JTM45s low end....

5F6-A

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My main amp for big gigs is my Pure Soul amp. Basically, a custom made JTM45 with NOS parts, Obsolete Electronics OT, a master volume and a parallel fx loop. It drives a couple of GEC KT66s... glorious. Cab is loaded with 2 x UK made Tayden True Brit speakers (Greenback clone).
The only thing I had to change was that I had to ask the builder to add a couple of minor tweaks to control the low end.

Is anybody else having problems with the low end of a JTM45 -esque amps? Thanks.

Pure Soul.PNG
 

goldtop0

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I've got a Ceriatone JTM45 and put Marstran trannies in it. It's an older one from 2006 with the white front panel.
No problem with the low end for me when playing through a 4x12 cab or 2x12.
What's happening with yours.........is it flabbing/farting out when pushing the speakers at high volume?
 

Geeze

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Marshall changed the caps filtering on their amps through the years to control / tighten the lows also went to SS on the rectifier. I have a JTM 45 clone [Satellite 'Cuda with KT66's] that has switchable rectification and not being a fan of sag I never take it off SS.

I keep trying to talk my amp guy into building a 45/100 with a bit more filtering and a switchable rectification. He's being resistant as I haven't found gear to tempt him with... Yet.

Russ
 

JohnnyN

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All JTM45s have loads of bass on tap. I run mine through a Marshall 1936 cab with 2 Greenbacks. I only use the bright channel and at high volume I most often set the bass around 10 o'clock.

My JTM45 RI is from 1991 and came with 2 x 50+50 caps, and Sovtek 5881 tubes. So the stock JTM45 RI is very well filtered, and the 5881s are not as bassy as 6L6 or KT66 tubes.

I replaced the caps to 32+32 for the Output/mains and 16+16 for the preamp, as they was on the JTM45s of the 1960s. I also installed swamp resistors and a pair of Gold Lion KT66.
More low end with KT66s, but seems to be fairly tight compared to (TAD short glass) 6L6 tubes, despite the modified lower filtering.

I don't feel I have a problem with the low end. What's your problem?
 

sonar

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It's not lack of, but focus for me with bass response on early JTM45 flavored amps. Even on the bigger EL34 quartet "100" watters I preferred to sacrifice some gain and go with a Super Bass circuit.

While not for everyone, the AB165 tightens things up... cheaper too. The downside with '165's for some is the tonestack.
 

The_Nuge

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Hi!
I find the bottom end a bit flubby on mine - it works very well for blues and classic rock with full chords, but less so for stuff with power chords or riffs in the low end of the neck. A SS rectified plexi-style amp is much tighter.
TAD sell a SS rectifier adapter that apparently makes the bottom end much tighter - for 20$ maybe worth a try?
 

Bogmonster

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The low end on the JTM45 is a bit spongy. I have a reissue from 2006 and I've done no mods to it. It sounds glorious!! But I always use the high treble channel and run the bass a 2, mids full and treble at 8. Presence usually at 5-6. Volume between 5 and 7. Sounds thick and creamy. I think that's the sounds these are known for. Not a high gain monster and that loose low end sounds great for blues and some classic rock.

I see guys jumping the channel on these and I never understood it myself. It just gives too much bass for me.

Love these amps!
 




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