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PostPosted: Wed Oct 11, 2017 3:24 pm 
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Hi there. I had some work stuff come up in a big way and sort of dropped off the face of the planet.

I had some really interesting results with my own A/Bing of the stock and modded configurations, as well as comparisons to my IIC+.

One thing that I did was get a decibel meter and dial in everything at exactly the same volume when I recorded.

I was not able to distinguish much difference between the recorded sound of the modded or stock Mark V *at volume* - I think I was recording at about 94db, which is pretty full-throated.

It might be ear fatigue, or maybe using the AT7s pushes the amp harder at lower volumes. I can't say for sure. I know that at lower volumes I've immediately been able to tell that the stock configuration was in play - the amp sounded dead to me. I've kept the AT7s and I love it.

The acquisition of a gen-u-ine Mark IIC+ also ended up consuming a lot of my time.

IMO - and I have sat down and A/B/C'd the amps and configurations in awhile, at a higher volume the stock and modded Mark V and the Mark IIC+ all sound epic. The modded V and the IIC+ also sound great at lower volumes and I've really not bothered to go back and play with the stock Mark V configuration at low volumes since my last big testing spree a few months ago.

I think I've reached to point where, if I had to get rid of everything but one amp, I'd keep the IIC+, but it's because it sounds good and it's rarer. The V sounds awesome and I get a bigger change in sound switching guitars and pickups than I do switching amps, for sure.

These are just my experiences. Your's (not anyone specific, I mean all y'all) may be different.

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PostPosted: Wed Oct 11, 2017 6:36 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
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Location: North Carolina
Wayno wrote:
Shame there's no schematic publicly available for the switching circuit as that would help me here.


That would help more than one. I did spend some time poking around the amp (no voltage applied) as I was trying to determine what signal line would control the "strobe mute" as that is how it was labeled on the TC-50. The term mute may be misleading and I do not mean to reference the user controlled function called mute.
There are several control signals that govern the strobe or silencer circuits. As is the case with my TC-50 when everything when silent (no signal from input to send, no signal from return to output, there was a hint of preamp signal that could be heard with all masters cranked but to no avail it seemed dead silent. I do not believe it is related to the same component that latched on in the TC-50. My assumptions on the channel mute, strobe, or silencer function (not relating to the mute or tuner out on the footswitch or control panel on the pull switch) is limited in believing the signal is sourced from one wire on the ribbon cable. I too had powered up the amp and forgot to hook up the cable. Along with silence, I was also getting a pulsed sound though the speaker. That may have been a bad tube I had in V1 as the pulse continued after I reconnected the wide ribbon cable.

I also decided to look at every JFET on the schematic. There seems to be a pattern in the nomenclature. So far there are 4 mute circuits (J175M1 - J175M4), eight function circuits (mainly on toggle switches or other) , labeled J175A through J175H and three EQ functions (J175SL, J175PS, J175EQ). If you remove the J175 and look at the legends on the ribbon cable connectors you may find the wire associated with that task. Wait, not that easy as it is a bit cryptic or it appears that way. Need to think about this... Also need to look at the other connector header legends and see if there is a pattern in that too.

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TC-50, JP-2C, MK V, Roadster, RA100
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PostPosted: Wed Oct 11, 2017 9:54 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
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Location: North Carolina
I did some poking around this evening and found that my assumptions were correct. The two mute circuits in front of the EQ and in front of the Phase inverter are controlled by a single signal. Both JFETS have a gate resistor of 330k (current limit and provides isolation between the gates). The signal is identified on the rear control board at the pin header, wire is 4th from end without blue stripe (assuming that would be pin 1). Also note that without power applied to the amplifier, the resistance from drain to source should measure anywhere from 50 ohms up to 80 ohms. It will appear as a low voltage due to the lack of energy on the gate. This is normal for a P channel JFET. Keep in mind the JFET will be conducing with zero volts in respect to the source on the gate. It requires +3 to +5 volts to cut off current flow (turns the JFET switch to off). The cable that has the MU signal on it is the long one that stretches from the rear of the chassis almost to the front and terminates on a header next to the inductor array for the EQ.

Here are some pictures I took with areas highlighted to indicate what resistor ties in the gate to the common signal MU. I also marked the position on the 8 wire cable where the MU signal is (4th from the end farthest from the inductor array). At this point it is uncertain if this is related to the Mute function on the control panel or footswitch. The ribbon cable near V4 does not appear to have any association to the mute circuit but with it unplugged there will be no signal from input to output. I found this out the hard way by forgetting to plug it back in. Opps.

https://www.flickr.com/photos/159449305 ... 7769651654

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Mk III (blue stripe), Mark IVb-WB


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PostPosted: Thu Oct 12, 2017 1:28 pm 
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Mark II

Joined: Thu Jul 13, 2017 7:01 pm
Posts: 109
dlpasco wrote:
Hi there. I had some work stuff come up in a big way and sort of dropped off the face of the planet.

