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Mesa D-180 Master Volume Mod

Y

you_never_know

Aug 24, 2009
49
9
#1
I just picked up a Mesa D-180 for dirt cheap. And of course, the first thing I noticed was that the Master knob is totally useless. I understand well how it works (it's a current limiter on the driver tube), and also why it sucks. It's basically the same as the S.O.B. guitar amp from the same era. The Mesa D-180 documentation seems to indicate that they also designed the D-180 for guitar usage, and that for bass, the expectation is that you'd leave it on 10.

The current limiter strategy was abandoned on the 400 series amps, where the Master is just a standard voltage divider in front of the phase inverter. It should be a trivial mod for me to change the Master over to this configuration.

I'm wondering if 1.) anyone has ever done this, and 2.) on the 400 series, do you actually use your Master volume, or do you just leave it all the way up?

Otherwise, the D-180 is a gorgeous sounding amp. I really didn't need a second rig, since I'm not really a bass player, but this was so cheap I couldn't resist.
 
#3
you_never_know said:
I just picked up a Mesa D-180 for dirt cheap. And of course, the first thing I noticed was that the Master knob is totally useless. I understand well how it works (it's a current limiter on the driver tube), and also why it sucks. It's basically the same as the S.O.B. guitar amp from the same era. The Mesa D-180 documentation seems to indicate that they also designed the D-180 for guitar usage, and that for bass, the expectation is that you'd leave it on 10.

The current limiter strategy was abandoned on the 400 series amps, where the Master is just a standard voltage divider in front of the phase inverter. It should be a trivial mod for me to change the Master over to this configuration.

I'm wondering if 1.) anyone has ever done this, and 2.) on the 400 series, do you actually use your Master volume, or do you just leave it all the way up?

Otherwise, the D-180 is a gorgeous sounding amp. I really didn't need a second rig, since I'm not really a bass player, but this was so cheap I couldn't resist.
Click to expand...
I totally disagree about it being useless.

Sure, all the volume increase is basically beteen 7 and 9.5, but gods, what a sound.

I think it might be possible to modify it using a pot with a different taper or whatever so that the increase is more gradual, rather than all right in that range and requiring tiny, minute adjustments.

Usually my channel 2 volume is at about 5-6, my master volume around 8.5-9.5. Bass is usually around 4-6, mids at 10 always, and treble at 1-2 (1 with new strings, 2 with worn out ones).

If you really want a traditional master volume and gain setup, honestly, just sell the D-180 to someone who will actually use its unique feature, and buy a Mesa Bass 400. If you put 6l6 tubes in the 400, it's basically the same amp as what you seem to want to modify the D-180 into.

Downunderwonder said:
Hands off friend. Please sell it to someone who appreciates it just as is. D180 Master on 9 is a delicious bass tone.
Click to expand...
Seriously, this.

No fuzz or overdrive pedal really comes close to the overdrive I can get with my D-180.

Using the graphic EQ to boost only, not cut, can make it an especially nasty, wonderful overdriven sound.
 
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#4
Korladis said:
I totally disagree about it being useless.

Sure, all the volume increase is basically beteen 7 and 9.5, but gods, what a sound.

I think it might be possible to modify it using a pot with a different taper or whatever so that the increase is more gradual, rather than all right in that range and requiring tiny, minute adjustments.

Usually my channel 2 volume is at about 5-6, my master volume around 8.5-9.5. Bass is usually around 4-6, mids at 10 always, and treble at 1-2 (1 with new strings, 2 with worn out ones).

If you really want a traditional master volume and gain setup, honestly, just sell the D-180 to someone who will actually use its unique feature, and buy a Mesa Bass 400. If you put 6l6 tubes in the 400, it's basically the same amp as what you seem to want to modify the D-180 into.


Seriously, this.

No fuzz or overdrive pedal really comes close to the overdrive I can get with my D-180.

Using the graphic EQ to boost only, not cut, can make it an especially nasty, wonderful overdriven sound.
Click to expand...
Since more convincing seems required, note there
is a little corner of hell, with a detuned banjo and off key harmonica playing 24/7, reserved for guitarists that cut the nuts off D180's.
 
#5
you_never_know said:
The current limiter strategy was abandoned on the 400 series amps, where the Master is just a standard voltage divider in front of the phase inverter. It should be a trivial mod for me to change the Master over to this configuration.
Click to expand...

Yep, and easily reversible in a few minutes if and when you might decide to do that. It's your amp, and strictly your business. Link Removed
 
#6
Get a "real" guitar amp. Also a regular master-volume is crap compared to Mesa's current limiter or a PPIMV w/ a Jose Mod. It's an attenuator almost. The OD will sound super natural and power-tubey unfortunately the draw back with those types of master volumes is they almost always only sound better past half on the master just like the D-180.
 
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#7
Passinwind said:
Yep, and easily reversible in a few minutes if and when you might decide to do that. It's your amp, and strictly your business. Link Removed
Click to expand...
Eh, I just think that if that's what the OP wants, he could do it way more easily by selling the D-180 (for its actual market value, not the dirt cheap price he paid) and getting a Bass 400, which is basically a D-180 with a more traditional master volume control. It's basically what he wants, already made.
 
#8
Korladis said:
Eh, I just think that if that's what the OP wants, he could do it way more easily by selling the D-180 (for its actual market value, not the dirt cheap price he paid) and getting a Bass 400, which is basically a D-180 with a more traditional master volume control. It's basically what he wants, already made.
Click to expand...

I think just grounding one lug on the pot is a great way to find out if he likes it better that way, and would cost nothing but a little time. I'd probably just take it out though, personally.
 
