nomad mods

[Tejas]

Hey there fellows,
I'm new here, but I did these mods and a couple of others and I thought you might like to hear my results.

Mud mod ----- Works great I love it. I also noticed that after doing this mod and running the amp thru a Jensen cab, there was no mud at all and the amp is plenty bright.

Series FX loop ------- This one was perfect for me for a couple of reasons, 1. I don't use the loop much, but when I do it is for delay and it works better as a series loop. and 2. I removed the pot for the FX loop and used the hole for a trim pot for the adjustable bias mod.

Bias mod ------- I took out the 15k bias resistor and replaced it with a 10k pot in series with a 10k resistor. I mounted the pot in the hole where the fx loop pot was. 10k minimum with another 10k adjustable seems to be spot on for several sets of tubes I have tried.

Here's is a mod that I came up with myself that I think was highly successful.
- I think the stock reverb circuit is garbage, so I fixed it.

The signal flow into the reverb driver is bottle-necked thru a 500pf cap and a 475K resistor.

The 500pf cap is only passing the most annoying high pitched frequencies into the driver to be
reverberated. I replaced it with a .02 Orange drop.

Next the 475K resistor is choking off quite a bit if signal and leaves the reverb pretty weak. I paralleled a 330k accross the existing resistor. That lets a bit more signal come thru and gives more reverb.

Coming out of the reverb recovery stage right before mixing back in with the dry signal, the signal is again cut off at the knees by a .005 cap. I replaced that with another .02 orange drop.

Result: good usable reverb that sounds lush and has no more ice pick feel.

Hope this is useful to someone.

Dave

 

[Ylo2]

I just did the two mud removal mods to my Nomad: 1) lifted one end of each 120 pF capacitor in the PI, 2) lifted one end of the .005 uFd capacitor in the effect return circuit, replaced with 47 pF. The .005 capacitor is located on the upper left edge of the PCB (when you are facing the rear of the amp), near the SOLO and OUTPUT controls.

Wow, what an improvement. CH 1 sounds more Fender-like. I actually LIKE CH 2 now! Using CH 3, pick harmonics just jump out of the speakers, and feedback is easier to get. I'm using the traditional Mesa 4x12 cabinet with Vintage 30s.

Most of the change seems to be in the very high frequencies above the range of the Treble controls. The Presence controls actually do something now. CH 3 can get a little bright, but rolling the Presence below 12:00 seems to take care of this without having to change the Treble level.

I'm going to have to spend more time with the amp, comparing previous and new settings, but I think these two mods together are fantastic. Thanks everyone for a great thread!

 

[thelastleroy]

Hey All,

New here as well, been looking for a way to spruce up the old Nomad 45 Head.... I did the "mud" mod (clipped one leg off the two PI caps) and so far it sounds great. I always wondered why I needed to run the treble control so high to get any brightness out of the amp, especially channel 3. Going to jam with the guys tomorrow and crank 'er up to actual concert volume for a real test. Can't wait.

After some reading it seems the best way to get the tone-sucking action out of your Nomad is as follows (Correct me if I'm wrong)

1- Use the Extreme power amp setting ---Done
2- Use the Modern modes of channels 2&3 ---Done
3- Perform the "mud" Phase inverter cap mod ---Done
4- Modify the reverb circuit to actually work properly ---Not yet, to be done soon!
5- Perform the Series effects loop mod ---Not yet, wondering if this is best for pedals in the loop only or for rack stuff too?
6- Perform the Adjustable Bias mod ---Kind of chicken to make the amp less foolproof, but the promise of superior tone will persuade me eventually
I also had an Idea.....

If the Extreme/Normal switch effectively switches between SOME negative feedback to NO negative feedback, Is there any reason why a pot couldn't be used instead to blend in the IDEAL amount of negative feedback to one's own ears? What components would I need for this, assuming it's possible?

 

[nomad100hd]

a pot would work just fine, or even a push pull pot. Not sure what size pot to use and you would probably want to have a resistor in series with the pot.

If you use any digital pedals in your loop, or anything that may have a latency you'll need to mod the loop to series.

 

[sevenchaos]

Has anyone tried to do extreme switch to 55 or 100?
I checked schemas and it's just basically pentode/triode switch, or am i wrong?

 

[nomad100hd]

recheck the schematic, it has nothing to do with pentode, triode. It turns on and off the negative feedback in the power amp. I don't know if anyone has done it but it can be done to any power amp.

It will loosen up the power amp and add more bass.

 

[thelastleroy]

OK, back from the Jam... here's the report.


The Mud mod certainly works. The amp is brighter overall, and I actually had to roll the treble back down to 12 o'clock or so on CH 2 and CH3 to avoid piercing a hole in the bassist's ear But really, the mod seems to have made channel 2 much more useful than ever before, as the tone is more articulate and less "mushy" in this channel. Channel 2 with the gain down low is an awesome dirty rhythm tone now (think Tom Petty), and with the gain turned up is a rippin' lead tone.

