Friedman BE-OD Pedal  [traced]

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Re: Friedman BE-OD Pedal

Postby rmroza » 30 Jun 2017, 02:25

Ok. Looked at both board. Found some minor things, but still N/G.

The #2 pedal which I had in the pedal sounds good, but has the noise. Flourescent lights off had no impact either
The #1 pedal which was in the enclosure just doesn't put out anything! Likewise, unlike the #2 where both LEDs on the right are on, on this one, only one is on and it is the one on the left of the set on the right.

With the above and both taken out of the box, but different issues, I have to assume it's build issues, but unaware what that may be. I replaced the #1 LED that wasn't on thinking that might help, but that also....nope.

Soo, here are the Hi-Res photos. I don't see any bridges or build problems unless I missed something!

Can't wait for the PC board version but still would like to get these going as I spent a lot of time already in hours and hours populating, building and troubleshooting.

Let me know if you guys see anything out of the ordinary.
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Re: Friedman BE-OD Pedal

Postby jalmonsalmon » 02 Jul 2017, 16:08

bugg wrote:The most recent schematic (as well as the layout/build info) is available at the bottom of this page:
http://www.buggfx.com/product/thermionic-distortion-pcb/

Oh I noticed on the build doc schematic it is missing a 100n cap that should connect to + of that 22uF cap and to ground.
I know the PCB has it so no worries there! :D
I cannot wait to make this one! Low on funds at the moment and Wifey says NO to my pedal building at the moment :slap:
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Re: Friedman BE-OD Pedal

Postby roberttomasz » 04 Jul 2017, 10:27

R6- ? :slap:
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Re: Friedman BE-OD Pedal

Postby bugg » 10 Jul 2017, 20:24

Awesome guys, I appreciate it!

An order of PCBs just came in today so most will be shipping this afternoon when I get home from work, the rest should be on their way in about a week.

Everything should be fairly self explanatory but don't hesitate to shoot me a message if you have any questions or problems.

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Re: Friedman BE-OD Pedal

Postby bugg » 12 Jul 2017, 02:59

rmroza wrote:Ordered on 6/27. Any updates??


Yep, yours went out today!
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Re: Friedman BE-OD Pedal

Postby bajaman » 18 Jul 2017, 04:43

although bugg's board is very nice it is however not using THE CORRECT schematic - the presence control connection is wrong for starters. I have built this according to the schematic that bugg uses and the presence is almost none existent - when connected like a previous v1.4 schematic it works but like others i am plagued by high frequency whistle when attempting to increase the gain control past minimum.
Seriously someone should either purchase and post clear pictures of the board under the top row of controls or reverse engineer this pedal properly because as it stands it is a trainwreck :roll:
Surely someone can figure this out instead of just guessing.
I will keep working on this but the pictures posted so far are not the easiest to see the pattern.
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Re: Friedman BE-OD Pedal

Postby bugg » 18 Jul 2017, 11:22

The presence control works properly on the one I built... Maybe others can chime in when they get theirs assembled.

Oscillations have been confirmed on the original unit with Gain / Trim maxed, I have the trim at just above 50% and there is no oscillation with the gain cranked wide open.
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Re: Friedman BE-OD Pedal [schematic v13]

Postby bajaman » 18 Jul 2017, 11:44

Okay folks - I have spent the last few hours running simulations and trying to get to the end of this ridiculous thread.
There has been some great work done by jokerx and others in trying to decipher this mess and one forum member has come very close to the correct scheme. :wink:
One thing that puzzled me with both my simulations and the pedal i built to evaluate bugg's thermionic distortion is those 4 clipping diodes :hmmm:
Bugg suggests using 1N4148 diodes and others have speculated about schottky diodes etc. , but in the simulations these are never driven into clip until well after the following back to back leds are driven into saturation. I looked at the code on the SOT23 devices that Friedman is using - 1A7 and tried to determine exactly what these components are. Mr Friedman has marked the board D5 and D6 which suggests that these are diodes, and yes, they are, BUT not dual diodes as some have speculated. :wink:
They are most likely pnp transistors connected with reversed base emitter junctions - indeed this is the only combination that possibly makes any sense if one examines the way they are connected on the board. :)
ZXTP25015DFH-74334.pdf

Take a look at this pdf - code: 1A7 - a Zetex medium power high current (4A) pnp transistor
I believe these are available from Mouser - the nearest through hole equivalent appears to be the Zetex ZTX951 which is definitely available from Mouser , radiospares, etc.
When running my simulations with the latter (still looking for a spice model for the SOT23 device) I notice far earlier clipping - just after the second gain stage with the back to back leds in the feedback loop begins to clip. I tried simulating with several small signal pnp devices, but only got acceptable results when using 4A devices and the ZTX951 gave by far the best simulated results. i have ordered some and will replace the diodes in my build and report back, in the meantime .....
cheers :thumbsup
bajaman

ps:
Friedman BE OD V1.4-1.pdf

In my humble opinion, this is the most accurate schematic so far - the presence control is connected properly (and it works), you can clearly see the connection of C13 on one of the board photos and this is the same as that. :wink:
One thing puzzling me is why the need to connect the two leds LED3 and LED4 to the bias rail and not to ground :hmmm:
Possibly because they supply the bias voltage to the following gain stage through the treble control - surely C14 should be connected between the output of !C2b and the top of the treble pot , and the leds are connected still to C14, but now feed bias voltage directly to the top of this treble control :?: It seems more logical that way, and certainly explains why the need to connect the leds to v bias rail :wink:
One last thing - R997 and R998 are indeed 33k as has been pointed out previously - this gives a narrow bandpass bass boost centred around 80Hz
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Re: Friedman BE-OD Pedal

Postby bool » 18 Jul 2017, 12:50

Using transistors to clip would make perfect sense since transistors seem to be used as clippers in tube amps as well.
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Re: Friedman BE-OD Pedal

Postby bajaman » 18 Jul 2017, 13:26

Using transistors to clip would make perfect sense since transistors seem to be used as clippers in tube amps as well.

yes - but i was genuinely surprised how different the clipping was with lower current fater devices like the BC557 etc. - even the old BD140 (a relatively slow 1.5A device ) didn't clip as soon as the ZTX devices - quite an eye opener for me :scratch:
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Re: Friedman BE-OD Pedal

Postby bool » 18 Jul 2017, 14:31

Reading on ZTX these seem to be optimised for low saturation voltage switching application, so what you're saying makes perfect sense. (I think MPSA06 are used in tube amps???)

But while you are at simulation, I think you can shoehorn a close-enough characteristic (for DIYers) juggling the resistor values around that stage for users stuck with 1N4148. (or 1N400x which have a bit lower PN-drop).
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Re: Friedman BE-OD Pedal

Postby rmroza » 18 Jul 2017, 18:17

Goddamn it, we gotta get this thing right and under control!

Yes, someone confirmed earlier the schematic to use was v1.2, so unsure why v1.4 was pointed out, but everyone is soo excited about this that this was a case of too many chief and not enough Indians.

Yes, all of the Friedman amps use NPN MPAS06's for their clipping section (for the heavier clipping).

Now getting back to the design...I noted also all of the discrepencies...different component identification (e.g. R21 v. R12 or whatever) and pots working backwards. I'd like to see this cleaned up. I think the best way to approach it is to go back to the start and re-confirm everything. Assign who will do the tracing and schematic, then who wants to do the PCB?

I still have an original pedal and unmolested and eager to A-B. The tone I did get with the vero was fantastic and with whatever components were picked. They may be better and end product better than the Friedman, but MODs and changes IMHO shouldn't be added until you have the baseline design laid out...then make this Rev.1 Make Rev2. the new and improved model with say reverse polarity diode and components that the groups feels will be better.

Right now we have a schematic, but still ambiguity whether it is 100% verified. We have a vero design (but I can't seem to get working, at least outside a box). We have/had 2 different PCBs. The layouts I did get working again sounded amazing...however, so much noise un-usable. I brought up the question on component selection also back in the thread...maybe not so into the signal chain, but nonetheless differences from "baseline"

Can we clean this thread up and confirm once and for all schematic to original pedal? Then create and confirm a PCB?? I've personally spent hours, days, and weekends building and with nothing to show but lost time, which is very rare and valuable to me. I did recieve Buggs PCB, but reluctant to build it up until I'm assured at the end of the day it is correct or close and will work and noise free with a useable pedal. If the tone isn't there or noise floor not close to BE-OD, it's useless. I'm not certain is Weedman or Buggs PCBs are "verified". They appear to be, but until this gets sorted out, apprehensive to complete and invest more time in an unknown. Please your support and advise.
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Re: Friedman BE-OD Pedal

Postby caspercody » 18 Jul 2017, 18:53

RMROZA,

If you have a Friedman BE-OD pedal, please open it up and take pictures? Sounds like we need more pictures to verify the schematic.

