MN3005 vs V3205

[Govmnt_Lacky]

I would be in on assisting the design and testing of a V3205-based delay! 

I have 4 of them here that are collecting dust and are begging to be used!!!

[madbean]

The Aquaboy guide seems to scoff at the V3205, calling it the worst of the bunch and seems to prefer the shorter delay timed B3208 instead. The old Dirtbag build guide on the other hand seems to say that the difference is negligible.

Yeah, I kinda did a 180 there. Mostly because the more time I spent working through v3205 vs MN3005 on the DB and other delays I found more consistent problems with the v3205. It's passable, but not preferable. It works, and it's analog, and it is okay to use if you are willing to accept its limitations. But, it's just not an MN3005, esp. one @ 15v. Plus, with many, many hours of tweaking I have never been able to fix the odd decay the v3205 seems to have. I've been through the compander portion many times with almost every imaginable tweak and the v3205 just does not decay naturally. More to the point: even my Memory Boy from EHX gates through the compressor portion at very tiny volumes and that uses BL3208.

Anyway, the most significant change on the DB2014 is the addition of some hefty series resistors at the inputs of the two v3205 chips just before the biasing circuitry (these will be jumpered when using MN3005). The added noise of series resistance seems to cancel out some of the crap the v3205 spits out so the end result is better than before. But, I will put the same caveat on the DB2014 as the ABDLX: use MN if you got em. If you don't, do not expect a 100% representation of the classic DMM sound (but, at least a decent approximation of it).

I have been very tempted to go the opposite way and just design the next DB to be the real deal: MN3005 run at positive ground off a 24v supply. But, I don't think too many people would be happy with that decision. Maybe I could do a small run of those at some point, though. I did one of these for myself a few years ago and it is pretty awesome sounding.

[Scruffie]

What might be sensible is a limiter at the input, if the signal can't even get over 25mV then the BBDs wont distort, especially with a compander lending a hand too, setting the compander alone too heavy on the compression would cause issues.

A mash up of the Stereo Memory Man (as mono) & Deluxe could be fun and could slightly strip the design down, probably saving a dual opamp in the audio path, omitting the overload LED and associated circuitry (does anyone actually find that useful?) and the level pot... I'd guess that it'd only get a max of 500mS delay rather than 550mS with stripped back filtering but still that's pretty good.

As the bias on the MN/V/BL32XX series is nowhere near as stable with changing voltage as the MN30XX series I would add a charge pump and regulator on board just for a solid 9V as otherwise changing between supplies can cause mis-biasing, otherwise it'd have to run on 12V DC which might be annoying for some... it's a slight over-design but it beats a zener.

[Scruffie]

The Aquaboy guide seems to scoff at the V3205, calling it the worst of the bunch and seems to prefer the shorter delay timed B3208 instead. The old Dirtbag build guide on the other hand seems to say that the difference is negligible.

I have been very tempted to go the opposite way and just design the next DB to be the real deal: MN3005 run at positive ground off a 24v supply. But, I don't think too many people would be happy with that decision. Maybe I could do a small run of those at some point, though. I did one of these for myself a few years ago and it is pretty awesome sounding.

I'd be in to that, the positive supply bit isn't so bad as you can set a charge pump up to make -18V from 9V.

Perhaps to make it a bit more appealing you could offer 2 x 3008 daughter boards to compliment it?

[GrindCustoms]

It maybe does 1 year now that i've been seriously bitten by the BBD bug... and try to try as much stuff that i can with them.

I recently got a Ibanez AD9 that uses a MN3205 and it sounds ridiculously good, the «character» of the repeats is something to look for, probably the highest fidelity repeat that i've heard yet. With that said, the V3205 is a direct replacement for it's MN counterpart. Jer (the3secondrule) have swapped the MN3205 of his for a V3205 and digged it. I'm waiting on some of those to come in to also make the experiment.

So what i'm thinking here, the AD9 is at is source tweaked for those BBD opposite to the Dirtbag or Aquaboy...... where am i going with all this!?!

Couple V3205 are on their way to me, when time comes i'll make a daughter board for 2x V3205 and give them a try in the AD9 if working as good in «single» mode. Will then be able to know if they can stack well.

On the other hand i own that AquaPuss clone that Morgan had built on the early DIYSB AP3 boards, i've recently swapped the MN3005 in it for a MN3008...
With no surprise the available length of delay is shorter but no matter how i've tried to tune that circuit with the MN3005 i've never been able to get clean repeats like i do with the MN3008.... this thing now sound super clear and i've had the time to understand the biasing/clock and what not of MN's enough with the ABDX i did wich sound really damn good too....
The MN3008 just shines in the AquaPuss, being a short delay/slapback echo, the use of a shorter delay BBD in these just made sense to me, it stills run away into oscillation when not playing... like it should.

Good food for thoughts in this thread.

Rej

[Scruffie]

The MN3008 has a higher Vrms, better S/N & THD than the 3005 so that's no surprise that it's cleaner, it is a 'better' chip spec wise.

I'll be interested to hear how the AD9 gets on with the stacked v3205, if I did do this v3205 design though I wouldn't base it around the AD9 topology, which is very similar to a DM-2 (in fact you can just about build one on the Aquapuss board) as it can be improved further.

[GrindCustoms]

The MN3008 has a higher Vrms, better S/N & THD than the 3005 so that's no surprise that it's cleaner, it is a 'better' chip spec wise.

I'll be interested to hear how the AD9 gets on with the stacked v3205, if I did do this v3205 design though I wouldn't base it around the AD9 topology, which is very similar to a DM-2 (in fact you can just about build one on the Aquapuss board) as it can be improved further.

I'll post the results/soundclips when i'm done with in that NPD thread.

