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February 22, 2020, 10:32:15 AM

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91
Amplifier Discussion / Re: marshall G30R CD clean channel volume problem
« Last post by Jazz P Bass on February 12, 2020, 02:00:15 AM »
I would recommend 'grounding' the clean channel wiper.
That should kill the signal.
As yet, I have seen no resistance measurements of the circuit.
I would look at the junction of C49 & C 22 to ground.
What are the readings when the clean volume control is swept from min to max?
92
Amplifier Discussion / Re: Peavey Stereo Chorus NEW noise problem
« Last post by Psc on February 11, 2020, 11:54:02 PM »
Well, I am having a bit of trouble with my mini scope, but I did find something that seems odd to me.  I disconnected one of the speakers and attached the the dummy load, then fed a sine wave into the power amp.  I was surprised to find that I could hear the sound come from the still connected speaker.  It was quieter and not as clear as when you put it into the other input.  I also tried reversing it and got the same result.

Should the signal bleed to the other section?  I would have assumed it wouldn't.  But maybe it's normal?  It does cut out if I put a jack in the other power amp in. 
93
Amplifier Discussion / Re: marshall G30R CD clean channel volume problem
« Last post by g1 on February 11, 2020, 08:33:44 PM »
Yes, I meant IC3.  NJM2121D is a higher spec'd chip that will work fine there.  Mouser has stock.

Agree that it will not necessarily fix the issue.  Two other IC's that are used for both channels (so could possibly cause the crosstalk Enzo mentioned) would be IC1, and IC5, both are type 4558D.
94
Amplifier Discussion / Re: marshall G30R CD clean channel volume problem
« Last post by lordraptor1 on February 11, 2020, 06:09:42 PM »
well good news bad news, good news i ordered the 2120D op amp i needed, bad news they are manufacturer discontinued and mouser and digikey were out of stock and not ordering any more of them bummer, all other outlets have a MOQ of at least 50 pieces o.O.  and to be honest im not even sure this will fix the issue with the amp but i have tried everything else i could think of. 

so i at least got the opamp i need on order before there were none left in the USA, i mean sure there are a lot of ones listed from chinese sellers but personal experience and word of mouth suggest a lot of those "china" sellers are selling fake op amp chips ( guess china has no shame in that they will even fake ICs.
95
Software / Re: Zoom G5 software
« Last post by flester on February 11, 2020, 11:08:39 AM »
Now got it working with Audacity. Just had to mess with the sound input settings and install driver on PC. Emailed Zoom to see if I can get a download code for Cubase also. Maybe Audacity is just as good? Mainly just want to record my own ideas.

Sent from my SM-A505FN using Tapatalk

96
Amplifier Discussion / Re: marshall G30R CD clean channel volume problem
« Last post by lordraptor1 on February 11, 2020, 10:03:46 AM »
Ok, looking closer at the schematic, the reverb thing doesn't matter.  The reverb gets it's input signal after the switching IC, so it shouldn't be able to bypass the clean vol.

But I'd still like to establish that this is the correct schematic.  You do get reverb on the clean channel, don't you?
Here's a pic as yours didn't show.  The black line above the OD ch. controls show which are for OD channel.  Reverb is not included, but is over to the right, as it is 'global' and supposed to work for both channels.  Is this pic like your unit?



If the schematic is correct and the volume pot is not the source of the bleed, the only other place I can see would be the 2120 switching IC.

thanks for the 2120 ic, i have also been messaging marshall about the issue to which i just now get a reply back from marshall:

Joanna Green <joanna.green@marshall.com>
To:
lordraptor1@yahoo.com

Feb 11 at 2:03 AM

Hello Fabian,

 

Regarding your question, it could be IC3 at fault as this is switching between the two channels.

 

Kind Regards

 

This email (including any attachments) may contain confidential information,
​privileged information, or constitute non-public information. Any use of this
​information by anyone other than the intended recipient is prohibited.
​If you have received this email in error, please inform the sender
​immediately and delete this information from your systems.

