freestompboxes.org

alkuz1961 wrote:I'm sorry, but I can clearly see that this is not a 1A7. It's just a symbol, like an upside-down "i"

They are indeed fairchild BAV's but no matter, ZTX951 according to Bajaman are the winners!

ok...for the sake of CLARITY...

Are we now saying that mine (and Buggs) schematics are correct as far as the ACTUAL Friedman pedal goes? (identification of dual diode package not withstanding)

...and that bajaman has come up with the first MODIFICATION?

Apologies for shouting but this thread suddenly got very noisy again.

Yes that is correct. I'm working on verifying the trace against the original pedal this morning, but so far my PCB is correct.

Also worth mentioning, this isn't my schematic, I simply redrew the one posted earlier in the thread (by you and pakrat I believe).

"Just to clarify, I can't confirm that the component is a BAV99, but it is a dual diode, definitely not an NPN or PNP transistor."

Did you want me to desolder one and put it on my Atlas analyzer and see what readings i get??

"They are indeed fairchild BAV's but no matter, ZTX951 according to Bajaman are the winners!"

I think this is where we get into the baseline versus modification/personal opinion thing! Of course no one likes noise, but some people LIKE a mid-hump. Final version should be Baseline "verified" as off the shelf, then FSB veteran recommened changes IMHO.

"Are we now saying that mine (and Buggs) schematics are correct as far as the ACTUAL Friedman pedal goes? (identification of dual diode package not withstanding)

...and that bajaman has come up with the first MODIFICATION?"

Ahahah, looks like Yellow Boy beat me to it and baseline v. recommened modified.

Looking forward to the confirmation of the trace. I'm off to an all day Pandapalloza event today and dads birthday hosting tomorrow, so as usual, f**king swamped. But if you need me to check any components like I said on the analyzer or whatnot...let me know and I'll set aside time to desolder, read and resolder back up so i have something to A-B.

So....the dual diodes labeled D6 and D7 on the original pcb are the diodes in the feedback path of U2.1?
(they are now labeled D3, D4, D5, D6 on the Thermonic Build pdf)??

And....a super good sound substitute are diode-connected ZTX951 transistors which are in a TO-92 case?



all the other diodes are LEDs....(?)

just for clarity....

toneman wrote:So....the dual diodes labeled D6 and D7 on the original pcb are the diodes in the feedback path of U2.1?
(they are now labeled D3, D4, D5, D6 on the Thermonic Build pdf)??

all the other diodes are LEDs....(?)

That's correct.

rmroza wrote:"

Did you want me to desolder one and put it on my Atlas analyzer and see what readings i get??

If you don't want to risk toasting them with your iron I think you can isolate them enough if you remove C12 and R12..

I think we may be getting the ! or i confused with a 1 like alkuz1961 pointed out.. that looks like a manufacturer logo.

bajaman - Very cool find with the ZTX951

I thought I read somewhere that the BAV99 package was supposed to replace the need for 2 of the 1N5819 diodes but, I am not sure of the application..?

J0K3RX wrote:
I thought I read somewhere that the BAV99 package was supposed to replace the need for 2 of the 1N5819 diodes but, I am not sure of the application..?

Here is a schematic with a couple uses of the BAV99. Input protection and clipping.

Cheers Bugg! I'm not looking for any credit...I just tidied up what was discussed earlier. You took it to the next level and gave us something we can actually play with so thanks for that!

Can a mod PLEASE fix the [traced] link to point to something useful?!?

