My first flanger (delay line) kit.

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JR.
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My first flanger (delay line) kit.

Post by JR. »

I recently got a request to publish this old schematic because the PM suggested this circuit had "historical" significance (his words not mine). In fact this early flanger was used on Heart recording "Barracuda". One of the Fisher boys who played in the band back then bought my kit from the Popular Electronics article.

Here is the schematic of the Flanger configuration.
1220a.jpg
1220a.jpg (801.01 KiB) Viewed 12797 times
There was also an alternate configuration for pure delay with lower frequency filter tuning and lower clock frequencies, but a single MN3001 was not capable of very long delay/bandwidth products. .

For any so adventurous to replicate this circuit, I make no claims historical or otherwise. My well regarded studio delay line/Flanger (LOFT 440/450) used Recticon delay chops and a more complex circuit. Regarding history "reel flanging" was done with tape recorders many years earlier and I'm not sure who make the first commercial studio flanger (not me AFAIK).

FWIW I made and sold two accessory boards for this kit. One was a companding NR PCB based on a NE570 chip, and a sweeping clock circuit (That I can't find now, only evidence that I once sold one 40 years ago).

Circuit notes.
#1 ua 723 VR is not very critical to circuit performance, BUT the MOS delay device has output source followers and those follower pull up resistors get connected to +reg.The delay chip was designed to run from a negative supply with pull up resistors grounded. If the regulated supply has significant noise or ripple voltage (like cheap 3 terminal regulators) that noise can get injected into the signal so +Vreg needs to be clean.

#2 The opamps used (lm1458) are slow by todays standards but not problematic for a single rail (15vp-p) signal. Newer better opamps should not hurt (or help) the audio performance.

#3 the clock circuitry is two stage, the second stage is a CMOS D-type divide by 2 flip flop that generates a precise 50% duty cycle with adequate clock drive current. The input to the FF can be any duty cycle at 2x the desired output frequency. My published clock above using a CMOS logic part is just the cheapest way to do that. To make musical sounding Flanger sweeps I suggest a voltage to period convertor (like a LM311 comparitor with a cap charged by a current source, compared to a linear triangle wave ramping up/down.

JR
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mediatechnology
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Re: My first flanger (delay line) kit.

Post by mediatechnology »

Very cool. I remember that one.

What Popular Electronics issue?
I'm pretty sure I have it in storage.
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JR.
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Re: My first flanger (delay line) kit.

Post by JR. »

mediatechnology wrote:Very cool. I remember that one.

What Popular Electronics issue?
I'm pretty sure I have it in storage.
June 1976

JR
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Re: My first flanger (delay line) kit.

Post by emrr »

Thanks John, nice to see.
Best,

Doug Williams
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b1gtuna
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Re: My first flanger (delay line) kit.

Post by b1gtuna »

Thanks for sharing.
The circuit looks doable as a side project.
Gonna put this on my to-do list!
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mediatechnology
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Re: My first flanger (delay line) kit.

Post by mediatechnology »

John's project made the cover.

Read the June 1976 Popular Electronics issue here: http://www.americanradiohistory.com/Arc ... 976-06.pdf
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JR.
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Re: My first flanger (delay line) kit.

Post by JR. »

mediatechnology wrote:John's project made the cover.

Read the June 1976 Popular Electronics issue here: http://www.americanradiohistory.com/Arc ... 976-06.pdf
Not to brag but most of my kit projects made the cover... Can't buy that kind of advertising.

JR
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