Thursday 23 January 2014

Barber Small Fry

With 4 internal trimmers this was a pain to keep 1590B friendly.  As it sits it's 22 columns wide and so will just fit in if you file the sides down a bit (and insulate the side of the box next to the board with electrician tape or similar to avoid shorts).  It will however fit in vertically with the components facing down without too many problems.  The original was in a 1590BB size box with 4 external pots and a switch and so people may want to keep it in that size box anyway, but the option is there for 1590B if you want to cram things in.

The diode switching in this is unusual.  It has 7 diodes in the feedback loop plus a germanium to ground after the output of the first opamp stage which are controlled via the switch.  In one position you have 2 + 2 anti-parallel silicon diodes in the loop to give you a common symmetrical clipping that you have seen before.  In the centre off position you get 4 + 3 anti-parallel silicon diodes in the feedback loop which gives you asymmetrical clipping, and in the other position you get the 4 + 3 again, plus a germanium diode to ground after the first stage.

On top of that you also have the Dynamics pot which can bring 2 more germanium diodes, 1 + 1 anti-parallel, gradually through the sweep of the pot.

Lots of clipping options there!

Burn is the drive control, the Tone control is a simple low pass filter before the second stage and you then have further Bass and Mids trimmer controls on the board.  The other trimmers are for Presence and Note Shape.

Anyway, here's the interesting bits that Mr Barber writes about his original:

Three way toggle- This new control allows three distinct styles of symmetry to allow a perfect mate to your amps character.

8 knob control for tonal versatility-The Small Fry uses eight (including internal trim pots) control knobs as follows, Volume, Tone, Dynamics and Burn. Internal controls for Note shape, Bass, Midrange and presence. These controls allow the Small Fry to produce sounds ranging from sweet subtle sustain to smooth singing California amp style tones!

Unique controls- The note shape allows you to adjust your sound from tight and focused to a big round vintage tone, The dynamics control has earned a great reputation over the years for setting the transfer to smooth singing overdrive or raspy growling deep dynamics, continuously!

Barber adjustable phono style recovery stage- Most of our op-amp based overdrive pedals use a cool old style phonograph circuit to recover the frequencies lost in the overdrive stage, this worked great for vinyl and now works great for guitar overdrive! 







16 comments:

  1. Any equivalent IC for JCR4559?

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    Replies
    1. Just try any common dual opamp. JRC4558, LM1458, TL072, NE5532 etc etc

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  2. This one looks really interesting! I'll put it on my to do list ;)

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  3. It's like freaking Christmas! This is one I've been wanting to buy but have been
    too broke to afford. Where on Earth did you find a schematic? Now I know what to put in the enclosure that has been housing the Timmy I built...

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  4. I like this one. It suits my tone preference :)

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  5. can you verify cut count. looks like there was one two holes below 4u7 but then removed from the bottom layout with cuts and jumpers.

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    Replies
    1. Yes I do do this sometimes, move things about and forget to do it on the upper layout :o)
      But it doesn't matter, that cut can go in either position and it will work fine. I'll correct the layout, thanks.

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  6. assumed as much, just wanted to make sure it wasn't something I missed. Hoping to utter (type) those immortal words, "it's verified", later today. I will be using a B10 in place of the B5 Dynamics pot. don't have a 4559, but some of all the others listed. back to the iron.

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  7. it's verified. I tried several 4558 and a LM1458, all sounded fine. For what it is worth, I added an extra column at either end (wasn't really necessary) with the vision of hard wiring pots for external control of Shape, Presence, Mid and Bass. So far, adjusting the installed trim pots to taste seems to suffice. Based on the delicate nature of 1N34A's, I socketed D8-D10 in case of failures and also for some experimentation. D1-D7 are much more durable and were soldered in place. So far it sounds great! I really like the Dynamics control as well.
    Thanks for the layout and all you do, and so much for me thinking there was nothing left to build.

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  8. What would be the best way to a/b the "phono style recovery" section of this circuit, in order to compare with other type? To see, you know, if that's just hype.

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    Replies
    1. Where can I find the schematic for this pedal, I've looked in all the usual places and can't seem to locate it?

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  9. If you look at the schematic ( http://www.freestompboxes.org/download/file.php?id=16860&mode=view ), cap 82n should not connect to resistor 3K
    (between VR4(bass) and VR3(mid))

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