I had some really interesting results with my own A/Bing of the stock and modded configurations, as well as comparisons to my IIC+.

One thing that I did was get a decibel meter and dial in everything at exactly the same volume when I recorded.

I was not able to distinguish much difference between the recorded sound of the modded or stock Mark V *at volume* - I think I was recording at about 94db, which is pretty full-throated.

It might be ear fatigue, or maybe using the AT7s pushes the amp harder at lower volumes. I can't say for sure. I know that at lower volumes I've immediately been able to tell that the stock configuration was in play - the amp sounded dead to me. I've kept the AT7s and I love it.

The acquisition of a gen-u-ine Mark IIC+ also ended up consuming a lot of my time.

IMO - and I have sat down and A/B/C'd the amps and configurations in awhile, at a higher volume the stock and modded Mark V and the Mark IIC+ all sound epic. The modded V and the IIC+ also sound great at lower volumes and I've really not bothered to go back and play with the stock Mark V configuration at low volumes since my last big testing spree a few months ago.

I think I've reached to point where, if I had to get rid of everything but one amp, I'd keep the IIC+, but it's because it sounds good and it's rarer. The V sounds awesome and I get a bigger change in sound switching guitars and pickups than I do switching amps, for sure.

These are just my experiences. Your's (not anyone specific, I mean all y'all) may be different.



Nice one. 8)
You have a great collection man.
Bet that was a lot of fun to experiment with...!!

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PostPosted: Fri Oct 13, 2017 6:18 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2658
Location: North Carolina
I doubt it is the mute circuitry that is causing the issue with Wayno's amp. Since the ribbon cables are basically bridge connections from one board to the other, the Send and Return signals have to get to the back panel somewhere. Since the hard bypass for the FX loop is on the back panel along with the FX loop jacks, I believe the large ribbon cable next to V4 is the root cause of the issue. I too had forgotten to reconnect the cable and had the same issue but all was restored when I plugged it back in. So if the assumption is correct there may be some disconnect between the signal path for the FX loop which would affect both hard bypass and FX loop active modes. No signal will be passed from Send or Return and the sound will be muted. The low signal levels heard though the amp may just be the feedback circuits. Even if there is continuity found, it may just be a strand of wire making the connection or wire could be loose in the plug such that placing a meter probe onto the wire if used against the internal pin may be enough force to complete the circuit. It is either that or the small board along the back panel has something wrong with it. Removal of C39 should not be the cause for the amp to go silent as it only affects one tube that ties the grid to cathode on V4B. Besides that it should only affect CH3 and is not related to channels 1 and 2.

Also if there is another problem it was coincidental at best. Once can easily remove V4 and you would still have CH1 and CH2 (without reverb).

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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PostPosted: Sun Oct 15, 2017 8:35 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2658
Location: North Carolina
dlpasco wrote:
I was not able to distinguish much difference between the recorded sound of the modded or stock Mark V *at volume* - I think I was recording at about 94db, which is pretty full-throated.


dlpasco,

You are not alone on this. I took things one step farther and removed a capacitor. I can hear the difference when in the room but what seemed to be more apparent was the feel on pick attack as this shifted the response to a more forward attack (if that makes any sense). Feel and response cannot be captured with any microphones or video cameras. I wonder if this could be measured on an oscilloscope but that would be overkill and not necessary.

Sounds like you have had an interesting encounter with the IIC+. Sorry for my ignorance but is it a head or combo?

I would agree with the Mark V comments. The basic or fundamental tone will be there regardless of the tubes you are using. Some slight changes will be had with different tubes but that will not shift the frequency response of each stage enough to make a huge difference. With microphones you will capture the fundamental tone and miss out on the additional harmonics embedded in the output of the amp. Perhaps it could be done with several different microphones with small to large diaphragms, mass also plays a role in regeneration of the sound waves. Not something I am willing to purchase as some of the reference mics are quite expensive and cost as much as an amp.

Enjoy the IIC+ :P as for what amp to let go.... that is difficult to answer. If my house was on fire I would go down in flames while grabbing all of my guitars, perhaps I would grab the JP-2C and let the rest burn but would also want to take the TC-50... They are all replaceable. Guitars may be more difficult to replace depending on what it is. As it were I do not have any difficult to replace items, except for the dog and he will be rescued first bar none.

