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Topics - kothoma

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Open Discussion / Amp: Anyone tried a Peavey Valveking 20 II Combo?
« on: December 09, 2014, 12:38:32 AM »
Looking for a new tube amp in the lower price range I stumbled across the Peavey Valveking 20 II Combo.

Anyone any experience with it?

Open Discussion / unread posts since last visit --- empty?
« on: October 27, 2014, 01:00:48 AM »
Every Monday morning the same thing: clicking Show unread posts since last visit. returns an empty list.

Is it only me?

Open Discussion / (Grendel/RareWaves) Drone Commander times 4
« on: September 28, 2014, 07:19:30 AM »
I know someday I will build a work-alike.

Edit: (one is $360)

Open Discussion / 1-band parametric EQ
« on: September 24, 2014, 09:07:58 AM »
Does anybody know of a pcb for the following circuit?

(Based on

Any Diptrace/Eagle wizzard interested in doing a layout for oshpark?
Preferably with a quad opamp like the TL074. The fourth opamp could be used to buffer Vb.
Or if it saves space then one could replace the first opamp with a JFET or bipolar transistor and go with a dual opamp.

Open Discussion / Sanity check: Current Lover settings Gilmour/Summers
« on: September 20, 2014, 11:33:58 AM »
Any ideas on how these classic settings

would translate to settings on the Current Lover?

I have to commit: my current lover is populated (I guess more than a year ago) but not testet yet (but I remember to roughly calibrate it), I just need to find it in the chaos... I'm tinkering with the idea to somehow have some presets. Switching 4 poles would be all it takes.

(I guess I'm more into phase shifters, but I really need to finally finish this one...)

Out of curiosity: any idea/link to how it works?

Does anybody know where to source a stacked/concentric pot with one dual C50K and one G100K (or maybe a B100K)?
So essentially this is three pots for two knobs.
(The Boss MT-2 uses this for semi-parametric mids.)

Open Discussion / Anybody ever used a J310 JFET transistor for anything?
« on: November 23, 2013, 02:01:54 PM »
Um, anybody ever used a J310 JFET transistor for anything?
I guess it could successfully be used for buffers. I'm not very good at reading transistor data sheets. Could the JFET be used for preamp gain stages?

General Questions / Simple Mixer stereo vero layout?
« on: October 22, 2013, 10:41:38 AM »
Does anybody have or know of a veroboard layout for a stereo version of this using a dual opamp IC.
Maybe pots at the inputs instead of the output.

I know, it's a simple circuit, but I just don't feel like designing my own layout at the moment. Too many other things going on in my mind.

Open Discussion / Ringmodulator based on AD633
« on: September 21, 2013, 09:09:58 AM »
Inspired by this (thanks to Cortexturizer)
Something like this

Some classic circuits tweaked to perfection. The pedal is insanely pricey, but I get it. There's a lot going on in there. If I had enough time maybe just maaaybe I would attempt a build like this but I doubt I could pull it off. Not saying this is the most complicated build out there, but it would be an ultimate pedal for me, hells one could start a band around this pedal alone hahah.

I remembered the fun you can have with ringmodulators on synthesizers.
I also have a far memory of John Scofield using one on several occasions (probably from a Line 6 MM4 Modulation Modeler).

So that made me look for an easy solution to analogue multiplication (without using transformers and rectifiers like the old).
Here are some schematics:
Older designs seem to rely on the (obsolete?) 1496 ic. But there's also the AD633:

That chip does all the hard work and you just need to add an oscillator to have a carrier:

(based on

Has anyone here already tried this or a similar design?

Edit: I wonder why the op amps (at pins 1 and 3) are biased with a trimmer. Shouldn't ground be fine?

Edit 2: Of course, there should also be the option to use the input signal also on the second input (instead of the carrier wave) to get a nice octave up effect.

Open Discussion / Pale IC label prints (called that?)
« on: August 11, 2013, 03:06:39 PM »
Every time I see build reports with shiny white lables on ICs I feel envy and doubt.
As far as I recall all ICs I ever bought have barely readable label prints.
I have to hold them in different angles agains the light to read anything.
And my feeling is this got worse over the last decades.
Is it just me or my eyes?

BTW Transistors aren't really better.

Say you find that perfect amp setting for your living room.
What adjustments to the eq are expected for stage work?
I guess it would depend on room size, room acoustics and amp volume.
Is there an easy answer?

Why do I ask: how far do you get with presets? Less knobs, more music.

Open Discussion / not reachable?
« on: July 22, 2013, 11:34:00 AM »
Anyone else experiencing trouble when trying to send an email to ?
I sent an email 4 days ago and today I got an automated answer:

Mail delivery failed: returning message to sender

This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of  its recipients. This is a permanent error. The following address failed:

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