ADA Depot - A Forum To Support Users of ADA Amplification Gear
ADA Preamps => Original MP-1 => Topic started by: Chris5150 on April 30, 2020, 11:45:05 PM
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Hey all, I've recently done a cap job on one of my MP1's and it went well. I changed pretty much all of them on the tube board. I decided to tackle the other one I have that is noisy.
I replaced the 3 big caps on the tube board and the 3 big filter caps on the main board. I figured these were kind of the most important to do, and the soldering went well. Thankfully my MP1 still works after the cap replacement, but the noise is just as bad as it was. It is my newer of the 3, and I've noticed the input jack is of a normal TRS style, but it looks like it has the plastic washer to insulate it. The rear input jack looks different too compared to my other MP1s. I'm kind of puzzled on what to try next, mouser has been easy to find caps and such, but I'm really hoping to order some of the noise mod kits from MJMP once the shipping restrictions end. I'm wondering if I'm missing something else with these noise mods, the other MP1 isn't exactly the quietist either after my cap job, but my noise gates can tame it better then this one. I'm pretty novice when it comes to electronics, but if anyone can point me in the right direction that would be awesome. I saw the thread on the ground loop but some of that stuff in there is way over my head.
I can get some pictures if need be, thank you all for taking a look at this thread. Stay safe out there.
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Take some pics so I can have a look at it.
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Hey MJMP, thanks for taking a look. I have a bunch of pictures, but they appear to be too big to be uploaded at the moment. Is there anything in particular you would like to see? I' going to downsize what I have so I can upload, and can take some additional pictures under your guidance. Thank you.
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What happends noise wise when you unplug your guitar from the MP-1? Is it better ? Also is it noise, hum or both?
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It seems my room is picking up gnarly EMI interference from somewhere. I don't really get any low end hum from it, it's more like a high pitched whine. When I turn the volume up on the guitar it picks up crazy EMI, way more then the other units. I do happen to have top and bottom covers off and am playing it out of the rack, would this be why?
I definitely don't think it is a ground loop issue though. I recall that is more of a low end 60hz sound. This is just a crazy amount of EMI with a high pitched whine. Unfortunately it happens with all of my guitars, they all have humbuckers too so it's pretty confusing.
Looking at a frequency analyzer, the whine is at 3.5k, with harmonics at 2k, 1k, and a little activity at 125. The guitar feedbacks at those frequencies when I turn the volume up and let it ring out. Testing with my little pre amp pedal, it does not have the same high pitched whine, but definitely has EMI interference, although it is so much worse through the MP1. Plugging back the MP1, you instantly notice the whine and way more EMI. The whine honestly sounds like a b string harmonic at the 5th fret. When I unplug the guitar from the MP1 with the guitar volume off, at the MP1 input, the whine gets quieter, and gets a little louder when I plug in. I wonder if it's the MIDI clock or something?
Anyways, thank you for your help. It's a little difficult to describe, and the EMI seems to be worse at different times of the day. Just a very frustrating experience! It seems my room is located in EMI hell haha. Trying out with my other MP1s, it does not make the same high pitched whine, so this one is unique in that regard, as well in picking up so much EMI. The visible difference I have seen with this one is it is a later version with no top switch, and the instrument input is tied together both front and back. I have attached a picture showing the jack. I've also noticed the transformer is a little different then my other 2. Thanks again!
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It will pick up more noise with the covers off. Do you use the mp-1 on it's own? I mean nothing else attached to it (except a power amp).
It won't be midi since that is at 31.250 baud. You can't hear that and there has to be midi activity. Did you measure with the analyzer with you tone controls flat?
The 125 Hz will be 120Hz, you can see that. Got a lot of fluorescent bulbs or led lights in the room?
Don't see anything wrong on those pics, totally normal, from what I can see it seems like a V2.00?
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I do have the MP1 going straight into my interface. Right now it's guitar-MP1-interface. The sound persists through the headphone jack and through my power amp as well.
I'll set my EQ to flat and do the frequency analyzer again to get a clearer picture. I'll also put the covers back on to see if that helps.
On the other MP1, I replaced all of the caps on the tube board including the little ones, the 33uf/50v. Do you think it would help to replace those in this case as well to reduce the noise? I'd rather not disturb the board if it will not help, but if it can I have no problem doing that.
I've taken a screenshot of the analyzer. You can clearly hear the whine, the covers don't seem to make a huge difference.
My room just has normal incandescent lightbulbs, we don't have any dimmers in the house either. I've got it plugged into a Furman, the others seem to behave fine it's just this particular unit.
I have the gain set to OD1 6 and OD2 to 7.5. The other 2 work fine with this much gain and do not make the high pitched whine.
Thanks again for your time MJMP, I know diagnosing these issues without having the unit on hand can be pretty difficult, hope I am explaining myself well enough.
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Here is a screenshot of the analyzer with the guitar volume up but not playing anything, just so you can see the insanity I am dealing with. I am going to try to move out as soon as I can, just so I can regain some of my mental health haha. My room has a knack for making everything sound like noisy garbage, I'm very lucky I don't have any single coil guitars because I imagine it would be unplayable.
As far as that high pitched whine goes, could a op amp be bad? Regardless of the EMI, I still want to tackle that because my other units do not make that sound, hopefully it's nothing too crazy.
Thanks again for taking a look and for all your help! :thumb-up:
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I had a buddy drop by with an amp and we have confirmed that this room is just insane with EMI. Think I am going to have to put this on hold until I move out, I don't think there's anything I can do unfortunately. Thank you for your time MJMP!
