Looking for thoughts on the SAD1024A and MN3xxx versions of the A/DA flanger

[12Bass]

Hey Everyone,

Anyone care to share their thoughts on how the SAD1024A versions of the A/DA flanger compare with the MN3xxx versions? 

Looking at the schematics, the SAD1024A and MN3010 implementations appear fairly similar, as both run dual 512-stage BBDs in parallel-multiplex mode.  This configuration effectively doubles the sampling rate and helps to cancel clock noise.  On the other hand, recently redesigned versions based upon the MN3007 employ a single 1024-stage BBD and double the clock frequency to reach the same effective delay times as the dual 512-stage units.  The MN3007 design appears to have a disadvantage where clock noise is concerned; however, the faster (doubled) clock rate puts the clock beyond the range of human hearing (60 kHz +), so this may not be an issue in practice.  From the specifications, it appears that the Panasonic devices may have an advantage where noise and headroom are concerned, while the Reticon parts more easily handle high clock speeds and may have superior high frequency response.

Having recently built a SAD1024A version, I'm curious how the A/DA flanger sounds when using the MN-series chips.  Is there much difference at all in tonality?  Range?  Headroom?  Mojo?            

[Mark Hammer]

You're basically asking the question: What tastes better in a 10,000 gallon drum of water?  A teaspoon of garlic or a teaspoon of ginger?  The determining factors in the A/DA are the supporting circuitry, the particulars of the noise gate (and any unit-to-unit differences in component variation).  As long as it can clock as requested, the BBD matters little IMHO.  There IS some advantage to use of two parallel BBD sections when it comes to minimizing clock noise, but if you've bumped the clock speed up by a factor of 2x, those advantages recede in both importance and audibility.

[StephenGiles]

I think that Mark has summed it up beautifully. Always look at the supporting circuitry, which is why to my ears that Boss Flangers sound so limp. Mod the ADA for TDA 1022 and it will sound just the same.

[12Bass]

Interesting.... Thanks for the replies!

I'm working on "cleaning up" the surrounding circuitry with better op amps and other components, so this might help uncover nuances in the BBD chips.  Looking at the specs, it would appear that the distortion produced by a BBD device (~1%) is many orders of magnitude higher than modern high performance op amps (0.00005%), which suggests that it is a significant source of coloration.

Speaking of the noise gate (Threshold) circuit.... is that an actual audio path, or is the signal going through just used to trigger the gate?  I'd like to know because if the noise gate signal doesn't make it through to the output, then I won't bother upgrading the op amp in that section.  My suspicion is that the audio signal is used to determine whether or not the FET sends the delayed signal to ground, effectively acting as a gate on the flanged signal.  Basically, I'd like to focus on upgrading the components which are directly in the audio path of the flanger.

[oldschoolanalog]

Speaking of the noise gate (Threshold) circuit.... is that an actual audio path, or is the signal going through just used to trigger the gate

The signal goes into IC3A as audio and is rectified into a CV that controls Q1. All 4 op amps in IC3 are involved with some CV aspect of the circuit. IMHO, an LM324 works fine for this IC.
As far as:
"Basically, I'd like to focus on upgrading the components which are directly in the audio path of the flanger."
I have said this more than once; OK, here we go again...
You have to realize. As great as the A/DA is, the bottom line is it is a ~30 yr old design and has its own "personality" & inherent quirks. It is what it is. It is a gem from another time. It is not a panacea (not the vindaloo related kind, Stephen ). Upgrading components might not necessarily equate to "better/quieter"; unless you have it populated w/total crap.
You want "high end"? Build this:
http://www.jhaible.de/sonofstormtide/sonofstormtide.html
Mine is almost finished. I'll post a build report when it's done. Calibration should be fun. BTW, I know of at least 2 other members here who are also having a go at this one. How's it coming along, guys?
All the Best!

[Nitefly182]

IMO the MN3007 version sounds better and was lower noise to me. perhaps its because of the higher clock rate or the more modern delay line. Either way the fidelity and s/n radio were better.

[12Bass]

The signal goes into IC3A as audio and is rectified into a CV that controls Q1. All 4 op amps in IC3 are involved with some CV aspect of the circuit. IMHO, an LM324 works fine for this IC.

Thanks.  That's what I figured was going on with IC3.  I'll focus on IC1 and IC2.  Thinking of using an OPA1642 for IC1A/D, as FET input might make for a little lower noise in that section.  Not quite sure what I'll use in the other sections (using two dual SOICs adapted to 14-pin DIP)... probably low noise bipolars.

You have to realize. As great as the A/DA is, the bottom line is it is a ~30 yr old design and has its own "personality" & inherent quirks. It is what it is. It is a gem from another time. It is not a panacea (not the vindaloo related kind, Stephen ). Upgrading components might not necessarily equate to "better/quieter"; unless you have it populated w/total crap.

I take your point.  However, modifying stuff is a big part of why I enjoy building.  For me, it's fun taking an existing design and making it "better".  I've already made some improvements by changing a few capacitors.  You should see what I've done to my Eden WT-500.... the audio path is much cleaner and more natural-sounding than it came from the factory (using OPA211s and OPA827s, removed coupling caps, or using polypropylenes, bypassed Panasonic FM electrolytics, etc...).  I've gone through dozens of op amps trying to find what sounds better.  With a few tweaks, I think that the A/DA clone will provide what I want... for the near future anyway.  If I just wanted a good-sounding flanger I could have purchased a Strymon Orbit or something and called it done.  

You want "high end"? Build this:
http://www.jhaible.de/sonofstormtide/sonofstormtide.html

Yep... saw that one the other day.  Looks interesting, though I bit more than I'm willing to bite into at the moment.

