Tightening up the bottom end of the JTM45? (New Member!)

[Jazzydave]

Hey all! I'm new to the board and am going to take on a *first time* build here soon. I was a satellite tech in the Air Force so I'm hoping it'll go smoothly. Just follow directions, ask questions, and take it slow, right?

I was in Guitar Center the other day (I know, I know but...) and they had one of the Marshall JTM45 Reissues. I'd only played through the JCM series amps and many people have suggested the 45 to me so I thought I'd check it out. I grabbed a Gibby R0 (I play a slightly modded R7) and went at it. When I got that amp around 5-6 I couldn't stop. I was so impressed with the warmth and vibe of it that I ended up sitting there until someone finally broke my trance. THAT doesn't happen very often, especially with amps.

My only issue with it was how muddy it got in the low end. Now, keep in mind that I roll my highs back quite a bit. My usual amp setting are around B-5/6, M-3/4, T-4/5 and I roll my tone knob back slightly on my LP. That creamy yet articulate sound is what I go for and this amp seemed to nail it other than some mud there in the bottom.

After talking to another builder on here, he suggested the 45/100 and I even thought about going with the 50W Plexi bass (looks like I'd actually build the Lead first and then swap the necessary components to the Bass side after reading on here). I love that early Duane Allman tone and after doing some research and reading an interview from his tech, his reasons for using the Plexi Bass are similar to mine.

What do you all think? I don't think I need the 100w but I'm new to the Marshall world! So, any suggestions would greatly help.

Can I build the 45 and mod it somehow to be little tighter?
Will using an overdrive pedal clear it up (something transparent)?
What are the apparent electrical/physical differences between the Reissues and the Metro kits (to my understanding, the Metros are superior)?

Please feel free to just link me to other threads if these questions have already been answered somewhere! I've been surfing the forum for answers but there is a lot of info!

Here's a link to my youtube page to give you a feel for my style. Check out "Chicago." Its the closest to my electric style.

http://www.youtube.com/daveowens

Thanks you all! I'm excited to dig into this!

[Roe]

try changing the amp settings.- also try:
- decrease v1 cathode cap to 50uf or less
- decrease pi coupling caps to .047uf or even .022 or try decreasing the bias splitter resistors to 150k or 100k
- increase pi filtering to 32uf and mains to 48uf

[Jazzydave]

Right, like I said, I'm new to Marshalls so those are my "typical" amp settings for most Fender/Peavey type tube amps I've had. I know that Marshalls are a different beast. Next time I mess with that one I'll play with the eq a little more.

Thanks for tech info. I'll definitely take note of that!

[neikeel]

If you want a tight bottom end then build a 50watter, not a 45 unless you want to mod it.

In my experience if you want a good Marshall signature sound get a 50watter.

[Jazzydave]

I think I'm going to drive down there today with my guitar and check out the 50W Plexi reissue they have. I know its not exactly what I'll get with the kit but it won't be too far off.

How is the clean tone on them? That 45 blew me away. Are any of you running these through 2x12s or 4x10s?

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[PCollen]

Hey all! I'm new to the board and am going to take on a *first time* build here soon. I was a satellite tech in the Air Force so I'm hoping it'll go smoothly. Just follow directions, ask questions, and take it slow, right?

I was in Guitar Center the other day (I know, I know but...) and they had one of the Marshall JTM45 Reissues. I'd only played through the JCM series amps and many people have suggested the 45 to me so I thought I'd check it out. I grabbed a Gibby R0 (I play a slightly modded R7) and went at it. When I got that amp around 5-6 I couldn't stop. I was so impressed with the warmth and vibe of it that I ended up sitting there until someone finally broke my trance. THAT doesn't happen very often, especially with amps.

My only issue with it was how muddy it got in the low end. Now, keep in mind that I roll my highs back quite a bit. My usual amp setting are around B-5/6, M-3/4, T-4/5 and I roll my tone knob back slightly on my LP. That creamy yet articulate sound is what I go for and this amp seemed to nail it other than some mud there in the bottom.

After talking to another builder on here, he suggested the 45/100 and I even thought about going with the 50W Plexi bass (looks like I'd actually build the Lead first and then swap the necessary components to the Bass side after reading on here). I love that early Duane Allman tone and after doing some research and reading an interview from his tech, his reasons for using the Plexi Bass are similar to mine.

What do you all think? I don't think I need the 100w but I'm new to the Marshall world! So, any suggestions would greatly help.

Can I build the 45 and mod it somehow to be little tighter?
Will using an overdrive pedal clear it up (something transparent)?
What are the apparent electrical/physical differences between the Reissues and the Metro kits (to my understanding, the Metros are superior)?

Please feel free to just link me to other threads if these questions have already been answered somewhere! I've been surfing the forum for answers but there is a lot of info!

Here's a link to my youtube page to give you a feel for my style. Check out "Chicago." Its the closest to my electric style.

http://www.youtube.com/daveowens

Thanks you all! I'm excited to dig into this!

The JTM45 RI comes stock with 50uF filter caps on all DC power supply feeds, and has the stock 'mucho negative feedback' circuit with 27K on the 16 ohm tap. My suggestion is to change the V1 shared cathode resistor/capactior from 820/330uF to 820/25uF (or even 10uF). If that doesn't do it, then try changing
the V2a cathode resistor to 1K and/or the PI coupling caps from .1uF to .047uF (or .022uF ) would be my next suggestion.

[908ssp]

What cab were you playing through? Makes a huge difference. That said I really feel a Marshall needs to be played through a 4x12. That way you can run the bass on 1 and the mids on 10. Also the reissue is stupid bright unless you're playing it on 10 with an attenuator. You'll need a good attenuator in any event because all those amps are loud and the tone really doesn't come into its own unless the volume is at 8 or higher. I do think the 50 watt bass head [model 1986] is a wonderful head.

