ADA Depot - A Forum To Support Users of ADA Amplification Gear

Let's Get Technical => Schematics & Modifications (mods) => Topic started by: El Chiguete on February 16, 2014, 08:13:08 PM

Title: MarshallJMP Noise Mod
Post by: El Chiguete on February 16, 2014, 08:13:08 PM
Any of you guys have a before and after audio of the noise mod of MarshallJMP? I want to see just how much it works and to see if I need it or not.
Title: Re: MarshallJMP Noise Mod
Post by: El Chiguete on February 23, 2014, 10:29:54 AM
Here you can watch and hear the noise http://www.youtube.com/watch?v=UfEfvXF83DQ&feature=youtu.be (sorry for the audio lag). Any idea what type of noise it is?
Title: Re: MarshallJMP Noise Mod
Post by: El Chiguete on February 23, 2014, 04:29:28 PM
Or this ¨noise¨ is just something that you have to deal by cropping the recording and using plugins in your DAW?
Title: Re: MarshallJMP Noise Mod
Post by: GuitarBuilder on February 23, 2014, 09:34:09 PM
That sure sounds like AC hum to me......

Have you replaced any of the power supply capacitors?
Title: Re: MarshallJMP Noise Mod
Post by: El Chiguete on February 24, 2014, 05:44:47 AM
No, I haven't replaced anthing on it, maybe there is a list of parts that should be replace for a general maintenance for a 2o year old unit?
Title: Re: MarshallJMP Noise Mod
Post by: trader144 on July 11, 2014, 10:34:54 AM
Can someone post a clip of an mp-1 with the noise mod so we can compare?

Just crank the preamp and the amp and hit record; don't play.

I am dealing with the same issue and this sounds like standard tube gain. I would like to reduce it but when comparing tube amps and YouTube videos I am thinking that it is a necessary evil and a a noise mod might get rid of 25%, but even a 5150 head newer tube amp seems to still have this noise when cranked.

There is one guy on here who said his noise mod was extremely quiet, but I am comparing to solid state quietness.

I am wondering if a noise gate is the only solution for silence.

Thanks in advance.
Title: Re: MarshallJMP Noise Mod
Post by: h.e.l.shane on July 11, 2014, 03:06:22 PM
I dont have a clip...  But i did the noise mod to mine..  And it was stupid quite!!!  I mean that quite that guys swore it was solid state
Title: Re: MarshallJMP Noise Mod
Post by: trader144 on July 11, 2014, 03:47:21 PM
Thanks I needed to hear this
Title: Re: MarshallJMP Noise Mod
Post by: El Chiguete on July 11, 2014, 05:46:58 PM
I dont have a clip...  But i did the noise mod to mine..  And it was stupid quite!!!  I mean that quite that guys swore it was solid state

Which noise mod did you do? and what did you change?
Title: Re: MarshallJMP Noise Mod
Post by: trader144 on July 15, 2014, 04:51:04 AM
Does a new transformer (MDRT or stock) help reduce ground loop noise?

Title: Re: MarshallJMP Noise Mod
Post by: rnolan on July 15, 2014, 08:08:54 AM
Reducing ground loops is tricky it's related to what and where you plug stuff in to the power, basic, plug all into same power point.
MDRT gives you benefits apart from being 240/115 v friendly, better heater volts etc
Title: Re: MarshallJMP Noise Mod
Post by: trader144 on July 15, 2014, 10:10:04 AM
Thanks
I asked the wrong question sorry
What I meant to ask is: do the old mp-1 transformers contribute to the noise we hear in the outputs?

