EH Memory man faint steady high pitch wine

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2/25/1997 8:56 AM
Ryan	EH Memory man faint steady high pitch wine My old Memory Man chorus/delay has a faint steady high pitch wine when the delay knob is 3/4 or higher in the delay mode. does any one have a cure? Thanks.

 

3/4/1997 4:35 PM

Steve Morrison

Bucket-Brigade Delay chips as used in the MM use a high frequency clock to shift the analog samples from one stage to the next. At the shorter delay settings this clock is running at a frequency beyond your hearing range, but as you increase the delay the clock slows down to the point that you can hear it as a high-pitched whine. There may be a clock-null trimpot on the circuit board that can be adjusted to minimize the whine, but the null is never quite perfect. There's also usually a low-pass filter that smooths the samples together and reduces the level of any residual whine. Some delay boxes use a compandor to reduce noise, and if this is out-of-whack the whine would be more apparent. If your null-trim is properly adjusted and your filter and compandor are working up to spec, the only sure-cure is not to let the clock frequency get low enough to be audible, but of course this also means limiting the maximum delay you can get.

 

3/5/1997 12:30 PM

Mark Hammer

Is front of me is a 1979 review of the EH-MMD+chorus by Craig Anderton   from an issue of his shortlived newsletter "DEVICE", published from   1978-80. Craig notes that the clock signal is clearly audible at longer   delay settings and suggests using a noise gate to remedy the situation.   This tells us two things. First, your MMD is behaving normally.   Second the whine is enough of a nuisance to require drastic measures   such as a noise gate.     Craig also notes that the MMD has a single fixed low-pass filter, set   at a compromise value of 5khz to give best tradeoff of bandwidth and   clock noise for the widest range of delay settings. He further laments   the absence of a "tracking filter" which might optimize noise and   bandwidth for each delay setting (i.e., long delays = smaller bandwidth).     The ideal fix, of course is to implement such a tracking filter. The   ideal implementation is a bit of a major overhaul, so we'll avoid it.   There are, however, bone-headed mods which can do a simple n'stupid   simulation of it.     The MMD has a "Blend" control which continuously pans between dry and   wet signals. NOt having access to the innards of one, I'm not sure if   it's a single or dual-ganged pot. My guess is that EH's bargain basement   design philosophy nudged them towards a single pan pot, but I could be   wrong. IN any event, identify the "delay" input to the relevent pot and   connect a cap between that lug and ground. This will bleed off more   high end (some of which is clock and some of which is guitar) before   hitting the output and amp, which should tame the clock noise.     Since we'd like to keep as much bandwidth as possible, we'd obviously   like to easily remove the cap from the device when not needed. So,   here's a solution. Drill a hole in a convenient and safe location and   install a three-position-centre-off SPDT toggle switch. The centre lug   on the toggle switch is wired to the delay lug on the blend pot. The   two side lugs on the toggle switch each have a different cap soldered to   them, with the free ends of the caps soldered together, and connected to   the chassis of the switch (on a properly installed toggle switch, this   will provide a path to ground via the chassis of the box).     What values to select? A good idea is to remove the lid of the MMD, and   play with it on, and the delay set to the shortest delay time that   provides objectionable clock-whine. My hunch is that a starting value   of 1000-3300 pf might have some effect, but you can experiment with other   larger and smaller values. Once you find the *smallest* value that   produces a noticeable drop in audible clock signal, turn the delay to   the longest delay setting and try something about 3 times the value of   the first cap. Hypothetically, this should produce a comparable drop in   audible clock signal.     These two caps now become your new treble-cut caps to be wired to the   toggle. As you turn up the delay, just flick the toggle, and the whine   should be tamed. You can also use this treble cut to introduce different   echo ambiences. If you want to go whole hog, do the identical mod to the   "Feedback" control. The resulting treble cut has a cumulative effect each   time the signal recirculates through the delay line, with the signal   getting more and more mute. This has two nice effects. First, it tames   the "grit" that tends to accumulate with each iteration (an inherent   problem with analog delays). Second, since "real" echoes are not   timbrally identical with each iteration, more natural ambiences and   reverbs are created. If I'm not mistaken, the green MXR Analog Delay   had this hardwired into their feedback control and was a desired   feature of that device.     Hope this helps. I like noise gates, but anything I can do to eliminate   the need for them (and the wierd things they can do to the envelope) is   always a desirable thing for me.

 

3/6/1997 12:45 PM

CJ Landry

Mark you are definitly a knowledgable person, but what got me was when you said "drill a hole" . oooooouuuch. Man, drilling a hole in a pedal lke that is sacrilegious. I work on many pedals and when I see one that has holes drilled in it I know someone has Dicked with it and my price goes up. I am not doubting your ability and this is not a personal attack. But, tell him to try the simple things first. Christian

 

