Good evening - just got a JTM45

[Doc Holliday]

The TV is suppose to have more depth with it being a slightly bigger cabinet. The AX I think is the more popular.

The speakers are G12m 75hz reissues.

It sounds pretty good! Although the 75hz are the only models celestion make today. They stopped making the 55hz a while ago. Hence why you won't find them in a modern cab.

The cabs will be found for reasonable prices on eBay. I sold my 98 AX for about £250 recently.
I used the cash to buy 2x G12m speakers pre 1970. £ 160.00 each. Ouch!
But they're originals not reissues.

[JkGriffin]

Congrats...

One of my favourite amps of all times...

[sonofdavros]

Well, it seems I am on the verge of selling my excess gear. I would appreciate advice on which cab would be most suitable: 425A, 1960AHW, 1960AX or 1960TV.

[sonofdavros]

My only issue with this amp is the bottom end - it sounds a bit farty - not a nice sound at all. What about other owners?

[coldengray]

My only issue with this amp is the bottom end - it sounds a bit farty - not a nice sound at all. What about other owners?

I've found the best way to run a JTM45 is this:

Bass: 2 or less
Mids: 10
Treble: 8

I tried a bunch of different settings but found this to work the best. I use only the Normal input regardless if I'm using Humbuckers or Single Coils, volume on 6.

Keep in mind it was designed by Fender as a bass circuit so it's naturally going to be bassy. There is a very simple mod than can be done to reduce the bass, but it is easiest to just run the bass on 2 or less.

[Cousin Muely]

Little late but nice pickup man! Welcome to the forum.

[sonofdavros]

My only issue with this amp is the bottom end - it sounds a bit farty - not a nice sound at all. What about other owners?

I've found the best way to run a JTM45 is this:

Bass: 2 or less
Mids: 10
Treble: 8

I tried a bunch of different settings but found this to work the best. I use only the Normal input regardless if I'm using Humbuckers or Single Coils, volume on 6.

Keep in mind it was designed by Fender as a bass circuit so it's naturally going to be bassy. There is a very simple mod than can be done to reduce the bass, but it is easiest to just run the bass on 2 or less.

Thanks for the advice. I was running my EQs all very low, but I turned the Middle and Treble up quite a bit, and it's sounding a lot better. In my house, the bass channel sounds much nicer, but the acoustics in our rehearsal room are totally different, and absorb the high frequencies, so I have to use both channels in order to be heard.

[sonofdavros]

Oh, forgot to say I did get a new cab, following the sound advice on this forum.

[sonofdavros]

The bloke I bought my JTM45 from said the power valves were 2 x KT66. However, looking on the Marshall site, it says 2 x 5881. After Wiki-ing around, I'm a little confused. It seems to say the 5881 is also called the 6L6, but that is definitely different to the KT66.

Or is my 1991 model different from the modern ones?

[LiveFreeOrDie]

I have an AX, phenomenal!

[Anitoli]

The bloke I bought my JTM45 from said the power valves were 2 x KT66. However, looking on the Marshall site, it says 2 x 5881. After Wiki-ing around, I'm a little confused. It seems to say the 5881 is also called the 6L6, but that is definitely different to the KT66.

Or is my 1991 model different from the modern ones?

To my understanding the 5881/6l6gc are not interchangeble with KT66 without modification to the amp because the KT66 has a much different plate impedence which requires a different ouput x-former than a 6l6gc/5881.
The 5881's in circulation today are some type of Russian military tube used in military planes. Thay are similar enough to a 6l6gc that they will work but you will see a much better sound by using 6l6's. One that i like alot is the Tung-Sol 6l6gc-str.

[ClassicRock88]

The bloke I bought my JTM45 from said the power valves were 2 x KT66. However, looking on the Marshall site, it says 2 x 5881. After Wiki-ing around, I'm a little confused. It seems to say the 5881 is also called the 6L6, but that is definitely different to the KT66.

Or is my 1991 model different from the modern ones?

To my understanding the 5881/6l6gc are not interchangeble with KT66 without modification to the amp because the KT66 has a much different plate impedence which requires a different ouput x-former than a 6l6gc/5881.
The 5881's in circulation today are some type of Russian military tube used in military planes. Thay are similar enough to a 6l6gc that they will work but you will see a much better sound by using 6l6's. One that i like alot is the Tung-Sol 6l6gc-str.

Anitoli - I think that it has to do with heater current. I was looking around on TheTubeStore the other day and it said that they tested KT66's in a 6L6 based amp. The site said that the KT66's draw 1300ma of heater current vs 900ma for the 6L6 so you need to make sure that your power transformer can handle the extra load. Many can, but not all.

[mkstylee]

The bloke I bought my JTM45 from said the power valves were 2 x KT66. However, looking on the Marshall site, it says 2 x 5881. After Wiki-ing around, I'm a little confused. It seems to say the 5881 is also called the 6L6, but that is definitely different to the KT66.

Or is my 1991 model different from the modern ones?

Hi,
My JTM 45 is from 92 and running KT66's ,I was told mine had the 'TED b' mod to allow this
Look at a site called 'raw sewage' a jtm/bluesbreaker info site despite the name and look for the TED b' mod mine works fine on kt66's and sound great
Enjoy and welcome

[sonofdavros]

From what I've now heard, some of the early models were built based on the KT66.