Marshall Amp Forum - View Single Post - The JCM 900 and modification... Thoughts?

V-man · 09-17-2009, 07:38 AM

Sorry about my "thoroughness". The gist of passages are underlined for the helpful members who lack the time or attention span to wade through my prose.

These past months I have been rediscovering guitar and reacquainting myself with my gear. Lately I have been looking more into the sound dynamics of the amp and seeing what I can do to shape the tone. I have read all 100+ comments on the Harmony Central review board, along with people's impressions here, and what I have found is about 50% inconsistent opinion, and 50% unified criticism with respect to the 4100's capabilities.

What I have come to experience is the 3 knob EQ (+ presence) is a liability because it is a master EQ for both channels and there is minimal shaping with the manipulation of the knobs (particularly with treble and mid). The FX loop may also change the dynamics in sound for the worse, (or so it seemed in my experience, but this requires further experimentation). Finally, the amp has good cleans and a "working" ability to get some mud at sub-bedroom volumes, but it has been a difficult to dial in the tone that complements my style of music.

The consensus (with a dissenting minority) seems to be that the amp's crunch channel hits the nail on the head for "AC/DC" but that's as far as it goes, and between the lacking low end and the lack of high gain (despite the misleading moniker) leaves one rather disappointed for "the brootalz". I KNOW, I KNOW... I CAN HEAR IT NOW BEFORE THE FINGERS TAP THE KEYS: "sell the amp and get the amp you 'really' want."

Before the fingers DO tap that out, let me cut those of you off at the pass with the following:

1. This is my first halfstack, first tube amp, and the only Marshall I have known, and I have no intention of selling, let alone taking a bath due to the bad rap these have gotten. 2. I don't have the funds to swing another amp now so the option is deal with what I have stock and wait, or mod. 3. Who the hell knows what I need, or that the 4100 with/without mods isn't truly "the amp I really want"? Hey, I have even come across a front contending that you need to get out of Marshalls alltogether for post-80s metal. Sidestepping that arguably nonsensical statement, I don't see the point in playing russian roulette or merry-go-round with 2203KKs, Mesas, Framus Cobras, etc, etc that are impossible to demo in my area. What makes sense today is making the most of what I have and looking at other possibilities on the horizon (if necessary).

Other facts to consider:

- This is an early 90s EL-34 driven model.

- I have 2 MXR 108s and a Soundtank TS5 to shape tone

- I like the clean tone, and see potential in the crunch, but it is "thin," lacking low-end punch

- The TS5 adds some decent grain. MXR#1 gives a subtle improvement, but not enough to raise low end. MXR #2 (in conjunction) gives it thunder, but now it's got a muddy sound. This may be rectified with further experimentation.

- Master volumes rarely exceed 3.5 on the crunch and 5 on the clean, so some of what I am missing might be on the "loud" side of the amp that's hard to reach for long in the neighborhood.

- I would prefer reversible modifications, but having no plans to sell my first marshall means that the amp I love playing takes a higher priority than the amp I like collecting.

The three mods I know of thus far are:

Liam's Mod: seems "quasi-reversible" and simple, but may be the least effective for achieving a dramatic result.

TriodeAmplification mod: sold as instruction + pics. I am wary of sold instructions as this may be $30 for something marginally better/worse than Liam's mod + pics and have no idea about the extent of the mods.

VoodooAmps mod: Seems to have the most potential for improvement, reasonably well-reviewed, and the advertisement is suggestive that the mods are reversible, but this also is the most expensive and requires the cost and risk of shipping to/from Voodoo.