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#9
waltdogg said:
Get a "real" guitar amp. Also a regular master-volume is crap compared to Mesa's current limiter or a PPIMV w/ a Jose Mod. It's an attenuator almost. The OD will sound super natural and power-tubey unfortunately the draw back with those types of master volumes is they almost always only sound better past half on the master just like the D-180.
Click to expand...

I have a dozen "real" guitar amps. The issue is how the D-180 performs as a bass amp. The Master on the D-180 is all distortion and fizz once you get lower than 10. It doesn't just limit output to the power tubes. It increases distortion as the MV is lowered, even without a corresponding increase in preamp gain. My question is whether the MV on the Bass 400 is more useful. If it is, I'll do the mod. It's a 15 minute job.
 
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#10
you_never_know said:
I have a dozen "real" guitar amps. The issue is how the D-180 performs as a bass amp. The Master on the D-180 is all distortion and fizz once you get lower than 10. It doesn't just limit output to the power tubes. It increases distortion as the MV is lowered, even without a corresponding increase in preamp gain. My question is whether the MV on the Bass 400 is more useful. If it is, I'll do the mod. It's a 15 minute job.
Click to expand...
Why not just get a Bass 400?

Personally I would find its more traditional master volume/gain setup less useful (it's almost the same amp other than that). And yes, we know that the D-180's master volume is distortion on lower than 10, having experience with these amps.

For the record, the D-180 is currently my only bass amplifier, and has been for some time, and I am primarily a bassist. I find it to be an amazing amp, but then again, I really enjoy bass through an overdriven tube amp (that's part of the point, for me). Seriously, try it with the mids dimed, bass boosted a bit, Volume 2 on about 5 or greater, and the master on 9 or even 9.5. It's great.
 
#11
Ah, well, it's a lot easier for me to make a quick mod than it is to do all that gear hunting and swapping. And it costs nothing.

The growl out of this thing is incredible. Great body and tightness. There are a couple of good drive tones down to about 9. Dunno. I'll play with it some more and figure out what I want to do with it.
 
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#15
I have one too and I love it-I don't use it a whole lot anymore because of weight/convenience/lower headroom for some stuff that I do, but man I'll never get rid of it because of that tone. Is there an attenuator on the market that could handle that type of power? That might be the easiest way to keep the tone intact and lower the volume in a more linear fashion.
 
#16
Yeah, I run my at full master all the time - GREAT tone.

I also have a question - I currently own two D180`s. One with the graphic EQ, second one without it.

The VOL1/VOL2 act different.

As I understand VOL1 should not work while being plugged in into the second input - the first preamp goes into the second one, the second one goes into the power setion. So plugging into the second bypasses the first one entirely.

NON-EQ works this way, the EQ one does not - I need to set both volumes above 0 to get a sound.

Is that a thing they changed along the way?
 
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#18
I haven't plugged a guitar into it yet. The D-180 is actually very similar to the S.O.B. of the same era. The S.O.B. is a grossly undderrated guitar amplifier, mostly due to the Limit knob. The Limit knob works the same as the D-180 MV, although the S.O.B. still retains a traditional pre-PI MV. Like the D-180 Master Volume, if you leave the Limit knob all the way open, you have a tight, full-bodied amp. Although the S.O.B. was modeled after the Mesa MK I, it was voiced more aggressively, and isn't very similar to a MK II.
 
#19
I owned the D180 and must say it's one hell of a bass amp. I would not mod it since it's already perfection and doing so will probably impact resale. Best sounding bass amp I have owned. I have been using a Bass 400 non-plus as my main since 2005 and the D180 sounded sweeter!

I tried my best with it but it is not a great amp for guitar. The various master/gain1/gain2 controls dont really give you such a wide range of gain/OD tones. I found it was pretty much all or nothing. When I was trying to sell mine I had an old school Boogie era guitarist come over and try it out and he didnt get along with it either.

Cleans have insane headroom with the 6 6L6 power section but they are always a bit too forceful and direct. Gain/distortion can get quite br00tal but it is mainly incredibly searing on the top end and clean on the bottom end (like 250Hz down, it doesnt distort at all- which makes sense for a bass amp design as you want those freq to be rock solid at volume).

Even with pedals I couldnt get gorgeous guitar tones out of it. Let us know how it works out for you.

For Bass EQ like this:

Mid 8-10
Bass 2-3
Treble 2-3

For Clean Guitar EQ start somewhere around here:

Mid: 4
Bass: 7
Treble: 7

For Distorted Guitar EQ start somewhere around here:

Gain 1: 7
Gain 2: 3-4 (use this as your "volume")
Master: 0-1 (around 6-7 the power section starts really coming in)
Mid: 6-7
Bass: 6-7
Treb: 6-7
 
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#20
I agree that the mids should be very far up in comparison to the treble and bass knobs. It's a standard Fender tone stack, which basically just adjusts how scooped you want your tone to be. The EQ points on the D-180 are the same as the S.O.B., so its not really optimized for bass. The pull knobs help to fix that quite a bit. I'm kind of tempted to build something like an MEQ-5 to stick in the effects loop to really tweak the mids.

Does anyone use the channel 1 input for bass? I'm still exploring channel 2, MV on 10, and have been having a lot of fun with that so far.

I don't have a proper bass cab yet. I'm currently playing thorough a closed back Jensen 4x10 guitar cab, which actually sounds really sweet. Its only rated at 100W, so I haven't had a chance to get irresponsible with the volume knob and explore the drive sounds. I have an Ashdown ABM 410H on backorder, so it'll be a few more weeks before I really figure out what this amp can do.

Also, looking at the schematic, it looks like the send loop is immediately in front of the PI, so it probably makes more sense to stick a master volume knob in there rather than modding the amp. If I build the EQ unit, I'll just stick a gain control in there. I know that will be a great relief to many of you. :)
 
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