Darkglass - Vintage Microtubes  [schematic]

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

Got one it becase it had some huge issues; all sounds were horrible distorted and gating, only the gain potmeter did something.......

I found the problem to be the TL074 which were all shot. Replaced it with a new one and it again works like a charm!!
DSCF3958.jpg
DSCF3957.jpg
And some schematic; it doesn't state the capacitor values and my DMM that can read em is broken
Darkglass - Microtubes Vintage.JPG
'No more....... loud music.......'
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thoglette
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Post by thoglette »

Bernardduur wrote:I found the problem to be the TL074 which were all shot.
Wonder what killed it - you've usually got to try really hard to kill one of them. Any ideas?

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olejason
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Post by olejason »

Thanks for the schem!

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Bernardduur
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Post by Bernardduur »

thoglette wrote:
Bernardduur wrote:I found the problem to be the TL074 which were all shot.
Wonder what killed it - you've usually got to try really hard to kill one of them. Any ideas?
No idea! The owner got it second handed with these errors and hoped he could fix it! It was never resolved how it ended up being this way!
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Bill_Mountain
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Post by Bill_Mountain »

C19 looks way high???

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Bernardduur
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Post by Bernardduur »

Bill_Mountain wrote:C19 looks way high???
F***; typo! I'll upload a new version later!
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Bernardduur
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Post by Bernardduur »

Darkglass - Microtubes Vintage.JPG
'No more....... loud music.......'
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Bill_Mountain
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Post by Bill_Mountain »

I really like this design. It's clean simple and it allows you to scoop your mids and run it direct because of the LPF. I knew this was good pedal but seeing this really shows how much Doug gets bass players and their needs.

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Silver Blues
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Post by Silver Blues »

Yeah nope FML. Guys I apologize profusely. This is what I get for doing such a complicated layout so late at night. I've double-checked this version, it's a little ugly again but I THINK EVERYTHING IS CONNECTED WHERE IT SHOULD BE :shock:
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Darkglass VMT2.png

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OnTheTundra
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Post by OnTheTundra »

Where are we at with the cap values? I will build one from the last vero once those are posted.

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Silver Blues
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Post by Silver Blues »

OnTheTundra wrote:Where are we at with the cap values? I will build one from the last vero once those are posted.
Be sure to give it a once-over before you build it so I can fix any last-minute mistakes if they appear. Wouldn't want you to build something this big from an incorrect layout :mrgreen:

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Silver Blues
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Post by Silver Blues »

What I'd like to do, if you don't mind, is refer you here for the future. This is easier to keep updated without me taking up posts on this thread.

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vorokha
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Post by vorokha »

In the circuit there is a manifest error.
The frequency characteristic in this regard is far from the original.
R24 = 100k
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darkglass error.jpg
darkglass error.jpg (26.2 KiB) Viewed 12653 times

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Bigwan
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Post by Bigwan »

Sorry to dredge this up, but can anyone explain what the Era control is doing. My first thought was it was like a modified muff tonestack but I know it acts quite a lot on the midrange. Anyone?

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Bigwan
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Post by Bigwan »

Further to my previous question, is it a fixed low pass filter (R27 and C20) and variable high pass filter (VR2, R28 and C21)?

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Bernardduur
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Post by Bernardduur »

Bigwan wrote:Sorry to dredge this up, but can anyone explain what the Era control is doing. My first thought was it was like a modified muff tonestack but I know it acts quite a lot on the midrange. Anyone?
It is a simple mid filter (as can be found here)
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Post by rocket8810 »

i know it's been awhile since anything moved on figuring this one out, but if your dmm is still broken and want/can send it out, i'd gladly test it to figure out the missing caps. would be real nice to get this one right man. btw, great work so far.

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Post by ksenanekro »

do we have any news on this one? i've breadboarded this and got nothing really.... i've used the values i thought that would be ok, but the only thing i got is a working blend control.any guesses maybe about the caps??
thanks
Savvas

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Silver Blues
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Post by Silver Blues »

Ladies and gentlemen! I present to you, a complete, fixed and verified layout for the Darkglass Vintage Microtubes!
Darkglass VMT f.png
I have used three TL072 instead of a TL072 and TL074 because the latter arrangement was basically impossible to make a reasonable layout with. I have also added a 100K pulldown to the output per Savvas' recommendations.

The missing capacitor values, referencing the newest schematic in this thread, are as follows:

C18 @ JFET = 22nF
C18 in the filter network = 22nF
C16 = 22nF
C17 = 22nF
C8 = 220pF
C28 = 220pF
C24 = 1uF
C23 = 1uF
C20 @ last op-amp stage = 2.2nF
C20 @ Era control = 4.7nF
C25 = 1nF
C22 = 1nF
C27 = 1nF
C21 = 1nF
C10 = 220pF

Enjoy!

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Post by ksenanekro »

attention! there is a mistake on this schematic, so there is a mistake on the layout too...
the circuit round tone control, should be like a big muff's tone control..from c21 we should go to era pin3 and from era pin2 to the 10k resistor.

i've build the Silver Blues's layout above, and it worked, but didn't sound as good as in the demos. my friend that i build it for sent it back to me to see if i can make it bassier, and then i saw that the tone control part was similar to a B.M.'s. i immediately made the changes i suggested above and boom! sounds great! after that, i've build 2 more boards with an other layout i drew that allows a 1590b. So here is my layout. Verified
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darkglassvmt.png

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