JTM45 still practical ?

[SirJackdeFuzz]

Re: JTM45 still practical ?

Having worked on alot of those older Marshalls...Some of the changes I've seen from the JTM 45 series and into the metal panel Marshalls...

Changes in the tone stack values...250 pf .02 .02 and 56k slope resistor to 470 pf and above to .02 .02 33k slope...Bass models later were different..Some of the coupling cap values are .1 but more common were the .02 values..

Increased filter cap MFDs later to 50/50 from 32/32 etc..

Volume control Bright cap value changes on the later series made the amp brighter..

5881 over to EL34..

Rectifier to SS(As mentioned)

Like mentioned already....The Marshall sound evolved into being brighter,tighter,and more cutting and aggressive...

Christian is right in that I have seen 2 same year early Marshalls with different tone stack values and also the slope resistor values and where the feedback wire is connected on what leg of the speaker out jack... 47k vs 100k...This alone effects the gain of the amp also..

The JTM 45 lacks the .68 cap across V2's cathode on the preamp tube...Another reason that the later series that has/had this cap,also had quite a bit more gain because this cap sets the gain of V2...Not all JMP/Metal Panel Marshalls have this cap...I have a switch on my own 1987 50 watter that switches the .68 in and out and also switches in different cap values..Memory tells me it's V2,but I may be wrong and would have to see the schematic? ;o)

The combination of many small changes,really makes the JTM 45 and the later series Marshalls different animals..

So am i right in saying that if you build a JTM45 clone, you want to be as close to the 1st year production scematics as possible (as apose to current production layout) to get to the most desirable JTM45 tone ?

 

[jeremy]

Re: JTM45 still practical ?

depends on what you want out of the amp. id guess the first year is the closest to the 5f6a bassman

 

[JeffB]

Re: JTM45 still practical ?

The reissue 1987's are cool...I think they are more aggressive than most real Plexi panel amps I've ever played through but the basics of the tone is there...

Thats because the reissue 1987 is based on a 72 or 73 metalface No joke.


Marshall is all over the place on these reissue amps. Neither of the original reissues even made it far into production before bei g scrapped, redesigned on a different circuit, and redesignated X series. The 1959x got canned again immediately,had a redesign based on a very particular 1959 original, and became the SLP.

The 87x anf slp were redone again to add in the fx loop.

I had the original 87x. For my tastes it sounds better than the version with the loop (even with the loop switched out of the circuit). Just barks more like the real deal MFs. The newer versions sound more anemic,though it could be tubes I reckon.

 

[SirJackdeFuzz]

Re: JTM45 still practical ?

depends on what you want out of the amp. id guess the first year is the closest to the 5f6a bassman

With so many changes to the JTM45 in all of the years that is was(is) in producion, where would one find the-most-correct schematics, if you want to build one then ?

PS : did the schematics changed as Marshall made those changes over the years ?

 

[jeremy]

Re: JTM45 still practical ?

i think the schematic stayed about the same at least in the beginning. it was mostly a part/supply issue that caused them to be so different. when you cant get XXX you arent going to stop making amps so you use part XXY which is available

 

[SirJackdeFuzz]

Re: JTM45 still practical ?

i think the schematic stayed about the same at least in the beginning. it was mostly a part/supply issue that caused them to be so different. when you cant get XXX you arent going to stop making amps so you use part XXY which is available

Thanks Jeremy

 

[SG 61 Reissue]

Re: JTM45 still practical ?

Hi all, seems I'm responding to a older thread, but the issue is a new one to me. I discovered the easiest remedy was to incorporate a Marshall PB100 Power Break to the set up. This allows for some volume control while still getting that great overdriven tube sound! Also, volume control foot pedals are great for keeping that great sound, taking it down a bit and then punching it up during the parts when everyone is just going to town!

