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PostPosted: Sun Mar 04, 2018 10:05 pm 
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Mark III

Joined: Sun Feb 02, 2014 11:51 am
Posts: 172
Don’t delete the post. It is great info.

I have a theory on Bandit’s love/hate with the Mark V. I’m an engineer also, like Bandit. The Mark V is just a joy from an engineering point of view. So many options, so thoughtfully designed, it truly is an engineering masterpiece. (and a service techs nightmare, haha) My theory as to why Bandit just can’t part with the Mark V is that it is just too much of an engineering marvel. Deep down, in the heart of an engineer, there is a deep appreciation of what the Mark V accomplishes. The variety of tones, the quality of the tones (at least the one I have), the utter beastliness of channel 3, the classic crunch, punk and thick juicey tones in channel 2, and the pristine sparkle and clean of channel 1. The fact that it does not 100% live up to expectations (is it a lemon? does it just not sound like the ideal tone?) is a disappointment, but damn, it is an extremely well engineered piece of gear. Hard to get rid of it.

As for me.. I found I prefer the JAN AT7 in V4 (in V6 it seemed to reduce the gian too much). I haven’t looked back and I’m not interested in any more mods. Yes, the TC-50 and Rectoverb 25 are enjoyed very much, also. But, the Mark V always gives the biggest goose bumps (even bigger now with the vertical 2x12 Rectifier cab).


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PostPosted: Mon Mar 05, 2018 4:18 am 
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Mark III

Joined: Sun Sep 27, 2015 2:50 pm
Posts: 289
Location: Good ole England
Please do not delete the post Bandit. You are not responsible for anyone else or their mishaps. Nothing you have stated is dangerous/unsafe or destructive. People have been modding their amps since day one. And you and everyone else here sharing their knowledge and ideas is priceless in my opinion.

These new ideas have definitely spurred my imagination, I too am an engineer and have always had a curious mind taking things to bits to see how they work since I was a small child.

Funny anecdote; I once at age 7 ish decided I wanted to turbo charge my bed bugs game. For those who don't know what that is it is a small plastic toy ( about 12 inches big) bed with a battery powered ( about 3volt or so) motor and cam underneath that made a cardboard mattress vibrate, the object being to try to catch all these little plastic bugs that would bounce about on it. I decided it would be cool to bypass the battery compartment and wire the motor direct to the 240volt wall socket! Luckily for me (and I still don't know why, I was sure I wired it up correctly) literally nothing happened so I returned it to stock and then it worked again. Obviously the AC current from the wall socket wouldn't run the motor but how nothing blow up or caught fire or electrocuted me I guess I'll never know.

Anyhoo, these mods have spurred that fire in me again as I knew they would. But, and it's a big but, trust that I will not try it if I'm not confident in my ability to carry them out properly, I may have Essex amp repairs ( top top guys by the way) do it if I feel it's too tight for my level of soldering ability. Or I may leave it as is, haven't decided yet. Curiosity is addictive though haha.

We must all carry on sharing our thoughts and knowledge, it's how we all grow.

Thanks guys.

_________________
Her highness the Veenus
(Mark V/V4 & V7 12AT7 Combo)

2 x 12 Vertical Cab
GSP-1101

Gibson LP Studio with alnico ii pro
Schecter C1-XXX with emg 81/85 18v
Jackson Dinky XL with Duncan designed???
Sigma DNC-1STE


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PostPosted: Mon Mar 05, 2018 7:04 am 
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Triple Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 3059
Location: North Carolina
I would take the mods with a grain of salt. It is just a minor improvement to the overall tone. I did install all stock tubes and was not impressed. :cry: Sounded very much the same as it did (should have run the Vertical 212 cab but did not). The 12AT7 in V4 seems to be the fix since it keeps the gain of that stage similar to the other triode circuits. With the 12AX7 in V4, there is too much gain at the higher frequency range which does seem to contribute to some brittleness (I believe it is also the first NPN transistor that is also aiding the odd harmonic overtones. There is no bypass around the GEQ as the signal chain will always pass though the transistor network with it on or off. Thinking of what is next on my list. Will need to borrow the scope to see what is going on there. My assumptions for the odd harmonic source could be the transistor network.

What I did find though, with the 12AT7 and the additional mod I was on par with the JP-2C running the combo though the vertical 212. So I had an immediate side by side comparison. Still the Mark V is not the exactly the same which is fine with me. Perhaps it is closer to what I would expect a Mark amp to sound like. Definitely a far cry better than what it was before I even had been aware of this thread. So how does one get that magic mojo that can be found with the JP-2C or the IIC+, easy but comes with a price tag. Just buy one and be done with it.

When you look at the limited schematic the Mark V is not all that impressive. Sure there is more going on with the relay logic used for channel switching and voice selection along with a few simple JFETS. The amp is not that complex in reality but tight in its layout. Much of the components used to create the strobe mute and channel changes is on the main board. That definately adds to the complexity in appearance. that must have been a fun project to work on. I would hate to assemble the preamp board as it quite stuffed.

