E.W.S Tri-Logic II Bass Preamp  [traced]

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Re: E.W.S Tri-Logic II Bass Preamp

Postby george giblet » 02 Dec 2018, 23:57

I'm a bit confused about the mid caps.
The 12kHz treble might correspond to the 1k treble resistor.

The mid frequency specs for the Xotic Basses are the same as the EWS Trilogic II pedal.
The treble is different.
Bass XJ-1 (upto 2009 with switches on back)
Bass XJ-1T (2009/2010 and beyond, switches on front)
SW1: "Mid switch", +/-12dB @ 400Hz/800Hz
SW2: "Bright switch", +/-18dB @ 6kHz/12kHz

However Nikifena mentioned the basses had mid caps 47n and 100n.
I have this feeling the mid frequencies might have got moved on the EWS pedal but the printed specs were not?
I have no specs for the original Xotic Tri-logic pedal.

Anyway From what I can work out the models around are:
1) Xotic "Tri-logic Bass Preamp". (From <= 2006 upto 2011?)
Wide box pedal. Black.
2) Early model Xotic Bass XJ-1: sames specs as XJ-1T except switches on the back. trimpot on back. (From ???? to about 2009)
3) Later model XJ-1T. Toggle switches on front. Trimpot? (From 2009/2010 and beyond)
4) EWS Tri-logic II. Black (From 2011 to 2015).
5) EWS Tri-logic III. Grey/Silver Hammertone (2015 to now).
Bass freq switch. Treble Freq Switch. Mid freq Control.
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Re: E.W.S Tri-Logic II Bass Preamp

Postby george giblet » 03 Dec 2018, 05:42

EWS Trilogic II
Update V1.0 2018_12_02 to V1.1 2018_12_03

The other Xotic products do tend to use 50kB pots.
So I suspect this is correct.

Issues:
1) Not happy about 1nF cap. It has a black dot like a value small cap.
2) What to do about the 1k0 vs 1k8 treble cap issue.
3) Not happy about mid caps
4) The NE5532 opamp current draw looks too high for the current
consumption spec. Possibly RC4557D
--------------------------------------------------------
Bass: +/- 13.5dB @ 90Hz (Mid switch HI)
--------------------------------------------------------
1) 1n treble cap. I can see a black top on the cap
which would imply NPO/COG and small value.
It is quite possible it is 100pF like the 100pF NPO/COG input cap.

*** Chicago Mike (p1), Image 015, we can see this cap in 100pF

Also,OrionManMatt (p3) Handdrawn overlay shows 100pF

So clearly it *is* 100pF

2) Treble Resistor
After changing the 1nF cap to a 100pF cap we can revisit the
esponse specs and the 1k8 vs 1k0 treble treble resistor issue.

1k8: Treble: +/- 13dB @ 10kHz ; This now agrees with the Tri-logic II specs.

1k0: Treble: +/- 16.9dB @ 10kHz

The response is *very* close to the Xotic BB Tone control
when the Treble caps are doubled. Which *might*
be what is done in the Bass version Xotic BB.

3) Mid caps:

OrionManMatt (p4), it fairly clear on the mid cap
high-mid side: 473k
low-mid side: 154k

These are clearly correct, at least for his version of the
board, with the 1k0 treble cap.

Chicago Mike (p1) remembered on of the mid caps was 47nF.
The other cap is unknown.

Nikifena p6. On the Xotic Bass.
Mids 47n and 100n; maybe no 2.4k on mids(?)

Conclusion:
The hi mid-cap is probably 47nF.
The low mid-cap is probably 150n on the version with the 1.0k treble resistor.
The low mid-cap might could be 100n or 150n on the version with the 1.8k treble resistor.

The mid frequencies don't match-up with the published mid frequencies.

47nF: +/- 8dB @ 1.3kHz
100nF: +/- 9.3dB @ 520Hz
150nF: +/- 10.2dB @ 360Hz

4) The Opamp might be an RC4559.
Other's have speculated this part for Xotic Pedals.
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Re: E.W.S Tri-Logic II Bass Preamp

Postby george giblet » 03 Dec 2018, 08:48

I've been looking at thing too long.

I just came back to check it and I realized the 100pF I mentioned is actually across the other part of the opamp!!! What a dilweed :oops:

Ignore the thing about 1nF cap and the treble control spec update.

I'm surprised the specs line-up better with the smaller feedback cap on the tone control.

So how do we know the 1nF cap is 1nF?

EDIT
OK I can see where it came from, OrionManMatt's (p3) Handdrawn overlay.
So it must be correct?
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Re: E.W.S Tri-Logic II Bass Preamp

Postby george giblet » 03 Dec 2018, 22:54

OK I've fix up the mistakes and regenerated the performance specs.

Can't go any further without more pics or info.

One thing I can add is the Xotic XJ-1T bass looks like it uses the same PCB as the EWS pedal.
The switches and mid-caps are mounted on a second board which is wired to the main board.
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Re: E.W.S Tri-Logic II Bass Preamp

Postby george giblet » 04 Dec 2018, 04:19

I found a pic of an Xotic bass which had a large square PCB but still had the switches on the back (not the two toggle switches on the front). It had 100kB pots for the BMT controls! It also had two 8-pin opamps. I could not see a MOSFET.

So this thing is a big mess in terms of versions!

That bass had the same board as the original Xotic-tri-logic(1) pedal.

Maybe the square board with the two opamps is an old version and the smaller rectangular board with the MOSFET is a new version. That might explain "Tri-logic" preamp vs. "Tri-logic 2"/"Tri-logic II".
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