AMZ FX ANALOG ALCHEMY GEOFX MEF ROG MEF DIY WIKI

Phase 100 with mods

Started by armdnrdy, April 12, 2014, 03:03:46 PM

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armdnrdy

#20
October 12, 2014, 09:47:58 AM
I have done extensive "testing" with different LED/LDR combos...and have not been able to emulate a Vactrol that would have an adequate response for a phaser.

The problem seems to be in the response of the LDRs that are available. As Mark Hammer has pointed out...you can slow down the response of an LDR but...you can't speed it up.

LDRs in factory vactrols that work well for phase stages seem to have a fast "on time", a medium "off time", and vary resistance from fairly low (1-10K) to high. (1-10M)

LDRs are available that have an adequate resistance swing but, most have slower rise times. (Rise/Fall times 30-50ms)

There are a few project out there that have had success with "roll your own" LED/LDR combos...Dino's (digi2t) infinitephase build being one of them but...I might add that I have heard other phaser builds that do "work" but lack the depth of the original circuit.

I have had excellent results building the Mutron Phasor II using (3) VTL5C3/2s in place of the custom 6 LDR Hamamatsu optocoupler. The same has been achieved with Mutron Bi-Phase builds.

Two VTL5C1s as a replacement for the VTL5C3/2...
Physically..two single vactrols can be connected as you suggested with two VTL5C3s being the optimum choice to emulate the dual VTL5C3/2.

The VTL5C1 has similar rise/fall times...but the "off" resistance is greater which will change the slope of parallel resistance.
How will this sound? I'm not real sure if there would be much noticeable difference.

I would suggest either bread boarding the circuit... or leave room on the PCB for either option (dual/single vactrol) and socketing the Vactrol positions with SIL pins. Compare the results with sound samples of the original circuit.





I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Govmnt_Lacky

#21
October 12, 2014, 09:55:36 AM
Perhaps looking into the Doppelganger might help as well. An excellent Phaser AND... it uses LED/LDR combos. It has very good Rate and Depth responses too..  ;D
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

armdnrdy

#22
October 12, 2014, 10:00:24 AM
Quote from: Govmnt_Lacky on October 12, 2014, 09:55:36 AM
Perhaps looking into the Doppelganger might help as well. An excellent Phaser AND... it uses LED/LDR combos. It has very good Rate and Depth responses too..  ;D

I think he already went down that path Greg:

http://www.diystompboxes.com/smfforum/index.php?topic=108710.0
I just designed a new fuzz circuit! It almost sounds a little different than the last fifty fuzz circuits I designed! ;)

Govmnt_Lacky

#23
October 12, 2014, 10:07:24 AM
DOH!  :icon_redface:

Cart before the horse.... My apologies!  ::)
A Veteran is someone who, at one point in his or her life, wrote a blank check made payable to The United States of America
for an amount of 'up to and including my life.'

Fender3D

#24
October 12, 2014, 12:11:18 PM
Quote from: armdnrdy on October 12, 2014, 09:47:58 AM
...
The problem seems to be in the response of the LDRs that are available. As Mark Hammer has pointed out...you can slow down the response of an LDR but...you can't speed it up.
...

Yep, you can't speed it up, but...
you can force more mA on LED driver if you add another LDR following LFO sweep and modulating LFO depth.

Rising time remains the same, but LDR will be driven strongly enough to simulate a faster response.

Check TC phaser XII  :icon_wink:

"NOT FLAMMABLE" is not a challenge

grenert

#25
March 27, 2019, 07:40:52 PM
Reviving this dead, old thread to see if anyone had downloaded the factory schematics that Larry had previously posted.  He no longer has them, and the old link to the files on Dropbox is no longer working.  The only schematics on the web for this pedal are the GGG schematic and one traced one.  I don't believe the factory schematics are available anywhere now.  It would be great if anyone who has the file could re-post it for posterity and DIY happiness.
Thanks!

grenert

#27
March 29, 2019, 02:43:17 PM
Thanks for posting those, njkmonty!  I had seen the schematic from Bernard d'Uur elsewhere, but not the Portuguese page or Larry's modified schematic.   Still, there must be an original factory schematic around somewhere!   :icon_confused:

StephenGiles

#28
March 29, 2019, 05:10:52 PM Last Edit: March 29, 2019, 07:38:40 PM by StephenGiles
                                                                                                                     


Is this what you are looking for?
"I want my meat burned, like St Joan. Bring me pickles and vicious mustards to pierce the tongue like Cardigan's Lancers.".

StephenGiles

#29
March 29, 2019, 05:13:06 PM
Is it the same as this?
                                                   

"I want my meat burned, like St Joan. Bring me pickles and vicious mustards to pierce the tongue like Cardigan's Lancers.".

grenert

#30
March 29, 2019, 07:18:14 PM
Awesome!  That looks like an original, and based on the date of 1977, probably the original script version. 
This schematic confirms reports that the original design has a feedback resistor of 18K, whereas later versions seem to use 15K (and as used in the GGG clone).  That affects resonance and may explain some differences people have heard in tone between early and late versions.
Very cool, thanks!
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