# EH Memory Man needs repair...any techs in Canada?



## 335Bob

I have a EH Memory Man that needs repair. I want to have it repaired in Canada. I already had the inventor (Howard Davis) of this pedal inspect it at great expense. He said it works fine. So he ships it back and it still doesn't work and it's doing the same thing that made me ship it to him in the first place. This story could be longer. However, I'm hoping someone around here knows somebody (in Canada) who is competent in repairing these units and could point me in their direction. It would be much appreciated.

Regards,
Bob


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## shoretyus

Did you talk to anybody at Ed's Music or Bud's in Peterborough?


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## Rwinder

don't know anyone in canada but analogman repairs them. I'm sure it will cost a lot though


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## gtrguy

What's wrong with it?


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## 335Bob

Yes, I know Analogman does repairs and mods on these. The problem is, I've already spent over $100 dollars to have the same broken pedal returned to me. So with back and forth shipping to the US and the repair fee, I might as well toss it and buy a new one. Which I'm about ready to do anyways. (I'm thinking Diamond Memory Lane 2)

As far as to what it's doing. Loss of signal (low volume, murky sound) is the first thing. When the Blend knob is turned up (even slightly), the original signal disappears altogether. Set to echo only, the repeats distort and have a high pitched feedback to them. Which is impossible to dial out. Modulation sounds distorted even when mildly dialed in, again no original signal comes through, only the after-effect. Definitely not the sound that should come out of this thing.

I appreciate the suggestions and comments. 
Thanks.
Bob


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## Rwinder

If your going to toss it, i'll happily take it of your hands for spare parts for my DMM (let me know) sucks that howard davis couldn't fix it... that kinda scares me a bit as i was about to send mine to him to tune up... having second thoughts now. 

dealing with your original issues though, my DMM also has the murky sound this is what people love about the pedal. the volume issue, i assume you have adjusted the level knob? The blend knob thing is definitely not right...maybe the pot is screwed. 
as for the distortion are you slamming it with drive pedals? DMM's are known for clipping in this situation i can get mine to distort like you are describing.

^^^^I'm just covering all the bases..^^^^

You might want to call some music repair shops and see if anyone is up for tackling this, i've read that these pedals are "interesting" to work on. 

If i was you i would definitely be all over howard davis about this as you have already given him money and he didn't do what you paid for... 



335Bob said:


> Yes, I know Analogman does repairs and mods on these. The problem is, I've already spent over $100 dollars to have the same broken pedal returned to me. So with back and forth shipping to the US and the repair fee, I might as well toss it and buy a new one. Which I'm about ready to do anyways. (I'm thinking Diamond Memory Lane 2)
> 
> As far as to what it's doing. Loss of signal (low volume, murky sound) is the first thing. When the Blend knob is turned up (even slightly), the original signal disappears altogether. Set to echo only, the repeats distort and have a high pitched feedback to them. Which is impossible to dial out. Modulation sounds distorted even when mildly dialed in, again no original signal comes through, only the after-effect. Definitely not the sound that should come out of this thing.
> 
> I appreciate the suggestions and comments.
> Thanks.
> Bob


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## 335Bob

Rwinder said:


> If your going to toss it, i'll happily take it of your hands for spare parts for my DMM (let me know) sucks that howard davis couldn't fix it... that kinda scares me a bit as i was about to send mine to him to tune up... having second thoughts now.
> 
> dealing with your original issues though, my DMM also has the murky sound this is what people love about the pedal. the volume issue, i assume you have adjusted the level knob? The blend knob thing is definitely not right...maybe the pot is screwed.
> as for the distortion are you slamming it with drive pedals? DMM's are known for clipping in this situation i can get mine to distort like you are describing.
> 
> ^^^^I'm just covering all the bases..^^^^
> 
> You might want to call some music repair shops and see if anyone is up for tackling this, i've read that these pedals are "interesting" to work on.
> 
> If i was you i would definitely be all over howard davis about this as you have already given him money and he didn't do what you paid for...