Marshall Amplification plc, registered in England, Registered number: 805676.
​Denbigh Road, Bletchley, Milton Keynes, MK1 1DQ, England.

JOANNA GREEN​
RETURNS/CUSTOMER SERVICES MANAGER
+44 (0)1908 375 411
DENBIGH ROAD, BLETCHLEY, ENGLAND, MK1 1DQ

 
This email (including any attachments) may contain confidential information,
​privileged information, or constitute non-public information. Any use of this
​information by anyone other than the intended recipient is prohibited.
​If you have received this email in error, please inform the sender
​immediately and delete this information from your systems.

Marshall Amplification plc, registered in England, Registered number: 805676.
​Denbigh Road, Bletchley, Milton Keynes, MK1 1DQ, England.

they to seem to think that IC3 ( this is the 2120 im assuming you were talking about in the schematic) COULD be at fault causing the issue. 

97
Software / Re: Zoom G5 software
« Last post by phatt on February 11, 2020, 09:38:57 AM »
If it has a USB port then it's likely to work with most software and on most of the later win versions. You might need to update the USB interface.
Others here will likely know more.
Phil.
98
Software / Zoom G5 software
« Last post by flester on February 11, 2020, 04:22:20 AM »
I have a Zoom G3 which I want to connect to a PC for recording. It originally came with Cubase LE but that doesn't seem to be available any longer.  Not sure if the G3 is even compatible with Windows 10.
Any ideas? https://www.zoom.co.jp/products/guitar/g5-guitar-effects-amp-simulator-pedal

Sent from my SM-A505FN using Tapatalk

99
Hello Phil,

thank you for the reaction.


Still a few questions;
   
Quote
Just remove CR1 & CR2 for clean.
   Or you could wire up a switch to switch those 2 diodes in or out of circuit for clean or dirt.

  •   this means for each diode 1 off/on switch?
     so when the switch is OFF, that means that same diode is disabled ?
  • for my purpose of learning: are those CR1 and CR2 a 'bad' diodes, are there a 'better' one for possible replacement - or it's just old school SS amp design?

edit: found an info at  http://www.tpub.com/neets/book7/27m.htm ,  is this diode mod about same/similar thing - "Rectifier action of CR1 and CR2. NEGATIVE / POSITIVE ALTERNATION ?
 
 
Quote
With diodes out of circuit you will find there will be a lot more clean but being a small amp it will still distort when volume is high.

  • being a small amp as 'small' aka SS 15w or small because of the speaker?
    I will use a single 12" or (2x) 10" - so to an external cab.

Greeting

CR1 and CR2 are 1n4148.  These are very similar to the old 1n914.  While there is nothing wrong with these diodes, I know from experience that they tend to have a more "fuzz" type of distortion.  If you would like more of an "overdrive" sound, try replacing those two diodes with red LEDs.  Make sure you have them with one facing one direction, and one the other (just like the original diodes).  An even better idea is to solder in two sockets and then you can swap diodes at will and see what sounds best.  Some circuits, like my own 5th Gear Overdrive, use two different diodes.  In my case, 1n914 and a red LED.

Here are some diodes that you could try: http://smallbear-electronics.mybigcommerce.com/silicon-signal-1/ and http://smallbear-electronics.mybigcommerce.com/led-t-1-3-4-5mm-diffused/

And the sockets: http://smallbear-electronics.mybigcommerce.com/single-in-line-mill-max/
100
Amplifier Discussion / Re: Peavey Stereo Chorus NEW noise problem
« Last post by Psc on February 10, 2020, 07:09:12 PM »
Yes, that's correct.  I've got a bunch of resistors that will do the trick.  I also got a small portable scope that should do the trick.  I'm trying to get my hands on an old techtronix scope, but it might not be for a day or two. 
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