I will keep searching for an equivalent transistor to use in place of the ZTX951 modification but, so far it is the only device that has the almost ruler flat response characteristic from 90Hz to 8Khz with a very small very low Q 4db rise centred around 900Hz (simulated response with 500mv input signal, tight on full, gain on 20%, trim on 50% and treble, presence, bass controls on full.)
With the same settings using the 4 x 1N4148 (or the equivalent BAV99 pairs), there is a massive 20dB low Q boost at 3.5kHz shown in the response characteristic - more a presence boost than a mid boost
No wonder folks have reported oscillations, squealing and noise when the gain treble and presence controls are adjusted past 50%
YES - the schematic that yellowboy and pakrat and the board that bugg has provided is CORRECT and true to the actual Friedman BE-OD circuit
HOWEVER, I would strongly encourage those wishing to build this pedal to purchase one of bugg's excellent boards (still waiting for mine to arrive bugg ) and try the ZTX951 pairs - you could even fit a small toggle switch to switch between the diodes and the transistors.
I remember a Music Man amplifier using a similar clipping arrangement with transistors back in the late70s early 80s - I shall try and dig it up for you.
Have fun and enjoy the music
bajaman

the clipping section from the Musicman 2100-150 amplifier
A bit different but perhaps worth playing around with ?
cheers
bajaman

What about using an NPN instead of a PNP???

How about the complement of the ZTX951?
ZTX851---specs look very similar.....60V, 130MHz, 1.2W, TO92, still costs a buck each!

https://www.diodes.com/assets/Datasheets/ZTX851.pdf

Or.....

2 PNP and 2 NPN in feedback path?????

I am NOT crazy!!
Don't listen to those OtheR people behind the curtain!!

bajaman wrote:
the clipping section from the Musicman 2100-150 amplifier
A bit different but perhaps worth playing around with ?
cheers
bajaman

The stompbox cookbook has a good section on this circuit. Including variable clipping threshhold and transfer response (via gate r).

What are you using to sim Bajaman?

What are you using to sim Bajaman?

National Instruments Multisim 14.0
cheers
bajaman

What about using an NPN instead of a PNP???

How about the complement of the ZTX951?
ZTX851---specs look very similar.....60V, 130MHz, 1.2W, TO92, still costs a buck each!

Hi Toneman - thanks - I ran the sim with the ZTX851 and got the same response characteristics as the ZTX951
cheers
bajaman

ps: I tried sim with the Zetex spice model for the ZTX109 which i assume is their version of the BC109 , just to satisfy my curiosity - alas, there is that 18db boost centred at 3.5kHz - slightly lower than the 1N4148 but a big presence boost nonetheless - now i see why friedman added the bass boost control at 70Hz

The stompbox cookbook has a good section on this circuit

can you point me to the right chapter and i will take a look

Hi, I was a member who was watching with interest.

Recently, I looked at bugg's Thermionic circuit diagram and made it with a personal layout.
Bugg's pcb looked great, but I wanted to put it in the 1590A case, so I make it with my own layout.

I also made it with 4 x 1n4148 and I thought the sound was out of the question.
The only thing I missed was that I had to set the internal trimmer to zero.
Even with a little turning, there's a squeal even at about 12 o'clock in Gain / Treble / Presence.
Of course, leaving the trimmer at zero does not matter.
In fact, there's enough distortion even with the trimmer 0 setting, but I feel the explosive feeling when the trimmer is raised,
so I wanted to replace 4148 with the ztx951 that bajaman praised.
I was also curious about the sound, but I was attracted to the fact that the squeal disappears.

However, ztx951 is a BJT, and I haven't seen any example of clipping with BJT yet.

Could you tell us the diagram that bajaman applied ztx951?

also worth consideration are the ZTX851 and ZTX849 npn transistors - again connected with reversed base emitter junctions.
The ZTX849 is the flattest simulation yet - beats the ZTX951 by reducing the slight mid peak by 1 dB, although this would be difficult to hear in practice
Both the ZTX951 and ZTX851 devices are available http://www.rs-components.com if you are having any difficulty sourcing them from your local
cheers
bajaman

I carried out simulations with the Musicman Clipping circuit.
At first I used the ZTX109 transistor model and the 2N5088 model after,
featuring input voltages of 0.7 Volts and 2 Volts.
The output shows the same curve shapes in each case.
I believe that the applied transistor type is non-critical.