Darkglass Electronics - Microtubes B3K  [traced]

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POTL
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Post by POTL »

izikg wrote:
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
The attachment B3K_pre_drive_filter.png is no longer available
I also noticed that the BDDI has a similar filter
The attachment BDDI_PRE_DRIVE_FILTER.png is no longer available
Thanks,
Hi
The first figure - R8 C8 - controls high frequencies.
1) When the switch is in the center position, the high frequencies do not change.
2) When the capacitor is connected to ground, the high frequencies are cut off, this is the classic RC-filter
3) When the capacitor connects to the resistor, this parallel RC-filter, like the Marshall, in this mode, high frequencies rise.
The second picture is Bandstop filter - the filter does not let pass a certain frequency. In this case, this filter cuts low-mid freq, the frequency of 320 HZ is cut completely and the frequencies near it are also severely cut off.
Attachments
Снимок экрана 2018-06-20 в 8.12.46.png
Снимок экрана 2018-06-20 в 8.12.38.png
Снимок экрана 2018-06-20 в 8.12.38.png (9.92 KiB) Viewed 2008 times
Снимок экрана 2018-06-20 в 8.12.21.png
Снимок экрана 2018-06-20 в 8.06.46.png

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Post by POTL »

Hello everybody
I watched the circuit today and read Douglas's reports on the forums, at first I thought this pedal was an original development, then I realized that Douglas collected it based on the MXR M80, Sansamp Bass Drive Di and CMOS amplifier as Red Llama.
So, if you want to copy B7K, then I advise you to look at the equalizer circuits from m80 and bass driver di.

Regarding the control of the middle frequencies, you can change the frequencies using the DPDT toggle switch (as in the original).
Below is the scheme, you just need to connect the toggle switch to C2 and C5
You need to copy the central part of the circuit 2 times and select the components for the desired frequencies, I hope this helps you to copy the circuit :D
Image

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ray86
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Post by ray86 »

CD4049????

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Post by POTL »

ray86 wrote:CD4049????
Yeah, it's here.

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zyu
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Post by zyu »

Harold wrote: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
Hello!
One small mistake.
R5 should be installed before R4, and not AFTER it, as in your scheme.

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Post by jhergonz »

will try to build b3k with "ERA" knob like the Vintage microtubes, i'll just put B100k pot in series with the 33k(R23) resistor ... hope this will work just fine.

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Post by Pedro_Mariz »

I have some sugestions that worked for me:

- Increase the 220pF of the grunt switch to 470pF
- Reduce the 4049 feedback resistor from 470k to 330k
- Increase the 100R 4049 supply resistor to 1k
- Also make a boot's trap before the 9V input of the board, it means, put a 100R in series, like the rat, that gonna improve the noise performance

Yet, all these mods didn't worked well to me, and the pedal was more like a gate distortion, the oscilations stopped, but it could be more, I espected it.

So, my final solution was to replace all the 4049 section, to a mosfet muff distortion block, and gess what? Sounded lika a charm! ahahah No oscilations, giant sustain, all the switches did they role super well, I'm super gratful to all the mates that inputed so much information about this thread, that's my 2 cents.

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Post by jhergonz »

Pedro_Mariz wrote:I have some sugestions that worked for me:

- Increase the 220pF of the grunt switch to 470pF
- Reduce the 4049 feedback resistor from 470k to 330k
- Increase the 100R 4049 supply resistor to 1k
- Also make a boot's trap before the 9V input of the board, it means, put a 100R in series, like the rat, that gonna improve the noise performance

Yet, all these mods didn't worked well to me, and the pedal was more like a gate distortion, the oscilations stopped, but it could be more, I espected it.

So, my final solution was to replace all the 4049 section, to a mosfet muff distortion block, and gess what? Sounded lika a charm! ahahah No oscilations, giant sustain, all the switches did they role super well, I'm super gratful to all the mates that inputed so much information about this thread, that's my 2 cents.
May I know what do you mean by "mosfet muff distortion block"? I mean did you put the whole mosfet version of big muff or just one stage of it?

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Post by Whoismarykelly »

I'm having a weird oscillation issue with the level and drive controls at max on this circuit that I can't really figure out. I've seen a few folks mention a similar issue but no apparent resolution. Im wondering if it could be an issue with the JFETs since the rest of the circuit should have much variability between components.

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Post by alexradium »

Whoismarykelly wrote:I'm having a weird oscillation issue with the level and drive controls at max on this circuit that I can't really figure out. I've seen a few folks mention a similar issue but no apparent resolution. Im wondering if it could be an issue with the JFETs since the rest of the circuit should have much variability between components.
oscillation can be anything from jfet,trace layout,long wires to the pots,poor decoupling of opamp rails.

