185 seems a bit strong. I know Brians stuff is good though.

Well, as I said, I have no idea how Brian went about it, and I'm sure there's more than one way to skin the cat. BUT the heart of the BD-2 is a pair of discrete opamps--not ICs; and a tone stack taken right out of a Fender. Not surprisingly, the BD-2 sounds a bit like an overdriven blackface amp straight out of the box. This is something I'm sure Brian is plenty familiar with.

Sorry Ben I had forgot the topology of the BD2 and that it has a fenderish tone shaping section in there (control less). The BD2 tonestack is way simplified having a single tone control and it would be interesting to see if Brian has gone down the route of building a discrete op-amp stage or two.

Never mind. Only 3 trannies in that gutshot, and they are pretty far apart for a discrete op amp.

Gut shot taken from the video:

Thanks for the nice cap. 2x-sided board, though, so not much we can make of it. Except baseless speculation, which is always fun, so: Double Fetzer valve + tone stack + mosfet output stage, a la ROG? Nah, no trimpots. Then again: download/file.php?id=13073&mode=view.

Ben N wrote:Thanks for the nice cap. 2x-sided board, though, so not much we can make of it. Except baseless speculation, which is always fun, so: Double Fetzer valve + tone stack + mosfet output stage, a la ROG? Nah, no trimpots. Then again: download/file.php?id=13073&mode=view.

Ohhh, I love random guessing. I'll say 4 jfet stages (I'd take a guess at MPF102 fets due to their high pinch off voltage and generally clearer tone) with a gain stage and buffer stage running into the tone stack and gain control after the first stage, then two clipping stages and a volume control, the gain boost will switch in a couple of large caps over the source resistors of the last two clipping stages.. I'm pretty sure that's wrong straight away as all the Jfet stages look like they are gain stages and not buffers but it's fun to pretend...

It probably follows wamplers other ampish designs. matched JFETs, ROG style.

Ben N wrote:Nah, no trimpots.

But the drain and source resistors that must be in those "3 banks of 6" probably are the same or similar. I like how there are basically what look like test points for confirming 4.5VDC next to Q2, Q3, & Q4, along with a convenient place to drop in a probe to ground.

Q2/3/4 also appear to have small value caps to probably bleed off some high end, unless they are "peaking circuits."

Kind of interesting. A boatload of caps for just 3 transistors (with Q1 being my guess is an input buffer).

I guess those are J201.Brian is pretty consistent in choosing parts.

It sounds quite open, bright and dynamic for J201s, but you could well be correct.

it's pretty straight forward. jfet gain stages, j201 because I like how they sound most of the time. All of them sorted so we can use specific drain resistors. There's no magic, no voodoo.. just a circuit that I tweaked and tweaked on until it sounded as close to a twin as I could get it.

indyguitarist wrote:it's pretty straight forward. jfet gain stages, j201 because I like how they sound most of the time. All of them sorted so we can use specific drain resistors. There's no magic, no voodoo.. just a circuit that I tweaked and tweaked on until it sounded as close to a twin as I could get it.

Ahhh, so the J201 does return! Chhheeeeers Brian, it does sound pretty good. If you don't mind me asking how many Jfets don't make the grade sorting wise? I found that when I started sorting jfets around about 50% didn't meet my tolerance levels...

indyguitarist wrote:it's pretty straight forward. jfet gain stages, j201 because I like how they sound most of the time. All of them sorted so we can use specific drain resistors. There's no magic, no voodoo.. just a circuit that I tweaked and tweaked on until it sounded as close to a twin as I could get it.

Thanks, Nice bit of insight to the balck 65 design.

woohoo! my vague guess was right! I'd still like to see what kind filtering is goin on here.

briggs wrote:I found that when I started sorting jfets around about 50% didn't meet my tolerance levels...

I seem to remember Brian Marshall going thru all of that with the Liquid Sunshine, until he finally found a source (or sorting method) for consistent ones. But in that case, they are 2N5458's, right?

I personally don't care for doinking around with j201's because of the sorting part, even though they could all probably be sub-grouped for different projects.

But a tip of the hat to those who DO take the time to sort those things. I wonder how it ranks compared to picking fly shit out of pepper with boxing gloves on?