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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PostPosted: Sun Oct 15, 2017 1:05 pm 
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Location: Seattle
bandit2013 wrote:
Sounds like you have had an interesting encounter with the IIC+. Sorry for my ignorance but is it a head or combo?


It's an SG (60 watt with graphic eq, no reverb) head that Mike B modded for me: pull deep now activate the Hetfield/++ mod, and the mid knob serves the regular pull deep function.

It's a very nice little beast. Although all of these amps sound awesome, it can nail album tones exactly - the differences of the other amps isn't too noticeable at all until you turn this one on, then it's "OMG, that's the sound from Nevermind/Puppets/etc"

bandit2013 wrote:
I would agree with the Mark V comments. The basic or fundamental tone will be there regardless of the tubes you are using. Some slight changes will be had with different tubes but that will not shift the frequency response of each stage enough to make a huge difference. With microphones you will capture the fundamental tone and miss out on the additional harmonics embedded in the output of the amp. Perhaps it could be done with several different microphones with small to large diaphragms, mass also plays a role in regeneration of the sound waves. Not something I am willing to purchase as some of the reference mics are quite expensive and cost as much as an amp.


Yeah, I think that capturing the actual room sound of one of these amps would take about five microphones. Actually recording a great sound isn't heard: reproducing what you're *HEARING* is much more problematic.

bandit2013 wrote:
If my house was on fire I would go down in flames while grabbing all of my guitars


OMG that is the best answer I've ever heard. And yes, doggos into the lifeboat first :)

_________________
Mark IIC+, III, V, Recto Reborn, TC-50
Sold: JP-2C, V25, Road King II, Tremoverb, Electra Dyne, ROV25
Twitter:mammothguitar


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PostPosted: Sun Oct 15, 2017 1:57 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2658
Location: North Carolina
Besides, it would take too long to tear down the drum set.... I love that thing too. I may toss a bass or two into the flames just so I can watch them burn (only kidding I like my bass gear too but nothing to write home about).

If I did have to face a home fire, the dog would be a happy pup since that would mean no more loud guitars, drums and bass. Acoustic is okay but the electric or loud stuff is not. Well then again it could be my playing so I have to take that into consideration.

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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PostPosted: Sun Oct 15, 2017 3:10 pm 
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Mark III

Joined: Sun Sep 27, 2015 2:50 pm
Posts: 194
Location: Good ole England
Hi guys,

Been stuck at work again :cry: finally got a Sunday off and no V to rock out with, gutted.

Good to hear from dlpasco, great to read about your findings. Very jealous of your iiC+ :mrgreen:

Waiting on tech to check out my V as he's pretty busy. Will definitely post up his findings/fixes for you lot. You never know, it may help someone in the future if they have the same problem. Maybe start a new thread for it as I feel I've hijacked APEMAN's thread here a bit. Still, all relevant to the mods though I guess.

Massive thank you to bandit and you all for all your help with my V. Really appreciate the time you've put into helping me out and i've learnt a lot about the workings of the amp which I love. Even if I haven't been able to fix it myself, you've probably saved me a lot of tech time/expense by enabling me to give him as much info as possible as to what the problem may be. Really do appreciate this.

Thanks guys,

Wayno.

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Mark V/V4 AT7 Combo
2 x 12 Vertical Cab
Danelectro Fab Overdrive
Dunlop Cry Baby Wah

Gibson LP Studio with alnico ii pro
Schecter C1-XXX with emg 81/85
Jackson Dinky XL with Duncan designed???
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PostPosted: Sun Oct 15, 2017 6:01 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2658
Location: North Carolina
Hey, no problem, how else can one figure this thing out without a full schematic. I believe your issue is related to the ribbon cable you disconnected when you cut the leg to the cap. The ribbon cables also carry signals too. I have not decoded the other ribbon cables yet but at least the mute thing may not be the problem.

I have gone back to 12AX7s then back to 12AT7 in V4, now have both in V4 and V6. The tube swap is a good fix for the ice pick.

I think I have been the one hogging the thread. sorry. :roll:

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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PostPosted: Mon Oct 16, 2017 2:41 pm 
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Mark III

Joined: Sun Sep 27, 2015 2:50 pm
Posts: 194
Location: Good ole England
bandit2013 wrote:
Hey, no problem, how else can one figure this thing out without a full schematic. I believe your issue is related to the ribbon cable you disconnected when you cut the leg to the cap. The ribbon cables also carry signals too. I have not decoded the other ribbon cables yet but at least the mute thing may not be the problem.

I have gone back to 12AX7s then back to 12AT7 in V4, now have both in V4 and V6. The tube swap is a good fix for the ice pick.