3/7/1997 6:15 PM

Mark Hammer

Sound advice, Christian, and worth noting.     If I advocate "risky" procedures, it's only because the majority of   participants in this forum appear to have a level of technical knowledge   several cuts above your average alt.guitar lurker (apologies to the   average alt.guitar lurker), so I'm relatively confident - perhaps   undeservedly so - in their ability to undertake mods like this. So   far, I have yet to see any "What's a flanger?" submissions to this   forum, and I take that to be a sign of non-beginner status, and a green   light for many of the things I suggest. On the other hand, it may be   wiser to leave any such suggestions very cryptic so that only those in   the know will have even the foggiest idea about how to proceed with the   mod. You know what they say about a little knowledge...     The other aspect, of course, is the AMPAGE reader who is also a   VINTAGE GUITAR reader, and treats anything made before 1980 as sacred   and NTBDW (not-to-be-dicked-with; hmmm, have I coined a new net-term   here?). I started all this modification stuff some 20 years ago, when   much of the equipment in question was considered current rather than   vintage. A glance through many of the publications at the time contains   lots of "mods" for things that many vinto-philes genuflect to on a   regular basis. For example, Tom Henry (who partners with Jack Orman,   and has written many DIY articles in prestigious DIY mags) had an article   in DEVICE about modifying an Electric Mistress and EH guitar synth.   In each case, there was some drilling involved. (Of course both can   command stupidly high prices from vintage dealers depending on how "mint"   they are. To my mind, mint simply means not perfected yet.) Other articles that   popped up included mods to various phasers and delay lines of the era.   Craig Anderton, among others, had small pieces in GUITAR PLAYER about   modifying various pieces of vintage gear; e.g., a Clyde McCoy wah.   Such articles were always intended to increase the playability of the   pedal in question, without any regard to their collectability or value.     My sense is that your comment was not a reprimand, but a helpful   cautionary note to the adventurous who possess the spirit but not the   chops, and it is appreciatively taken in that spirit. That being said,   I have no qualms about dicking with vintage stuff when one *does* know   what one is doing.     I suppose this could well result in another thread, but it's important   to realize that most stompbox, and even many rackmount, effects in   commercial release provide only a handful of the features that are   inherent in the design, or that make the product more usable. This   often occurs for dumb reasons *like* drilling another hole and adding the   cost of a toggle switch, or pot and knob, to the cost of the product.   One need only go as far as the MXR line to realize that almost every   product they initially produced had only one or two knobs. Why? Because   that's what would fit neatly on the boxes they used (Hammond 1590B)   with the style of knobs they used. This resulted in a Distortion +   which lacked a much-needed tone control, an Envelope Filter that can   easily support range switching, a Dynacomp and Noise Gate that can support   variable attack and decay time, and so on. The Phase 90 and Phase 100   are criminally derelict in their absence of controls. Electroharmonix products also   tended to stick in switches, or preset trimpots, where chassis-mount pots   would have been preferable, and minimized the controllability of their   products. A glance at EH price-lists from the early 80's indicates that   such short-cuts resulted in a product line which was VERY competitively   priced, and put effects into the hands of users who couldn't have afforded   them otherwise. However, a similar glance at the kinds of products being   generated these days by Boss and DOD indicates that consumers want the   bells and whistles which were omitted in earlier product lines. Among   the best selling distortion units are the Boss Heavy Metal and Metal Zone.   One of the things that goosed their sales was the presence of sophisticated   EQ-ing to tailor the sound. Count the number of knobs on Boss and DOD   pedals now, compared with their sales literature 10 years ago, and the   knob count is up from about 2.5 to 3.5 on average (by Hammer's patented   rapid gaze count technique). The list goes on an on, and includes both   guitars and amps, with only a few "New Cokes" in the batch.     The bottom line here is that there are many wonderful devices out there   that could be made even more wonderful (without destroying what made them   wonderful in the first place) with a few simple changes. I sense this is   a philosophy shared by many participants in AMPAGE, so I don't think of   this as any kind of a defiant statement, merely something that needs to   be said out loud once in a while.     Okay, back on track. The mods I suggested create many more possibilities   for analog delay lines (I'm actually going to try them on my MXR Digital   Delay, if time permits. Anything that has true analog pots carrying signal   are fair game.). When you DO drill your hole, remember:   1) you don't want aluminum shards shorting anything out on the board   or getting in the pots   2) you don't want to drill through the pc-board or wires   3) you don't want to electrocute yourself   4) you don't want to drastically alter the opportunity to sell something   if you think you might need/want to sell it at some point, and might   have trouble drumming up a customer for it   5) you don't want to wreck a nice paint job   6) you don't want to situate a switch/pot where they will be unwieldy   to use, or where they will incur noise or otherwise degrade the signal   path   7) you don't want to drill a hole that's too big and results in a shaky   installation     Whew! My chest feels lighter now. Ladies and gents, fire up your   drills and soldering irons!

 

3/8/1997 6:19 AM
Christian Landry	Mark,   Your reply is GREAT!!. You sound like an intelligent person and one who I could talk to for hours. You give good tips and you are definitly in the know when it comes to guitar effects. I have been interested in getting some of the old articles you mention. Do you have any? I would love to trade for some articles I have gathered so far. Christian

 

3/8/1997 12:21 PM

Mark Hammer

Thanks for the vote of confidence. I've been slacking off   from my teaching duties this past week (it's March break at   the college where I work), so I've been a bit more prolific   than I can normally afford to be. With school resuming in the   next 48 hrs (and an onslaught of grading in the works), I may   be pressed for time. What I will try to do, however, is compile   a list of relevent articles that appeared in both DEVICE and   POLYPHONY during their hayday years. Craig Anderton was at the   helm of each of these, and was among the contributors, along   with Tom Henry, Jack Orman, John Simonton, and other DIY   noteworthies. When it's done, I'll post it. Until then, I best   get back to work. I welcome any questions, but can't guarantee   a prompt response.

 

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