Rusty Box/Traynor TS50B - are these caps backwards? + any tips

[MrStab]

i took the charge pump out of the equation altogether, i think my camera's just a bit misleading with the LED brightness. i'm using 1K resistors (one via. Millennium Bypass) - i did some testing with the circuit load hooked up and it seemed like the right balance for this one. i went with red for lowest current consumption.

weirdly, since boxing, interference seems to have gone. i say "weirdly" because it's just unusual in my experience with RF/external interference. i straightened out the knobs a bit:



it's for my singer's bro-in-law, so worst-case scenario it's not an outright witch hunt if he doesn't like it. lol
(i was only recently informed that imgur is a hive of adolescent tomfoolery, but i'm too deep into the habit now)

[psychedelicfish]

Looks nice! Any chance of a sound sample?

[duck_arse]

why wouldn't he like it? it's got knobs, switches, lights, shiny bright metal  .....

[MrStab]

here's a coupla clips on a shit cam, with the pedal going into the front of the amp. i didn't think to record when actually trying it as a preamp. well, going straight through my amp's FX return at least - is a bit more defined that way, but the MG's preamp doesn't adulterate it too much.

please excuse the shitty improv, quality, the fact i'm using a guitar/amp and not a bass, and (what i hope was) hot glue residue which was since cleaned off. lol

[MrStab]

the dude just came  over and tried it into the Aux input on a Cube 30 Bass amp - much more beef. success!

[jordan s]

I wanted to say that I built this using the most recent strip board layout, mostly with spare parts I had laying around. I did need to use shielded cable for the input and jumper and change the value of C2 to get the noise down to a useable level. I'm using a 12V DC wall wart with a 6v regulator for vbias. So far, sounds awesome. We'll see how she teams up with my 1400 watt power amp tonight.

[rankot]

I've built this using schematic from this thread and my own PCB layout. It works fine, but it's a little bit too noisy. I use 350kHz charge pump to provide ±15V from standard 9VDC, but noise is audible and this charge pump is almost noiseless, so I presume it's not the source of the noise. [edit: I tried to decouple V+ & V- to ground with 10u capacitors and noise level does change, so it seems that my charge pump is also pumping the noise. I will investigate this further.]

However, I noticed that another version of this preamp - found in Traynor TS120B, have two differences compared to this on (Traynor TS50B, actually):

• Gain pot is A100k instead of A1M;
• There's a 47p capacitor parallel to gain pot.

So I tried to add that cap and the huge amount of noise is gone. What I want to ask is: is it normal for such a circuit to be noisy, as it has really big amplification factor, or there's something else I should try to fix?

I used TL071, BC550C (don't have MPSA18) and BC640 instead of MPS8599 (similar characteristic). Maybe those BC640 are wrong choice? Some good info could also be found here: https://www.diystompboxes.com/smfforum/index.php?topic=110526.msg1014149#msg1014149

[rankot]

So I tested this with normal ±15V PS (regulated with linear regulators), which is quite quiet

Guess what? The noise level of Traynor preamp is the same as with SMPS.

It could be nice to test this with some other kind of transistors, maybe those BC640 I picked are too noisy? The trouble is they use ECB pinout, instead of usual CBE/EBC