Fairfield Circuitry - The Barbershop (gut)  [traced]

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jighead81
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Post by jighead81 »

Yeah Fremen, the 47R (R10) is part of the protection circuit. I left all that off of my build. I did the vero off tagboard, works great.

I wonder where this tone switch is implemented in the circuit? I'm sure it's for the highs, but where would that go? On the 10n input? Gonna play around with some alligator clips and other caps tonight

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maortojn
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Post by maortojn »

Has anyone found out about how to implement the new tone switch into the previous layouts? Or about other changes to the circuit from v1 to v2? All answers appreciated!

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knutolai
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Post by knutolai »

you could try a cap to ground from the NPN base. That should give you a post-distortion LPF

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maortojn
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Post by maortojn »

Thank you for the tip! I'll try it out :thumbsup

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zedsnotdead
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Post by zedsnotdead »

Sorry for necro post, but does anyone confirmed where the tone switch is going, and what values are used on V2?

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Brazdj
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Post by Brazdj »

Would anyone mind and post their voltages from a successful build? I am getting strange voltages akin to those posted much by others much earlier.

Shame I had this thing working no problem like 6 months ago, finally got around to boxing it up and now it is a volume pedal. The JFETs are not driving enough to actually induce clipping...or that is what it feels like.

I am most curious of the gate voltages successful builders have.

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Brazdj
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Post by Brazdj »

Ignore previous request.

For future builders: This pedal absolutely needs to be biased to ~6 volts on the J201 drains. With the stock resistors as shown on the layout at the tagboard site (8.2k and 9.1k), my drains had voltages around 7.25 to 7.6. At these voltages, the pedal is pretty much a volume pedal other than at extreme pot rotations.

Either use 20K trimmers or install everything as shown w/ the stock resistors and then use the voltage law to back out the correct resistance V= I*R. You can measure the voltage drop across the resistor, solve for I since you know R. You want a Voltage drop ~ 9.XX - 6 = 3.xx. Then the R you use = 3.xx/I.

Or to do it one step. Measure your voltage drop across the resistor then: Rnew = 3.xx / (V drop-from-old / R old)

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deltafred
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Post by deltafred »

A friend bought one recently, I was very impressed so built one.

Not having any J102 FETs I substituted 2N5457, used 10k presets for the drain resistors and biased them to 6v.

Total fail. At best it was a clean boost, at worst nothing. Turning the sag control caused it to cut out, and the boost control did next to nothing.

The J012s arrived today and I put 2 in. What a difference although I don't think that it has much gain as the original, using the same bass resulted in no overdrive. When I swapped to a G&L SB-2 (crazy hot output) it came to life.

Is the schematic below, originally posted by WhiteKeyHole on page 3, the correct one to use?
Fair2.png
Fair2.png (5.07 KiB) Viewed 3685 times
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plush
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Post by plush »

deltafred wrote:Is the schematic below, originally posted by WhiteKeyHole on page 3, the correct one to use?
I don't think so. Afaik, there is still no correct shematic on the web.

2 main things that drive me nuts:
-no pulldown resistor to drain output cap (jesus, it pops)
-sag control does not work as it does on demos

Something is definitely missing.

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snk
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Post by snk »

Hi,
I built this pedal yesterday, and it works fine, except that the SAG knob doesn't seem to do anything on my build :?:
Plush (and/or other members), did you manage to find what was making yours not working as expected either ?

Also, i think it rolls off the bass a bit too much to my taste. Should i increase the 10nF cap right after the input, or maybe the 100nF cap at the output ?

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Manfred
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Post by Manfred »

snk wrote:Hi,
I built this pedal yesterday, and it works fine, except that the SAG knob doesn't seem to do anything on my build :?:
Plush (and/or other members), did you manage to find what was making yours not working as expected either ?

Also, i think it rolls off the bass a bit too much to my taste. Should i increase the 10nF cap right after the input, or maybe the 100nF cap at the output ?
Messure the voltage at lug 1 of the SAG potentiometer and have a look if the read voltages varies.

Try capacitors from 22nF to 33 nF for C4.

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snk
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Post by snk »

Hi, Manfred :thumbsup
Thank you, i will read the voltage at lug 1, and try a bigger input cap.

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Manfred
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Post by Manfred »

and try a bigger input cap.
Hi Snk,

The roll-off frequency of the input circuit is 8Hz.
If you increase the input cap to 100nF the roll-off frequency goes down to 0.8 Hz.
The roll-off frequency of the filter formed by C4, R6 POT1 and R9 is 24 Hz.
The roll-off frequency due to the bypass capacitor is about 30Hz.

Maybay I have misunderstood, what do you want more or less bass content?

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snk
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Post by snk »

I would like more bass content.
As it is, built to spec, it cuts quite a lot of bass content (i would say below 100Hz).
It sounds good, the bass is rather clean, but it is very audible that there is some bass loss.

That is strange to read that the pedal is supposed to left all the content above 30Hz is supposed to be untouched, because there is actually some signal loss in the bass range.

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Post by Manfred »

snk wrote:I would like more bass content.
As it is, built to spec, it cuts quite a lot of bass content (i would say below 100Hz).
It sounds good, the bass is rather clean, but it is very audible that there is some bass loss.

That is strange to read that the pedal is supposed to left all the content above 30Hz is supposed to be untouched, because there is actually some signal loss in the bass range.
Roll-off frequencies for other bypass capacitor values:
22uf -> 14Hz
47uF -> 6Hz
68uF -> 4Hz

Roll-off frequencies for other couple capacitor values:
68nF -> 17Hz
100nF -> 12,6Hz
150nF -> 8Hz

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snk
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Post by snk »

Hi,
I just made a test : I recorded a synth loop, first dry then processed through the Barbershop.
You can listen to it here, and i think you will hear the bass loss (initially, the Barbershop's gain is a bit high, so after a couple seconds i lower the gain a bit to get less saturation and more volume matching).
https://vocaroo.com/i/s1hbEMYHXUHY

Then, I played both loops at the same time, and compared their spectrum : in pink, you can see the DRY sound, and in GREEN, you can see the processed sound.
barbershop freq.png
- The Barbershop seem to be cutting the low end below 100hZ, with around 10dB loss at 50Hz.
- It also seems to increase the Highs (which is to be expected with a harmonic-generating device, and which is not an issue).

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Post by plush »

snk wrote:I would like more bass content.
I guess you may want to increase C4 then.

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snk
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Post by snk »

I increased C6, and the bass is back :)
By the way, I tried with a buffer after the pedal, and also the bass came back. I think i will build a small buffer, and put it in the enclosure, so i will be safe wherever i put the pedal in my chain.

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Post by Manfred »

snk wrote:I increased C6, and the bass is back :)
By the way, I tried with a buffer after the pedal, and also the bass came back. I think i will build a small buffer, and put it in the enclosure, so i will be safe wherever i put the pedal in my chain.

The roll-off frequency is depend on the load, then you are on the right track by adding the buffer with a suitable input resistor to fix it.

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snk
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Post by snk »

Yes, i am planning to add this little buffer :
Image
http://tagboardeffects.blogspot.com/201 ... ffers.html
I know that the 1M resistor gives the impedance, so this should be good, right ?
Should I make the cap bigger, to let more bass through, or does it have another purpose in the circuit ?

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