I
iismet
Guest
Re: JTM45 still practical ?
How so - my understanding is he copied the 5F6-A circuit damn near to the letter.
How so - my understanding is he copied the 5F6-A circuit damn near to the letter.
JTM45 still practical ?
- Thread starter SirJackdeFuzz
- Start date
JeffB
Let it B
Re: JTM45 still practical ?
According to marshall literature of the time, Ken Bran, and Doyles book, this is not the case Christian.
According to marshall literature of the time, Ken Bran, and Doyles book, this is not the case Christian.
Soulcrusher_X
New member
Re: JTM45 still practical ?
Excuse the newbish question, but what are the tonal differences between the JTM45 and the Plexi 50s?
Excuse the newbish question, but what are the tonal differences between the JTM45 and the Plexi 50s?
JeffB
Let it B
Re: JTM45 still practical ?
Solid state rectifier and EL34s are the biggest changes. Much tighter and mid focused amp. As the years went by the amps got gainier, brighter, tighter, and louder. The speaker cabs changed pretty drastically too..from 20 and 25w greenbacks..to the 30w bass versions (now what we would call the h30) which alot of guitar players used BITD.
Of course they varied more than guitars, and you can find some real screamers in those early heads,.and some comparatively mellower metal faces from the early 70s. But generally later amps are crunchier and brighter.
Solid state rectifier and EL34s are the biggest changes. Much tighter and mid focused amp. As the years went by the amps got gainier, brighter, tighter, and louder. The speaker cabs changed pretty drastically too..from 20 and 25w greenbacks..to the 30w bass versions (now what we would call the h30) which alot of guitar players used BITD.
Of course they varied more than guitars, and you can find some real screamers in those early heads,.and some comparatively mellower metal faces from the early 70s. But generally later amps are crunchier and brighter.
the guy who invented fire
Fuzzy. Guitars
Re: JTM45 still practical ?
The output trannys they used were only about 30 watts a pop however they often changed parts based on what they could get their hands on so they were all over the map in various ways.
The output trannys they used were only about 30 watts a pop however they often changed parts based on what they could get their hands on so they were all over the map in various ways.
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the guy who invented fire
Fuzzy. Guitars
Re: JTM45 still practical ?
I'll have to go back to the Marshall Book but thats fine...
No need in going nuts over wattage anyway...they all varied a lot.
I'll have to go back to the Marshall Book but thats fine...
No need in going nuts over wattage anyway...they all varied a lot.
the guy who invented fire
Fuzzy. Guitars
Re: JTM45 still practical ?
Which Plexi 50 is the question...JTM-50 is a JTM-45 but with EL34's...then there are the 1986 Bass amps which are pretty much the same as the JTM-50 but with a SS rectifier then the 1987 lead amps which have different preamp values and a completely different sound and feel...
Marshall amps changed SO much between 1962 and 1972 it's not even funny...
Which Plexi 50 is the question...JTM-50 is a JTM-45 but with EL34's...then there are the 1986 Bass amps which are pretty much the same as the JTM-50 but with a SS rectifier then the 1987 lead amps which have different preamp values and a completely different sound and feel...
Marshall amps changed SO much between 1962 and 1972 it's not even funny...
everdrone
New member
Re: JTM45 still practical ?
my experience is 15 watt combos are enough to play with drums, but a lil more wattage is nice for a loud solo or competition with another stubborn
guitarist... but ya like 30 watts and an attenuator is nice:
http://www.humbuckermusic.com/guitar-amp-attenuator.html
my experience is 15 watt combos are enough to play with drums, but a lil more wattage is nice for a loud solo or competition with another stubborn
guitarist... but ya like 30 watts and an attenuator is nice:http://www.humbuckermusic.com/guitar-amp-attenuator.html
Soulcrusher_X
New member
Re: JTM45 still practical ?
Thanks for the small recap. I've never really played much with a NMV ANYTHING, Marshall or otherwise. Ive also mostly played higher gain amps. I recently have been really digging the lower gain channel on my JSX. I know it's still a MV amp, and the gain is probably still about as much as an 800, but Ive been having a blast without all the saturation and compression of high gain.
After my current amp project, I'm thinking doing something more 'classic'. I just dont know what path on the Marshall road to build from. I just know that it's going to be 50w or less.
Thanks for the small recap. I've never really played much with a NMV ANYTHING, Marshall or otherwise. Ive also mostly played higher gain amps. I recently have been really digging the lower gain channel on my JSX. I know it's still a MV amp, and the gain is probably still about as much as an 800, but Ive been having a blast without all the saturation and compression of high gain.
After my current amp project, I'm thinking doing something more 'classic'. I just dont know what path on the Marshall road to build from. I just know that it's going to be 50w or less.
the guy who invented fire
Fuzzy. Guitars
Re: JTM45 still practical ?
As a general rule as Marshall amps went forward from 1962 they got more aggressive overall.
The JTM-45 is big, warm, round and due to the tube rectifier has a nice soft compression to it, the lows are big, the highs are soft and the mids are slightly pulled back.
The JTM-50 is sort of the same overall vibe and sound but it's a little stronger, has more aggression in the midrange and has a bit of bark that most 45's don't have.
After they they started the 1986/1992 Bass amps and 1987/1959 Lead amps...the preamps in the Bass amps were more or less the same as the earlier JTM-45/50 amps but the lead amps got a push in the upper mids and a trim of the low end.
