Vintage Fuzzes\Boosters Voltage Readings

[Mr.Kite]

Hi folks, first post here! 

I've just discovered breadboarding and I'm extremely excited, especially since I'm getting already astonishing results, to my ears at least...

I have an old (pot dated 1976) JEN Super Double Sound Fuzz\Wah, which is basically a Vox Distortion Booster (V8162) without control knobs and a Vox Super Cry Baby in the same enclosure. I've breadboarded the fuzz circuit with stock resistor values and a BC209 (Hfe=204, Q1) and a "unknown" transistor (Hfe=211, Q2) which looks and sounds like a BC107\8\9. On the schematic and in this picture we can find BC108A trannys, which should have an Hfe around (or even below) 200:





The Double Sound, on the other hand, has BC238B trannys with an Hfe probably around 300, or even higher! So, they bias differentely, with stock resistors values. I've measured my vintage unit, after 15 minutes or so, at room temperature, to "stabilize" the voltages:

Battery: 9.11v

Q1: c -> 1.31v
      b -> 0.61v
      e -> 0.00v

Q2: c -> 6.36v
      b -> 1.31v
      e -> 0.69v

While on the breadboard something like:

Q1: c -> 1.4v
      b -> 0.65v
      e -> 0.00v

Q2: c -> 5.5v
      b -> 1.4v
      e -> 0.75v

I got closer with some resistor swap and they sounded IDENTICAL to me, except a little more compression from the old unit, but a tiny tiny amount...I just wanted to see if I was able to get even closer, and I did, but it sounded better to me around 5.5-6v, not over...

My question is: do you think they used those higher gain trannys on purpose, without altering the resistors and biasing it very "high", or they just used what they had lying around? 
Maybe the circuit actually calls for lower gain trannys? Or they wanted a more "distortion" like charachter in 1976? Who knows, I think I'll stick with 5.5-6v at Q2c and build the final clone, with pots, even if the volume control is useless, you have to leave it wide open! 
While the "fuzz" control arrangement is interesting, it sounds like a fuzzy OD at about 75% or so... 

This is my original:



I'm breadboarding a LPB-1\Screaming Tree, a Dallas Rangemaster, and a Tone Bender MK 1.5, and I think I'm in the ballpark with all the circuits, but if some of you wants to share readings of vintage units with me\us, I would be extremely grateful!

Happy builds to everyone! 

Cheers!

[duck_arse]

welcome to the forum, MrKite.

if you want more volume, move the 100nF output cap 'closer' to the collector. increase the value of the 270R whilst decreasing the value of the 10k. maybe try 680R and 9k1, something like that. it's easy on the BB. your collector voltage should/will shift about a little.

[Mr.Kite]

Thanks!

Yeah, I know that trick for the volume, works flawlessly...

In your opinion, the higher bias on the JEN version of the circuit, was on purpose or "accidental"? It is definetely fuzzier at lower voltage, maybe they were trying to get a smoother sound out of the old circuit, in 1976? I think I prefer a slightly lower voltage, today there are better distortion pedals than a fuzz face! But maybe, back then, biasing it higher was a way to make it sound more "distortion like"?

If someone has voltage readings of vintage units (FF, Tone Benders, Rangemasters etc...) and wants to share with us, this could become a very interesting thread...

There are a couple of things that I don't fully understand in the circuits I'm breadboarding: first, in a LPB-1, when the power supply voltage goes DOWN, Q2c voltage goes UP??
And second, what's the purpose of that 18k output resistor in the fuzz section of the JEN Double Sound? Certainly it doesn't attenuate the signal "per se", maybe increases the output impedance, and so cuts the volume because there's a Vox Wah with a low input impedance hardwired right after it? So it doesn't overload the Wah circuit when used simultaneously?

[PRR]

The mojo is in that Ducati "bipolare" capacitor on the right.

Kidding! 

Ducati now makes motorcycles, very sleek fast bikes. 1944, SIATA made a cute little bike-engine. By 1950 Ducati was making them. Later the fastest 250cc on the road, then some wicked 2-bangers. Ownership was passed around; currently VW.



I had seen Ducati caps before, and got curious. Indeed In 1926 Antonio Cavalieri Ducati and his three sons... founded Società Scientifica Radio Brevetti Ducati ...to produce vacuum tubes, condensers and other radio components..


The radio-parts operation Ducati Elettronica was split from the bike-shop in the 1950s and is still around under new name and expanded products.

[thermionix]

Being for the benefit of OP... (sorry, had to)

first, in a LPB-1, when the power supply voltage goes DOWN, Q2c voltage goes UP??

There is no Q2 in an LPB-1.

[Mr.Kite]

Being for the benefit of OP... (sorry, had to)

There is no Q2 in an LPB-1.

Yeah, thanks, it was a typo!

But Q1c voltage still goes up when the PS goes down... 

[Mr.Kite]

I had seen Ducati caps before, and got curious.

Yes, I know Ducati, I'm italian by the way!

The other day I found this in a local electronic shop:



Which is full of these:



There's also some Ducati cap, like the little blue electrolytic on the far right...Philips, Sprague, it seems good stuff!

I have a 1970 Vox Wah with a Ducati Bipolare: IME, they started using it in 1965-66, and stopped in 1970-71, but it may vary...



Uh, and these are the guts of the 1976 JEN Super Double Sound:



Quite different components, but the only different value is the 4.7uF cap vs the 4uF Ducati Bipolare in the Vox: it increases slightly the "boost" of the sweeping frequency, which coupled with a longer travel in the JEN gives them two distinct voices. The Vox sounds like Hendrix, the JEN like Jimmy Page, if we want to simplify...

[duck_arse]

those Ducati caps must have 'a very distinct tone', and they must go very fast, indeed. are those silver single ended "things" visible thru the side polystyrene/styroflex caps?

[Electric Warrior]

I have a 1970 Vox Wah with a Ducati Bipolare: IME, they started using it in 1965-66, and stopped in 1970-71, but it may vary...

The Wah was introduced in 1967. Pot codes could be earlier, though.

I have an old (pot dated 1976) JEN Super Double Sound Fuzz\Wah, which is basically a Vox Distortion Booster (V8162) without control knobs and a Vox Super Cry Baby in the same enclosure. I've breadboarded the fuzz circuit with stock resistor values and a BC209 (Hfe=204, Q1) and a "unknown" transistor (Hfe=211, Q2) which looks and sounds like a BC107\8\9. On the schematic and in this picture we can find BC108A trannys, which should have an Hfe around (or even below) 200:
(...)

The Double Sound, on the other hand, has BC238B trannys with an Hfe probably around 300, or even higher! So, they bias differentely, with stock resistors values. I've measured my vintage unit, after 15 minutes or so, at room temperature, to "stabilize" the voltages:

Battery: 9.11v

Q1: c -> 1.31v
      b -> 0.61v
      e -> 0.00v

Q2: c -> 6.36v
      b -> 1.31v
      e -> 0.69v

While on the breadboard something like:

Q1: c -> 1.4v
      b -> 0.65v
      e -> 0.00v

Q2: c -> 5.5v
      b -> 1.4v
      e -> 0.75v

I got closer with some resistor swap and they sounded IDENTICAL to me, except a little more compression from the old unit, but a tiny tiny amount...I just wanted to see if I was able to get even closer, and I did, but it sounded better to me around 5.5-6v, not over...

My question is: do you think they used those higher gain trannys on purpose, without altering the resistors and biasing it very "high", or they just used what they had lying around? 
Maybe the circuit actually calls for lower gain trannys? Or they wanted a more "distortion" like charachter in 1976?

(...)

I'm breadboarding a LPB-1\Screaming Tree, a Dallas Rangemaster, and a Tone Bender MK 1.5, and I think I'm in the ballpark with all the circuits, but if some of you wants to share readings of vintage units with me\us, I would be extremely grateful!