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Current amps: TC-100, TC-50, JP-2C, MK V, Roadster, RA100


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PostPosted: Mon Mar 05, 2018 7:43 am 
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Triple Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 3059
Location: North Carolina
Considering my amp collection, the amps that I like the most have one thing in common. They all have class A/B power amps. The one I favor the least is the only one that has a Simul-Class power amp which is the Mark V. Interesting. Still the Mark V does have its merits plus a 10W cathode biased class A mode. It is interesting how that is all accomplished. Sure what is there not to admire in the design. Newer amps that emerged since 2016 generally do not require a change in preamp tubes to satisfy the tone junkies but some people are never satisfied so to no end they will roll until they loose interest. The Roadster can use a preamp tube upgrade to keep it out of the mud and the same would apply to the Royal Atlantic. Mark V, well depends on year it was made. Still have an issue to get past the power tube singing at reduced volume I hear the tubes vibrating at certain low frequencies it is annoying. Considering the other two amps that I have owned with Simul-Class power (MKIII and MKIV) they too have had that symptom. Perhaps it is related to the extended Class A function which is probably harder on tubes than the typical Class A/B format. Sure I have killed many pairs of tubes in the Mark III but that was due to heavy use, never replaced a tube it he Mark IV until I got the Mark V. I have had more failures with the V than any other amp I have ever owned. So my bias towards the Mark V in general can be in favor or dislike at any given moment. That love/hate thing. At times it sounds great and other times it is not very rewarding. Probably reason to why I have more amps than I need. I put all of the amps in a row in one room. Perhaps I have gone a bit too far.

Image

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Current amps: TC-100, TC-50, JP-2C, MK V, Roadster, RA100


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PostPosted: Mon Mar 05, 2018 5:42 pm 
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Mark III

Joined: Thu Jul 13, 2017 7:01 pm
Posts: 200
*Cab envy mode engaged*

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Mark V
Mark V:25
Mark III (Red Stripe)


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PostPosted: Tue Mar 06, 2018 1:10 am 
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Mark III

Joined: Tue Aug 21, 2012 5:47 am
Posts: 352
bandit2013 please don’t delete post! My warranty runs out in August and I’m very keen to do this mod.


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PostPosted: Tue Mar 06, 2018 6:53 am 
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Triple Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 3059
Location: North Carolina
Not sure what the mod will do for you.... I did notice a difference but now getting used to it, hard to tell what that difference really is. I may unsolder the one jumper on V6A and see how much of a difference there is to verify it is not perceived difference simply because a simple mod was made. You know, you think it sounds different because something was done.

I did the GEQ trick last because I could not find the parts on the PCB. That was not much of a change since IIC+ mode has the series resistor on V6A in use but MKIV shorts it out. Extreme voice also has the series resistor in the circuit. That basically separates the three voices.

I am thinking on what happens with Extreme mode. It appears RMY9 only does one thing, shorts out a 0.001 cap for IIC+ and IV but keeps it in the circuit for Extreme. I could not find any other reference for that relay. Me thinks to pull the 0.001 cap and tie it into the presence control so it is always there. This is not a suggestion but a thought. I much prefer the dynamics of the extreme voice on CH3 and wonder what would happened with reduced feedback in the IV and IIC+ modes. My hunch is this would nail the JP-2C since the closest voice on my Mark V is Extreme. If I do something I will chime in on it.

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Current amps: TC-100, TC-50, JP-2C, MK V, Roadster, RA100


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PostPosted: Mon Mar 12, 2018 9:25 pm 
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Mark III

Joined: Tue Aug 21, 2012 5:47 am
Posts: 352
Looking forward to hearing how that goes.


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PostPosted: Tue Mar 13, 2018 6:14 am 
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Mark III

Joined: Sun Sep 27, 2015 2:50 pm
Posts: 289
Location: Good ole England
Just been taking a sneaky smoke break at work and was pondering over the Mark V and iiC+ schematics...

There's a 15uf cap (C2) on the cathode of V1a that's switched in and out by a Jfet (J175A). On the iiC+ that cap is switched too and labelled "bass shift", I'm assuming that's switched in for iV and Extreme modes and out for iiC+ mode. Unless of course it's for the ch1 and 2 voicing. Just thought I'd mention it. Would be great if there was a switching matrix schematic available hey!

