[sdiy] Fwd: [funwithtubes] Vacuum Tube Multitasking - The Erla Superflex

Darren Shorsky dschnidsky at hotmail.com
Fri May 21 22:42:52 CEST 2021

ouch!!  sorry to hear that about your -12v. supply.
prolly best to do tubes on a separate supply.

i'm aware that Metasonix has posted quite a bit of info. around the web about soe of his older projects & there's a supply or two in there.

From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of ShedSynth via Synth-diy <synth-diy at synth-diy.org>
Sent: May 21, 2021 7:38 PM
To: synth-diy at synth-diy.org <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Fwd: [funwithtubes] Vacuum Tube Multitasking - The Erla Superflex

I did try building this…


…but the heater ate my -12V rail.

From: Synth-diy <synth-diy-bounces at synth-diy.org> On Behalf Of Darren Shorsky via Synth-diy
Sent: 21 May 2021 20:11
To: synth-diy <synth-diy at synth-diy.org>; cheater cheater <cheater00social at gmail.com>
Subject: Re: [sdiy] Fwd: [funwithtubes] Vacuum Tube Multitasking - The Erla Superflex

Interesting question......  I'd love to know more.

Hopefully the likes of Eric Barbour come by on occasion.

I think this is the first time I've seen/heard anything about tubes on the list.

Thanx, d.


From: Synth-diy <synth-diy-bounces at synth-diy.org<mailto:synth-diy-bounces at synth-diy.org>> on behalf of cheater cheater via Synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>
Sent: May 21, 2021 5:45 PM
To: synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>
Subject: [sdiy] Fwd: [funwithtubes] Vacuum Tube Multitasking - The Erla Superflex

I seem to remember a filter design where the audio and the CV were in
the same signal, and the CV was very large compared to the audio,
essentially a bias, that set the cut-off. Was that the Moog filter

I wonder if this is where the inspiration for such a filter came from.


---------- Forwarded message ---------
From: Mark <mark.erdle at gmail.com<mailto:mark.erdle at gmail.com>>
Date: Fri, May 21, 2021 at 2:14 PM
Subject: [funwithtubes] Vacuum Tube Multitasking - The Erla Superflex
To: <main at funwithtubes.groups.io<mailto:main at funwithtubes.groups.io>>

In the early 1920s vacuum tubes and the circuitry to operate them were
expensive items, so there was a great incentive to get the most bang
for the buck out of each tube. As early as 1915, engineers realized
that it was possible to have a single triode vacuum tube amplify audio
and radio frequency signals at the same time. One of the more
successful reflex radio kits was the Erla Superflex of 1924/25, but
with the price of vacuum tubes dropping after an RCA patent expired,
the reflex design became obsolete by mid 1925 and the TRF and
superheterodyne took over the radio market.

Robert Lozier takes a look at an Erla Superflex in this video:

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