Darkglass - Microtubes B3K / B7K  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
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fersynes
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Post by fersynes »

I Made it, just had 2 mistakes:
I put 1 transistor inverted
The vcc is conected to level lug 1 not 3

It sounds very well but I expected more. The grunt Switch changes are quite imperceptible but paying attention you can note it. I never tried an original one to tell if it is similar but sounds well for me.

I only tried in active sub series bass

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miguelmoita
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Post by miguelmoita »

That is exactly my opinion of the one built fersynes.It sounds well too but I expected a little more. The sound of Darkglass is definitely there. That grit!! but it does not have brutal and dirty sound that I expected. In a passive bass this gets more present in my opinion.
The VMT, which is a very similar circuit, sounds much more the way I expected. More vintage of course, but more responsive also, and you clearly can reach more types of sounds when tweaking the controls.

I never compared it with the original too, but I have been playing with a B7k, and is a totally different beast. Thus, I never compared both side by side to see the differences.
The schematic that I upload here was based on a GUMA board, I will check if I miss something and mount it to see if it sounds the same.

Cheers

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olyaneko
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Post by olyaneko »

Tell me please, but you have a B7k circuit, too, I would have looked it up too. And I've already redrawn your scheme, but I still have not had time to make it. If you want, I'll also put .lay here (why then i only have one file to attach) :oops: ...
B3K Clones Pre Proj.jpg
P.S. Sorry my bad english :oops: ...

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olyaneko
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Post by olyaneko »

mmm, this PCB (Sprint Layout files) :oops: ...
B3K Clones Pre Proj.zip
(31.84 KiB) Downloaded 661 times

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miguelmoita
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Post by miguelmoita »

Nice job olyaneko.
I have an original B7K, but the trace is very difficult because is all SMD. I never done it. Thus, I opened it just to check how close is the B3K that I drew. All the ICs and transistors are there, but the passive components are difficult to get. It also has more 1 or 2 TL074 chips that must be responsible for the equalization.
The B3K that I drew is based on the GUMA board.

Have a nice build.
Cheers

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olyaneko
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Post by olyaneko »

miguelmoita thank you :oops: ,...mmm, i'm still just learning this :oops: ...

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albru80
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Post by albru80 »

HI!
I've drawn a vero based on the schematic (http://tagboardeffects.blogspot.fr/2017 ... mment-form) and all of us there seem to have the same problem: general low gain and Gain pot not working properly when Grunt switch is in the middle position.
The Guma Drive shows 6 x 10K resistors instead of 5 (not sure if part of the footswitch circuit)
Is you pedal working correctly?
Thanks for your help.

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miguelmoita
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Post by miguelmoita »

Just saw now the tagboardeffects thread! Woow, very proud to have a schematic that I drew in there!! :D
Unfortunately is not perfect! but well, I done my best!

Yes, I remove the switching circuit of the Guma board. It uses a relay to make the true bypass. The switch the relay on/off the circuit includes a BC547B , a 10k resistor and a 100n capacitor, a 1N4148 diode and a 78l05. So you may also find those missing components in my schematic.
I also removed a 100R resistor that is used in series with the Vcc supply and the V+ pin of the CD4049 chip. I supposed that's for noise proposes, so I removed it. The VMT board does not have that transistor too.

I just mounted the Guma board and tried both side by side. I it seems they sound exactly the same. I played with a sadowsky metro bass that allows me to turn on and off the active preamp. As I expected, it's a huge difference. And the passive sounds so much better! When I use in active mode I have to turn the knobs at full to have a some nasty drive that is not even close to what I want. But in passive, I get that sound with Blend, drive and Level at 1 o'clock. When I turn to full rotation the Blend and Drive is nasty, gritty and awesome. If you put the level at full rotation it becomes very very loud compared to your clean sound, something that does not happen in active mode.
The grunt switch is very subtle in both, but also on the B7k that I tried. So, does not surprise me.

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fersynes
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Post by fersynes »

I made it work well. just change a cap as it is suggested in the website of the gumma drive and I think sounds better this way. Soon Will upload a picture with the enclosure finished!

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jmwreck
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Post by jmwreck »

Hi guys, I am sorry if I might be off-topic but since Guma Drive was mentioned here, I have done both the Drive (B3k) and Antique (Vintage).

Image

Image

Image

The Antique works fine but I am having a problem with the Drive (B3k) because I got a cutting out sound, it seems that the distortion sound will get disconnected and all that's left is the clean sound, but it sounded great when the distortion kicks in. It feels like something is wrong with the switching, I always got a loud pop or the best way to describe it is like when you are playing a clean sound and then someone was messing or plugging/unplugging a cable to your distortion (parallel) sound, or when you hit the tip of your cable/plug to your guitar jack when your amp is turned on, or it's like a crackling sound (my pots don't crackle when I rotate them). Both the clean and the messed up sound varies in time, maybe milliseconds away. One thing I noticed was that after several minutes of fiddling with the pots and toggle or just by leaving it untouched, the messed up sound disappears slightly but it is still there waiting to happen.

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miguelmoita
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Post by miguelmoita »

jmwreck that thing is beautiful!! Nice job!
Regarding the cracking sound. I got that kind of cranking when I was breadboarding the circuit. The problem seemed to come from CD4049 chip, because when I probe the circuit the cranking apear after this cheap, before it sounded ok. I tried another chip but the cracking did not change, and then I gave up.
I dismounted the circuit to build the VMT, that worked great at first attempt. Then I tried the B3k again and it worked fine (with the problems that I already mention in the thread, but it sounded like the guma drive).
Soo, I never really found the reason behind the cranking, but my suggestion is that you change the CD4049 chip. If it continuous to crank the sound, try to probe it before and after the chip the see if it is there.

