Darkglass - Vintage Microtubes  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.

Re: Darkglass - Vintage Microtubes

Postby johnk » 12 Apr 2017, 05:05

i drew up an etchable pcb for it, but i want to test it first before i post it, but i'm pretty sure that i got it right.
i used own the original and i remember well how it sounded so i should be able to tell if it sounds like the orig.
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Re: Darkglass - Vintage Microtubes

Postby johnk » 13 Apr 2017, 00:37

okay. i built and tested it and it works perfect except the 'era' control is nowhere near as effective as on the original. IMO, there must be something amiss in the schematic.
i i tried it both ways as per these schematics and neither way is like the original pedal.:
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Re: Darkglass - Vintage Microtubes

Postby johnk » 13 Apr 2017, 07:00

hmmmm. Darkglass describes that the era interacts with the Drive knob to shape the character of the pedal, but i don't really see how it can, being that it's located post the drive/distortion part of the circuit as per the posted schematic.
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Re: Darkglass - Vintage Microtubes

Postby Frank_NH » 13 Apr 2017, 18:01

johnk wrote:hmmmm. Darkglass describes that the era interacts with the Drive knob to shape the character of the pedal, but i don't really see how it can, being that it's located post the drive/distortion part of the circuit as per the posted schematic.


Just perusing this on my lunch hour. It looks to me that the Era control is just a variation on the BMP tone control. But...it's missing a resistor to ground at the junction of lug 3 and C21 in the first schematic. That resistor would form a HPF with the 1 nF cap when the Era control was all the way up. I don't know if there is a gut shot somewhere, but you could look for a resistor near the 1 nF. Otherwise experiment (start with something like 100K to ground, and go up from there to retain more lows).

The last two op amps are Sallen-Key filters to chop off the high end somewhat, probably a good thing since this is being used for bass...
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Re: Darkglass - Vintage Microtubes

Postby johnk » 13 Apr 2017, 18:10

yeah, i was going to try adding a resistor to it.
i also just ordered a GUMA antique overdrive which is supposed to be an accurate clone of the VMT and i intend to trace it to see if it matches the posted schematics.
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Re: Darkglass - Vintage Microtubes

Postby Silver Blues » 13 Apr 2017, 18:17

It was actually from pictures of that board that I determined the missing capacitor values. I was just looking at it again to see if I could figure out the connectivity, but there's only so much I can do without having the physical board in front of me. As far as I can tell right now Era 2 and Era 3 are actually connected to each other, don't know if that helps.
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Re: Darkglass - Vintage Microtubes

Postby johnk » 13 Apr 2017, 19:19

i think that ERA 2&3 are connected together too. it may be wrong cap values but the GUMA antique appears to have the same values in the BOM.
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Re: Darkglass - Vintage Microtubes

Postby johnk » 13 Apr 2017, 19:21

i think that ERA 2&3 are connected together too. and yes the GUMA antique has those values in the BOM.
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Re: Darkglass - Vintage Microtubes

Postby stangwarrior » 20 Apr 2017, 09:03

Just completed ksenanekro's version and it works ok.Two of the pot as reversed - you should swap blend 1 and blend 3, and drive 1&2 should go to volume 1.ERA works as it should i think, tho i don't own the original and can't compare...
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Re: Darkglass - Vintage Microtubes

Postby miguelmoita » 21 Apr 2017, 19:29

Here is the my schematic based by the ones the johnk did with the values of Guma Antique. There are very few adjustments. I have it in my breadboards and it sounds awesome but I do not have the original to compare. I own the B7k, and it definitely sounds like a Darkglass.
I am going to make a tone transfer image in the next days, I will post here.
Regards,
Miguel
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