IMO the MN3007 version sounds better and was lower noise to me. perhaps its because of the higher clock rate or the more modern delay line. Either way the fidelity and s/n radio were better.

Thanks.  This is helpful information.  Thought that the MN3007 might have a bit of an edge in the SNR department.  Just curious what you mean by "sounds better"?  From the spec sheets it appears that the Panasonic parts might be somewhat lower distortion, so that might explain higher fidelity, if that's what you mean.  Any aspect of the SAD1024A version which you prefer?  

I'm still wondering if the parallel-multiplex configuration used with the MN3010 and SAD1024A has much impact on the tonality?  The designer behind the BYOC flanger seemed to think so.  Something I noticed on the schematics is that the SAD1024A version has two 0.01 μF capacitors in parallel going to ground at the input to the BBD, while the MN3007 version only uses one.  This doubling of capacitance (0.02 μF) appears be rolling off the highs more in the SAD1024 circuit.

--

It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring. - Carl Sagan

[12Bass]

Oops...

[StephenGiles]

It all depends what you want to do with the ADA - impress your wife/girlfriend in your bedroom, then worth the effort. But in a band situation it surely won't make any difference at all.

[Mark Hammer]

You want "high end"? Build this:
http://www.jhaible.de/sonofstormtide/sonofstormtide.html
Mine is almost finished. I'll post a build report when it's done. Calibration should be fun. BTW, I know of at least 2 other members here who are also having a go at this one. How's it coming along, guys?

I am particularly interested in hearing people's thoughts about Jurgen's implementation of "theta processing" in the Storm-Tide, especially since he hasmade it a defeatable feature.

As a potential standalone mod to just about any flanger, and the sort of thing that many could easily whip up a small add-on daughter-board for with a garden variety quad op-amp (the way that Francisco Pena did with 4-additional swept phase-shift stages for the Ropez phaser), it holds much promise.  The question is: Do people find it a worthwhile sonic addition for single instruments, or is it only the sort of thing that stands out in a multi-source mixdown situation in the studio?

N.B.: "Theta processing" refers to the addition of fixed phase shift to the lowest portion of the spectrum, between the BBD and the mixing stage.  The added phase shift spreads out the lower notches a little farther apart (principally moving them downwards), while leaving the mids and highs in the wet signal untouched.  The original experiments, by Bernie Hutchins at Cornell (and detailed in Electronotes back in 1978 or 79) used considerably more phase-shift stages, but it was eventually reduced to 4 in the Eventide Instant Flanger, which Jurgen attempts to emulate/extend.

[12Bass]

Perhaps it is worth mentioning that I've never heard an A/DA flanger, so I have no preconceptions about what this flanger project is supposed to sound like.  Basically I chose to build this particular flanger because I already had an SAD1024A and determined that the A/DA design was one of the best out there.  So, because I have no strong desire to recreate the "A/DA sound", I have no qualms about making modifications to suit my taste.  One of the first changes was the installation of hybrid quad op amps in the audio path, using OPA2211As and an OPA1642; these are much better chips than the LM324s.



After playing around with my A/DA flanger clone, I have made a few observations.  Listening to the delay line only, there is a noticeable improvement in signal quality as the delay time is shortened.  Also, from adjusting the manual (delay) control, I've found that the SAD1024A has more output at lower delay times (slower clock).  This may lead to a somewhat more pronounced flange in the lower ranges of the sweep than in the high ranges, because of the greater proportion of delayed signal at lower frequencies.   Is this output differential similar in all BBDs?

The low pass filtering before and after the BBD is definitely lowering the fidelity of the delayed signal.  I'm not sure of the filter design; however, after changing a few capacitors, I've been able to greatly increase the fidelity of the BBD line.  Would be interesting to know the math behind the filter design, cutoff points, etc....   My suspicion is that the low pass filtering is set to considerably less than f/2, or roughly 17 kHz for the longest delay time (14 mS).  While sweeping the clock, I noticed that there may have been some aliasing audible with the more gentle low pass filter, but only when the clock frequency is very low (~20 kHz or less), but I'm not planning to use such low sampling rates.    

I tried different capacitor values in the feedback loop (C18, C19), but found the original values seem to produce the best "swoosh".  I liked the idea of allowing more highs in the regeneration so that it would sweep through the really high harmonics, but it made the flanger sound thin, and perhaps more metallic.  Might play more with that later.

The A/DA sound samples I have heard seem to have a smoother LFO sweep.  Mine is a bit "lumpy".  It's fine when slow, but doesn't sound good fast at all, IMO - too erratic.  Presently just using the two 33 μF caps back to back as shown in the schematic.  Any suggestions on making a smoother sweep?

Any other suggestions of observations would be appreciated!

[StephenGiles]

The filtering is very sparse, but then so is it in the other great sounding flanger of old - the Electric Mistress. What is the point of filtering out all of the good in a flanger - the grunge

[12Bass]

The MN3007s arrived from Hong Kong a few days ago, and I just finished building an MN3007 retrofit board for my SAD1024A A/DA flanger clone.  Disconnected R19 and patched the output of the MN3007 to point G on the PCB, so the circuit should be essentially the same as the newer version.  I've only tested one BBD so far.  The Panasonic chip does seem to be flanging, but I'm not sure if it is quite working correctly as there's a bit of hum that wasn't there before.  From what I can tell the sound is somewhat different than the Reticon, but at this point I can't make any useful comparison.

Curious about the trimpot on the output of the MN3007 (TR6 ?).... is it supposed to be for balancing the delay with the straight signal?  Mine seems best a near 100%.

Will be doing more testing over the next few days....