I think I have been the one hogging the thread. sorry. :roll:


No apologies Bandit. You have took APEMAN'S great thread he started here and helped it evolve into the behemoth that it has become. You've given some great advice and insight into the reasons behind the effectiveness of the AT7 mod in both V4 and V6. And you've helped me with my problem along the way. Thanks to you I now have AT7's in V4 and V6 in my V and when it was working it sounded heavenly good. Looking forward to getting it fixed, missing it now.

_________________
Mark V/V4 AT7 Combo
2 x 12 Vertical Cab
Danelectro Fab Overdrive
Dunlop Cry Baby Wah

Gibson LP Studio with alnico ii pro
Schecter C1-XXX with emg 81/85
Jackson Dinky XL with Duncan designed???
Sigma DNC-1STE


Last edited by Wayno on Tue Oct 17, 2017 6:46 am, edited 1 time in total.

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PostPosted: Mon Oct 16, 2017 3:40 pm 
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Mark II

Joined: Thu Jul 13, 2017 7:01 pm
Posts: 109
Wayno wrote:
bandit2013 wrote:
Hey, no problem, how else can one figure this thing out without a full schematic. I believe your issue is related to the ribbon cable you disconnected when you cut the leg to the cap. The ribbon cables also carry signals too. I have not decoded the other ribbon cables yet but at least the mute thing may not be the problem.

I have gone back to 12AX7s then back to 12AT7 in V4, now have both in V4 and V6. The tube swap is a good fix for the ice pick.

I think I have been the one hogging the thread. sorry. :roll:


No apologies Bandit. You have took Bandits great thread he started here and helped it evolve into the behemoth that it has become. You've given some great advice and insight into the reasons behind the effectiveness of the AT7 mod in both V4 and V6. And you've helped me with my problem along the way. Thanks to you I now have AT7's in V4 and V6 in my V and when it was working it sounded heavenly good. Looking forward to getting it fixed, missing it now.


You know how it is with/what they they say about absence.

Those 1st chords you play when it returns will be be most awesome experience you've ever had.
Glad to hear progress is being made. Steps in the right direction for sure.

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PostPosted: Fri Oct 20, 2017 7:07 pm 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2658
Location: North Carolina
I was thinking about re-biasing the V4B circuit. Change in the cathode resistance and anode resistance to get a closer gain using a 12AX7 as I am getting with the original using the 12AT7. Nah, that is too much effort and work required to get very little in return. Tube swap is the best solution. I do not need the amp to sound like the JP-2C as I have one of those. The 12AT7 does a good job at getting close enough. Then there are the other preamp tubes you can change to fine tune the tone. I am happy with the Mark V where it is at. Yep it has its unique tone to it, not as ice pick bright any more and the change in speakers made a huge difference in my books. Running the Mark V combo with the OTR speaker and a 112 open back extension cab with the same speaker in it.

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Current amps:
TC-50, JP-2C, MK V, Roadster, RA100
Old friends I sometimes miss:
Mk III (blue stripe), Mark IVb-WB


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PostPosted: Sat Oct 21, 2017 5:54 am 
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Mark III

Joined: Tue Aug 21, 2012 5:47 am
Posts: 320
Are you guys using pentode or triode with this "mod"? I've been using triode cause that's what the manual says to use if you want a more authentic Iic+ sound. But today I read an article about the guitarist from slipknot talking about how much he loves the jp-2c and about Hetfield running the iic+ into a Marshall powerm amp. In his words he said Hetfield did because the iic+ had no balls because it was wired triode. Anyway I flicked the switch and bam, more balls :twisted:

Edit, I may have the pentode/triode thing arse about face.


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PostPosted: Sat Oct 21, 2017 6:04 am 
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Mark II

Joined: Thu Jul 13, 2017 7:01 pm
Posts: 109
barryswanson wrote:
Are you guys using pentode or triode with this "mod"? I've been using triode cause that's what the manual says to use if you want a more authentic Iic+ sound. But today I read an article about the guitarist from slipknot talking about how much he loves the jp-2c and about Hetfield running the iic+ into a Marshall powerm amp. In his words he said Hetfield did because the iic+ had no balls because it was wired triode. Anyway I flicked the switch and bam, more balls :twisted:

Edit, I may have the pentode/triode thing arse about face.


Thats probably just his preference.

Its not about balls tonally, its an output type thing. The more scooped darker nature of Triode and the feel are more vintage Metallica I'd say, when not slaved through a Marshall, for my money, but the overall volume is less than Pentode, and the feel is different in Pentode..... I heard from a interview with Flemming Rassmussen that slaving into the Marshall its was to bring more dirty/heavy to the tone, as he felt the IIc+ was too clean/civilised.

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