I also have discovered that foot pedal company Wampler Pedals makes just about the best line of pedals ever! I bought 2 recently - the Black 65 that pairs amazingly with my vintage 1967 Fender Showman 15, and the Plexi Deluxe. The Plexi Deluxe really is like having 3 pedals in one, and so you can set them to model a few different Marshall amps. In addition to my SG 61 Reissue (with the Classic 57 Pickup's that I love) I also play a Rickenbacker 360. Everything works perfectly together! the sweet spots pretty much work across the board.

Best of luck to everyone!

 

[BanditPanda]

Re: JTM45 still practical ?

Hi all, seems I'm responding to a older thread, but the issue is a new one to me. I discovered the easiest remedy was to incorporate a Marshall PB100 Power Break to the set up. This allows for some volume control while still getting that great overdriven tube sound! Also, volume control foot pedals are great for keeping that great sound, taking it down a bit and then punching it up during the parts when everyone is just going to town!

I also have discovered that foot pedal company Wampler Pedals makes just about the best line of pedals ever! I bought 2 recently - the Black 65 that pairs amazingly with my vintage 1967 Fender Showman 15, and the Plexi Deluxe. The Plexi Deluxe really is like having 3 pedals in one, and so you can set them to model a few different Marshall amps. In addition to my SG 61 Reissue (with the Classic 57 Pickup's that I love) I also play a Rickenbacker 360. Everything works perfectly together! the sweet spots pretty much work across the board.

Best of luck to everyone!

This is a necro thread to say the least but I didn't see anybody mention a PPIMV mod. That solves any volume issues without compromising tone. Or am I wrong ?

 

[Chickenwing]

Re: JTM45 still practical ?

This is a necro thread to say the least but I didn't see anybody mention a PPIMV mod. That solves any volume issues without compromising tone. Or am I wrong ?

PPIMV is still pre the power tubes, so if you are getting the tone by pushing the power tubes then It will change your sound. Pros and cons. Swings and roundabouts.
I have a JTM clone with a master volume. It works pretty good, but it isnt the same as having the power tubes wide open.
Everything in your signal chain affects your sound.

 

[LLL]

Re: JTM45 still practical ?

LOL at the original question...

 

[mxaniac]

Re: JTM45 still practical ?

Guys, i know there are many members here that love the allmighty JTM45 . . .


. . . but there is no master volume on that monster.


So, my question is : for how many people here, is the Marshall JTM45 still a practical amp ?
To get that sweet tone, you pretty much have to crank a 30watt KT66 to ten.
(...some would say the best sounding Marshall ever made !)

I do not gig . . . but i do jam with friends every now and again.

These days everyone is jumping on the 'lil low-power'ed amp band wagon.
Is there still a place for the very 1st Marshall model ?

Thanx.

I didn't go through all 6 pages but with Yellow Jacket tubes or attenuators can lower the volume and still push tubes. Additionally I have an old amp where the master volume was added after the fact however it does affect reverb and tremolo with how it was added.

 

[jeremy]

Re: JTM45 still practical ?

yellow jackets change the tone a lot, i had a set and let them go. they do lower the volume but the tone change wasnt something i liked. a good attenuator can help for sure but there is still a trade off, especially when you get into heavy attenuation. there is no magic. even speakers that change the flux to reduce volume effect the tone, although ive found its one of the better solutions for 1x12 amps but multi-speaker setups make that option less appealing

 

[Lake Placid Blues]

Re: JTM45 still practical ?

I have decided that my JTM45 sounds so good stock to not mod it at all. Yeah it can get pretty loud, but I have great sounding MV amps I can use.
I do have an 80 watt 12" speaker that sounds real good that is not very loud that I might build a Blusebreaker looking 1x12 cab for. Probably less than 94 dbs. That's like 6 dbs attenuation I could try that. But I don't sweat the JTM45 being loud because it's not my only amp option. It's not nearly as loud as a 100 watt plexi, but it is the closest sounding alternative to one.

 

[jeremy]

Re: JTM45 still practical ?

a little brown fender deluxe sounds surprisingly marshall like actually