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Post by skizoide »

Hi. After all, sorry for my english.

I had one unit for repair the footswitch, and I retraced the schematic, because I had seen a lot of problems with the ones I saw in google. The PCB said it was rev 3.1
I saw a few free pads of components. I had made a new one based on the new schematic, and compared with the original unit, and I can say it had the same sound. Here it is the "new" schematic, if someone it's interested.
I read a lot of people (including me) having issues with the grunt switch in the middle position and the gain pot maxed, and now the problem is gone. Some of the differences with the first schematic:
- Level pot is B100k
- Two of 2,2uf electrolytic caps instead of the 1uf non polarized.
- No 22p caps.
- Two 2,2nf caps replaced for 1n.
- The attack switch is On-On.
Attachments
Darkglass B3k - Schematic.pdf
Darkglass B3k Schematic (PCB rev 3.1)
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Post by deltafred »

I've just read this thread again and see that quite a few of you are are referring to a 4049 which has a different internal schematic to the 4049UBE.

The UBE stands for un-buffered which means it will work as a linear amplifier where the 4049 will not.

I'm wondering if this is the reason that some of you are having difficulty getting it to work correctly.
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Post by Manfred »

I have to disagree, the 4049 is always a hex inverting buffer independent of the letters following the numbers, the 4050 is a hex non inverting buffer.

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Post by deltafred »

I stand corrected.

I always understood that there were buffered and un-buffered versions of the 4049 and when you used them in analogue mode you needed to use the UBE version.

(I do know that the 4050 is non inverting so not suitable for use as an analogue amplifier.)

Edit.
I just read your post again. There is no such thing as an non inverting 4049, a 4049 is a Hex inverter no mater what suffix letters it has. When I said different internal schematic that is what I meant not a different logic function.
Last edited by deltafred on 30 Sep 2020, 14:06, edited 1 time in total.
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Post by Manfred »

deltafred wrote: 30 Sep 2020, 10:14 I stand corrected.

I always understood that there were buffered and un-buffered versions of the 4049 and when you used them in analogue mode you needed to use the UBE version.

(I do know that the 4050 is non inverting so not suitable for use as an analogue amplifier.)
Ok, I have not seen this before, I am interested, do you got a datasheet of the non-inverting 4049 which you can attach?

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Post by deltafred »

Manfred wrote: 30 Sep 2020, 11:14 Ok, I have not seen this before, I am interested, do you got a datasheet of the non-inverting 4049 which you can attach?
I never mentioned a non inverting 4049, there is no such chip. I said it has a different internal schematic i.e. it has a logic level buffer on the output.

Looking on the net I can only find the 4049UBE datasheets but I'm sure when I was working on logic boards in the 80's that both buffered and un-buffered 4049 (and 4069) excisted. I shall have to go into the attic and dig out my old CMOS data books.
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Post by deltafred »

Ok, here's something for a start.
https://www.ti.com/lit/an/scha004/scha0 ... e.com%252F
A Texas Instruments guide to using buffered and un-buffered CMOS.

If you look at the transfer characteristics (Figs 5 & 6) you can see that the buffered basically has 2 states, 1 and 0 whereas the un-buffered has a slope with curved ends, This is what enables the un-buffered to be run in linear mode (and also what gives the CMOS overdrive it's characteristic soft clipping sound).

Table 4 states "Ultra-low-frequency systems,
inputs <1-kHz sine wave or ramps with tr, tf > 1 ms" un-buffered is recommended to avoid oscillation.

This may be why some builders have experienced "crackling" as the 4049 goes into oscillation when it receives low frequency signals.
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Post by Manfred »

Thanks for the paper but I was already familiar with these CMOS devices.
In the beginning of the 80s I was working as a developer for test equipment electronics, we had used the 4xxx CMOS series frequently, including the 4049.
Therefore I am surprised that a 4049 non-inverting buffer has never been mentioned in application notes etc.
So I thought that there is a special datasheet for it.
It is rather unusual that there is one device with the same name and pin-out with different functions.

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Post by JiM »

No one is talking about a non-inverting 4049 here, there is no such thing. This is about buffered or not.
One inverting CMOS cell would make a non-buffered inverter, e.g. found in a 4049UBE.
Two inverting CMOS cells would make a non-inverting buffer, e.g. found in a 4050.
Three inverting CMOS cells would make a buffered inverter, e.g. found in a 4049B.
I only give negative feedback.

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Post by deltafred »

I gotta ask, where is a non inverting 4049 mentioned, I read the whole thread this morning and didn't see it.

I admit that I only looked at the schematic posted by skizoide.

I see JiM beat me to it.
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