_________________
Her highness the Veenus
(Mark V/V4 & V7 12AT7 Combo)

2 x 12 Vertical Cab
GSP-1101

Gibson LP Studio with alnico ii pro
Schecter C1-XXX with emg 81/85 18v
Jackson Dinky XL with Duncan designed???
Sigma DNC-1STE


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PostPosted: Tue Mar 13, 2018 6:48 am 
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Triple Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 3059
Location: North Carolina
Having a complete set of schematics would be ideal. Unfortunately I have no clue what modes that cap is used. I did write some notes on the printed Mark V schematics. For some reason I have Mark IV=2.2uF in that part of the schematic. Also the IIC+ has a 15uF cap instead of a 2.2uF cap on the 5Va cathode (what would be equivalent to this position anyways). For location on the IIC+ it would be V3B, on the Mark III it would be V3A (both have the 15uF cap) and the Mark IV is also V3A but has a 2.2uF. Increasing the capacitance value is not very difficult if you can fit the cap in there, just solder it into place in parallel to what is there already. A 10uF cap would do the trick. I did check Digikey and they are available in the molded form, 50V rated axial leaded variety. It is almost tempting to get a few caps to experiment with. Tantalum capacitor would be more desired than the aluminum electrolytic type. Making a change to the bypass cap on V5A would definitely increase the bottom end. Tempting..... I would personally leave V4 as is (except C39 delete). I was even thinking about adding some components to V2B and create another gain stage and place it between the gain tap and the V2A circuit. My OCD is having issues with that unused triode but that may be best left alone.

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Current amps: TC-100, TC-50, JP-2C, MK V, Roadster, RA100


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PostPosted: Tue Mar 13, 2018 8:52 am 
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Mark III

Joined: Sun Sep 27, 2015 2:50 pm
Posts: 289
Location: Good ole England
Yeah v2b is tempting to get involved I know :twisted: think that might be a bit overkill in the gain stakes though?

I wonder... if J175A was removed and a simple single pole switch wired in its place you could manually select the original "bass shift" feature of the iiC+?

Shame that the eq coupling cap and v6a's cathode bypass caps are not switched by Jfets rather than relays, it would be fairly easy then to swap them out for single pole switches and then you'd be able to manually select pretty much all the same features as the originals pull pot options and you could also select the eq or non eq coupling cap that Doug west likes! Best of all worlds! Don't imagine this would be so easy with the relays used. Unless you could isolate all the individual power supplies to them which seems to me to be probably not worth the headache. Also probably redundant with your previously mentioned mods. I am curious about the possibility of adding "bass shift" to iiC+ mode though. Maybe that along with your last two mods and C39 would be more than enough anyway. Hmmmmmmm, the mind boggles.

_________________
Her highness the Veenus
(Mark V/V4 & V7 12AT7 Combo)

2 x 12 Vertical Cab
GSP-1101

Gibson LP Studio with alnico ii pro
Schecter C1-XXX with emg 81/85 18v
Jackson Dinky XL with Duncan designed???
Sigma DNC-1STE


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PostPosted: Wed Mar 14, 2018 4:21 am 
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Mark III

Joined: Thu Jul 13, 2017 7:01 pm
Posts: 200
Would be quite a thing to add 'Pull Deep' from the III too..... different effect, utterly sublime when used well.
Adds weight by the tonne. Would make the V inclusive of the III beyond the similar three channel format usage..
But for now certain settings with Extreme fill that role..

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Mark V
Mark V:25
Mark III (Red Stripe)


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PostPosted: Thu Mar 15, 2018 5:06 pm 
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Triple Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 3059
Location: North Carolina
Well I have not removed the jumper yet and probably will not. Extreme voice is incredible now with the mod. Mark IV is also more deserving of its name. Actually both seem to be comparable to the JP-2C more than the IIC+ voice but the mode does make it more ideal. MkIV is almost like the CH3 of the JP with the gain control pulled out.

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Current amps: TC-100, TC-50, JP-2C, MK V, Roadster, RA100


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PostPosted: Fri Mar 16, 2018 9:55 am 
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Bottle Rocket

Joined: Fri Nov 14, 2014 10:03 pm
Posts: 10
How do we do this jumper mod? I understand that it sounds fuller, but does it also help with gain?


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PostPosted: Fri Mar 16, 2018 2:55 pm 
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Mark III

Joined: Sun Sep 27, 2015 2:50 pm
Posts: 289
Location: Good ole England
Thinking further about the cathode of v1a, making the bypass caps manually switchable could really help beef up Edge and Crunch on ch2 as well. Could be an interesting added bonus of any mod done here however wouldn't be independent of changing channels which could be a problem if the effect is good on ch3 but not so good on ch2.. Looking through the schematic there's a hell of a lot of switching going on with ch2 so it shouldn't really change the character of the ch2 modes too much I wouldn't have thought. Its essentially just increasing the gain of v1a, which come to think of it would effect every mode on every channel. Hmmmm, again if only the switching matrix was available and could be modded a manual switch could be exchanged for a channel specific tweak to the switching circuit.

_________________
Her highness the Veenus
(Mark V/V4 & V7 12AT7 Combo)

2 x 12 Vertical Cab
GSP-1101

Gibson LP Studio with alnico ii pro
Schecter C1-XXX with emg 81/85 18v
Jackson Dinky XL with Duncan designed???
Sigma DNC-1STE


Top
 Profile  
 
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