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I'll keep that in mind. I bought a matched pair of JJ's.

Don't pay too much for them. Shop around. I bought some from a guy in the UK thru eBay.

Every time you change a transistor, you should check and adjust the biasing. This is especially true with Ge. Otherwise you're changing more than one thing when you swap out a Ge transistor. Q3's bias has a major effect on tone. Q3-C should be around 4.6V.

The two leakage currents I measure are Iceo and Ices. Ices is basically the same as Icb since E & B are shorted together when measuring Ices. The one I pay the most attention to is Iceo (collector current with B not connected to anything). How much is not enough? How much is too much? How...

Yes.

Getting the right amount of light on the LDR is the critical. LDRs are EXTREMELY sensitive to light. It is easy to put too much light on the LDR and if that happens, then it recovers (resistance goes up) very slowly. A diffuse LED is better because it spreads the light more evenly over the...

Correct. The DC bias can come from anywhere, as long as it's the right voltage. Check out the biasing in the Big Muff II. Stage 1 biases stage 2. Stage 2 biases stage 3.

Dear God, you can't rotate the pic on your phone? :LOL: We're talking about R3 & R4, yes? Opamps need a DC bias source for every input pin. In other words, every input pin must have a DC path to somewhere. The output of that opamp, or another opamp, or GND or Vref, whatever is appropriate...

I think we've wandered far enough off topic. ;)

In theory, yes. And it might work in some cases. Do you ever wonder why Boss & Ibanez put buffers before and after their FET switches?

Nope. But they can be purchased in an SMD package. So can a 555.

CD4053 is not a perfect switch. One has to consider on-resistance, off isolation, linearity, crosstalk and charge injection. They can and have been used successfully when applied correctly. They are more reliable than relays, although a relay does not significantly impact the reliability of a...

The BJT is there to help filter the signal going to the CLK pin. Personally, I think that design has a weakness in that any switch noise or chatter can clock the 4013 more than once and leave the relay in a random state. The 555 and 40106 circuits both have a hold-off function built-in. Once...

It really depends on which relay you're using. IF you're powering the 555 on 9V, and IF the relay coil current is <20mA, THEN the 555 has sufficient margin. Not a lot of margin, but enough. One could always add a MOSFET to a 555 to get more relay current capability.

Here's another. Two of the unused gates can be used to construct a 2nd relay driver, if needed.

Maybe make R19 a trimpot. In the Deluxe Reverb, R19 is 6.8K, so it's a matter of personal taste.

1. If we install a 9V reg and want the option to run on 9V, then it must be an LDO (low-drop-out) reg. A 78L09 will not make anything close to 9V if it's powered by 9V. 2. If you're referring to the schematic in post #1, then yes it is designed to be connected to the power input jack. The...

Yes.

It's the typical Marshall MID control. Fairly subtle and interacts with the TREBLE knob. It has the most effect when BASS & TREBLE are turned up.

A minor update. I moved D3, changed it to Schottky and added R16. Now it makes that special grind at low gain settings that HamishR likes so much.