Friedman BE-OD Pedal  [traced]

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Re: Friedman BE-OD Pedal

Postby J0K3RX » 15 Jun 2017, 22:54

bmxguitarsbmx wrote:I like both Groovenut's ideas. I was able to get volume cleanup by simply omitting the BAV99 clipping diodes (admittedly on accident). Lowering the gain of this stage, through r9/c8, seems promising to me.


You could make R9 a B25K pot..
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Re: Friedman BE-OD Pedal

Postby bool » 16 Jun 2017, 11:17

On both "nfb-clipping" gain stages, the clipping diodes are wired/padded with a series resistance. So the "soft knee" is fixed. One mod to try would be to replace the resistors (22k in both stages) with something like a 50K pot (or a trimmer), and dial-in your own soft-knee.

The second stage (inverting clipper) could use leds instead of standard diodes to increase the headroom for a hair and you could replace the 220k gain resistor with a 100k+120k combo and a on-off-on switch to choose gains 10 (original), cca. 4,5 and 5,4 ... etc.

The original circuit topology is clean and allows for much home tweakery.

Perhaps the baddest mods could be presented to Mr. Friedman himself, like "from teh internets with Love ..."

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Re: Friedman BE-OD Pedal

Postby Groovenut » 16 Jun 2017, 15:24

rmroza wrote:Thanks Groovenut

I don't like the pot suggestion as that's only going to change the taper of when the gain comes in, but the amount on the bottom and top with the pot at "0" and 10" will still remain the same.

I'm ok with the "10" gain on the top side. I'm looking to take away gain from the bottom side, so really need it to go from like -5 to 10 or -10 to 10. We're missing the below "0" gain.

Since the first gain stage is fixed, this is very similar to Dave's amps. He keeps the 1st gain stage fixed, basically at "10" but with a given set of gain based on plate, cathode values and voltage divider, so ideally, stage 2 is there it would need to be controlled and similar to his amp(s). I'll try it once built up and get more usefull gain so that is goes from booster thru distortion instead of distortion to more distortion and no boost nor overdrive....a more useful pedal. Put two on the pedalboard and have one as an OD and one a full on distortion based on gain levels! :)

There's no real reason you cant change R5 to something like 4k7 or 10k or better yet put a switch across it so you can have both a buffer or the original amplifier stage. Friedman's real amps (BE and HBE) both "suffer" the same "gain starts too high" issue (if that's even an issue). Placing the gain control after the second gain stage just limits your ability to control the gain, plain and simple. However, without completely changing this design there are ways to get better perceived gain control. The main reason I suggested the LOG gain pot is, as I stated 2% on a LIN pot may actually be with the pot fully counter clockwise, whereas most LOG pots will be 2% at about 9 o'clock and 15% at about noon. If you combine this with making R10 smaller, say 4k7 or 10k, you can move the lowest gain level of the stage down. As designed, GS2 is 22k/22k+1=2, so even with the gain pot at zero there is an amplification factor of 2. This may be to keep the LEDs from dropping out of conduction and avoiding an audible change in the distortion.
If you look at the gain levels of each stage you can see this thing will distort pretty much even the smallest signals GS1=2.77, GS2=2.77-47.5, GS3=10, GS4=1-10
You could get a bit more headroom by doubling the number of diodes in GS3 (BAV99). This should give you about the most headroom before this stage hits the rails. The only reason I wouldn't go with LEDs as a replacement in that stage is they will change the distortion character. I suppose you could run an LED + BAV99 for higher headroom and still maintain the original clipping character.

just a few thoughts....

:thumbsup
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Re: Friedman BE-OD Pedal

Postby bool » 16 Jun 2017, 15:41

Leds would def change the character. More of the same kind of diodes would also change the character a bit; but less compared to changing them to another type.
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Re: Friedman BE-OD Pedal

Postby caspercody » 17 Jun 2017, 01:16

Are there two or four BAV99 diodes in the original circuit? Reason I ask is looking at the BAV99 data sheet there are two diodes in one BAV99

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Re: Friedman BE-OD Pedal

Postby Groovenut » 17 Jun 2017, 02:35

caspercody wrote:Are there two or four BAV99 diodes in the original circuit? Reason I ask is looking at the BAV99 data sheet there are two diodes in one BAV99

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Rob

There are 2 BAV99 packages on the pcb, so 4 diodes total
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Re: Friedman BE-OD Pedal

Postby bool » 18 Jun 2017, 12:51

When comparing datasheets for BAV99 and 1N4148, across different makers, it appears that 99's and 4148's have a bit different knees and forward voltages at low currents. Also different junction capacitance, but in such a low register that it is doubtful it would get "heard" at guitar range.