When they first set the bias for this circuit they certainly did it for transistors of a certain gain range, so whichever variant came first is probably the one that is biased as intended. That said, the B gain group is just the next bigger one, so the difference in voltages isn't all that dramatic (at least if those BC208As were in the same range as the transistors you used in your build). We can't say wether they used a higher gain transistor on purpose, but apparently it does the job in this circuit, so they didn't bother rebiasing it.
Matching (or mismatching) of the transistors makes a difference in tone in this type of circuit. Are sure the difference you're hearing is the gain and not the transistor selection?

As for the Tone Bender MK1.5:

Battery: -9.99V
Q1 C -0.31V B -0.08V E 0V
Q2 C -7.64V B -0.31V E -0.24V

Q1C is rather high in this one and Q2 rather low. We're in Fuzz Face territory here. It may have been cold when I took the measurement. I'll recheck once I get to restoring the pedal...

[Mr.Kite]

those Ducati caps must have 'a very distinct tone', and they must go very fast, indeed. are those silver single ended "things" visible thru the side polystyrene/styroflex caps?

Yes, there are also some of those...Styroflex, Electro, Polystyrene, Ceramics, good assortment of values but not "all", still good for 5€!

[Mr.Kite]

The Wah was introduced in 1967. Pot codes could be earlier, though.

When they first set the bias for this circuit they certainly did it for transistors of a certain gain range, so whichever variant came first is probably the one that is biased as intended. That said, the B gain group is just the next bigger one, so the difference in voltages isn't all that dramatic (at least if those BC208As were in the same range as the transistors you used in your build). We can't say wether they used a higher gain transistor on purpose, but apparently it does the job in this circuit, so they didn't bother rebiasing it.
Matching (or mismatching) of the transistors makes a difference in tone in this type of circuit. Are sure the difference you're hearing is the gain and not the transistor selection?

As for the Tone Bender MK1.5:

Battery: -9.99V
Q1 C -0.31V B -0.08V E 0V
Q2 C -7.64V B -0.31V E -0.24V

Q1C is rather high in this one and Q2 rather low. We're in Fuzz Face territory here. It may have been cold when I took the measurement. I'll recheck once I get to restoring the pedal...

I was referring to the use of the Ducati Bipolare in general: it was used by JEN since the mid 60's, in other circuits, as in the Vox\JEN Distortion Booster, which was available since late '65, and many other circuits...You're correct, the Vox Wah came later in 1967...

Interesting: likely the trannys on my DS are "less" matched than the ones I chose, I will experiment with some "mismatching"...

Cool! Thank you very much for the voltages! Didn't know they were THAT different from a Fuzz Face: by ear, I guessed that Q2c voltage sounded better higher than 4.5v, and I settled at about 5.5v for a bit, but I tried 7.0v (9.0v PS) and it sounds good too! I can definetly hear a more "abrasive" tone, more asymmetrical clipping, but more clarity and definitition, less compression and more articulation, but I have to experiment with other trannys, I'm using a OC72N (Hfe=45, Leak=0.00mA, Q1) and a SFT353 (Hfe=79, Leak=0.21mA, Q2) and I had to increase the 47k resistor to about 68k to get in the ballpark, but those trannys sound GOOD! 

So, in your opinion, Q1c=~0.25v and Q2c=~7.00v with 9.00v at the board would be a good extimation of an avarage vintage unit?

p.s

45 and 79 with such a low leakage seem very "weak" for this circuit, but actually I get TONS of fuzz and SUSTAIN out of this circuit at the moment, so, it works!
I have to say that I have the pot maxed all the time, but how do you use fuzz pedals?
I'm using 100kA volume pot, 5uF\25uf\0.01uf caps and standard resistors, except for the 47k\68k...

[Electric Warrior]

Interesting: likely the trannys on my DS are "less" matched than the ones I chose, I will experiment with some "mismatching"...

