Mark IIC+ Reissue

[Darkstar2]

If you think the hum eliminator will work with the mimiq power source, just use the internal battery. I doubt it will change the hum issue. Most switch mode power supplies that are commonly used for small pedals are typically double isolated. Not sure if the hum eliminator will do much.

If you are looking at this unit, it is not compatible with instrument level signals. This is line level only and will not work in front of the amp. I was curious and read its description. It is in the right arena though but not going to give you what you need.
https://www.morleyproducts.com/hum-eliminator/

First time I saw Lehle has a stereo version of the P-split. Cool. I have the single version so I can run two amps with one isolated. but when running two amps with FX on the front end, you need to be able to isolate the left and right signals. This will work just like the single. I have used the single with the input and then isolated output (not using the direct output) to I could run three amps with the Mesa Switch track (tuner out is not isolated and that resulted in some issues when I tried to connect the JP2C in the two Mark VII amp configuration. The P-split helped to isolate the JP2C from the other two amps.
I think this would work and is suitable for instrument levels. Also works in the FX loops too as I have use one to split the signal to slave into another amp. What is cool about the P-split, it does not require any power to use it. It is completely passive.

https://www.lehle.com/lehle-p-split-stereo

I opened up one of the Mesa Switch track units, it does have dual transformers, one for each output A and B. I assume the Radial bigshot ABY may be similar but not all ABY switches have dual isolated output, usually just one has the isolation transformer and the other does not. I looked up the bigshot on Radial engineering website as I wanted more details. It only has one isolation transformer on output B. The isolation transformer is what provides the DC ground isolation between the two amps to cut out that hum or buzz. It also has a phase switch and ground lift to disconnect the common ground between the two amps. Sometimes if you are using two of the same amp, for example, two Badlander 100W amps, it may not matter much if the two amps are not isolated when there is a common ground. The same can be said with the TC100. It may be possible to run the Mimiq between the ABY switch and the amps. Just know once you run any FX unit between the amp and the isolated ABY switch that has stereo in and out will no longer have the dc ground isolation between the two amps. Most FX units have a common ground. The output and input grounds are not isolated between the left and right circuits. This does not seem to be an issue with FX loops with different amps if and only if they have a solid ground connection since the chassis should be earth grounded and the ground on the SEND and RETURN jacks are connected to chassis ground. That is usually safe to run to a stereo FX unit and best if the two amps have a balanced output or are the same model and type.

What I am trying to say if you have the mimiq connected between the amps and the ABY switch, expect to have that hum problem. I have the mimiq pedal too as it was suggested by another person who runs stereo TC100's. Similar to the Strymon Deco. When I have run a stereo double tracker, it is usually taking the mono guitar input, splitting to stereo and each stereo output is going to a separate Mesa Switch track that is connected to two amps on each. 2BAD and 2Mark VII. I could probably run the mimic to the 2 badlanders without needing isolation between the two amps. However, the Marks seem to be very sensitive on the inputs. This holds true to the JP2C as well. When using two Mark amps, even if they are the same, I have to have the ground lifted on the Mesa Switch track to prevent noise and ground loop hum. Nothing can be inserted in between the ABY switch and the amps unless they are separate devices. I just got done reviewing the Mimiq manual, it states you can use it in the FX loop even at line level but does not indicate if it is line level compatible. That is one location I have not tried with the Mimiq. I favor the Strymon Deco as I can set it up as a doubler, delay or even chorus. Mimiq has more of a chorus effect. Curious how it would sound in the FX loop assuming it does not get burdened by the output levels. Using any pedal including the Strymon Deco in between the ABY switcher with an isolated output and any tube amp will lose that isolation you got from the ABY switch since the device does not run fully isolated channels. I did test the input and output terminals on the Mimiq, the outer rings are all connected to chassis ground. If you must use that in front of the amp, I would recommend the Lehel P-Split and select the noisy amp (probably the JP2C) and run the mimiq output to the input and then the isolated output to the amp. That would isolate the amps input from the common ground. If using in the FX loop on both amps, with the amps plugged into their respective power, you can use a digital meter to test for circuit ground connections of both amps meaning the jack outer ring or the sleeve of a guitar cable plugged into the send jack. Test between both amps. Do not power up the amps, just test for common ground on the FX jacks. If they are earth grounded through the chassis and the ground prong on the plug it would be fair game to use the Mimiq in the FX loop of both amps. This is assuming the output levels of both amps are at the same level. If they are different, one amp will have more influence on the FX than the other. Generally why I run two identical amps when running stereo FX units. Tried it with the Mark VII and JP2C, it was not a good match. However, the Reissue and the JP2C were perfect matches on the FX levels. As I said, I have never tried the mimiq in the fx loop as it is described in the manual.