So for those that built the circuit with 4148's, it would appear that raising the 22k resistor in series with BAV99s - when used with 1N4148s - a bit, say to 24k or 27k; would likely produce the clipping character a little bit closer to what goes on in the original.

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Re: Friedman BE-OD Pedal

Postby kirilpetroff » 18 Jun 2017, 15:49

Few days now since I built the BE OD. Thanks to everybody doing the hard work of tracing it - I know the SMD components of the original are not making the job easier.
I want to share some of my experience building the circuit. I kept strictly to the schemtatic of ver 1.2. However my clone was heavily oscilating - especialy at higher trimmer settings. After reading everything on the forum and triple checked for mistakes, shielded the input and output nothing seemed to help. I noticed however that lower HIGH and PRESENCE settings stop the oscilation. So I replaced C12 with 470pF instead of the original 120pF. That solved the problem and the circuit still has more than enough high end. I suspect that either some component I used was waaaaaay out of specs or the highcut capacitors C12, C9 or C13 might have different values in the original pedal. (Could also be the placing of components, but I'm experienced enough to avoid placing inputs and outputs nearby).
I would ask somebody who has the original to double check them just in case!
Now about the sound: That's the best high gain pedal (not amp) cirquit I heard or played. Compared it yesterday on a gig with a Wampler Triple Wreck clone I made before. It's simply better for the classic 80's rock lead sound I'm after in this pedal. The Triple Wreck can do other things (like the scooped mids sound) but for good lead sound - It can't match the BE-OD. Especially the TIGHT control is what impressed me the most.

P.S. Maybe it would be good to design a pedal with stereo pot for the GAIN and the TIGHT together (but working backwards). So more gain would give you less bass on the input and low gain more so (Just an idea...). Still the taper of both doesn't make it practical for this exact cirquit and it would need a lot of tweaking to make it right.

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Re: Friedman BE-OD Pedal

Postby rmroza » 19 Jun 2017, 06:08

Well,I almost finished building it up yesterday, then I realized the layout had things like "C1" and such on it!!

I realized I had built it up to an older version that the latest!! Man, I was pissed

Then I noticed on the final, it gives instructions on what to do is you have this version! I made all of the amendments to cap and resistor value, removed/didn't put in the one cap but stopped with the last step is says to put in the 100n cap but it should go to ground and not B+!! Does that mean I have to add a jumpe to ground or something?? If I can get this resolved, I can finish it and A-B it. someone let me know. so I shelved it and built up an amp design I've been working on over the rest of yesterday and today while I figure out how to hook it up

F-ing sux because it's almost done and I'm stuck. I don't have any more veroboard either!! arrrr. Not happy
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Re: Friedman BE-OD Pedal

Postby pakrat » 20 Jun 2017, 02:49

rmroza wrote:Well,I almost finished building it up yesterday, then I realized the layout had things like "C1" and such on it!!

I realized I had built it up to an older version that the latest!! Man, I was pissed

Then I noticed on the final, it gives instructions on what to do is you have this version! I made all of the amendments to cap and resistor value, removed/didn't put in the one cap but stopped with the last step is says to put in the 100n cap but it should go to ground and not B+!! Does that mean I have to add a jumpe to ground or something?? If I can get this resolved, I can finish it and A-B it. someone let me know. so I shelved it and built up an amp design I've been working on over the rest of yesterday and today while I figure out how to hook it up

F-ing sux because it's almost done and I'm stuck. I don't have any more veroboard either!! arrrr. Not happy


Hope this helps:
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Re: Friedman BE-OD Pedal

Postby rmroza » 20 Jun 2017, 18:51

pakrat - Yep. That's makes it very easy and I can utilize the board, thanks! :) There were additional updated instructions for the veroboard also I'll need to do "- The link under the trimmer (from lug 1 to lug 2) needs to be moved up one row (between lug 2 and lug 3). Eliminate the cut under the trimmer by jumping it left to right."!!