Keep in mind that they gain was always creeping up in these amps as the years went on and also very note worthy...Marshall was growing as a rapid rate in the early days so they were always running out of parts and using whatever they could get they was as close as they could get. This lead to old Marshall amps being all over the map in terms of overall tone and even thought there are some fairly consistent tonal aspects of the old Marshalls you can get 2 1987 amps made on the same day they might sound rather different.
As a general rule as Marshall amps went forward from 1962 they got more aggressive overall.
The JTM-45 is big, warm, round and due to the tube rectifier has a nice soft compression to it, the lows are big, the highs are soft and the mids are slightly pulled back.
The JTM-50 is sort of the same overall vibe and sound but it's a little stronger, has more aggression in the midrange and has a bit of bark that most 45's don't have.
After they they started the 1986/1992 Bass amps and 1987/1959 Lead amps...the preamps in the Bass amps were more or less the same as the earlier JTM-45/50 amps but the lead amps got a push in the upper mids and a trim of the low end.
Keep in mind that they gain was always creeping up in these amps as the years went on and also very note worthy...Marshall was growing as a rapid rate in the early days so they were always running out of parts and using whatever they could get they was as close as they could get. This lead to old Marshall amps being all over the map in terms of overall tone and even thought there are some fairly consistent tonal aspects of the old Marshalls you can get 2 1987 amps made on the same day they might sound rather different.
Soulcrusher_X
New member
Re: JTM45 still practical ?
The 12au7 has only 20% the amount of voltage gain as the ax7, but delivers almost 10x the amount of current, which will drive the power tubes a bit harder. The TC of the au7 is also a bit lower, so it's easier to pass the signal from the last gain stage to the power tubes. The plate resistance of the au7 is almost 1/10th that of the ax7 and current draw is quite a bit higher, so the bias voltage may be a bit lower at the power tubes. In some cases, the voltage drop can be severe.
The 12au7 has only 20% the amount of voltage gain as the ax7, but delivers almost 10x the amount of current, which will drive the power tubes a bit harder. The TC of the au7 is also a bit lower, so it's easier to pass the signal from the last gain stage to the power tubes. The plate resistance of the au7 is almost 1/10th that of the ax7 and current draw is quite a bit higher, so the bias voltage may be a bit lower at the power tubes. In some cases, the voltage drop can be severe.
STRATDELUXER97
Stratoblaster Tone Meister
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..
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..
STRATDELUXER97
Stratoblaster Tone Meister
Re: JTM45 still practical ?
Forgot to mention that the JTM 45 had a shared cathode...Later they went to split cathode setup..Some slight differences in the cathode cap value 250 mfd or 330 mfd...
Forgot to mention that the JTM 45 had a shared cathode...Later they went to split cathode setup..Some slight differences in the cathode cap value 250 mfd or 330 mfd...
Soulcrusher_X
New member
Re: JTM45 still practical ?
Excellent. Thanks for the history lesson. From what it sounds like.....I just need to build one of each.
Excellent. Thanks for the history lesson. From what it sounds like.....I just need to build one of each.
Soulcrusher_X
New member
Re: JTM45 still practical ?
Man, I really need to try and play one. How close are the reissues? I keep seeing a 1987x in a shop near me, but never thought about trying it out. I think I need some vintage tones.
Man, I really need to try and play one. How close are the reissues? I keep seeing a 1987x in a shop near me, but never thought about trying it out. I think I need some vintage tones.
the guy who invented fire
Fuzzy. Guitars
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...
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...
STRATDELUXER97
Stratoblaster Tone Meister
Re: JTM45 still practical ?
If it doesn't need filter caps and is in decent tonal condition...Worth listening to...I keep mine clean(Mine is almost tweed Fender clean) and I run pedals into it...Just a great sounding amp with lots of harmonic overtones and this kind of 3D like clean tone...I totally re-did my 73 from pcb over to HW..
MY Redone Board....Done back in 04 or so?
If it doesn't need filter caps and is in decent tonal condition...Worth listening to...I keep mine clean(Mine is almost tweed Fender clean) and I run pedals into it...Just a great sounding amp with lots of harmonic overtones and this kind of 3D like clean tone...I totally re-did my 73 from pcb over to HW..
MY Redone Board....Done back in 04 or so?
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STRATDELUXER97
Stratoblaster Tone Meister
Re: JTM45 still practical ?
I've not worked on any Marshalls after the JCM 800 series and I prefer the 800 series and earlier Marshalls,though I did play years ago through a JCM 2000 and I Liked it's clean tones....I feel the less crap that is inside an amp,the better the tone...One of the things I hate about the mesa stuff,is all the switches,push/pull buttons....Just too much crap to deal with! ;o)
I've not worked on any Marshalls after the JCM 800 series and I prefer the 800 series and earlier Marshalls,though I did play years ago through a JCM 2000 and I Liked it's clean tones....I feel the less crap that is inside an amp,the better the tone...One of the things I hate about the mesa stuff,is all the switches,push/pull buttons....Just too much crap to deal with! ;o)
SirJackdeFuzz
New member
Re: JTM45 still practical ?
The way you put it, makes me believe the JTM45 is the perfect amp, tone wise !
I like that !
The way you put it, makes me believe the JTM45 is the perfect amp, tone wise !
I like that !
