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Ok I think I'm done playing with the brown preamp side of my plexi mods. Iv'e come up with a tone I'm very satisfied with and works well with kicking the boost in. At this point my ez81 didn't survie the school of hard knocks and I'm waiting for some replacments. So I started poking around the res section . Was looking at the boost output tube selector mods.

Question

1. The ldrs have an internal resistance that changes with the amount of current flowing thru them corect (I used a different value boost resistor)

2. So I'm thinking Im gonna have to play with values in the schematic to get the resitance I want?

3. Could I not do the foot switchable boost with the relay or would that be to much pop when kickink in with a foot switch ?


I'll post some clips in the brown thread when i get a new ez81.

thx

An idea I have used before that works and does not use LDRs or relays.

The cap switch pops because the capacitor goes from charged to uncharged very quickly as the cap is toggled in and out of the circuit. The trick is to always keep the cap charged. If you put a large resister in series with the cap it allows a little current to flow into the cap and keep it charged, then when you switch the resistor out of the circuit the cap doesn’t see an inrush of current to charge itself.

Put a large resistor (>100K) in series with your boost cap. Run wires from either side of the resistor to a normal mono Cliff jack. You can then use a guitar cable and have a SPST footswitch to toggle the boost function. The SPST switch shorts out the resistor and engages the boost.

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We also did publish a soft boot switch in the resource section using specifics LDRs if interested

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

The sIII boost is a big one. We should try this out on it.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Ok I'll try the resistor cap thing. easily implemented. But what about the effect of the long cable run

Has negible resistance so it doesnt matter (only 1 or 2 ohms).

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Has anyone tried this on an sIII?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Tried it and confirmed.

Used 1M resistor.

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Was there a boost resistor as well or just the cap?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Just a cap but a resistor wouldn't change anything. Tried a resistor too and no popping still.

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http://pdfelectronics.com

I'm not sure I understand the wiring of this modification... could someone post a schematic of the change?

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Thanks...

I tried 1M, 220K and 100K. 100K being the best but it did not eliminate the pop. The stock switching is from the cathode side, not the ground bus side. I put it across the two 2K7s right on the board.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps