[sdiy] Flanger???

Gene Stopp gene at ixiacom.com
Thu Jun 27 20:59:57 CEST 2002

Hey *that's* an idea... not only that, the amp is slightly clipping!!!
Remember I said that the transformer is 33 VAC, and the power rails of the
amp are near +/- 40 volts? There were minor flat spots on the triangle
peaks. I'll bet I harmonic'ed the winding. Hey I just invented a new phrase

I had already formulated the following plan: convert the oscillator to an
EXAR 2206 with sine wave output and change the transformer to a great big
(>10 amp) 24 VAC unit. For modulation, I will try an analog switch selecting
one of two pre-trimmed trimpots driving the frequency control current pin on
the 2206, through a back-to-back diode AR enevlope generator with adjustable
time constants. The analog switch will be controlled by a D (data? delay?)
flip-flop in a toggle configuration (Q-not to D) and clocked either by a
very slow pulse train, a push-button, or a footswitch for a
"swoosh-on-demand" function.

The trimpots will be trimmed so that the min and max AC frequency does not
get out of range. I do not want to fry my tape deck. A simple depth pot from
a regular sweep LFO may get out of hand or be hard to trim (i.e. trial and
error with smoked parts due to the error part!).

Best Regards,

- Gene

-----Original Message-----
From: Grant Richter [mailto:grichter at asapnet.net]
Sent: Thursday, June 27, 2002 11:24 AM
To: Gene Stopp; synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Flanger???

The triangle has a discontinuity at the switch over point. This is going to
cause a voltage spike in the inductor as it tries to continue the current
flow. You would be a lot safer using a sine wave, this should prevent
unexpected insulation failure.

> I'm fairly sure that the amp isn't running DC thru the transformer...
> outputs look symmetric around zero on the scope, power trannys aren't hot,
> pretty sure the inputs are AC coupled... OK yeah I haven't actually
> *measured* anything, that would be cheating, wouldn't it?

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