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Original 1960s JTM45 vs. a 1990s re-issue JTM45
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Original 1960s JTM45 vs. a 1990s re-issue JTM45
Tele, SG, LP Jr, '76 Ibanez Artist & Tokai LS92 + FUZZ boxes into a '66 AB165 Bassman & 2X12 (55Hz Greenbacks) / '73 Orange OR120 & 2X12 (V30 & SwampThang) / Orange Thunderverb 50 & PPC212 / Marshall Vintage Modern 50 & 2X12 Genz Benz g-Flex / Laney Klipp / Laney AOR Pro Tube 100
"...it's a tree with a microphone" - Leslie WestTags: None
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
The main difference is higher value filter caps. There are some minor differences such as the values of the mixer resistors and such. I was surprised to learn that many 60's 45's used 100pf bright caps instead of 500pf. Some of these differences are not bad from a functional perspective, though. As Jeremy wrote not bad amps.
Some of the important bits are close to 66-67 JTM, such as the Drake transformers and the large amount of negative feedback.
The reissue uses 5881s instead of KT66s but this is easily changed. Back in the 90's people were pulling the 5881s and putting in KT66s. The Sovtek "5881" during the 90s is actually more like a 6L6GC than a 50's 5881. Today's current production reissues of real 5881s might be interesting because the earliest 45's used real 5881s before they switched to kT66s.
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
Originally posted by jeremy View Posti dont remember details but there are quite a few differences, not bad amps thoughTele, SG, LP Jr, '76 Ibanez Artist & Tokai LS92 + FUZZ boxes into a '66 AB165 Bassman & 2X12 (55Hz Greenbacks) / '73 Orange OR120 & 2X12 (V30 & SwampThang) / Orange Thunderverb 50 & PPC212 / Marshall Vintage Modern 50 & 2X12 Genz Benz g-Flex / Laney Klipp / Laney AOR Pro Tube 100
"...it's a tree with a microphone" - Leslie West
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
Originally posted by Lake Placid Blues View PostThe main difference is higher value filter caps.
There are some minor differences such as the values of the mixer resistors and such.
I was surprised to learn that many 60's 45's used 100pf bright caps instead of 500pf.
Some of these differences are not bad from a functional perspective, though. As Jeremy wrote not bad amps.
Some of the important bits are close to 66-67 JTM, such as the Drake transformers and the large amount of negative feedback.
The reissue uses 5881s instead of KT66s but this is easily changed.
Back in the 90's people were pulling the 5881s and putting in KT66s.
The Sovtek "5881" during the 90s is actually more like a 6L6GC than a 50's 5881.
Today's current production reissues of real 5881s might be interesting because the earliest 45's used real 5881s before they switched to kT66s.
How will a 100pf bright caps differ from a 500pf then ?
According to you, how might a 90's RI differ in tone and feel to the real deal 1960's JTM45 ?Tele, SG, LP Jr, '76 Ibanez Artist & Tokai LS92 + FUZZ boxes into a '66 AB165 Bassman & 2X12 (55Hz Greenbacks) / '73 Orange OR120 & 2X12 (V30 & SwampThang) / Orange Thunderverb 50 & PPC212 / Marshall Vintage Modern 50 & 2X12 Genz Benz g-Flex / Laney Klipp / Laney AOR Pro Tube 100
"...it's a tree with a microphone" - Leslie West
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
There are a few vids about of comparisons. The new one have a few other changes that make them not sound like the originals if you are interested in vintage accuracy.
There was a RI just recently I think where they got things like transformers and chokes made to original spec - this version sounded much closer, especially paired with an accurate speaker as well. Of course the cost was huge too.
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
Originally posted by SirJackdeFuzz View PostIn laymen's terms, what would higher filter caps do to the tone of those very early JTM45s?
How will a 100pf bright caps differ from a 500pf then ?
According to you, how might a 90's RI differ in tone and feel to the real deal 1960's JTM45 ?
A 100 pf makes the volume taper and the gain sensitivity more bassman and less plexi. 500 pf is the correct value according to Ken Bran, but apparently the 100 pf cap was also used. The reissue uses 480 pf because it is more common today.
The use of higher filtering in an off the shelf production line amp makes sense because the affect on the sound and feel is minimal but avoids possible problems of hums ghosting and so forth.
One the the unexpected things about my JTM45 experience is the importance of the rectifier. You can completely change the personality of the amp by rolling in different rectifier tubes or even using a solid state plug in rectifier. The rectifier can override all the above subtleties of tone and feel and differences between an original and a reissue. A rectifier that supplies a lower voltage and more dynamic current supply will change the headroom of the amp and also the amount of sag when the amp is run loud. 5881s will have less head room than KT66s and a different bias point for the sound you want. Obviously, different rectifiers affect the bias as well.
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
Originally posted by AlexR View PostThere are a few vids about of comparisons. The new one have a few other changes that make them not sound like the originals if you are interested in vintage accuracy.
There was a RI just recently I think where they got things like transformers and chokes made to original spec - this version sounded much closer, especially paired with an accurate speaker as well. Of course the cost was huge too.