Cool! Thank you very much for the voltages! Didn't know they were THAT different from a Fuzz Face: by ear, I guessed that Q2c voltage sounded better higher than 4.5v, and I settled at about 5.5v for a bit, but I tried 7.0v (9.0v PS) and it sounds good too! I can definetly hear a more "abrasive" tone, more asymmetrical clipping, but more clarity and definitition, less compression and more articulation, but I have to experiment with other trannys, I'm using a OC72N (Hfe=45, Leak=0.00mA, Q1) and a SFT353 (Hfe=79, Leak=0.21mA, Q2) and I had to increase the 47k resistor to about 68k to get in the ballpark, but those trannys sound GOOD! 

So, in your opinion, Q1c=~0.25v and Q2c=~7.00v with 9.00v at the board would be a good extimation of an avarage vintage unit?

p.s

45 and 79 with such a low leakage seem very "weak" for this circuit, but actually I get TONS of fuzz and SUSTAIN out of this circuit at the moment, so, it works!
I have to say that I have the pot maxed all the time, but how do you use fuzz pedals?
I'm using 100kA volume pot, 5uF\25uf\0.01uf caps and standard resistors, except for the 47k\68k...

There are plenty of Fuzz Faces that measure just like this MK1.5. These readings are not different at all. Arbiter biased the circuit just a tad colder than Sola Sound - to fix the temperature problem I guess, as MK1.5s quickly get farty when it's warm. Below 0.2 for Q1C and above 8V for Q2C should be closer to average for MK1.5s. Unfortunately I haven't seen that many voltage readings yet. They're set up exactly like Q2 and Q3 in a MKII, which average around 0.16V on Q2C with an average supply voltage of 9.4V (batteries.. how is that for randomizing things? ), but I don't know if they were selecting transistors any differently for MK1.5s.

That said, voltages in Fuzz Faces can vary quite a bit. Some measure as high as 0.7V on Q1C, bringing Q2 down to 4.5V. But that's really extreme. Still works well, though. As you can see, the usable range is quite wide, so the exact specs of the transistors are not all that critical. Lots of tranistor types should sound good without re-biasing, as long as they're reasonably matched (or mismatched, whichever one prefers).


45 is a little low, yes, but the NKTs Arbiter used were not all that gainy either. They had a spec of 30 to 90 according to the datasheet and there was quite a bit of leakage involved (or they would have had to use a bigger resistor on Q1C, as you did). OC75s, as used in the MK1.5, tend to be quite leaky and a little higher gain.

I was referring to the use of the Ducati Bipolare in general: it was used by JEN since the mid 60's, in other circuits, as in the Vox\JEN Distortion Booster, which was available since late '65, and many other circuits...You're correct, the Vox Wah came later in 1967...

Vox introduced a Distortion Booster in 1965, but it wasn't the italian made one. The first version had germanium transistors and was based on the FZ-1. It's successor had circuit based on the MK1.5/Fuzz Face topology, but it's different from the the circuit we are discussing here. These were probably british made. There was also an american made version based on the same topology, but again, different. The italian made V8162 was introduced in 1968 from what I understand.

[Mr.Kite]

Great info, thank you very much!

I just can't find a Distortion Booster schematic "similar" to a FZ-1, just these two which are both FF-like:





My JEN has the first one, which came later, from my understanding, and was the "plug at the guitar" one...

[Electric Warrior]

The second one should be a V8161, which is a tweaked version of the american V816 with a volume control: http://www.effectsdatabase.com/model/vox/v8161
I haven't ever seen one of these in stompbox format.  All the variants I was talking about were of the "plug-in" variant.

I don't think schematics of two british variants are available online. I only had the chance to trace them recently.
Both circuits came in red enclosures. http://www.effectsdatabase.com/model/vox/v816#pictures
A picture of the germanium circuit can be found here: https://www.seymourduncan.com/forum/showthread.php?242782-Installing-Effects-INSIDE-a-Guitar-or-Bass.

Edit: Maybe the author of the schematic was writing about these: http://www.effectsdatabase.com/model/vox/aria/distortionbooster
They didn't pre-date the plug ins, though.

[Mr.Kite]

Edit: Maybe the author of the schematic was writing about these: http://www.effectsdatabase.com/model/vox/aria/distortionbooster
They didn't pre-date the plug ins, though.

Definitely!