Bearfoot - Model H  [traced]

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tube-exorcist
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Post by tube-exorcist »

earthtonesaudio wrote:A JFET wired like that makes a "low leakage" diode. You'll sometimes see them used in low-drift peak detectors or sample/hold circuits.
...or since 22 years in guitar amplifiers like the boss mg-80:
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Post by celadine »

They´re diode connected JFETs. No big deal. I find they sound very similar to mosfet clippers.

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Post by phibes »

I still get a kick out all these "Hiwatt sound" in a box pedals. Do the guys designing really know what a Hiwatt sounds like or does everybody just base their Hiwatt sound opinion from Pete at Leeds (Which isn't a very good representation of the Hiwatt sound in my opinion)?

:slap:
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Post by RnFR »

so what's the deal with the model with the 4049ube? is that the Bjfe version? i thought these were supposed to be the same!!! WTF??? not cool, man.
phibes wrote:I still get a kick out all these "Hiwatt sound" in a box pedals. Do the guys designing really know what a Hiwatt sounds like or does everybody just base their Hiwatt sound opinion from Pete at Leeds (Which isn't a very good representation of the Hiwatt sound in my opinion)?

:slap:
totally! Leeds is all Superfuzzy!
tube-exorcist wrote:
earthtonesaudio wrote:A JFET wired like that makes a "low leakage" diode. You'll sometimes see them used in low-drift peak detectors or sample/hold circuits.
...or since 22 years in guitar amplifiers like the boss mg-80:
thanks for clarifications guys. i learned something today.
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Post by WhiteKeyHole »

There is a photograph on Flickr of a BJFE Model H that basically looks like the Stone Grey. Must be two BJFE versions, as the one in the photograph doesn't seem to have a trimmer. Makes sense. Would be pretty pointless to release the Bearfoot and the Mad Professor otherwise. Single PCB for three Bearfoot models.

What did they clear up? They told you what it is, where it's been used, not why it is. What is the reason for its low leakage.

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Post by Whoismarykelly »

phibes wrote:I still get a kick out all these "Hiwatt sound" in a box pedals. Do the guys designing really know what a Hiwatt sounds like or does everybody just base their Hiwatt sound opinion from Pete at Leeds (Which isn't a very good representation of the Hiwatt sound in my opinion)?

:slap:
Same. I built a DR103 which is basically THE Hiwatt a while back and even with all the controls on 10 it doesnt have 1/4 of the gain of most "Hiwatt pedals" have at 9:00 on their gain controls. Even the biacrown models with the extra gain stage aren't super gainy in any way.

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Post by ShortScaleMike »

Unverified first pass vero - any comments/corrections/build reports are more than welcome

Thanks to all involved in the trace/schematic effort so far
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Post by phibes »

Whoismarykelly wrote:
phibes wrote:I still get a kick out all these "Hiwatt sound" in a box pedals. Do the guys designing really know what a Hiwatt sounds like or does everybody just base their Hiwatt sound opinion from Pete at Leeds (Which isn't a very good representation of the Hiwatt sound in my opinion)?

:slap:
Same. I built a DR103 which is basically THE Hiwatt a while back and even with all the controls on 10 it doesnt have 1/4 of the gain of most "Hiwatt pedals" have at 9:00 on their gain controls. Even the biacrown models with the extra gain stage aren't super gainy in any way.
Exactly! I got a 77' DR103 and with everything dimed, I'll get as much break up as these pedals have at their lowest setting. If I was use my SG with hotter pick ups I can get a little more but with my Black Beauty with low output PAF's, it's just pure fucking headroom. Sends a twin reverb home crying everytime. Once you go Hiwatt, you don't go back!
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Post by earthtonesaudio »

WhiteKeyHole wrote: What did they clear up? They told you what it is, where it's been used, not why it is. What is the reason for its low leakage.
The geometries of the PN junctions are vastly different between a standard diode and a JFET. Low leakage is the reason JFETs have high input impedance. If you want better than that you'll have to do a lot of advanced reading.
rocklander wrote:hairsplitting and semantics aren't exactly the same thing though.. we may need two contests for that.

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Post by WhiteKeyHole »

Thanks, though I do understand the why of it -- the question was posed for rhetorical effect. I was pushing that he seek a real clarification.

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Post by RnFR »

WhiteKeyHole wrote:Thanks, though I do understand the why of it -- the question was posed for rhetorical effect. I was pushing that he seek a real clarification.
well, i would think that since a high leakage device(Ge), essentially puts some sort of capacitance in parallel, reducing high end info whether to gr or in an nfb loop, a low leakage diode would keep all of the high frequencies in the clipping section.

how'd i do?

edit: or would it be resistance, effecting low end to gr, or gain in an nfb? can't remember at the moment.
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Post by earthtonesaudio »

Leakage current in a reverse biased PN junction makes the diode behave a high-value resistor. Typical small signal diodes (1N4148 etc.) have leakage currents in the fractions of a nano-amp at room temperature and at low voltage. JFET diodes have leakage currents in the femto-amps.

The JFET will have significantly more capacitance than a small signal diode, but still probably less than 10pF.

My gut tells me the reason for the JFET clippers in lieu of small-signal diodes is purely aesthetic and has nothing whatsoever to how it functions electrically.
rocklander wrote:hairsplitting and semantics aren't exactly the same thing though.. we may need two contests for that.

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Post by RnFR »

you know, whatever the difference was, I didn't think it would be much. thanks for the explanation.
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Post by WhiteKeyHole »

That's good to hear. Thanks for taking the time to suss it out.

:thumbsup

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Post by ShortScaleMike »

Very nice, nicely done! My layout isn't verified so I'd say yours is the defacto standard.

The dimensions are pretty similar (22x16) vs (20x15) so I doubt it's going to cause anyone issues to get into a B box.

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Post by method »

I found this vero layout in a zip file stash I'd collected on my hard drive a few months ago. It is verified.
bjf_Model-H.png

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Post by LooseCannon »

Hey guys,
I'm interested in building the Model H, the layout calls for two reverse audio pots.
Could I use different pots instead of these?

Can't find those nearby.

Thanks!

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Post by Nocentelli »

Two options:

Use linear pot, and the high gain settings will be all bunched up at 3-5 o'clock.

Use normal audio pot, but reverse the wiring of the pot lugs 1 and 3 (so use 1 and 2, not 2 and 3 for gain): The controls will work backwards, but taper will match the original.
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Post by LooseCannon »

Nocentelli wrote:Two options:

Use linear pot, and the high gain settings will be all bunched up at 3-5 o'clock.

Use normal audio pot, but reverse the wiring of the pot lugs 1 and 3 (so use 1 and 2, not 2 and 3 for gain): The controls will work backwards, but taper will match the original.

I'll use the second option then. Thanks!

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Post by fretzburner »

method wrote:I found this vero layout in a zip file stash I'd collected on my hard drive a few months ago. It is verified.
bjf_Model-H.png
Is the source and drain orientation correct?Like C4 and R4 should be at center pin of 2N5952?

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