MN3007 ADA Flanger Clone Questions

[Nitefly182]

Yeah its a little more complicated than the average build

[oldschoolanalog]

 A/DA Flanger (mn3007) distortion
« on: Today at 05:56:41 PM »   
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I just built one of the flangers from the new board, and i'm having an issue with it distorting. if i have the range and manual knobs below 50% it works fine, but anything about that and the top of the sweep distorts a lot. i've tweaked the bias trim and the sweep trims a ton and i can't seem to get rid of the white noise/distortion that's occuring. any thoughts on what could be going on?

Try adjusting TR6. This controls the level of the BBD output. I might be set too "hot". Also, what signal source are you feeding it? A bit more info would help alot. I'm at work now. More later...

[allmonochrome]

as far as what i'm feeding it, i'm just playing a strat straight into it. i was able to minimize the distortion a bit more but there's still and audible slightly distorted LFO sweep in the background. is that normal?

[oldschoolanalog]

More than the gate can resolve?

[allmonochrome]

well the threshold knob gets rid of it when i'm not playing but it can be heard in the background when i strum at all. it's not bad but it's definitely present.

[StephenGiles]

More than the gate can resolve?

I didn't nother with the gate - the noise is all part of a flanger to me. Try changing R13 to the BBD bias trim to 4k7 which should provide a better range to trim out the distortion.

[Paul Marossy]

Just revisitiing the TL074 vs. LM324 IC chip question again. The one thing that the LM324 claims on the data sheet is that it has a "high voltage gain" of 100dB, and the TL074 data sheet does not a specify voltage gain or at least I don't know where to look for that info on the data sheet. I didn't see it anywhere.

So, I'm thinking that perhaps the LM324 is what is needed if a TL072 does not have similar voltage gain characteristics as a lower gain may make the effect less "intense". I have some LM324s coming from Mouser, so maybe I can do an A/B test to see if there is a really audible difference between them.

Comments and/or opinions?

[puretube]

LM324 can go to gnd!

(TL074 has an A_VD (large-signal differential voltage amplification) specified as: "V/mV" (~200) ).

[StephenGiles]

More than the gate can resolve?

I didn't nother with the gate - the noise is all part of a flanger to me. Try changing R13 to the BBD bias trim to 4k7 which should provide a better range to trim out the distortion.

"nother" how's your nothering missus?  I meant bother!!

[Paul Marossy]

LM324 can go to gnd!

(TL074 has an A_VD (large-signal differential voltage amplification) specified as: "V/mV" (~200) ).

Pardon my ignorance, what does that mean? Does that mean that the TL074 has more gain than the LM324?

[oldschoolanalog]

Look at the "real" A/DA schematics (with a grain of salt, of course). Revs 3,4 & Rev. D (the one w/SAD1024). No where in the audio path can an LM324 be found. 1/2 LM 324 is used in the gate circuitry in all 3 revs. The other 1/2 is used in the CV circuitry. A variety op op amps can be found in the audio section. 3403, 1458, 4741, 1458, 348 seem to be the ones specified (depending on the rev.) The LFO is a 1458 in all 3 revs. That's the "paper" side of things.  In my 3010 based reissue things are a bit different. There is one LM324 (1/2 is the LFO, I haven't traced where the other 1/2 goes) and all the rest are TL074's & TL072's. I've used/tested TL072/4, LM324, OPA4228, MC33174, in audio portions of my A/DA builds. All with good success. No excessive noise issues. For the LFO I've used LM2904's & MC33172's. Chosen for low current consumption; they both work fine. So, what am I getting at?
Many roads lead to Rome. Try a variety of op amps and use what you've convinced yourself sounds best. Or; just use what you have on hand at the time. That's why I tried the OPA4228. By the way, it doesn't sound any better than a TL074 in this circuit.
More later...

[Paul Marossy]

Look at the "real" A/DA schematics (with a grain of salt, of course). Revs 3,4 & Rev. D (the one w/SAD1024). No where in the audio path can an LM324 be found. 1/2 LM 324 is used in the gate circuitry in all 3 revs. The other 1/2 is used in the CV circuitry. A variety op op amps can be found in the audio section. 3403, 1458, 4741, 1458, 348 seem to be the ones specified (depending on the rev.) The LFO is a 1458 in all 3 revs. That's the "paper" side of things.  In my 3010 based reissue things are a bit different. There is one LM324 (1/2 is the LFO, I haven't traced where the other 1/2 goes) and all the rest are TL074's & TL072's. I've used/tested TL072/4, LM324, OPA4228, MC33174, in audio portions of my A/DA builds. All with good success. No excessive noise issues. For the LFO I've used LM2904's & MC33172's. Chosen for low current consumption; they both work fine. So, what am I getting at?
Many roads lead to Rome. Try a variety of op amps and use what you've convinced yourself sounds best. Or; just use what you have on hand at the time. That's why I tried the OPA4228. By the way, it doesn't sound any better than a TL074 in this circuit.
More later...

Thanks for clearing that up. I only ask this because on this bill of materials, http://www.moosapotamus.net/IDEAS/ADAflanger/ADA_MN3007/ADAflanger_MN3007_BOM.htm, it states that IC-1, IC-2 & IC-3 are all LM324s...

I do have the Rev 3 & Rev 4 schematics and know about the other IC chips that have been used in the earlier versions of the real ADA Flangers, I have all of those data sheets printed out and in my ever-growing ADA Flanger file. Anyhow, the newer IC chips clearly outperform what they had available in the late 70s/early 80s.

[Paul Marossy]

Well, my MN3007 IC chips came in the mail today. I put one in and the circuit started up with no problems... whew! I was hoping that I wouldn't have to do any troubleshooting as it's a pretty complicated circuit. A little tweaking of the trimpots and it's working nicely. Just a couple of small bugs to work out, but overall I am very happy with it. It really has a pretty wide range of sounds and effects, very fun little toy! 

One of those small bugs is that I can hear a bit of a slight distortion in some parts of the sweep with the knobs at certain settings. Is that normal?

Also, on some parts of the sweep, I can hear a very high pitched "whine" with my head phones on. I would guess that it's somewhere around 20-22kHz.  Is that "normal"? I tweaked all of the trimpots to make everything sound as good as possible, but that whine is still there. It may not be audible when playing thru an amp, though. I'll have to do a little more testing...

[Nitefly182]

Well, my MN3007 IC chips came in the mail today. I put one in and the circuit started up with no problems... whew! I was hoping that I wouldn't have to do any troubleshooting as it's a pretty complicated circuit. A little tweaking of the trimpots and it's working nicely. Just a couple of small bugs to work out, but overall I am very happy with it. It really has a pretty wide range of sounds and effects, very fun little toy! 

One of those small bugs is that I can hear a bit of a slight distortion in some parts of the sweep with the knobs at certain settings. Is that normal?

Also, on some parts of the sweep, I can hear a very high pitched "whine" with my head phones on. I would guess that it's somewhere around 20-22kHz.  Is that "normal"? I tweaked all of the trimpots to make everything sound as good as possible, but that whine is still there. It may not be audible when playing thru an amp, though. I'll have to do a little more testing...

You are getting clock bleed which means you have the clock frequency set too high. Try tweaking TR4.

My build has some clipping as well. That seems to be a typical issue I think.

[Paul Marossy]

Well, my MN3007 IC chips came in the mail today. I put one in and the circuit started up with no problems... whew! I was hoping that I wouldn't have to do any troubleshooting as it's a pretty complicated circuit. A little tweaking of the trimpots and it's working nicely. Just a couple of small bugs to work out, but overall I am very happy with it. It really has a pretty wide range of sounds and effects, very fun little toy! 

One of those small bugs is that I can hear a bit of a slight distortion in some parts of the sweep with the knobs at certain settings. Is that normal?

Also, on some parts of the sweep, I can hear a very high pitched "whine" with my head phones on. I would guess that it's somewhere around 20-22kHz.  Is that "normal"? I tweaked all of the trimpots to make everything sound as good as possible, but that whine is still there. It may not be audible when playing thru an amp, though. I'll have to do a little more testing...

You are getting clock bleed which means you have the clock frequency set too high. Try tweaking TR4.

My build has some clipping as well. That seems to be a typical issue I think.