Can a GOOD amp tech do the necessary changes (exlc. the transformers off course) if asked to do so ?Tele, SG, LP Jr, '76 Ibanez Artist & Tokai LS92 + FUZZ boxes into a '66 AB165 Bassman & 2X12 (55Hz Greenbacks) / '73 Orange OR120 & 2X12 (V30 & SwampThang) / Orange Thunderverb 50 & PPC212 / Marshall Vintage Modern 50 & 2X12 Genz Benz g-Flex / Laney Klipp / Laney AOR Pro Tube 100
"...it's a tree with a microphone" - Leslie West
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
Originally posted by Lake Placid Blues View PostFiltering affects the feel of the amp, more than it does the sound. I have my JTM45 with original filter values and it is not spongy or flubby at all. I am using a 5AR4 rectifier.
A 100 pf makes the volume taper and the gain sensitivity more bassman and less plexi. 500 pf is the correct value according to Ken Bran, but apparently the 100 pf cap was also used. The reissue uses 480 pf because it is more common today.
The use of higher filtering in an off the shelf production line amp makes sense because the affect on the sound and feel is minimal but avoids possible problems of hums ghosting and so forth.
One the the unexpected things about my JTM45 experience is the importance of the rectifier. You can completely change the personality of the amp by rolling in different rectifier tubes or even using a solid state plug in rectifier. The rectifier can override all the above subtleties of tone and feel and differences between an original and a reissue. A rectifier that supplies a lower voltage and more dynamic current supply will change the headroom of the amp and also the amount of sag when the amp is run loud. 5881s will have less head room than KT66s and a different bias point for the sound you want. Obviously, different rectifiers affect the bias as well.Tele, SG, LP Jr, '76 Ibanez Artist & Tokai LS92 + FUZZ boxes into a '66 AB165 Bassman & 2X12 (55Hz Greenbacks) / '73 Orange OR120 & 2X12 (V30 & SwampThang) / Orange Thunderverb 50 & PPC212 / Marshall Vintage Modern 50 & 2X12 Genz Benz g-Flex / Laney Klipp / Laney AOR Pro Tube 100
"...it's a tree with a microphone" - Leslie West
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
Yes and yes and... yesss.
I have one of those 90's JTM45 reissues (1996).
In 2003, I followed these instructions to get mine to original spec, but I also purchased a PTP kit.
These are the no-BS, real-deal, amp modding notes to make your amp a true mid-60s circuit JTM45...dig it:
http://raw-sewage.net/jtm45ri_mods.html
(note: my amp is no longer a JTM45, but a '68 plexi circuit)
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
Originally posted by LLL View PostYes and yes and... yesss.
I have one of those 90's JTM45 reissues (1996).
In 2003, I followed these instructions to get mine to original spec, but I also purchased a PTP kit.
These are the no-BS, real-deal, amp modding notes to make your amp a true mid-60s circuit JTM45...dig it:
http://raw-sewage.net/jtm45ri_mods.html
(note: my amp is no longer a JTM45, but a '68 plexi circuit)
Gonna look into it right now.Tele, SG, LP Jr, '76 Ibanez Artist & Tokai LS92 + FUZZ boxes into a '66 AB165 Bassman & 2X12 (55Hz Greenbacks) / '73 Orange OR120 & 2X12 (V30 & SwampThang) / Orange Thunderverb 50 & PPC212 / Marshall Vintage Modern 50 & 2X12 Genz Benz g-Flex / Laney Klipp / Laney AOR Pro Tube 100
"...it's a tree with a microphone" - Leslie West
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
Originally posted by LLL View PostBTW, I would recommend the new make "Sozo" capacitors over Mallory.Tele, SG, LP Jr, '76 Ibanez Artist & Tokai LS92 + FUZZ boxes into a '66 AB165 Bassman & 2X12 (55Hz Greenbacks) / '73 Orange OR120 & 2X12 (V30 & SwampThang) / Orange Thunderverb 50 & PPC212 / Marshall Vintage Modern 50 & 2X12 Genz Benz g-Flex / Laney Klipp / Laney AOR Pro Tube 100
"...it's a tree with a microphone" - Leslie West
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
Originally posted by SirJackdeFuzz View PostAny reason in particular for this option LLL ?
I think they're clearer-sounding... but not like Sprague Orange Drops.
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Re: Original 1960s JTM45 vs. a 1990s re-issue JTM45
Originally posted by LLL View PostI originally put Mallorys in during my JTM45 mod phase... when I modded again for '68 plexi (not a whole lot of changes) I replaced all Mallorys (except presence pot cap) with Sozo (new make).
I think they're clearer-sounding... but not like Sprague Orange Drops.Tele, SG, LP Jr, '76 Ibanez Artist & Tokai LS92 + FUZZ boxes into a '66 AB165 Bassman & 2X12 (55Hz Greenbacks) / '73 Orange OR120 & 2X12 (V30 & SwampThang) / Orange Thunderverb 50 & PPC212 / Marshall Vintage Modern 50 & 2X12 Genz Benz g-Flex / Laney Klipp / Laney AOR Pro Tube 100
"...it's a tree with a microphone" - Leslie West
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