Well, the situation with Howard Davis is a long story. He suggested replacing the 24volt power adapter, which I did. Also, the way he shipped it back, I got dinged for customs fees, I tried to make my case to Canada customs. They want my original sales receipt showing I originally bought it in Canada. Don't have it/can't find it. Ugh! Let's just say he will "repair" it if I send it to him. However, I have to pay shipping to and fro. (Here we go, again) This is what is keeping me from doing this. I've put enough money into it. And if it comes back with the same issue? I'll probably go postal or something of the sort. kkjuw
Now, as to the murky sound. I know what you are saying. Keep in mind, I've had this pedal for 5 years and have used it extensively. So, I've probably exhausted the many ways to get decent sound settings out of it. That being said, it sure don't sound like it used to. Actually, it's quite unusable the way it is. So, possibly I'll post it as a parts deal. I don't know yet. I'll see if I can get it fixed this side of the border.

Thanks for the input.
Bob


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## Rwinder

Sorry i couldn't be more help. maybe try calling some of the bigger boutique stores like 12th fret in toronto and see if they know of anyone in canada that could fix it. For some reason i keep thinking that there is an effects modder based in Montreal, may be worth looking into. 

Wish i could be more help.


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## kat_

Was there anything that happened that may have caused it to break? Maybe a power surge?

Have you opened it up and looked around? Is there anything that looks like it has come loose or shorted out? Anything noticably burnt?

Post some pics of the inside and see if anyone on the forums notices anything that could cause what you're describing.


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## liddokun

Some pictures would definitely help. I know there are plenty of pedal veterans lurking on this forum. A few pictures of the front and back of the circuit board and all the controls and wiring would go a long way and trying to diagnose this.


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## Esoterik

kat_ said:


> Was there anything that happened that may have caused it to break? Maybe a power surge?
> 
> Have you opened it up and looked around? Is there anything that looks like it has come loose or shorted out? Anything noticably burnt?
> 
> Post some pics of the inside and see if anyone on the forums notices anything that could cause what you're describing.


+1, pics would be great. I'm an electronics tech so I might be able to help out.


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## zurn

Hi, surely you have thought about it but is there a reason you didn't just try to find another one on Ebay ?


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## mhammer

Well I'm gonna be at my in-laws in Washago over the Xmas break if you want to bring it by and let me have a look at it.

Know that the DMM has had all manner of incarnations over the years, with different ones having different sorts of Achilles heels. For example, one issue used a trio of SAD1024 delay chips, each of which necessitated additional trimpots and adjustments. This was eventually replaced with an MN3005 which dropped the trimpot count down.

Can you pop it open and tell us what chips are in there? That would help a lot to provide some preliminary advice on what to look for.


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## liddokun

I was hoping you'd chime in here Mark. I was going to offer to have a look at it, but I'm not so great at delay pedals yet. Ha! In time!


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## mhammer

Well if Buckhorn didn't appear to be as close to the Washago/Orillia area as it is, I wouldn't be making the offer. I'm generous, but I'm not crazy.:smile:


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## 335Bob

mhammer said:


> Well I'm gonna be at my in-laws in Washago over the Xmas break if you want to bring it by and let me have a look at it.
> 
> Know that the DMM has had all manner of incarnations over the years, with different ones having different sorts of Achilles heels. For example, one issue used a trio of SAD1024 delay chips, each of which necessitated additional trimpots and adjustments. This was eventually replaced with an MN3005 which dropped the trimpot count down.
> 
> Can you pop it open and tell us what chips are in there? That would help a lot to provide some preliminary advice on what to look for.


Opened it up, nothing looks amiss. I tried taking some pics, they come out too fuzzy for diagnosis of anything. Definitely this one has the MN3005 chips. The board looks clean, no damage or loose wires. I didn't think I'd see anything. This pedal has been in the center of my board and pretty much shielded by the other pedals on the outer perimeter. So it still looks new.