Channel 3 however is still lacking in my opinion, it has the snark and attitude of a great amp, without the body to back it up. Today more than ever I noticed the difference in character between CH 2 and 3. I regret to report that like many before me that the amp sounds great on it's own but gets lost once the band picks up.

Channel 1 sounds great, and running the power amp in the "extreme" mode almost sounds like turning on a compressor on this channel. Very nice.

...starting to wonder if I should proceed with modding this head further or trade it up for something new before I make into too much of a Frankenstein???

 

[nomad100hd]

i think the eq is hurting channel 2 try changing the slope resistor on the eq for channel 2 to the value on channel 3. Also you might try some KT77's in the amp.

 

[playdosboogies]

Tried the "mudmod", no audible difference to my ears.

My nomad has just been sitting for a couple years so i figured i would give it a go. I got my nomad as part of a bigger trade deal a few years ago, and after fiddling with it a bunch of times, and trying different tubes etc.. covered it up and forgot about it. I have to say it is absolutely the most unmusical tube amp i have ever owned, i can't see how mesa let this one hit the market. I am a huge mesa fan too, not bashing here. I have modded (simple stuff) a few times, and most of my marshalls are modded, but if the inherent tone isn't doing it for you, no amount of modding is going to make a terrible amp into a good one. I'll just dump mine off on craigslist and chalk it up as a lesson learned.

 

[nomad100hd]

do you have hearing loss? when i modded mine everyone in my band at the time was like wow!

 

[playdosboogies]

LOL. No hearing loss. Unless my doctors have just been giving me passing grades because of my mad skilllzzzz..... I can also very easily discern tonal differences between tubes,speakers,cables etc.... That's just what I experienced. I don't think it would be a stretch to think that everyones experiences might be different?

 

[nomad100hd]

i'm just being a jerk! it's not like a night and day wow this amp is now amazing difference.

 

[playdosboogies]

i'm just being a jerk! it's not like a night and day wow this amp is now amazing difference.

Well you DO have a lot more experience with this particular amp than i do, so i imagine you're ears are a lot more in-tune with that nomad sound. I have played with mine for probably a total of about 4-5 hours on it over a period of months. I'ts quite possible/probable that you are noticing changes to the tone that i am not noticing. It's all good... I bet Jeff Beck or Gary Moore could get better tones out of a Nomad than i could out of a stack of Dumbles. It's in the fingers anyways!

 

[nomad100hd]

at first i didn't think it sounded much different, but it defiantly set in the mix different.

 

[thelastleroy]

here's some shots of the PCB inside a Nomad 45 head, before any mods.

 

[Ylo2]

Tried the "mudmod", no audible difference to my ears.

The PI mud mod is kind of subtle. I did the second mud mod too (reduces the capacitor value in the EFX return). This REALLY made a big difference IMHO.

I can't argue that at some point it is less hassle to just buy a different amp, and the Mark V sure looks tempting! But before going this route, I figured the Nomad mods were easy to do and easy to reverse and so worth a shot. I'm pretty pleased with the results -- this a whole different animal now.

 

[sevenchaos]

recheck the schematic, it has nothing to do with pentode, triode. It turns on and off the negative feedback in the power amp. I don't know if anyone has done it but it can be done to any power amp.

It will loosen up the power amp and add more bass.

Whoops, my bad
Well no need to think about these mods anymore cuz i just bought mark iii green stripe fully loaded :lol:
As much as i liked my nomad and did many gigs with it , mark just seems to fit my playing style and needs much better.

This thread is still cool, and as i love to build amps and stuff i always like to see that there are still dudes like me, true tweakers

 

[thelastleroy]

Hey All,

Just thought I'd post my progress with the Nomad 45 Head.

Still only done the PI cap removal mod, but just picked up a 1x12 one-off custom speaker cab, open back with a 30-watt Weber 12A125 alnico magnet speaker. This thing sounds like God to me and has improved the tonality of channels 1 and 2 even more. I find myself liking channel 3 less each time i play it. Oh well. Going to do the efx loop mod soon and try some other voodoo magic on this head to get it up to snuff.

Anyone else have experience with quite a bit of line hum and general hiss on the dirty channels with this amp? Any ideas where to start cleaning up the noise?


Happy New Year anyways,


Pat the Cat

 

[nomad100hd]

yep channel 3 more just there as a tease. Almost usable but just not quiet there.

 

[thelastleroy]

Would anyone be able to post a quick guide to the Mud mod mk11 and the reverb mod? I want to do these but don't know where the components are located on the board.

Also is there a full schematic for this amp available online?