Black Arts Toneworks - Quantum Mystic

V1nce69 · Post by **V1nce69** » 13 Apr 2015, 07:51

This is my pedal. I bought it after having built a copy based on the layout from Tagboard, which I wasn't satisfied with.

Here are a few pics and my drawing of the pcb:
pcb values

: pcb values

pots

: pots

pcb drawing

: pcb drawing

I'll try to post the schematic separately, as it won't upload; I always get a blank page when I try.

V1nce69 · Post by **V1nce69** » 13 Apr 2015, 19:36

And the schematic:

: BT Quantum Mystic - schematic

Notes for the parts:
C1 and C8 are polyfilm "Greenies*,
all 1µF capacitors (C2, C4, C6, C7) are polyfilm,
C3, C5, C9, C10 and C11 are polyfilm too,
C12, C13, C14 are electrolytic,
D1, D2 are 1N270 Germanium,
D3 is 1N4001,
IC is TL074CN,
resistors are metal film except for R1, R9 and R12 that are carbon comp in my unit.

Resistor for the led (3mm blue) is quite an unusual high value with 5k1.

soulsonic · Post by **soulsonic** » 13 Apr 2015, 22:13

A DOD250 with active tone controls tacked onto the output...

V1nce69 · Post by **V1nce69** » 15 Apr 2015, 21:37

I made some slight editions to the schematic wanting it to be as accurate as possible to the pcb layout.
They are in the 9v supply chain. The same parts are connected as before, it's just the order the is not exactly the same.

Here it is:

: BAT Quantum Mystic - schematic v. 1.01

johnk · Post by **johnk** » 16 Apr 2015, 22:26

I made a PCB of it according to the posted schematic but it's definitely not working properly.

apollomusicservice · Post by **apollomusicservice** » 17 Apr 2015, 09:47

My schematic looks a little different.

Dirk_Hendrik · Post by **Dirk_Hendrik** » 17 Apr 2015, 11:06

apollomusicservice wrote:My schematic looks a little different.

It does indeed! It's readable. Or better, there's a clear signal flow to be followed.

However apollo;
- I do wonder about the feedback resistor for the first opamp. 1Meg or 500k? And I have never seen a resistor with a reverse log curve.

- Are you sure there's no cap involved in the Bass control section?

apollomusicservice · Post by **apollomusicservice** » 17 Apr 2015, 11:10

correction

Dirk_Hendrik · Post by **Dirk_Hendrik** » 17 Apr 2015, 11:54

Thanks.

And how about that bass control?

V1nce69 · Post by **V1nce69** » 17 Apr 2015, 13:34

Dirk_Hendrik wrote:Thanks.

And how about that bass control?

According to my pedal there's one 10n cap between bass 1 and bass 3, and another one between mids 1 and mids 3.

Sorry if my schematic isn't readable, I tried my best but still have a lot to learn in electronics. It was quite complicated to draw with this IC…
Maybe the drawing I made when tracing the original pcb can help you verify/compare both schematics.

: BAT Quantum Mystic - drawing

apollomusicservice · Post by **apollomusicservice** » 17 Apr 2015, 14:15

You've done a good job. With the help of your Installation sketch I'll try to do wiring diagram for comparison.

Dirk_Hendrik · Post by **Dirk_Hendrik** » 17 Apr 2015, 15:39

V1nce69 wrote:
Dirk_Hendrik wrote:Thanks.

And how about that bass control?

According to my pedal there's one 10n cap between bass 1 and bass 3, and another one between mids 1 and mids 3.

I know there is

It must be.

But apollo was in a hurry doing his corrections.... and apollo definitely should know that cap is there

and...
No flame intended Vince. You did a good job. After that, try to understand how the various building blocks of the circuit connect together (and Rome was not build in a day!) and therefore how the signal flow is in the circuit. Then you will understand why apollo's schem is more readable.

Although it may be hard to find em (read: I'm too lazy to search

) forummite Sinner has done rather excellent drawings of schematics where he chopped them up in the various buiding blocks.

johnk · Post by **johnk** » 17 Apr 2015, 15:56

I'm pretty sure that Vince is correct that the feedback resistor in the first gain stage is a 1M and not a 500K.
I got mine working but the tone stack isn't all that effective except for the mids control.

apollomusicservice · Post by **apollomusicservice** » 17 Apr 2015, 17:02

johnk wrote:I'm pretty sure that Vince is correct that the feedback resistor in the first gain stage is a 1M and not a 500K.
I got mine working but the tone stack isn't all that effective except for the mids control.

You're right. Thank's.

Dirk_Hendrik · Post by **Dirk_Hendrik** » 17 Apr 2015, 17:33

Don't mention

johnk · Post by **johnk** » 17 Apr 2015, 17:59

cool.
and are you sure that the cap connecting lugs 1 & 3 on the bass pot is a 10n? it seems that it might be a higher value to me. (maybe a 47n or a 100n?)

johnk · Post by **johnk** » 17 Apr 2015, 18:40

nevermind. a 10n works fine there.

johnk · Post by **johnk** » 17 Apr 2015, 19:07

here's my built, tested & verified layout with 3 board mounted pots for the tone stack:

http://johnkvintageguitars.homestead.co ... Layout.png

thanks to Vince and Apollo!

culturejam · Post by **culturejam** » 17 Apr 2015, 19:08

soulsonic wrote:A DOD250 with active tone controls tacked onto the output...

Good to see you, Martin!

V1nce69 · Post by **V1nce69** » 18 Apr 2015, 08:50

johnk wrote:nevermind. a 10n works fine there.

Hi john,
I re-checked my pedal and I can confirm that the cap between lug 1 and lug 3 of both bass and mids pots is a 10nF (code is 47L 103).
Also the resistor R4 in the feedback of the first opamp is a 1meg (brown-black-black-yellow-brown), not a 500k.
When I first studied the pedal I unsoldered all ambiguous resistors and measured them with a multimeter.
You can refer to my first post, there's a pic of the board itself with all the components values.

Your layout looks great as they always do.

Black Arts Toneworks - Quantum Mystic [traced]