Interesting the Deco can handle line level signals so may be ok in the FX loop. However it has a boost to it so that may not be ideal for the FX loop. Thanks for bringing up the Mimiq. Been a long time since I had it out of its box.

Wow, I can't thank you enough Bandit for running through that mental setup! I use the Mimiq after the BigShot ABY splitter (the Bigshot switches between clean and dirty amps), so the Mimiq is splitting a single source into two sources (2 dirty amps at once). I'd need a stereo splitter after the BigShot if I were to run the Mimiq in the amp loops... hence the Lehle you suggested? I really wonder how exactly John Petrucci does it as he runs the Mimiq to two JP2Cs...

 

[Darkstar2]

Wow, I can't thank you enough Bandit for running through that mental setup! I use the Mimiq after the BigShot ABY splitter (the Bigshot switches between clean and dirty amps), so the Mimiq is splitting a single source into two sources (2 dirty amps at once). I'd need a stereo splitter after the BigShot if I were to run the Mimiq in the amp loops... hence the Lehle you suggested? I really wonder how exactly John Petrucci does it as he runs the Mimiq to two JP2Cs...

OK I was pondering this further -- what if I had another way to isolate a signal from the Mimiq? Like this:

https://www.sweetwater.com/store/detail/CoolSwitchPro--art-coolswitchpro-isolated-a-b-y-switch

So taking one of the two signals from the Mimiq with a device that isolates/ground lifts to help eliminate the hum?

 

[Appleridge]

After checking mine, it has the same hum as Ola’s video. Also, the same hum as my IIb+ and my III+. I have 415’s in it though…I’ll toss the 445’s back in and see if it’s any diff.

 

[bandit2013]

OK I was pondering this further -- what if I had another way to isolate a signal from the Mimiq? Like this:

https://www.sweetwater.com/store/detail/CoolSwitchPro--art-coolswitchpro-isolated-a-b-y-switch

So taking one of the two signals from the Mimiq with a device that isolates/ground lifts to help eliminate the hum?

Yeah, that is basically it. You can use a P-split single, run the one channel into the input and use the isolated output to the amp. The other amp will connect direct to the mimic. If the amps were the same, say two JP2C, you may not need to be concerned on input dc coupling between the two same amps. This does not always hold true.

If John Petrucci is having success with the Mimiq direct to two JP2C amps, the key thing here is the two amps are the same and not different makes and models. That will change things and lead to noise issues to figure out.

The key to hum elimination when running more than one amp at a time, switched or all of them on is to have a clean line between the amp's input and the ABY switcher that should have all of its outputs isolated. If your ABY switcher is used with three amps, I assume it has a tuner out? If that is the case, CHA, tuner out and the input will all have the same ground plane and CHB will be isolated with or without ground lifting.

Adding anything in between the amps cannot be shared by the other channels or you end up back at square one without having isolation. It is the DC coupling on the amp's input that gets shared from one amp to the other and so on. I think we are hijacking Appleridge's post. This was all about the Reissue IIC+. If you want, we can extend this in a different thread or in private.

 

[bandit2013]

@Darkstar2 I do have one comment about this subject. A single P-split III will do the job to isolate one amp from the other. So you can get one of those and used it on one of the channels left or right side. Just connect the amp to the isolated output. Mimic can be fed by the two A and B sides as a stereo setup or if you want to use those two amps all the time for high gain, and the DC for clean, run the DC on the channel B since that is isolated. Then take the side A and connect to the mono input. Decide which amp you want to isolate, say the Mesa, lets assume the left channel output, connect to P-split III input, then the iso output to the JP2C input. Now it will be isolated from the Ceriatone King Kong as that will be on the right channel directly connected to the mimiq. The P-split III has a ground lift and phase shift so you can select to lift ground or change the phase. If it does not cancel out the hum, use the P-split III on the Ceriatone instead. The P-split III will sort of take place of that isolated output on the ABY switcher. However, it will give you the ability to shift the phase if there is any sound cancellation when both JP2C and King Kong are running. Note that when one amp is on standby and the other is not, you may experience some loud hum but once both amps are active, that should go away. The only issue is that you will not be able two switch between the JP and the KK amps. That would actually sound sic in a good way as I did like running the JP2C in tandem with the TC100. I used the P-split II before I got my hands on the Mesa Switch track which is a fully isolated and buffered ABY unit with a mute function. I doubt you will find the stereo format for the P-splilt. Now that I see it is available but where to get it? I may want one. I sometimes use the P-split II and P-split III. The P-split III has improved tone response as the P-split II did rob some tone from the signal. Not sure if the FX loop trick will work as the JP2C and the King Kong (based on a hot rodded Marshall ) will have completely different styles of FX send circuits. I suspect the King Kong will have a lower source impedance if it is based on the Marshall circuit (cathode follower). It probably would not matter as I have shared a common stereo effect with the JP2C and MWDR without any noise issues. Same with the TC100. Generally when the amps are different, you could always run a dry/wet rig. Mesa/Gibson did a short video on that. He did not demonstrate what happens without proper isolation between the two amps as he was using the Mesa Switch track as the ABY switch unit. Bummer



Just for S&G while the Reissue was out on one of the cabs. I turned it on, got it out of standby and measured the DC voltage on the guitar cable. I was only able to measure 1.56mV which is not much. Typical guitar signal runs around 750mA. If I borrow the oscilloscope from work, I could get a real measurement from a calibrated instrument. So tempted to see what happens when two amps are connected together with a pedal without isolation. Most tube amps will have a 1 Meg pull down resistor on the input, and that input is directly connected to the control grid of the first gain stage. High impedance into a self-biased class A tube circuit, well, there will be measurable dc voltage on the control grid due to the electron flow from the cathode to the plate as it is biased by the plate and cathode resistors. I was surprised it was much closer to 0 as I assumed it would have a slight negative voltage on it. Perhaps the +1.56mV is why I have a low frequency hum with the amp. Something to look at. Need to test another amp and see what that measures at. A few mV is enough to make noise that will get amplified by the first gain stage. I hope this is enough before we end up hijacking the threat. I would rather keep it to the Reissue IIC+ but the measured voltage could be something to look into.

 

[bandit2013]

I was able to regain some of my hearing yesterday. When I measured the voltage on the input just out of curiosity, I decided to swap all of the power tubes with the STR448 (grey) which are just as long as the stock STR445 that came in the amp. Tight fit but after hearing it (sort of) it sounded good. Did not hear the same hum, it was there but more reduced. Not bad. Still cannot hear full spectrum of the sound so my opinions on the STR448 may change when my hearing returns to normal. I can hear out of the left ear better than the right ear. That makes it hard to listen to how the amp really sounds. I want to get back to playing the guitar but so far it is tough when you cannot hear the full spectrum of sound. When it returns, I will explore some preamp tube swaps. The hum is more dominant with the lead mode than on clean which is a good thing. Helps me narrow it down. Still have the stock preamp tubes in the amp but I did try some other tubes to see if that would fix the issue.

I do have some ideas but doubt it will correct it. It may be a heater wire too close to something, to my knowledge, Mesa uses jumper wires for the heater supplies and it is not on the circuit board. Have not looked inside yet. If and when I do, I may see if I can move any wires or cables that may be the issue. Doubt I can do much to fix it, but so far it was not as noisy as it was with the STR445 tubes in the amp.