[PCollen]

What cab were you playing through? Makes a huge difference. That said I really feel a Marshall needs to be played through a 4x12. That way you can run the bass on 1 and the mids on 10. Also the reissue is stupid bright unless you're playing it on 10 with an attenuator. You'll need a good attenuator in any event because all those amps are loud and the tone really doesn't come into its own unless the volume is at 8 or higher. I do think the 50 watt bass head [model 1986] is a wonderful head.

re: "..stupid bright" ...you know you can improve on that by removing the bright cap on the Bright channel volume control.

[908ssp]

What cab were you playing through? Makes a huge difference. That said I really feel a Marshall needs to be played through a 4x12. That way you can run the bass on 1 and the mids on 10. Also the reissue is stupid bright unless you're playing it on 10 with an attenuator. You'll need a good attenuator in any event because all those amps are loud and the tone really doesn't come into its own unless the volume is at 8 or higher. I do think the 50 watt bass head [model 1986] is a wonderful head.

re: "..stupid bright" ...you know you can improve on that by removing the bright cap on the Bright channel volume control.

In the store when testing? I'd like to see that.

[Jazzydave]

That's true...I had a hard enough time finding a cord that wasn't connected to the side of a display!

Let's talk in terms of TONE vs. components - what are the major differences between the RIs and the Metros? I've been listening to the sound clips on here (great btw) but I don't have much to compare them to. I know some of you have been long term Marshall players!

Again, thanks!

[neikeel]

The Marshall 1987x RI is quite a gainy amp (typical 1972-76 'Metal Panel' spec) even though it looks like a smallbox plexi. The Metro can be made to that spec if you want but equally can be made to the 1986 spec (with a 100pF bright cap on bright volume) which is what you probably want to build from your description of tone influences.

I currently have three Marshalls (Model 1989 from '70, Model 1987 from '76 and Model 1959 from'68) I had a JTM45RI but built a metro and sold the original. I found that the RI was relatively tame for my taste and not really knowing why I did all the retro mods which made it sweeter and softer but not the rocker that I wanted (at the time I had a Fender Deville 2x12 for clean sounds). My metro is '66 spec and very much a blues amp IMO unless you goose it with a pedal, using a pair of Alnico Golds helps keep things lively tho'. I also have a Metro Model 1987, Metro JTM45/100, Metro 1959 ('67 spec) and Metro 1959 ('68 spec).

The Metros are all very good consistent high quality reliable amps, they may not have the Mojpo of a really good Vintage Marshall but those are truly hard to find (there are vintage duds as well as stars - just like vintage guitars).

Quality of trannies is generally better from Metro and Marstran than current offerings, although some people have found nice RIs that they can dial in a nice tone with, I have not been a huge fan of MM but some people are (they tend to be quite bright and harsh in some amps). Don't forget Chris M makes some nice trannies (slightly darker tone than Marstran and Metro).

If you trial a 1987x take a short patch code with you to bridge low bright input with high normal input and plug guitar into hi bright input that way you tame some of the offensive highs and give it a bit of girth too.

[Jazzydave]

Being that I'm not up to par on what everything does inside the amp quite yet, a description like that is great. I think that some people (and there's nothing wrong with it) seem to get wrapped up in the physical/electrical aspects vs. tone. I'm the type that will take a VOS Les Paul, buff it out to be shiny, change the pickups, tuners, etc if I like the tone - I'm not a collector nor do I worry that much about the resale value. Although, I won't buy a new one. Haha

So, what I'm getting at is that its all about tone to me. Like I said, I loved that 45 RI down at GC. My main concern is that I'm going to put all of this time and effort and not like it! I'm sure that's everyone's concern but after listening to many of the clips and vids, I don't think it'll be that big of an issue.

Thanks guys!

[ThunderOne]

Aaaah, Tone! The crux of the matter! I think that you'll find plenty of satisfaction with either. Just keep in mind that the 1987X is more of a hard rock amp vs the more bluesy nature of the JTM45. I have both and love them both equally. They're different, that's all. So I suggest you get one of each , for starters... I remember when I got my 1987X, the first thing I did was to remove the bright cap (a 4700pf lego block cap located at C5 on the pc board) but after about 18 months, I found the amp lacked some bite at higher settings, so I installed a 100pf cap on the volume 1 pot. Easy fix. It's now just great that way.

[PCollen]

What cab were you playing through? Makes a huge difference. That said I really feel a Marshall needs to be played through a 4x12. That way you can run the bass on 1 and the mids on 10. Also the reissue is stupid bright unless you're playing it on 10 with an attenuator. You'll need a good attenuator in any event because all those amps are loud and the tone really doesn't come into its own unless the volume is at 8 or higher. I do think the 50 watt bass head [model 1986] is a wonderful head.

re: "..stupid bright" ...you know you can improve on that by removing the bright cap on the Bright channel volume control.

In the store when testing? I'd like to see that.

The guy is DISCUSSING a JTM45 RI characteristic (i.e., 'stupid bright') he noted when demo-ing one in a store. Therefore, he could improve on the 'stupid bright' characteristic he experienced IN THE STORE with the RI , if he experiences the same characteristic when he gets the amp HOME or BUILT, by removing that 100pf bright cap on the Bright volume control (as many knowledgeable and experienced players of JTM45's do).

[908ssp]

Actually he wasn't only...

I think I'm going to drive down there today with my guitar and check out the 50W Plexi reissue they have. I know its not exactly what I'll get with the kit but it won't be too far off.
...........
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