Question for MF-104SD owners

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dc_Sux
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Question for MF-104SD owners

Post by dc_Sux » Fri Jul 06, 2012 2:39 am

Hi,
I was very surprised to find an SD for sale at an authorised Moog dealer in Copenhagen when I was there recently, so took the opportunity and purchased it.
There are a couple of issues with it however, and I wanted to check that they are definitely abnormal, before looking into shipping it back under the guarantee.

Firstly, the feedback seems to be considerably limited. The manual (of the 104z at least) says that you should start getting infinite repeats with the feedback knob at about 8. You can see in this video below, that I can push mine all the way to 10 without getting infinite repeats. Certainly there is no chance of self-oscillation.

http://www.youtube.com/watch?v=3s2catYc ... e=youtu.be

Secondly, I get a frequent fluttering noise bot when there is signal passing through the pedal and when there isn't. This occurs at all settings. It is quite loud. I would expect a bit of background noise, but this is more than I was expecting and doesn't, to my ears, contribute to the "warmth" of the pedal. You can see this occurring in the following video.

http://www.youtube.com/watch?v=14aj1Xbx ... e=youtu.be

Unfortunately the sound on the videos is rubbish. You can't really hear the fluttering nose in it, but you can see it on my soundcard's level meter. They were recorded with the iPhone.

If any other SD owners can help clarify that these are abnormal behaviours, then I will look into getting the pedal back to Copenhagen.

Thanks

Tommy

77jordan
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Re: Question for MF-104SD owners

Post by 77jordan » Fri Jul 06, 2012 11:42 am

The feedback problem is abnormal; it should self-oscillate.

It's normal for the pedal to make noise when engaged, but when it's not it shouldn't make noise.

dc_Sux
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Re: Question for MF-104SD owners

Post by dc_Sux » Fri Jul 06, 2012 11:50 am

That's what I thought. Thanks man.

Croyote
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Re: Question for MF-104SD owners

Post by Croyote » Fri Jul 06, 2012 5:24 pm

77jordan wrote:The feedback problem is abnormal; it should self-oscillate.

It's normal for the pedal to make noise when engaged, but when it's not it shouldn't make noise.


77jordan, you have indicated that you own a 104z that has been modded to be a 104SD. This is not the same thing as the 104SD.

I have owned both a brand new 104Z and a brand new 104SD. The 104SD has a slightly different circuit design and/or trim pot settings from the factory, it's not just the additional two chips that set it apart.

THe 104SD was designed to be much darker and warmer, like a vintage reel-to-reel sound-on-sound tape machine. The built in filters are much stronger. The 104Z is brighter and self-oscillates easily.

On a factory stock 104SD, you cannot get it to self-oscillate on the longest setting, period. You can get it to self-oscillate if you put something in the feedback loop with a great deal of gain or output. It will also self-oscillate relatively easily on the shorter settings. Honestly, I consider the 104z to be a little hyperactive in comparison.

What may be a fluttery noise . . . might actually be the sound of the BBD's being maxed out and resonating. This is actually a piercing high pitch noise, something a LPF or EQ following the delay can rectify.

Otherwise, you may have two problems:

First, the output multiplexer IC could have been blown by a voltage spike, or reverse polarity. Look at the board and see if everything looks normal.

Second, the jumper pins on the daughter board (2nd level board w/ extra BBD's) could be touching the chassis resulting in a ground loop. In all cases, the pins should be insulated and/or trimmed. At one point, my delay stopped echoing; and I thought it had been damaged! I took it to my friend who is an electrical engineer and he pinpointed those jumper pins. He trimmed and insulated them. I've had no problems and my delay has been as good as new since his repair.

Good luck!

dc_Sux
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Re: Question for MF-104SD owners

Post by dc_Sux » Fri Jul 06, 2012 6:25 pm

Mate, thanks so much for the comprehensive reply. I really appreciate it.

Thing is, I can't get it to self oscillate, even at shorter delay times. I'm sure it can't be feeding back as much as it should be on the maximum setting. I can't get close to an infinite repeat.

I'm afraid I'm a total electronics novice. I have no idea what the multiplexer IC is , or even what jumper pins are. I certainly wouldn't be confident trimming anything!

EricK
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Re: Question for MF-104SD owners

Post by EricK » Fri Jul 06, 2012 10:06 pm

If it's not the jumper pins, then there is something else with the 104z that causes the problems. Something (possibly a voltage spike somewhere down the line) is causing the output to blow. There is a resistor that needs to be added as is the "permanent fix" from the factory.

This is part of the reason (other than the lack of BBD chips) in my opinion that has caused the 104z to be DC.
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Re: Question for MF-104SD owners

Post by Croyote » Mon Jul 09, 2012 2:43 am

EricK wrote:If it's not the jumper pins, then there is something else with the 104z that causes the problems. Something (possibly a voltage spike somewhere down the line) is causing the output to blow. There is a resistor that needs to be added as is the "permanent fix" from the factory.