I appreciate your offer to look at it. I won't be able to come by during the holidays. Just too crazy around here, leaving very little time. The only way I could get it to you is by mail with return postage included. If you think you can fix it, I'd be more than happy to cover your time/parts. I understand if you don't have the time. I hardly have time to do any of my own projects. Again, I appreciate everyone's offer to help out with this.


Thanks,
Bob


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## mhammer

So 2 MN3005 chips?

I'll dig around for a schematic and try and make some productive suggestions for what to look for as preliminary troubleshooting.


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## 335Bob

Yes, 2 MN3005 chips. You mean this schematic?








Got it from here.
http://www.schematics.ca/modules/PDdownloads/visit.php?cid=67&lid=476


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## Rwinder

hey just a little heads up

If your thinking of replacing your DMM there is one in spaceman music ottawa for $189 which is a smoking deal, it looks mint. didn't play it though...


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## mhammer

335Bob said:


> Yes, 2 MN3005 chips. You mean this schematic?
> 
> 
> 
> 
> 
> 
> 
> 
> Got it from here.
> http://www.schematics.ca/modules/PDdownloads/visit.php?cid=67&lid=476


Well that's one of them, at least.

Does the chip complement appear to be the same as yours? If so, then you will see there are three trimpots visible in the bottom part of that schematic. The one on the far left (100k) sets the bias voltage to the BBD. The bias voltage needs to be set right. A little on the high or low side, and the chip will pass signal but in a distorted fashion. If higher or lower than that, the chip stops passing signal. It isn't fried, necessarily, just not working right under those conditions. frequently, complaints about broken or disappointing delay pedals, flangers, and chorus pedals come down to that adjustment. happily, it can be tweaked all over the place wiothout destroying anything. The worst that will happen is you'll lose track of the sweet spot and have to find it again. Pros will look for the sweet spot with a scope and signal generator, but you can do it by ear and have 98% the precision of a scope job. Note that there is a 100k bias trimpot for each MN3005. (check to the far left of the schematic)

The MN3005 has essentially two pathways internally, one driven by the "tic" from the clock generator, and the other driven by the "toc". Put them together and they make a complete picture of the signal. They need to be in proper proportions to do so, though. Some manufacturers achieve that balance through equal-value fixed resistors, and some through trimpots. EHX uses trimpots here (the 5k unit). When the balance is not spot on, the clock signal can become more audible (whine). Like the bias trimpot, you can tweak them all over theplace without damaging anything, you just lose the sweet spot.

Finally, most BBD chips will introduce some difference in output signal level, relative to input. EHX tries to maintain level balance by sticking in an op-amp stage between and after the delay chips to bring the signal up to unity gain level. That would be the other 100k trimpot (shown lower right). Like the other two, it can be tweaked to your heart's content, and all you stand to lose is the sweet spot.

As for the malfunctioning of the Blend control. That may be as simple as just replacing the pot with another 10k unit.


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## Voxguy76

335Bob said:


> Well, the situation with Howard Davis is a long story. He suggested replacing the 24volt power adapter, which I did. Also, the way he shipped it back, I got dinged for customs fees, I tried to make my case to Canada customs. They want my original sales receipt showing I originally bought it in Canada. Don't have it/can't find it. Ugh! Let's just say he will "repair" it if I send it to him. However, I have to pay shipping to and fro. (Here we go, again) This is what is keeping me from doing this. I've put enough money into it. And if it comes back with the same issue? I'll probably go postal or something of the sort. kkjuw
> Now, as to the murky sound. I know what you are saying. Keep in mind, I've had this pedal for 5 years and have used it extensively. So, I've probably exhausted the many ways to get decent sound settings out of it. That being said, it sure don't sound like it used to. Actually, it's quite unusable the way it is. So, possibly I'll post it as a parts deal. I don't know yet. I'll see if I can get it fixed this side of the border.
> 
> Thanks for the input.
> Bob


Bob,

The least of your worries i'm sure but Customs should have only charged you on the price of repair job and even thats iffy. If you decide to send it back to the states for repair, before you send it back go to your local customs office and bring the pedal with you. Ask them for a Y38 for a temporary exportation for repair. They will probably affix a small serial number sticker on the pedal and stamp the green card. Its just proof that you owned the item prior to it re-entering Canada again. No Officer in his right mind will charge you again upon its reimportation..