On ground loop noise, you provided some good advice earlier and I had good results with the Ebtech ground loop bug.
Title: Re: MarshallJMP Noise Mod
Post by: rnolan on July 16, 2014, 06:13:13 AM
Absolutely, every component in a circuit adds noise, my understanding is the MDRT adds less noise than the original tanny MJMP will know better why (my guess (partly from pics of them) is coz it's 2 trannys in one but separated ?) so rather than the various taps off the coil all in one. Not that I'm an expert in transformer design but wrapping more coils of copper around where the inner taps come out must have some effect.
Also the tranny "is" the signal in that it provides the Eddy electrons into the circuit(s) that go on to make/amplify the guitar signal.  This then becomes a gain structure conversation.  When you add gain, it boosts the signal and the noise.  The better the signal to noise ratio of each component, the less noise is boosted along with the signal for the same output. So the idea is to have as much signal as the component(s) in the circuit will take without clipping/distorting and stay as far away from the "noise floor" as you can. A lot of noise can be reduced by just getting your gain structure right/optimal.
However, when you exacerbate the situation by using tubes to create distortion (not the original intention of a tube BTW) which is basically overloading/clipping/compressing each gain stage (2 in each 12AX7 so 4 in all, or 6 in 3TM), the noise is boosted even more compared to the signal (it (the noise) is not clipping/compressing, just getting boosted/gain).  So the lower the noise floor of each component, the better.  Various components that do much the same thing in the circuit can have very different signal to noise ratios/noise floors (for a various reasons). Generally better S/N components cost more.  There's an interesting post on here somewhere where he swapped out all the opp amps in his MP1 selecting only the best he could source (freq response/noise floor).  Reported result was amaizing reduction in noise and total opening up of the sound.
Title: Re: MarshallJMP Noise Mod
Post by: Sparker on July 16, 2014, 01:59:41 PM
Ok, my 2c:

1. "my understanding is the MDRT adds less noise than the original tanny"

The MDRT transformer will not add any less noise than the original ADA transformer.
It will, however deliver more current and higher voltage (which are good) than the original ADA transformer.

2. "Also the tranny "is" the signal in that it provides the Eddy electrons into the circuit(s)
that go on to make/amplify the guitar signal.  This then becomes a gain structure conversation".

Each output from the power transformer (whichever one) is rectified, filtered and regulated (where needed) to remove power
line noise, so as not to play any part in inducing "bad stuff" into the signal amplification chain.
Title: Re: MarshallJMP Noise Mod
Post by: rnolan on July 20, 2014, 07:04:39 AM
1. "my understanding is the MDRT adds less noise than the original tanny"
The MDRT transformer will not add any less noise than the original ADA transformer.
It will, however deliver more current and higher voltage (which are good) than the original ADA transformer.
So better signal to noise ratio ??
Title: Re: MarshallJMP Noise Mod
Post by: Sparker on July 20, 2014, 12:39:46 PM
You will have to explain that reasoning to me.
Title: Re: MarshallJMP Noise Mod
Post by: rnolan on July 22, 2014, 07:24:57 AM
Hey Sparker, thanks for all the good tech help here BTW  :thumb-up: very much appreciated.
So where I'm coming from, first MJMP says (on web site) that MDRT = less noise (and some other beneficial aspects), also he's said the original MP1  tranny wasn't as well designed as the MP2 tranny (partly cos I was agitating/inquiring for a MDRT for MP2).  Also, when electrical widgits work hard they make more noise (typically), it seems that the MDRT is designed to not work as hard and creates less ripple (so filters don't have "as" much to do and the diodes aren't being hit as hard with pulses).  For me, optimum S/N is about getting the gain structure right and all things involved working well within their tolerances (partly why audio files over spec their trannys a bit).
Hope that make sense ?
Cheers R
Title: Re: MarshallJMP Noise Mod
Post by: robertkoa on August 02, 2014, 04:48:04 AM
Thanks I needed to hear this

I purchased a 1.38  on Ebay  in  2010  which has  "noise mods"  per the old ADA Site.

I just started playing it again -don't have a way to record it but it's  quiet through headphones and  adding
very little noise to the  POD XT effects.

Less noise than the front end of most tube guitar Amps, excellent Mod, I was lucky  to buy one this way .
Title: Re: MarshallJMP Noise Mod
Post by: rnolan on August 03, 2014, 06:01:09 AM
Absolutely, good score  :thumb-up:
Title: Re: MarshallJMP Noise Mod
Post by: trader144 on November 05, 2014, 07:49:31 AM
I am going to be doing a noise mod in the future and possibly a mdrt later on.

Which of my MP-1s should I mod?
The trusty beat up one which has been with me for 25 years with the blue caps, or my scratch free backup that I got from a guy's studio rack with the gold caps?

What is the difference between the blue and gold caps?

David

Title: Re: MarshallJMP Noise Mod
Post by: MarshallJMP on November 05, 2014, 11:09:48 AM
I would mod the oldest one which seems to be a V2.0,the other one is a V2.01.Difference between the 2 is the grounding.

The diff between those caps is the company that made these.The blue ones are normally lelon caps.
Title: Re: MarshallJMP Noise Mod
Post by: trader144 on November 05, 2014, 01:20:54 PM
Ok old one it is.
Thank you
Title: Re: MarshallJMP Noise Mod
Post by: trader144 on November 30, 2014, 05:52:23 PM
So I earned my first ADA Depot sticker and completed the noise mod to my stock unit.
thank you to MarshallJMP for all of the support, parts and instructions (and fast shipping).

