MXR - M-163 - Sustain (Commande Series)

Tonetweaker · Post by **Tonetweaker** » 08 Feb 2011, 06:03

Hey everyone...

I saw a mention of the MXR Sustain pedal in the thread about the Marshall ED-1 Compressor. I just happened to get one I bought a few days ago on eBay in the mail tonight, so I thought I'd take a few quick gutshots since there didn't seem to be much info available on it.

Cheers...
Steve

roseblood11 · Post by **roseblood11** » 08 Feb 2011, 14:53

Great!

Maybe you could identify all the parts values? It´s very prone to errors to do that just with the photos...
I always use this program for the color codes: http://www.electronics2000.co.uk/download.php

And a backlighted photo of the component side would help a lot.

Are you sure that it´s the M-166? I thought it was called M-163, as M-166 was a delay unit?
They sell a schematic for a "Sustain M-163" here, but $10 is too much, I think:
http://www.schematicconnection.com/stor ... rodtype=66

lolbou · Post by **lolbou** » 08 Feb 2011, 15:53

roseblood11 wrote:Are you sure that it´s the M-166?

My bad, it was a typo...

Tonetweaker · Post by **Tonetweaker** » 10 Feb 2011, 05:23

roseblood11 wrote:Great!

Maybe you could identify all the parts values? It´s very prone to errors to do that just with the photos...
I always use this program for the color codes: http://www.electronics2000.co.uk/download.php

And a backlighted photo of the component side would help a lot.

I use the same program. I think I recommending to someone here not too long ago as well...

I will definitely crack it back open and see about getting some component values for you this weekend. I can also see about some better pics too. I happened to be curious about this circuit, so I just snapped a few quick ones while I had it open, but if there's interest in reversing it, I'll be happy to do a bit more to help the cause.

I also have a few other old vintage pedals that have come in this week that might generate a little interest, so I'll probably take some gutshots of those as well.

Cheers...
Steve

roseblood11 · Post by **roseblood11** » 10 Feb 2011, 08:20

Tonetweaker wrote: but if there's interest in reversing it,

Tonetweaker · Post by **Tonetweaker** » 12 Feb 2011, 06:25

I will get to this tomorrow... I haven't forgotten you guys.

I got side-tracked this evening with a couple of other vintage pedals that I can't seem to stop playing with... a nice sounding Aria Distortion (DT-5), Tech-21 Double Drive (Limited Ed.) and a really strange one... an EXR Projector. I guess I'll have to pull these apart next...

Cheers...
Steve

Tonetweaker · Post by **Tonetweaker** » 13 Feb 2011, 05:29

OK, everybody... I pulled this bad boy apart again, and took a few more close-up pics. I'm definitely a little rusty on my component identification skills, but I took a stab at everything I could. There were definitely a couple of problems though, so perhaps you guys could give me a hand to help ID a few of the components. The board is pretty solid, so back-lighting didn't provide any clues to the traces on the back side. The board is pretty widely-spaced though, so I just took a bigger pic of the trace side to aid in drawing out a schematic. I'll keep it apart for awhile, so if there are any questions on where anything connects, give me a shout and I'll try to clear up any gray areas.

Here's the trace side...

Here's a pic of the main body of the component side, with annotated component values...

Here is a close-up of the components near the pots, which were hard to see on the main photo...

The main problems I had in the identification process were as follows:

1.) There were 5 transistors on the board with absolutely no labeling (circled on the middle picture)... It appears as though they might have been painted over somehow during manufacturing. The other was clearly labeled and identifiable.

2.) The diode next to the power jack did not appear to be labeled in a way that made sense to me, but part of the markings may have been hidden beneath. If I had to guess, I'd say it's a 1N914.

3.) A few of the caps and other components had labeling that was a little unfamiliar to me (I'm definitely rusty). When in doubt, I wrote exactly what I saw on the labeling.

Upon closer inspection, it's pretty obvious that this board has had a couple of amateur repairs done. The pots, power jack and battery leads were obviously resoldered (poorly)... and the "repaired" red battery lead came right off when I removed the board from the case. I also spotted an obvious cold solder joint on one of the pots. I'll have to unpack one of my irons and do some clean-up/repair work to this one.

The board measures 4 1/16" x 2 3/4" (104mm x 70mm), for anyone interested.

I may try to draw out a schematic myself, but I've never done that with any CAD tool, so it may take me awhile. In the meantime, if anyone else wants to take on the task, I'll do anything I can to assist the cause. Just let me know.

Cheers...
Steve

roseblood11 · Post by **roseblood11** » 13 Feb 2011, 10:14

Many thanx!

The output pot might be 100k ("101", coded as caps). Audio taper?
Then Sensitivity then is 1M, probably audio taper as well?

the diode in the last picture looks like a 1n4148

the ceramic caps are 50pF

The 2n4126 is a genereal purpose pnp-SI, maybe it could be replaced by 2n3906

the green caps might be 15µF tantalums

rn 112b pc and 111 pc are codes for switchcraft jacks:
http://www.datasheetarchive.com/pdf-dat ... 96758.html

transistors? No idea...

This is what "mictester" wrote about this kind of circuit in the Marshall ED-1 thread:

The other approach that I really like is to use the transconductance amp (OTA) in the negative feedback loop of an op-amp. This minimises the ill effects of the poor OTA, and allows the gain cell to benefit from the quality available from the op-amp.

Look at the Morley (Tel-Ray) compressor that uses a 3080 and a TL074. It's simple, but very effective. Also have a look at the (somewhat rare) MXR Sustain Unit - not the Dynacomp. Again, the OTA provides the negative feedback for a TL072 op-amp. MXR's transistorised rectifier was a bit "over the top" in the Sustain Unit, but it worked really well.

The only downside to this configuration is the more limited range of control available, but the smooth control and the low noise and distortion go a long way to mitigating the problems. You can cascade the gain cells for much more control, and I've done this in a commercial product for the broadcast industry. The sequential gain cells were so effective that it wasn't really necessary to use overshoot prevention clippers (with all the distortion they introduce).

I couldn´t find a Morley/Telray compressor with a tl074, but this looks quite similar, maybe it helps:
http://www.morleypedals.com/vcoes.pdf

Tonetweaker · Post by **Tonetweaker** » 13 Feb 2011, 20:00

roseblood11 wrote:I couldn´t find a Morley/Telray compressor with a tl074, but this looks quite similar, maybe it helps:
http://www.morleypedals.com/vcoes.pdf

Many thanks, roseblood. I appreciate you taking the time to clarify the component markings...

BTW ~ I did have an example of a Morley comp that uses TL074s. Perhaps this is the one mictester was referring to?

Here it is...

morley pro compressor.pdf: (255.02 KiB) Downloaded 279 times

I'm still working on a schematic for this thing. I've DL'd ExpressSCH since I don't know of a better program for drawing schematics.

Cheers...
Steve

Dirk_Hendrik · Post by **Dirk_Hendrik** » 13 Feb 2011, 20:44

errrrr....
thread hijack.
I used to have a distortion from this commande line. Traded it in years ago. Anyone interested in the schem*? I should scan it since I did not use CAD at the time (appox '92-'94).

*
it was the worst distortion I've ever encountered...

Tonetweaker · Post by **Tonetweaker** » 13 Feb 2011, 21:01

Dirk_Hendrik wrote:errrrr....
thread hijack.
I used to have a distortion from this commande line. Traded it in years ago. Anyone interested in the schem*? I should scan it since I did not use CAD at the time (appox '92-'94).

*
it was the worst distortion I've ever encountered...

Sure. It'd be interesting to take a peek at anyway. Sometimes, a lesson in what not to do is just as important as what is...