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## hollowbody

riffboy76 said:


> Bob,
> 
> The least of your worries i'm sure but Customs should have only charged you on the price of repair job and even thats iffy. If you decide to send it back to the states for repair, before you send it back go to your local customs office and bring the pedal with you. Ask them for a Y38 for a temporary exportation for repair. They will probably affix a small serial number sticker on the pedal and stamp the green card. Its just proof that you owned the item prior to it re-entering Canada again. No Officer in his right mind will charge you again upon its reimportation..


Hey thanks for the info! I got dinged with customs for a Sparkledrive that was being repaired for me, and I did some yelling but got nowhere with it. I'll definitely remember this next time!


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## Rwinder

riffboy76 said:


> Bob,
> 
> The least of your worries i'm sure but Customs should have only charged you on the price of repair job and even thats iffy. If you decide to send it back to the states for repair, before you send it back go to your local customs office and bring the pedal with you. Ask them for a Y38 for a temporary exportation for repair. They will probably affix a small serial number sticker on the pedal and stamp the green card. Its just proof that you owned the item prior to it re-entering Canada again. No Officer in his right mind will charge you again upon its reimportation..


Great info, i was thinking about this but wasn't sure how to get it done. 

thanks


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## gtone

It was those fargen bastage Canada Customs dudes playing your DMM that messed it up! 9kkhhd


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## Ringwraith

Hey guys
I know this is an old thread but I was wondering how ya made out with your DMM??
I'm wondering if mine needs tweaking. It's working ok but the delay seems pretty hissy. 
Maybe that's part of the mojo but I wonder if it can be cleaned up at all.

Cheers
Sean


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## mhammer

1st and 2nd generation delay pedals were generally hissy. There are ways to deal with the hiss, but they tend to deviate from the original design. To some extent, it would also depend on the circumstances under which it becomes hissy. For instance, a typical DMM of that era would be more noticeably hissy at the longest delay time and most feedback/regeneration. One of the issues made without a compander chip would also be noticeably hissier than an issue with one. There are also issues that have small gain trimpots inside that bring the level up to an optimum for the next delay chip, in order to maintain maximum S/N ratio. So, the hiss may not be a permanent aspect of the design but simply the result of some drift in the fine-tuning over the years that can be easily remedied with a small screwdriver.

Do you experience objectionable hiss ALL the time with it?


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## Ringwraith

Heya MHammer, thanks for your reply!

My DMM PCB says EC2002_Rev_D
There are 7 trim pots, it's an adapter powered pedal.
It has the 4 MN3008 & 4 CO4558N chips.
It also has 2 other chips...
Philips SA571N / J81874 / Jnr0209 Q
HCF 4047BE / W99180352 Malaysia (under pot)




I recorded some sound files to demonstrate the noise.
The unit works pretty good besides the hiss I'm wondering about. 
The files are recorded going into my Chandler TG2 direct inputs.
Left is the echo out only & right is the direct out.
There is quite a bit of hiss on the echo out even when not playing/delaying. 

While the hiss is more noticeable at longer delays (460ms)
I also hear it on shorter ones & when not playing.
I recorded a few examples so hopefully you'll be able to hear if it's normal
or it could use a tweak. I couldn't find a schematic that has my chip layout 
so I'm not sure which trim pot does what & don't want to fiddle until I'm sure.
I have no problem changing out parts if needed, I've built a few pedals/tube amps
& recording gear so if there are other mods that may help let me know. I read that
changing the 4558's may help clean it up. What do you think? 

Thanks again
Sean

DMMNoise01.mp3
DMMNoise02.mp3
DMMNoise03.mp3
DMMNoise04.mp3


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## mhammer

I'm unfamiliar with that particular issue, but a few things are immediately apparent from the sound files. One is that the hiss is pretty much 95% from the delay path. On that last sample you can almost hear the hiss pulsing with each repeat. It would appear to be an issue from the "turn of the century", when the world's supply of MN3005s had pretty much dried up, but MN3008s were still around in reasonable supply, and Coolaudio hadn't started producing MN3205 clones yet.

As to what the individual trimpots are for, there is a lot to mull over. Typically, there will be one trimpot for adjusting the bias voltage at the input to the BBD. When there is more than one BBD (and this one has 4 MN3008s, for a total of 8192 stages), sometimes the designer assigns one per BBD, and sometimes they use only one and share the bias voltage with all the chips. It is also a common practice to fine-tune the balance of the two complementary outputs from each BBD to optimize the cancellation of the clock signal (a major source of hiss), though some designers decline to do so, preferring instead to simply use two same-value resistors on the BBD output. It was also the case that EHX elected to insert an op-amp gain stage between BBD chips in series, to compensate for the fact that BBDs can lose a bit of signal, and included a trimpot to set the gain of that recovery stage. Finally, it is also common practice to include a) a master clock adjustment trimpot to set the maximum delay appropriately, and b) a feedback trimpot to bring the maximum feedback setting just up to the point where you get lots of repeats but not easy or unstable oscillation.

So, with so many possibilities, and so many trimpots, it is difficult, in the absence of a schematic and parts layout, to say what each of them does. The picture I'm including here, that was part of a thread where I answered questions on this very pedal about a year ago, shows two ways in which this was done. The top is for the 4xMN3008 issue and the bottom is for the 2xMN3005 issue that preceded it. I can't vouch for its accuracy, but what we see here is 7 trimpots. Starting from the left, there is a 100k bias trimpot feeding the input pin of the MN3008, but a pair of 2k4 resistors are used to balance the outputs. Then we have an op-amp feeding the 3rd MN3008, with a 100k gain-setting trimpot and another 100k bias trimpot. That 3rd MN3008 also uses a pair of 2k4 resistors tobalance the outputs, but the fourth MN3008 has, you guessed it, a 100k bias trimpot and a 5k pot to fine-balance the outputs, in stead of a pair of 2k4 resistors. Why they have been content to do the fine balancing for one chip but not the others is beyond me, since they are contribute clock noise that needs to be "nulled" out. But like I say, I can't vouch for the accuracy of the schem provided, although I suspect it probably is accurate. The 7th trimpot shown brings the level of the delay signal back up again.

The diagram shows the pins that each trimpot connects to, and their value (remember that 100k = 104 markings on the trimpot), so you can confirm for yourself if the diagram corresponds to your unit. If it does match what you have, then it may well be that the 5k balancing trimpot is your prime target. Never having used one of these pedals close-up, I have no idea if the noise level can actually be imporved upon, or if yours is noisier than the majority.

As for the 4558 chips, yes there are better chips on the market, and they might conceivably reduce some hiss, but I suspect the hiss you hear is largely from the clock and from a mis-adjustment of the balance trimpot/s.


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## Ringwraith

Ok (wow lots of info thanks!!)

Looking at the end of that top schematic, it corresponds to my layout.
The R,C,U numbers aren't totally accurate but the values & connections are.

So I can turn the 5K pot without messing things up?? What about that last 100k pot?

Cheers
Sean


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## Ringwraith

Ok the suspense was killing me so I went ahead & played with the 5K & 100K trims... 

The 5k was set in the middle, going either way didn't realy affect the hiss but introduced 
a faint high pitched frequency. So I guess it's set at the optimal level in the middle. The 100k
after that 5k brought up the overall volume but the S/N ratio sounded the same I believe. It did
drive the feedback a lot harder so raising this pot made me lower the feedback level in order to 
control it. The 100k pot was set "just" past it's lowest setting & I've put it back pretty much there.
It seems to me the noise is coming before this stage.
Any suggestions? ;-)

Sean


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## mhammer

Well, certainly consult this thread, and see if there is anything I might have missed: Deluxe Memory Man, MN3008 building

Actually, reading through it now, it seems the schematic showed what a guy was going to do, not what exists in the 4xMN3005 issue.

However, here's another potential source of noise. It is common on delays where there is a single bias trimpot to "decouple" the bias voltage by means of a cap between the wiper of the trimpot, and ground. Think of it like smoothing the power supply, but at a micro/local level. As near as we can tell, EHX skipped out on that part. It likely isn't make or break, but since it is dead easy to experiment in a nondestructive way, try sticking a cap to the relevant solder pads on the solder side of the board for each of those trimpot, and see if it makes any difference. A quick scan through the schematics of a number of well-loved commercial analog delays says that a 1uf electrolytic (+ side going to the trimpot wiper) ought to do it.

Finally, part of the objectionableness of the hiss is the way in which it seems almost gated. Here is most of the schematic of the 2xMN3005 reissue: http://img.photobucket.com/albums/v474/mhammer/DMM.png
You can see that there is a 1uf capacitor from pins 1 and 16 of the NE570 compander chip. This sets the attack/decay constants of the compressor (pin 1) and expandor (pin 16) halves of the compander circuit. Pin 16, however, has an additional 1.5M resistor in parallel with the cap. This helps to produce a slightly faster decay in the expansion than in the compression (normally, they would be identical). Just for the hell of it, if you have a 1M resistor, and can find the pads where the 1.5M goes, tack on the 1M on the solder side for a moment, and listen to what happens. It might produce a more gated sound, or maybe decay fast enough that you don't notice the hiss as much. Hard to predict.

Now, the NE570 is touted as being a bit quieter than the NE571, so there is that to consider, but I've never heard anyone rave about how much quieter anything was, now that they stuck an NE570 in there. So it may not be worth the trouble and cost to source one. In the case of the 4558s, though, an NE5532 or LM833 (both easily and cheaply available) is a quieter pin-for-pin replacement.

Conceivably, there is some sort of magic voodoo cap replacement, of the sort that guys like Keeley does, that may be quieter in this context. Unfortunately, I have no words of wisdom to provide here, other than it _might_ be possible.


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## surfguitar

mhammer said:


> Finally, part of the objectionableness of the hiss is the way in which it seems almost gated. Here is most of the schematic of the 2xMN3005 reissue: http://img.photobucket.com/albums/v474/mhammer/DMM.png
> 
> Now, the NE570 is touted as being a bit quieter than the NE571, so there is that to consider, but I've never heard anyone rave about how much quieter anything was, now that they stuck an NE570 in there. So it may not be worth the trouble and cost to source one. In the case of the 4558s, though, an NE5532 or LM833 (both easily and cheaply available) is a quieter pin-for-pin replacement.
> 
> Conceivably, there is some sort of magic voodoo cap replacement, of the sort that guys like Keeley does, that may be quieter in this context. Unfortunately, I have no words of wisdom to provide here, other than it _might_ be possible.


I have a DDM that sounded like "eggs frying" as I turned up the level and I've tracked it down to some cold solder joints (they didn't exactly flow solder these boards). With that fixed, I found the schematic link you posted for the DMM and it seems to match mine. Mine being an EC_2002_Rev_E with an SA571, CD4047, 4558's, 2 x MN3005's.

I noticed you mentioned replacing the 4558's with the lower noise NE5532 and I've ordered some of those to try out (Im going to socket them so I can swap with the 4558's). Kind of a spring project...

Any way, apart from my chance to say THANKS for posting that schematic I was wondering if you have any information on the procedure for setting the trim pots? I have a function generator and dual trace scope.

I'm still debating about changing the lower quality caps on the board for better ones. Just not sure it would make a big difference. Or for that matter any difference...

Mel


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## kugua

I made a clone DMM.sounds good ,but hiss at background .I test it maybe the hiss is come from NE571 .I took of the resisitor of pin 16 .the sound is not like originally sound it's be very good.not fade in.[video]http://www.tudou.com/programs/view/u4Mkc-KwtWg/[/video] here is the hiss sound.I wanna find some ideas toreduce it.I tested it today.the noise of hiss frequency 2000HZ---4000HZ.


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