My local electronic store had Veroboard, so I picked some up yesterday. I built up TWO boards yesterday to the "current" layout! I was missing a couple components, so I borrowed them from the inital board (I'll replace later).

Unfortunately, the pedal did not work!...but I've been working 16-18 hour days, so will check it as time permits, but unable to get going and A-B, so just worked on finishing an amp I'm working on which I almost got ready working til 12am! I'll finish tonight.

Soo, can someone also point me to the "final" schematic?!? There are 2 or 3 different people with schematic posts or so it appears and different versions!!
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Re: Friedman BE-OD Pedal

Postby caspercody » 20 Jun 2017, 20:04

I think if you click the "Traced" in the description it will forward you to the reply with the schematic.
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Re: Friedman BE-OD Pedal

Postby bmxguitarsbmx » 20 Jun 2017, 20:30

caspercody wrote:I think if you click the "Traced" in the description it will forward you to the reply with the schematic.


Sadly, that would be an error. The "[traced]" got pushed a bit prematurely. I have built the last three latest versions posted. They all work.
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Re: Friedman BE-OD Pedal

Postby jalmonsalmon » 21 Jun 2017, 03:59

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Re: Friedman BE-OD Pedal

Postby rmroza » 21 Jun 2017, 16:59

Soo, this is the latest schematic link?!? http://www.freestompboxes.org/download/file.php?id=29573&mode=view

I got the new amp design working and done yesterday! Wow! Funking amazing! 20 amps....best in the house!

Now I can work on trying and getting this pedal complete tonight after work and A-B it...I hope.
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Re: Friedman BE-OD Pedal

Postby jalmonsalmon » 22 Jun 2017, 01:37

http://www.freestompboxes.org/viewtopic.php?f=7&t=27775&p=260737&&sid=0b2f99809e11ab1e8a1a955f12e33825#p260737

From what I can tell, this is the one to use... one I drew up on the test posts is not 100% correct.
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Re: Friedman BE-OD Pedal

Postby bmxguitarsbmx » 22 Jun 2017, 04:11

rmroza: that one will be very far from correct/fitting your layout

jalmonsalmon: that one will not bias up.

Use this one. I have built it and it sounds good. It is, as far as I know, what Alex based his layout on.

download/file.php?id=29554&mode=view
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Re: Friedman BE-OD Pedal

Postby rmroza » 22 Jun 2017, 14:30

Ok, thanks. Yeah, I took the layout and was following the paths on a couple schematics and the two I did, neither fit the actual layout, so did not appear right. I'll check this one also.

Is anyone doing a PCB layout?!? WIll be much less time consuming than all of the components, cuts and jumpers.

I'd like to finish this build and A-B it. Reviewed one video yesterday and tone did not appear right, but could be the person, his amp, etc.
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Re: Friedman BE-OD Pedal

Postby bmxguitarsbmx » 22 Jun 2017, 23:24

rmroza wrote:Ok, thanks. Yeah, I took the layout and was following the paths on a couple schematics and the two I did, neither fit the actual layout, so did not appear right. I'll check this one also.

You could... edit it. You know, DIY style.
rmroza wrote:Is anyone doing a PCB layout?!? WIll be much less time consuming than all of the components, cuts and jumpers.

Yeah, obviously. If we value our time at all, we would just go buy it. What's the fun in that though?
I have serious doubts that any of these schematics are correct. I know you are an engineer, so I figured you could trace all connections on the pedal.

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Re: Friedman BE-OD Pedal

Postby bugg » 23 Jun 2017, 03:35

I had some PCBs fabricated based on the most recent schematics, built one today. Sounds fantastic!

It's been a few months since I owned the original so I can't give an A/B comparison but all of the controls seem to react as expected and the thing sounds massive. Plenty of gain (with trim at 50%) and plenty of volume.

Thanks to everyone involved for the effort!

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