This is part of the reason (other than the lack of BBD chips) in my opinion that has caused the 104z to be DC.
dc_Sux wrote:Mate, thanks so much for the comprehensive reply. I really appreciate it.

Thing is, I can't get it to self oscillate, even at shorter delay times. I'm sure it can't be feeding back as much as it should be on the maximum setting. I can't get close to an infinite repeat.

I'm afraid I'm a total electronics novice. I have no idea what the multiplexer IC is , or even what jumper pins are. I certainly wouldn't be confident trimming anything!
DC, I don't know much about what a Multiplexer IC is but its something that CS told me. I would be able to identify the problem if the output is unreasonably distorted . . . Find an electrical enginner w/ pedal/analog delay/Moog knowledge to take a look. Don't return it!

Now my echoes are darker, and a little fuzzy as they go on, and do lose definition each time, but I'm pretty sure it's normal behavior not distortion. My engineer pal, Dale Diamond, who invented the Wait States Delay by Sound Substance says that's pretty normal for BBD's.

Erick, I don't want to get into it, but I think you've mentioned that you've never had the jumper pins of your daughter board altered or insulated; and, your pedal still misbehaves. Is that right?

Ever since getting the pins fixed, mine has behaved dependably and always as expected. I practice with it several times a week (if not every day). Someday, I will send it in for the spillover mod, and for the voltage protection IC, but I'm in no rush. The pedal will oscillate at the short settings easily, but it's not like the Wait States or the 104z which oscillate wildly. It's just a little more chill. 8)

Search deep within the threads for detailed pics and answers, I'm too lazy to post a link and keep rehashing this topic.
:lol:

dc_Sux
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Re: Question for MF-104SD owners

Post by dc_Sux » Mon Jul 09, 2012 9:45 am

Croyote wrote:oscillate wildly
intentional Smiths reference?

Sound advice man. I've actually found a guy in London who services a lot of Moog gear and is willing to take a look at it for me.
I'll search the forum as suggested. Will keep you posted.

EricK
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Re: Question for MF-104SD owners

Post by EricK » Mon Jul 09, 2012 2:43 pm

Croy,
Self-Oscillation wasn't the only problem mine had. I think a resistor needed replacing in the output buffer. They installed a protection diode as a permanent fix and as one of the techs told me they set it up where they ran 1000 volts through it and that didn't cause any problems. My jumpers also do not touch the chassis. It's been to mood I think three times.

My point was that I think that jumper issue wasn't the only one that the Z was suffering from. Sometimes the output would be so low, the echoes were never heard.

Eric
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Re: Question for MF-104SD owners

Post by Croyote » Thu Jul 12, 2012 2:13 am

EricK wrote: My jumpers also do not touch the chassis.

My point was that I think that jumper issue wasn't the only one that the Z was suffering from. Sometimes the output would be so low, the echoes were never heard.

Eric


I dug up the report on the pedal's issues from Dale: "the pedal has two mechanical issues that I can see. Those pins you mention are indeed pushing up against the chassis. There is a connector on the stomp switch that's pushing against the bottom plate. When pushing on the bottom plate, this pushes the motherboard up and those pins get pushed up against the chassis. The whole unit will have to be disassembled. there just isn't enough clearance in there to do it any other way."

The problem is not that the pins touch the chassis when you look at them, but when it actually operates . . . the whole thing is too flexible so metal parts make contact when you stomp, tweak, etc. and mess up the current flow, or whatever.

Therein lies the rub.

77jordan
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Re: Question for MF-104SD owners

Post by 77jordan » Fri Jul 13, 2012 2:56 pm

can you post clips with guitar please!?

EricK
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Re: Question for MF-104SD owners

Post by EricK » Fri Jul 13, 2012 7:48 pm

Croyote wrote:the whole thing is too flexible so metal parts make contact when you stomp, tweak, etc. and mess up the current flow, or whatever.
Im not an engineer by any means, but I don't think I can accept at face value the theory about flexibility. Ive always been curious as to the expansion of the hot glue that holds the daughter board on there though. There is a significant gap between my jumper and the chassis that it would take very forceful and intentional compression of the frame to validate that theory. Tweaking alone, especially on a rack mounted unit isn't going to accomplish that. It may be true on your unit but I don't think this is the case with mine. I can't deny theres a short though if ur guy threw it on a scope. This seems to be the general consensus.

How would protection diodes be the solution for this problem?
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Re: Question for MF-104SD owners

Post by Croyote » Sun Jul 15, 2012 12:36 am

77jordan wrote:can you post clips with guitar please!?


I would love to, but my lust for Moog devices (among others like Metasonix) has precluded my acquiring of recording gear. I've got a few mics, but I purely depend on the kindness of friends, and engineers/artists who've acquired me for sessions.

I've a few recordings where I pushed the external feedback loop pushed into oscillation using other pedals, but nothing that features the beauty of my pedal's interior loop. One day . . . if I don't sell it to acquire skrill for a Vo. (that day might be closer if my 104m order would get completed already . . . starting to get pissed off about that :twisted: )
:?

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