Thanks
Rob

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Re: Friedman BE-OD Pedal

Postby bugg » 18 Jul 2017, 19:01

I know of four people (including myself) who have built the pedal from my PCB and been satisfied with the results. The controls all behave as expected and the noise floor is reasonable for a pedal with this much gain.

I can't confirm nor deny bajamans comments, the guy knows his stuff and I'm not going to argue with him. :D

With that said, in my personal build the presence control works like it should.

You have the original pedal AND the PCB, you'd be the most qualified to build the thing and A/B the circuits.

Better yet, do like caspercody suggested and open yours up and post some pics. I'll be more than happy to update my layout if someone confirms a better schematic. If this happens I'll gladly replace the PCB for shipping cost alone to anyone who isn't satisfied with the results.

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Re: Friedman BE-OD Pedal

Postby caspercody » 18 Jul 2017, 19:52

Bugg,

Thanks for the over, I just got my board yesterday and it is quite beautiful and well made. Worth the money!

Looking at the board and schematic, I do not think it would be to hard to add the presence per Bajamans suggestion.

Do you have the layout showing the components numbers and values? The schematic just shows the value and the board just shows the component number. Trying to match them up to change the presence.

Thanks
Rob
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Re: Friedman BE-OD Pedal

Postby toneman » 18 Jul 2017, 22:12

Yeh, i've started a folder with all the versions of schematic and a text file of all the changes and additions :?

As soon as my pcbs arrive i should be ready to build!?! ha ha! :scratch:

Yeh, having part numbers associated with values would be a BIG help in communicating any mods/improvements! :thumbsup

still dont see how a series pot makes for a "presence" (midrange) control :hmmm:

the v1.4 schematic looks the most likely to succeed imho.

big wheels keep on turning.........

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Re: Friedman BE-OD Pedal

Postby bugg » 18 Jul 2017, 22:42

http://www.buggfx.com/files/Thermionic.zip
Schematic (for PCB) has been updated with reference designators.

I'm looking now, if I can come across one of these in the $150 range I'll buy it and we'll put an end to this madness.

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Re: Friedman BE-OD Pedal

Postby bajaman » 18 Jul 2017, 22:47

bool
using 1N4148 (x4) diodes as clippers instead of the 2x ZTX951 transistors increases the overall gain of the pedal by 20db centred around 6khz :shock:
no wonder this thing squeals and is super noisy with the wrong clipping devices - the choice of this particular transistor plays a major role in the compression and gain structure of this pedal :wink:
Interestingly, I tried simulations with MPSA56 pnp devices and got similar results to the 1N4148 diodes albeit with a slightly decreased top end gain but nonetheless absolutely useless for this circuit.
Playing with the feedback resistor when using 1N4148 or MPSA56 lowers the gain overall but then reduces the bottom end response around 100hz by 20db which again is useless.
Using a single pair of BAT85 schottky devices only increases the gain by 9db at 6khz BUT at the same time reduces the gain at 100Hz by -12db, effectively tilting the almost flat response characteristic with the ZTX devices like a see-saw. i even tried 2x red leds but just got the same response as with the schottky diodes but with 6 db more gain !
On the face of things, these ZTX951 or similar devices are crucial to nailing the response characteristic of this pedal - diode clippers will NOT work properly :!:
I shall keep experimenting with other pnp transistors and hopefully may find a suitable alternative. My ZTX951 transistors arrive from http://www.rs-components.com today - looking forward to fitting them and will advise results.
cheers :)
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Re: Friedman BE-OD Pedal

Postby bajaman » 18 Jul 2017, 23:53

@Bajaman, the amended shcematic you posted above, is there any areas you may think might be dubious due to pictures not having enough detail to trace ?


In the v1.4 schematic: C8, R9, and R10 are more likely connected as in bugg's thermionic distortion diagram :wink:
C10 is not fitted as far as i can see.
C5 is far more likely to be 47p as in bugg's schematic - possibly even lower in value :wink:
Perhaps R12 should be placed in a similar place to R15 in the following gain stage (connected to the inverting input ) :hmmm:
really - someone who has the pedal should use a multimeter and measure for accurate schematic layout at the very least before anybody tries to build this pedal :slap:
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Re: Friedman BE-OD Pedal

Postby toneman » 19 Jul 2017, 00:43

bugg wrote:I'm looking now, if I can come across one of these in the $150 range I'll buy it and we'll put an end to this madness.

there's one on Ebay right now for $149.99 + shipping
http://www.ebay.com/itm/FRIEDMAN-BE-OD- ... 1438.l2649
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