Author Topic: Marshall amps summary for reference (Read 13040 times)

JamesHealey · « **Reply #45 on:** December 17, 2007, 09:33:59 AM »

im tossing up at the moment if I should get an older marshall next year or so.. I really like marshalls especially the 800s and SLPs

kluson · « **Reply #46 on:** December 18, 2007, 11:04:06 AM »

just one thing the JTM 45 is a 30 watt amp and not 45W. Actually testing mine I can get 27watts. I have played around with output transformers and found all kinds of results based on the different clones around today
It really is a sweet and very versatile amp.

Twinfan · « **Reply #47 on:** December 18, 2007, 11:24:09 AM »

They vary, depending on components and valves used. Around 35w is a fairly 'normal' output. My JTM45/100 (when it's built) will probably be around 65 watts not 100.

kluson · « **Reply #48 on:** December 18, 2007, 11:25:22 AM »

hi twin fan,
how are you measuring that output?
cheers

kluson · « **Reply #49 on:** December 18, 2007, 11:26:27 AM »

sorry also meant to ask what load?

Twinfan · « **Reply #50 on:** December 18, 2007, 11:51:27 AM »

I'm not measuring anything! Just going by what I've read in several places and what I've been told by people.

kluson · « **Reply #51 on:** December 18, 2007, 01:26:49 PM »

Hi Twin fan,
when you measure them you'll be very lucky indeed to get 35w, as I said I can get 27 from mine and 19 from my BFDR, Still loud though!
enjoy your JTM 45 they really are the business amps. Let us know how you get on with the build
Good luck

HTH AMPS · « **Reply #52 on:** December 18, 2007, 06:21:52 PM »

The fairly conservative output on the JTM45 is because of the OTs used. The primary Z used (8k) isn't really optimum for the best power transfer.

Marshall solved this later on when they changed to EL34s by choosing the right OT. The EL34 50w OTs had a primary Z of 3.5k which gives 'at least' 50w on the earlier heads with high B+ (a bit less on the early 70s 50w heads with lower B+)

:twisted:

kluson · « **Reply #53 on:** December 19, 2007, 08:43:05 AM »

Quote from: HEAVIER THAN HELL

The fairly conservative output on the JTM45 is because of the OTs used. The primary Z used (8k) isn't really optimum for the best power transfer.

Marshall solved this later on when they changed to EL34s by choosing the right OT. The EL34 50w OTs had a primary Z of 3.5k which gives 'at least' 50w on the earlier heads with high B+ (a bit less on the early 70s 50w heads with lower B+)

:twisted:

spot on,! but it does make for a great sound, and it's still loud enough to use with a Live drummer no problem.

Twinfan · « **Reply #54 on:** December 19, 2007, 08:52:54 AM »

That depends on your drummer ;)

JJretroTONEGOD · « **Reply #55 on:** December 19, 2007, 03:21:43 PM »

thanks for that, really interesting info there!

HTH AMPS · « **Reply #56 on:** December 19, 2007, 06:33:13 PM »

Quote from: kluson

Quote from: HEAVIER THAN HELL
The fairly conservative output on the JTM45 is because of the OTs used. The primary Z used (8k) isn't really optimum for the best power transfer.

Marshall solved this later on when they changed to EL34s by choosing the right OT. The EL34 50w OTs had a primary Z of 3.5k which gives 'at least' 50w on the earlier heads with high B+ (a bit less on the early 70s 50w heads with lower B+)

:twisted:

spot on,! but it does make for a great sound, and it's still loud enough to use with a Live drummer no problem.

Heh, we'll see how loud it is when I've got my JTM45/100 up and running.

I have no need for another amp but Twinfan got me GASing for a 45/100. I'd originally planned a dual OT version but it looks like I've secured a really good deal on some b-stock trannies (bent bell-end feet, missing screws and the 4ohm tap cut short). I can live with those 'issues' in order to get the trannies cheap.

:twisted:

Twinfan · « **Reply #57 on:** December 19, 2007, 06:37:47 PM »

Nice move matey! Mine should be completed in Feb sometime :D

You'll probably have yours done first? You'll have to let me know how it sounds in person.....

JamesHealey · « **Reply #58 on:** December 20, 2007, 10:35:31 AM »

informative.. nice to see this kinda stuff.

already knew it but still useful.

JamesHealey · « **Reply #59 on:** December 31, 2007, 10:28:24 AM »

what about the early 80s JCM800s with no master volume and pre-amp control.. and 4 inputs?

aka the JCM800 MkII's