OK, I will give that a second look. Thanks.

[oldschoolanalog]

My build has some clipping as well. That seems to be a typical issue I think.

This is starting to confuse me. It really shouldn't be an issue; typical or otherwise. The circuit with the 3007 retrofit board that I tested had no such issues. I sent Charlie the same board to test and he reported no problems. Give me a chance to build mine (I'm waiting for some parts) so I can hear/see what's going on.

One of those small bugs is that I can hear a bit of a slight distortion in some parts of the sweep with the knobs at certain settings. Is that normal?

What part of the sweep? And what settings? Your observations are greatly appreciated. I need to get to this resolved.
Maybe in the mean time someone with a completed build could either audio probe it or check things out on a 'scope to find out where the distortion/clipping occurs in the circuit?
I'm on the case. Thanks for your patience.
Dave

[Paul Marossy]

What part of the sweep? And what settings? Your observations are greatly appreciated. I need to get to this resolved.
Maybe in the mean time someone with a completed build could either audio probe it or check things out on a 'scope to find out where the distortion/clipping occurs in the circuit?
I'm on the case. Thanks for your patience.
Dave

I'll try to make some notes on this sort of stuff after I get home from work today, if I have any time to sit down and mess with it.

BTW, just for the record, I am using a $1.00 thrift store wall wart to power mine - a 12V 500mA wall wart. It puts out around 18V with no load on it.

[bajaman]

I purchased a board from Moosapotamus - very nice board too! However I was less than overjoyed when i plugged my guitar in and played it (after setting it up with a frequency counter, a scope and the correct ADA calibration procedures). So - I set to work reading, downloading ALL the ADA schematics I could find and comparing them to the Boss BF2 etc.
Here is what I discovered (the board I am using is the one designed to accomodate the Panasonic MN3007 BBD chip - modified by oldschoolanalog).
The board has an additional 78L05 regulator fitted (silkscreen is 180 degrees wrong for this IC!!!!) to power the CMOS and BBD chips - why!!
I fitted a 47 ohm resistor in it's place (input to output pin on the board) to obtain the much higher headroom available ( the MN3007 is designed to work from + 15v dc anyway!!).
I fitted an additional 22k resistor (track break required) in series with the 10n capacitor and the inverting input of the gain stage immediately following the BBD outputs.
This allows a much deeper flanging effect to be heard (it could be a 20k preset with a 10k in series fitted externally if desired ).
I noticed more than one person on another 38 page  thread on this site, complaining about the wobbly unatural and unusable high speed and partial solutions to this problem.
Okay - the original ADA flanger used a SAD1024 and then a MN3010 when the SAD became scarce. Both of these chips can give a 1024 stage delay, HOWEVER, they are both used as 512 stage delays in the ADA Flanger - take a closer look at the schematics - that's right, the inputs and outputs are paralleled in BOTH cases.( the MN3010 is two independent 512 stage delay lines)
The oldschoolanalog suggestion to use the MN3007, which is a single 1024 stage delay line has merit - it is still relatively easy to source and cheap (compared to the MN3005 and MN3010 etc.) BUT because we are now using double the delay line of the ADA Flanger we need to double the clocking speed to get the same results.(perhaps two MN3007 chips stacked would get closer to the MN3010 performance??!!).
The correct clocking speed should now be 69.6KHz to 2600KHz (not 34.8KHz to 1300KHz as in the ADA calibration specsheet)- don't worry the additional current buffers (CD4049) fitted, easily allow the MN3007 to be clocked at this higher speed.
I had to increase the 82k in series with the clock range trim pot to 150k to set the higher clocking speeds.(R65)
In conclusion - after these modifications the TRUE sound of the ADA Flanger was heard at last. I am genuinely surprised that no one has seemed to notice that the MN3007 was double the delay line length required for this circuit though.
cheers
bajaman

[neil411]

Bajaman,

Correct me if I'm wrong. I count three mods:

1. Get rid of the 15V regulator and put a a 47 ohm resistor in it's place.

2. Add a 22k resistor in series with the 10n cap

3. Replace R65 (82K) with a 150K resistor.

Is that it?

Thanks

[StephenGiles]