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jmwreck
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Post by jmwreck »

miguelmoita wrote:jmwreck that thing is beautiful!! Nice job!
Regarding the cracking sound. I got that kind of cranking when I was breadboarding the circuit. The problem seemed to come from CD4049 chip, because when I probe the circuit the cranking apear after this cheap, before it sounded ok. I tried another chip but the cracking did not change, and then I gave up.
I dismounted the circuit to build the VMT, that worked great at first attempt. Then I tried the B3k again and it worked fine (with the problems that I already mention in the thread, but it sounded like the guma drive).
Soo, I never really found the reason behind the cranking, but my suggestion is that you change the CD4049 chip. If it continuous to crank the sound, try to probe it before and after the chip the see if it is there.
Thanks miguelmoita, I will try and change it tonight because I have removed the pots and switches last night to check if there are errors on my soldering. I have tested the connections with a tester and everything seems fine. Before the disassembly, I have played it for a while and the crackling sound was still there.

I will try to probe it as per your suggestion and check on the CD4049.

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bmxguitarsbmx
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Post by bmxguitarsbmx »

miguelmoita wrote:...
I also removed a 100R resistor that is used in series with the Vcc supply and the V+ pin of the CD4049 chip. I supposed that's for noise proposes, so I removed it.
The 100r will change the clipping behaviour and likely the gain of the cd4049. I'm not that familiar with cd4049 circuits, but I do know that lowering the V+ actually increases gain. I know from building discrete bsp250/bs170 inverters that putting a 100R in there does change the tone enough to hear.

Hope this is helpful:)

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Harold
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Post by Harold »

Here's another schematic based on the GUMA: http://peperspedals.blogspot.nl/2017/02 ... cb-to.html and the update on that: http://peperspedals.blogspot.nl/2017/03 ... pdate.html

I also made a Vero out of it, but I still haven't checked it: http://diyl.sait.nl/guma-drive-darkglass-b3k
Attachments
darkglass.png
DIY-Layout.com: Online stripboard layouts

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izikg
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Post by izikg »

jmwreck wrote: I am having a problem with the Drive (B3k) because I got a cutting out sound, it seems that the distortion sound will get disconnected and all that's left is the clean sound,
Hi
I also get this cutting out when at high gain , I found that high frequencies noise is amplified and causing this problem on the drive opamp.
I suspect it has something to do with the filter before that opamp , but I just can not understand it.

does any one know this filter design or can explain that
B3K_pre_drive_filter
B3K_pre_drive_filter
B3K_pre_drive_filter.png (1.82 KiB) Viewed 4569 times
I also noticed that the BDDI has a similar filter
BDDI_PRE_DRIVE_FILTER
BDDI_PRE_DRIVE_FILTER
BDDI_PRE_DRIVE_FILTER.png (15.94 KiB) Viewed 4569 times
Thanks,

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psychepool
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Post by psychepool »

Unfortunately, I also get a gain drop after gain pot 8 ~ 90%.
I made a VMT(uses 4049) but it doesn't have this problem.

There is no switch yet for debugging convenience. Does the problem disappear when change the mode?

I made my own layout for the 1590A case.
05E8CBCC-C89B-45D9-A129-FBCF77386C98.png
I've seen it several times, but it looks like there are no layout problems and I have not found any errors in the board that I made yet.

I will try to remove the 4049 that is working normally in the VMT and plug it into the B3K.

I hope that the debugging information is released.

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psychepool
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Post by psychepool »

Yesterday, I installed Attack / Grunt switches. (both on-off-on toggle)

The problem of gain reduction has disappeared when I operate the attack switch on both sides.
There was no problem turning the gain pot to the end.

Apart from this, I also thought that I did not feel dirty/brutal sound enough than I thought,
But when I operated the Grunt switch, the amount of drive was increased and the low-end grawing was way better.

There is still a gain reduction problem in the attack switch center setting, and the amount of drive is still not enough even though I switch the Grunt mod,
but The sound itself is good enough and I do not think there will be any inconvenience to use it personally.
I will house it to the 1590A case without further debugging.

I waiting for the VMT deluxe and B7K circuits are released.

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psychepool
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Post by psychepool »

Done it.
I made it by the layout uploaded at upper.
AD13D5BA-D066-4FAF-877C-7A145D53C82B.jpeg
64E247AE-4815-4DFD-9C3C-78993C09C3C9.jpeg
I also made a VMT with 1590A case. Production notes are written here.
viewtopic.php?f=1&t=25589&p=269679&hili ... ss#p269679
The same thing should be taken into consideration when producing the above B3K layout.

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izikg
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Post by izikg »

psychepool wrote: I made my own layout for the 1590A case.
looks grate psychepool.

i suspect the gail problem is due to noises added on the filter stage just before the gain amplification.
i belive that a well planed pcb reduces that noise. but the vero bord most of us use has a configuration that doesent reduce the noise.
on your tiny packaging the noise problem is even bigger.

but all of the above is a theory (i did not had the time to prove that). the fact i did confirmed is that when the gain problem starts the output of the gain opamp has alot of high frequancy energy which i suspect causes the problem.

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psychepool
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Post by psychepool »

izikg wrote: i belive that a well planed pcb reduces that noise. but the vero bord most of us use has a configuration that doesent reduce the noise.
on your tiny packaging the noise problem is even bigger.
I agree with your opinion. I've had similar experiences in the past (problems when creating the same circuit in different layouts).
Therefore, I think it is a problem that can not be solved.
I am very tired because of the gain reduction debugging, and I am satisfied with the current state, so I am going to use it without additional debug.

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