Based on my situation, what do you think? Also are there other mods you can add or recommend? Also, bear in mind I will be spending some time tone shaping while I research these alternatives before doing anything, and of course, I am receptive to any tone-shaping input you may have as well
TIA

09-17-2009, 07:38 AM	#1 (permalink)
V-man Senior Member Join Date: Jan 2009 Posts: 226	The JCM 900 and modification... Thoughts? Sorry about my "thoroughness". The gist of passages are underlined for the helpful members who lack the time or attention span to wade through my prose. These past months I have been rediscovering guitar and reacquainting myself with my gear. Lately I have been looking more into the sound dynamics of the amp and seeing what I can do to shape the tone. I have read all 100+ comments on the Harmony Central review board, along with people's impressions here, and what I have found is about 50% inconsistent opinion, and 50% unified criticism with respect to the 4100's capabilities. What I have come to experience is the 3 knob EQ (+ presence) is a liability because it is a master EQ for both channels and there is minimal shaping with the manipulation of the knobs (particularly with treble and mid). The FX loop may also change the dynamics in sound for the worse, (or so it seemed in my experience, but this requires further experimentation). Finally, the amp has good cleans and a "working" ability to get some mud at sub-bedroom volumes, but it has been a difficult to dial in the tone that complements my style of music. The consensus (with a dissenting minority) seems to be that the amp's crunch channel hits the nail on the head for "AC/DC" but that's as far as it goes, and between the lacking low end and the lack of high gain (despite the misleading moniker) leaves one rather disappointed for "the brootalz". I KNOW, I KNOW... I CAN HEAR IT NOW BEFORE THE FINGERS TAP THE KEYS: "sell the amp and get the amp you 'really' want." Before the fingers DO tap that out, let me cut those of you off at the pass with the following: 1. This is my first halfstack, first tube amp, and the only Marshall I have known, and I have no intention of selling, let alone taking a bath due to the bad rap these have gotten. 2. I don't have the funds to swing another amp now so the option is deal with what I have stock and wait, or mod. 3. Who the hell knows what I need, or that the 4100 with/without mods isn't truly "the amp I really want"? Hey, I have even come across a front contending that you need to get out of Marshalls alltogether for post-80s metal. Sidestepping that arguably nonsensical statement, I don't see the point in playing russian roulette or merry-go-round with 2203KKs, Mesas, Framus Cobras, etc, etc that are impossible to demo in my area. What makes sense today is making the most of what I have and looking at other possibilities on the horizon (if necessary). Other facts to consider: - This is an early 90s EL-34 driven model. - I have 2 MXR 108s and a Soundtank TS5 to shape tone - I like the clean tone, and see potential in the crunch, but it is "thin," lacking low-end punch - The TS5 adds some decent grain. MXR#1 gives a subtle improvement, but not enough to raise low end. MXR #2 (in conjunction) gives it thunder, but now it's got a muddy sound. This may be rectified with further experimentation. - Master volumes rarely exceed 3.5 on the crunch and 5 on the clean, so some of what I am missing might be on the "loud" side of the amp that's hard to reach for long in the neighborhood. - I would prefer reversible modifications, but having no plans to sell my first marshall means that the amp I love playing takes a higher priority than the amp I like collecting. The three mods I know of thus far are: Liam's Mod: seems "quasi-reversible" and simple, but may be the least effective for achieving a dramatic result. TriodeAmplification mod: sold as instruction + pics. I am wary of sold instructions as this may be $30 for something marginally better/worse than Liam's mod + pics and have no idea about the extent of the mods. VoodooAmps mod: Seems to have the most potential for improvement, reasonably well-reviewed, and the advertisement is suggestive that the mods are reversible, but this also is the most expensive and requires the cost and risk of shipping to/from Voodoo. Based on my situation, what do you think? Also are there other mods you can add or recommend? Also, bear in mind I will be spending some time tone shaping while I research these alternatives before doing anything, and of course, I am receptive to any tone-shaping input you may have as well TIA __________________ Gibson: '88' Explorer 90, Flying Vs - '02' V-Factor, '06' RI, '07' RI Jackson: '92' Rhoads Tribute, '92' Rhoads PCS, '02' KV2 '92' ESP/Hill King V '04' Epiphone Goth V '84' Marshall 1992 '93' Marshall 4100 '97' Crate Blue Voodoo BV-60 Combo