New ZVex '59 Sound

[MarkL]

So from what I've seen and heard, I'm liking the new ZVex dirtbox that remulates the '59 Bassman tone.  In the video demos, Vex suggests that the topology of the circuit would be very similar to the Box of Rock -- anybody have a guess as to what components would be altered or removed/added in order to get the circuit to behave more like a driven Fender Tweed?  I wonder if it's as simple as that, or if there are some additional maneuvers involved in the production of this device that the BOR didn't have.

[Betty Wont]

Check out the pedalpcb.com Tweed Sound.

[somnif]

I always chuckle at how recursive Zach's designs are. The Box of Rock is a Distortron with a SHO jammed onto the output. The Distortron is essentially 3 cascaded SHOs with some tone shaping.

I swear that man just wants to corner the worlds markets on overpriced BS170 boxes in the form of pretty stompable art pieces.

[somnif]

Check out the pedalpcb.com Tweed Sound.

So based on that, the differences would be the coupling cap between the first two MOSFETs, the gain on the second MOSFET, the coupling cap between the second and 3rd MOSFET, the tone cap, and the PedalPCB board doesn't include the final "Boost" SHO shoved on the end. So.... yeah, not a whole hell of a lot. (Oh also the Drain-gate resistor on the 3rd FET is different)

I also think there is a typo in the BOM/on the board, as it lists the gain resistor on the 3rd BS170 as "358". Its 330 ohm in the Box o' Rock, so I'm not sure if thats meant to be 358 ohm (random?) or just a mis-typed value. And the D-G resistor on the third BS170 is "521k", another strange value.

edit: missed a thing

[somnif]

If one did want to add the "boost" function they could get a little SHO board, perf board or something like Rullywow's "back-of-a-pot" sized affair from OSHPark, and wire the output of the main board to a switch to the input of the SHO to output. Pot layout would be a bit janky, but its an easy enough mod.

https://oshpark.com/shared_projects/nsJTeQK0 the SHO board I mentioned. Something like 3$ for 3 of them.

[MarkL]

I just looked at the pedalPCB project.  The changes are SO slight.  I mean, I figured there'd be some minor changes but THAT minor? 

Yet still, the effect is very nice.  It's a very pleasing sound and determining which components to change to get it probably took some time and strategy.

The switch of R11 from 1M to 521K I am assuming creates some asymmetry in the third MOSFET, am I correct?

Do you think that the TYPE of caps in this circuit might make an audible difference?  That is, multilayer ceramic vs. WIMA or Poly, etc., in specific places?

[BuGG]

I also think there is a typo in the BOM/on the board, as it lists the gain resistor on the 3rd BS170 as "358".

That's weird as hell isnt it?   It's been a few months since I traced that one so I must admit I can't remember, but I have those values notated in more than one place so I swear that must have been correct.   I wish I could find the pics of the board but they're apparently long gone.

Personally I just used a 360 ohm and 510K ...    It's a great sounding pedal.   Not sure it's worlds apart from a BoR, but that was a great sounding pedal too.   

[somnif]

I also think there is a typo in the BOM/on the board, as it lists the gain resistor on the 3rd BS170 as "358".

That's weird as hell isnt it?   It's been a few months since I traced that one so I must admit I can't remember, but I have those values notated in more than one place so I swear that must have been correct.   I wish I could find the pics of the board but they're apparently long gone.

Personally I just used a 360 ohm and 510K ...    It's a great sounding pedal.   Not sure it's worlds apart from a BoR, but that was a great sounding pedal too.   

I wonder if the board was gooped and the 358/521k were the values measured off the parts themselves.

That said, I can almost picture Mr. Vex ordering up a few thousand custom tolerance resistors in those values, all in his maniacal battle against the DIY scene. "Muahaha, those exact values are essential for the tone! Take THAT you scallywags!  /thunder /lightning /lawyers"

[thesmokingman]

when you consider that the BoR has been out a very long time in the diy community(also the SHO, super duper, etc) it is almost a shame that zvex ended up being the one to come back around with a massaged version ... especially since a number of the bsiab ii mods would be applicable to the BoR. may have to revisit this one ...

[MarkL]

"Thunder/Lightning/Lawyers" -- a little known B-side by Warren Zevon...