high gain mods for MV 100

[9VOLT1967]

I am awaiting my 100 watt MV kit and am looking for mods for high gain.
Thanks

[demonufo]

Well, firstly, you can remove that 10K resistor on the far left, and replace it with a 4.7K. (Some people like to go down to 2.7K, but I find that far too squashy and buzzy, in fact I never go below a 6.8K here, because I just don't need that much gain.)

On the board is a 820ohm resistor which can be paralleled with a .68 cap, which will add more gain in the midband only. Try it and see what you think.

Another one to think about, is the 470pF/470K pairing on the board can be replaced by anything down to a 68K, which adds a little. Again, I find this one a bit on the squashy/compressed side. Personally I like sticking with the 470K and dropping to a 250pF here. These go between the input jacks and the pre-amp gain, but in the kit are mounted on the PTP board.

There are a few other mods that can be done, but that is your starting point for higher gain.

If you need more still (and if you do, I fear you may have chosen the wrong amp for you) you can always alter the plate load resistors in the phase invertor. These are 82K/100K as standard and can be raised to add more gain. Again, you don't want to go mad here, and you do need to increase them both by approx. the same amount together. eg 100K/120K

My recommendation is to only ever do one mod at a time, and try and live with the mods for a while before going on to the next.

I also recommend giving your amp a good breaking in period before starting on the mods, as the sound WILL change the more you use it.

Other simple mods include changing the mid pot for a 50K for more mids (will be slightly more mids on minimum though) and lifting the purple NFB wire from the impedance selector, and installing a .0033uF capacitor in line, for more bass. If that adds too much, you could always try a .0047uF.

You may have seen mods elsewhere recommending you to change values of caps on the board to add bass, but this has a pretty horrible, loose effect on this particular circuit, and I really don't recommend you bother trying.

There are a few other mods out there for 2203/2204 circuits, but these are the only ones I've ever had any success with. Anything else always got returned to stock values.

[toner]

...If you need more still (and if you do, I fear you may have chosen the wrong amp for you)...

+1
However, demonufo listed some great options and I agree, don't go crazy all at once. Give each mod some time. The V1 cathode resistor and V2 cap are good starting points. The V1 resistor alone does quite a bit.

2203 isn't a gain-monster but it all depends on what you want. You may like it in stock form. I would give it a couple of weeks before starting mods. If more gain is really an issue (not tone that will improve with time), then try some of the suggestions above.

[itsonlyadam]

Interesting. How much gain, essentially, would these mods yield? Are we talking hair metal gain? Also, I've noticed no one has suggested an added preamp tube... yet. Would that be too much? Just curious as I am thinking of doing a 2203 with 6550s and would love to be able to get some serious hair metal tones with my Les Paul.

[demonufo]

Yes we are easily into hair metal territory here. After all, many of them will have used 2203/2204's anyway. Adding a pre-amp tube to an amp that is already cascaded is IMO unnecessary. There is plenty of gain to be tapped into here. Especially if you go into the plate load route as well (but not too much)

[toner]

I agree with demonufo. A lot of those bands were using late 70's MV amps or JCM800's. The type of gain that I was talking about that wouldn't be ideal with a Marshall MV is stuff like a Mesa Rectifier, Peavey 5150, etc. Those use extra tube gain stages.

Plus, you can always boost the input with pedals like a clean boost or EQ for more gain. I've seen pictures of Iron Maiden master volume amps with MXR distortion+ pedals duct-taped to the front. somebody's "custom mod", I guess

[itsonlyadam]

The type of gain that I was talking about that wouldn't be ideal with a Marshall MV is stuff like a Mesa Rectifier, Peavey 5150, etc.

YUCK! It makes me sick just thinking about those amps (Mesa, Peavey, etc.). I guess it's time to let the hair spray fly!

[demonufo]

The type of gain that I was talking about that wouldn't be ideal with a Marshall MV is stuff like a Mesa Rectifier, Peavey 5150, etc.

YUCK! It makes me sick just thinking about those amps (Mesa, Peavey, etc.). I guess it's time to let the hair spray fly!

Hey, don't forget the leather trousers and the makeup!

[toner]

YUCK! It makes me sick just thinking about those amps (Mesa, Peavey, etc.).

just an attempt to retain some self dignity and set the record straight...
I'm not a fan of those either! They're popular but so is a lot of crappy music. oh, well...

[9VOLT1967]

I appreciate all of the info on circuit mods. I will try one at a time and give each time to breath before moving on to the next if necessary. I am open to the extra pre-amp tube if needed, but it doesn't sound needed. I am looking for a Soldano & CAA type gain structures and I think they are 5 stages, but have experienced a master volume plexi with only 4 stages with plenty of gain.

[JGR]

You can get a lot of gain out of three stages, but it gets pretty harsh sounding if you start running each of the stages flat out, and you will be better off adding another tube at that point. The trick is knowing where that point is. Generally speaking, if you take the stock circuit, and add a cathode bypass to the second or third stage (I wouldn't do it on both) and drop the 10K down a bit, and then still want more gain, its time to add another stage. I would also raise the 820 up somewhere between 1.5 and 2.7k so it doesn't get too harsh sounding. Regarding the 470P/470K networks, I wouldn't mess with those for more gain (distortion), but rather frequency response. Try removing the second 470P altogether if you want some more low end, and if you still want more low end, try subbing the first 470 with a 1000 or 2000. You will also want to consider adding grid resistors to the inputs of the second and third stage to help keep feedback under control, eliminate blocking distortion, and tame any buzziness.

Also, don't forget the NFB loop. You can really alter the feel, gain, and character of the amp.

JR

[demonufo]

it gets pretty harsh sounding if you start running each of the stages flat out

I agree, but also rather than add all the gain at one stage, it is mostly better to add a little bit in different areas, depending on your tastes.

Also, don't forget the NFB loop. You can really alter the feel, gain, and character of the amp.

JR

I'd totally forgot about that . A more subtle effect on gain, but can affect the feel more. May or may not be to the original posters tastes, but certainly areas which should be looked into.