That reminds me, Dirk. Ever play around with an old Aria Distortion (DT-5)? I got one in this week... I only had a few minutes to play around with it, but it seemed to have a pretty good, crunchy sound to it.

Tonetweaker · Post by **Tonetweaker** » 13 Feb 2011, 22:11

Does anyone know exactly what the white box component labeled ".1J100" is? It looks like a polyester cap to me, so I'm guessing the ".1J" part means 100nF ~ 5%, but then I'm not sure what the "100" part that follows is supposed to represent?

lolbou · Post by **lolbou** » 13 Feb 2011, 22:18

Tonetweaker wrote: but then I'm not sure what the "100" part that follows is supposed to represent?

Rated at 100V...

Tonetweaker · Post by **Tonetweaker** » 13 Feb 2011, 22:22

lolbou wrote:
Tonetweaker wrote: but then I'm not sure what the "100" part that follows is supposed to represent?
Rated at 100V...

Excellent! Much appreciated!

Tonetweaker · Post by **Tonetweaker** » 14 Feb 2011, 03:05

Ugh. I am having some trouble drawing this out properly. Until I figure out what those transistors are, I'm not sure how to go about drawing all this out. I was going to temporarily just use a generic NPN transistor as a placeholder, but then again, there's not even any guarantee that the base is the middle lead.

Anyone have any ideas how to identify the mysterious masked transistors?

roseblood11 · Post by **roseblood11** » 14 Feb 2011, 08:48

Maybe they used discrete FET stages where the Morley has opamps?

Dirk_Hendrik · Post by **Dirk_Hendrik** » 14 Feb 2011, 11:18

Tonetweaker wrote:That reminds me, Dirk. Ever play around with an old Aria Distortion (DT-5)? I got one in this week... I only had a few minutes to play around with it, but it seemed to have a pretty good, crunchy sound to it.

As far as I know I only have the DT10 (but it seems I forgot to list it on my site) but it did not really leave an impression... Should give it another chance,

Tonetweaker · Post by **Tonetweaker** » 16 Feb 2011, 05:09

roseblood11 wrote:Maybe they used discrete FET stages where the Morley has opamps?

Could be, but I hate to guess on something that important. I'll have to dig into this again this weekend and see if I can find out any more information.

Dirk_Hendrik wrote:
Tonetweaker wrote:That reminds me, Dirk. Ever play around with an old Aria Distortion (DT-5)? I got one in this week... I only had a few minutes to play around with it, but it seemed to have a pretty good, crunchy sound to it.
As far as I know I only have the DT10 (but it seems I forgot to list it on my site) but it did not really leave an impression... Should give it another chance,

It might be worth another listen... I'm not sure what the differences are in the circuits between the two, but the DT-5 seemed pretty solid for a straight-up hard rock/metal distortion. It's not very subtle, but it'll definitely give you a nice power chord.

Cheers...
Steve

Tonetweaker · Post by **Tonetweaker** » 22 Feb 2011, 03:24

Just wanted to check in here... I haven't forgotten the tracing/schematic for this. I had to go out of town this weekend, so I'm hoping to pick it up again later this week. Still having trouble with these transistors though. No idea what I'm looking at, so I may get the tracing done, but I think the component ID will still be a major hurdle.

I may just bite the bullet and buy that schematic (blasphemy, I know...

).

Cheers...
Steve

Dirk_Hendrik · Post by **Dirk_Hendrik** » 28 Feb 2011, 07:14

Tonetweaker wrote:
Dirk_Hendrik wrote:errrrr....
thread hijack.
I used to have a distortion from this commande line. Traded it in years ago. Anyone interested in the schem*? I should scan it since I did not use CAD at the time (appox '92-'94).

it was the worst distortion I've ever encountered...
Sure. It'd be interesting to take a peek at anyway. Sometimes, a lesson in what not to do is just as important as what is...

Here it is in the way I did handdrawings in 1995. There is some stuff which I would like to recheck though...

MXR - M-163 - Sustain (Commande Series) [schematic]