Out of curiosity, wich delay circuit would be more appropriate to use the V3205?

[Scruffie]

The MN3008 has a higher Vrms, better S/N & THD than the 3005 so that's no surprise that it's cleaner, it is a 'better' chip spec wise.

I'll be interested to hear how the AD9 gets on with the stacked v3205, if I did do this v3205 design though I wouldn't base it around the AD9 topology, which is very similar to a DM-2 (in fact you can just about build one on the Aquapuss board) as it can be improved further.

I'll post the results/soundclips when i'm done with in that NPD thread.

Out of curiosity, wich delay circuit would be more appropriate to use the V3205?

That's a matter of opinion but i'm not a fan of the 3rd order sallen-key topology and has been discussed the chips do not seem to stack well, also relying on the compander to compress the signal down to manageable levels for the BBD leads to issues and adding series resistance to the BBDs isn't exactly the best way to deal with clipping either.

I have a feeling some of the unnatural decay of the v3205 mentioned can be reduced by simply improving the pre smoothing/anti-aliasing filtering.

All speculation but some places to start.

[GrindCustoms]

The MN3008 has a higher Vrms, better S/N & THD than the 3005 so that's no surprise that it's cleaner, it is a 'better' chip spec wise.

I'll be interested to hear how the AD9 gets on with the stacked v3205, if I did do this v3205 design though I wouldn't base it around the AD9 topology, which is very similar to a DM-2 (in fact you can just about build one on the Aquapuss board) as it can be improved further.

I'll post the results/soundclips when i'm done with in that NPD thread.

Out of curiosity, wich delay circuit would be more appropriate to use the V3205?

That's a matter of opinion but i'm not a fan of the 3rd order sallen-key topology and has been discussed the chips do not seem to stack well, also relying on the compander to compress the signal down to manageable levels for the BBD leads to issues and adding series resistance to the BBDs isn't exactly the best way to deal with clipping either.

I have a feeling some of the unnatural decay of the v3205 mentioned can be reduced by simply improving the pre smoothing/anti-aliasing filtering.

All speculation but some places to start.

So in other words, a new design!

[madbean]

What might be sensible is a limiter at the input, if the signal can't even get over 25mV then the BBDs wont distort, especially with a compander lending a hand too, setting the compander alone too heavy on the compression would cause issues.

Clever! Twin diodes to ground might do the trick here. I will check that out on my build. It might be preferable to a large series resistance.

[culturejam]

I was coming here to suggest some type of passive limiting on the input of the BBDs to keep the input below the headroom limits of the V3205. Looks like I had the right idea. 

[Scruffie]

The MN3008 has a higher Vrms, better S/N & THD than the 3005 so that's no surprise that it's cleaner, it is a 'better' chip spec wise.

I'll be interested to hear how the AD9 gets on with the stacked v3205, if I did do this v3205 design though I wouldn't base it around the AD9 topology, which is very similar to a DM-2 (in fact you can just about build one on the Aquapuss board) as it can be improved further.

I'll post the results/soundclips when i'm done with in that NPD thread.

Out of curiosity, wich delay circuit would be more appropriate to use the V3205?

That's a matter of opinion but i'm not a fan of the 3rd order sallen-key topology and has been discussed the chips do not seem to stack well, also relying on the compander to compress the signal down to manageable levels for the BBD leads to issues and adding series resistance to the BBDs isn't exactly the best way to deal with clipping either.

I have a feeling some of the unnatural decay of the v3205 mentioned can be reduced by simply improving the pre smoothing/anti-aliasing filtering.

All speculation but some places to start.

So in other words, a new design!

To a point  not saying the wheel needs reinventing though.

What might be sensible is a limiter at the input, if the signal can't even get over 25mV then the BBDs wont distort, especially with a compander lending a hand too, setting the compander alone too heavy on the compression would cause issues.

Clever! Twin diodes to ground might do the trick here. I will check that out on my build. It might be preferable to a large series resistance.

The trick used in many flangers in the feedback loop of an opamp there the 'distortion' added by the clipping is a benefit to that jetty flange sound we love, it's probably an improvement over nasty clipping in a delay but still not ideal.

I was thinking more a long the lines of a compressor at the input stage, something like this -

It's not ideal but with some high Q filters, a balance should be possible to get a decent sound.

I'm looking over the MN3205 datasheets as we speak... the specs were worse than I remembered! But these steps will help.

Edit: If you're going to use diodes I don't think 1N4148 are going to cut it, the THD by the time that signal level is reached is... well not pretty.

[jubal81]

So, does this mean that using 4 mn3008s would yield an even better result than 2 mn3005s?

[GrindCustoms]

So, does this mean that using 4 mn3008s would yield an even better result than 2 mn3005s?

In theory the answer should be yes. The other day Forrest and I where chatting about that... and the conclusion upon reviews of the older DMM with 2x MN3005 and those with a quad of MN3008, the 08 where more silent in their operating.

Note, i don't know shit, just saying this on top of my head.

[Scruffie]

So, does this mean that using 4 mn3008s would yield an even better result than 2 mn3005s?

It would depend on your definition of 'better' but potentially yes but also potentially no... to get the best you'd definitely want a scope, setting up 2 BBDs is much easier by ear than 4.

So, does this mean that using 4 mn3008s would yield an even better result than 2 mn3005s?

In theory the answer should be yes. The other day Forrest and I where chatting about that... and the conclusion upon reviews of the older DMM with 2x MN3005 and those with a quad of MN3008, the 08 where more silent in their operating.

Note, i don't know shit, just saying this on top of my head.

Of course it's quieter, all the components are new in the new one, no value or bias drift, no dry caps, better tolerances, no internal transformer and modern opamps.