I had planned on doing a before and after recording to post here, but the pre-mod recording failed and I didn't know it.

Here is what I think I hear:
1. Significantly more and cleaner definition and highs with the new components. My stock board sounded dull compared to this.
2. My Bass EQ has to be set much higher than ever before.
3. Probably less noise...but as I said I cannot make a direct before and after comparison. I'll post a comment once I get a chance to crank it.
4. When pushing V1 to 6.0+, I still need to run a noise gate as I can still hear the tube snow.
5. Is it solid state quiet without a noise gate? No...but that is too much to expect.

Now I know why people send their boards to someone else...lots of tiny soldering and lots of patience required.
Title: Re: MarshallJMP Noise Mod
Post by: rnolan on December 01, 2014, 02:03:02 AM
Go David  :thumb-up: >:D , hopefully you didn't burn yourself with the soldering iron LOL, I always seem to.
Title: Re: MarshallJMP Noise Mod
Post by: MarshallJMP on December 01, 2014, 01:24:24 PM
Maybe an explanation for the higher bass eq is that if you have a dull sound you have the perception of having enough bass response,but if you get more highs you have to compensate by turning up the bass,I guess.
Title: Re: MarshallJMP Noise Mod
Post by: El Chiguete on December 01, 2014, 05:30:28 PM
Here is what I think I hear:
1. Significantly more and cleaner definition and highs with the new components. My stock board sounded dull compared to this.
2. My Bass EQ has to be set much higher than ever before.
3. Probably less noise...but as I said I cannot make a direct before and after comparison. I'll post a comment once I get a chance to crank it.
4. When pushing V1 to 6.0+, I still need to run a noise gate as I can still hear the tube snow.
5. Is it solid state quiet without a noise gate? No...but that is too much to expect.

Has anyone else notice so much change in tone after the mod?
Title: Re: MarshallJMP Noise Mod
Post by: trader144 on December 01, 2014, 08:05:18 PM
Would the new op amp be a large contributor to the sound change?

The sound is much cleaner and crisper than ever before.
What I am missing is the fat mid-punch I used to have.
Title: Re: MarshallJMP Noise Mod
Post by: MarshallJMP on December 02, 2014, 11:00:17 AM
The opamp make the sound a little different but you describe a big change,so normally not.Check if C32 is soldered correctly,the brown 270pF cap near the opamp.
Title: Re: MarshallJMP Noise Mod
Post by: trader144 on December 03, 2014, 06:51:10 AM
Thank you for the help
I am going to wait until I hear the mdrt
Title: Re: MarshallJMP Noise Mod
Post by: MarshallJMP on December 03, 2014, 08:41:32 AM
ok
Title: Re: MarshallJMP Noise Mod
Post by: trader144 on December 12, 2014, 10:59:34 AM
Got a chance to crank it.
Definitely much lower noise than before the noise mod and the highs are clear as a bell


My mids are really scooped though and it looks like C32 is soldered correctly.
I have the mid eq up to 10 now when I never had it past 4
It might just be that my caps were really really bad or maybe my ears now want more mids.

If I were to do the 3.666 eq mod for the mids, since I just want more range (higher settings) in the mids and I do not want to change the bandpass range, can I get away with just replacing R151 with a trimpot?

The trimpot seems to control the voltage after the op amp and it does not appear to change the bandpass filter range and I really don't want to calculate the cutoffs.

I know I could add an eq pedal or rack after the eq into the send/receive jacks but trying to prevent more stuff.

David

Title: Re: MarshallJMP Noise Mod
Post by: MarshallJMP on December 12, 2014, 11:14:13 AM
Yes changing R151 should do the trick.
Title: Re: MarshallJMP Noise Mod
Post by: trader144 on December 14, 2014, 09:30:41 PM
Well....I owe some apologies.

Just discovered that the EQ on my G Major was turned on and it was cutting the mids, so it wasn't the MP-1 after all.
Good news for me is I now like to crank the MP-1 mids and then later in the signal chain cut them with the G Major EQ - very different EQ bands of course.

Sorry all.
Title: Re: MarshallJMP Noise Mod
Post by: rnolan on December 15, 2014, 03:37:35 AM
The hardest thing I found with MP1/2 and associated kit is when to stop, I'm happy, that's my sound, they are so versatile  >:D