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Looking at the second pic, looks insane. :o The first one looks like it's a 1kHz with some harmonics on 2,3 and 4 kHz.
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Looking at the second pic, looks insane. :o The first one looks like it's a 1kHz with some harmonics on 2,3 and 4 kHz.
It's crazy man, I tested a AM radio in my room and it barely gets reception either. I feel bad for hacking up these units for no reason. At least I learned some things!
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Ok very strange .
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So out of boredom I ended up changing the rest of the small caps on the tube board. There was a definite positive change and the high pitched whine is now gone. Crazy.
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Crazy but good :thumb-up:
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@5150 Can measure a voltage for me? ON the tubeboard you see 2 resistors mounted horizontally, both are 10k (Brown Black Orange Gold) measure on the right side (red lead of the meter) of one of them (black lead of the meter to ground or chassis) , you should have +- 190V. Let me know.
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@5150 Can measure a voltage for me? ON the tubeboard you see 2 resistors mounted horizontally, both are 10k (Brown Black Orange Gold) measure on the right side (red lead of the meter) of one of them (black lead of the meter to ground or chassis) , you should have +- 190V. Let me know.
Hey man, sorry it took so long for me to get around to this. I am measuring 174-176V at both the brown black orange gold resistor.
Also, I turned the gains all the way up, and started going up on the master volume, nothing in the input, and this high pitched whistle shows up at around 7.5 -8 and gets progressively louder until the EQ clip light comes on bright. Then when going down on the master volume on the initial step down, the whistle gets higher in pitch and fainter, then goes back to it on the next step. The whistle goes away once you hit 7. When you max the EQ it is much worse.
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I measure 214 VAC at the tube board connector to the transformer, then 174-176 VDC at the resistors.
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Did you measure this at the left side of the resistor? You need to measure on the right side of the resistor.
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Did you measure this at the left side of the resistor? You need to measure on the right side of the resistor.
Yes, my apologies, it was the wrong side. Now testing the correct side the resistors measure 188-189V.
Have you ever experience a high pitched whistle with one of these things? I'm starting to wonder if it's an op amp. Thanks!
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There are 3 shielded wires coming from the tube board to the main board, try to move them around, see if that does anything with the whistle. Use a wooden pencil just to make sure you won't get zapped by touching something on the tubeboard !!
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Uhm...it reminds me in some way of a similar issue with my MP1 after mods (but mine also has a MDRT transformer inside)...
I really pissed of poor MJMP a lot about it...sorry mate.... :bow:
Have a look here: http://adadepot.com/index.php?topic=1992.135
I ended to fix the issue by placing an external buffer between guitar and MP1's Input...that's something you can try, if you have any buffered pedal (any Boss, for instance...just put it there, the buffer is alway active...), so I didn't mind about it anymore.
But it would be interesting to see if it's the same issue on your side and if it will finish to have a different and common solution. :banana-skipping-rope-smiley-e
@rnolan: hey hombre! News from MikeB? Are you guys doing all right?
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Hey Max :wave: , this does seem similar to the issues you were having, not sure if it's quite the same :dunno: .
Mike and I are ok, both still have our jobs. Triple whammy here in Oz, years of drought, worst fires ever (we were blanketed in smoke over xmas/new year) and now the virus... Last I spoke with Mike he was getting a new kitchen (with all that entails). Going into winter here, getting very cold. How's things in Italy? you guys copped a huge battering from the virus...
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Hey Max :wave: , this does seem similar to the issues you were having, not sure if it's quite the same :dunno: .
Mike and I are ok, both still have our jobs. Triple whammy here in Oz, years of drought, worst fires ever (we were blanketed in smoke over xmas/new year) and now the virus... Last I spoke with Mike he was getting a new kitchen (with all that entails). Going into winter here, getting very cold. How's things in Italy? you guys copped a huge battering from the virus...
Yep.
Such issues can make you go crazy. Slight differences, from case to case.
The only one, as far as I remember, having the exact same problem as me, same MP1 and same mods was MikeB...maybe, after the kitchen's affair, he will run a test with external buffer? Or he's already done with that? :lol: :lol: :lol:
Happy to see you're doing fine, guys.
I'm in touch with a friend from Melbourne and I was really astonished about fires in Australia and Siberia last year.
So sad...so crazy.
Now the COVID-19...no rest for Aussie people... :facepalm:
About Italy....our first problem is...the italians.
After almost 3 months of total lockdown, now everyone (not me) is going out everywhere like crazies.
I'm not sure if the government is fooling us to scare people or if people is stupid and we're risking a second and worst phase.
Very dangerous moment.
Nothing compares to USA and Brazil, but I wouldn't play with fire as people is doing here right now.
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I finally had time to mess with it and taking a chop stick and applying pressure to the wire to the tube board changed the pitch of the high frequency whine. Applying a buffered effect (BOSS SD-1) did not help. It appears plugging in a guitar with the volume knob turned off introduced another whine of lower frequency while the high frequency whine gets worse but lowers in pitch a hair.
Edit: Thanks again for all your help and direction!
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I finally had time to mess with it and taking a chop stick and applying pressure to the wire to the tube board changed the pitch of the high frequency whine. Applying a buffered effect (BOSS SD-1) did not help. It appears plugging in a guitar with the volume knob turned off introduced another whine of lower frequency while the high frequency whine gets worse but lowers in pitch a hair.
Edit: Thanks again for all your help and direction!
Yup.
As Richard correctly predicted, looks like a different issue. :dunno: