Fender vs. Marshall - just how diff will they sound ?

[Gr8Scott]

Re: Fender vs. Marshall - just how diff will they sound ?

WOW . . . that close !

Thanx man !




How would your clone differ from a 'regular' JTM45 then ?
Please do tell . . . just what was done to your amp ? Hot Rodded ?

Thanks

James

To find out all the specifics, you should contact Scott_F yourself and ask him. I do know it has Heyboer transformers and it also has a switch to alter the tone stack slightly for a touch more midrange. Definitely a killer amp.

 

[SlowGroove]

Re: Fender vs. Marshall - just how diff will they sound ?

just fwiw.... Both these amps used carbon composition resistors which change value depending upon the temperature in which they are exposed to. (take a reading for a true CC resistor and then heat it up and see how far it drifts off, you might be surprised..)

5F6-A's chassis has the tubes facing downward, the JTM45 has the tubes facing towards the top. Why does this matter?? Heat rises! Marshall's usually have tubes facing up, Fender's usually face down.

Just one small thing to think about.

Jeff

And that does make you think !



James

 

[Gr8Scott]

Re: Fender vs. Marshall - just how diff will they sound ?

I checked the published schematics of the Fender 5F6-A vs those of the JTM45. Although Bran seems to remember there being a difference in coupling cap values, the schems show them to be the same. Additionally there's no difference in the tone stacks between them either.

There are crucial changes between the JTM45/Tweed and the later plexis with solid state rectifiers though. The tone stack on the SS rectified Marshalls uses a 33k slope resistor and 500pf treble cap, instead of the 56k and 270pf treble cap as on the 45/Tweeds. The coupling caps in the power amps are different too. These coupling cap changes will make the SS rectified plexis considerably tighter. The SS plexis also took the negative feedback from the 8 ohm tap (with EL34) and used a different NFB resistor. The combination of differing coupling caps, power supply (higher voltages and much higher filtering) and rectification methods, tone stack, and NFB changes made the SS rectified plexis different. A tighter, brighter, but dirtier, sound.

The SS rectified amps for bass such as the 1992 (100 watt) and 1986 50 watt as used by Duane Allman kept most of the JTM45 specs in these small details, because of the bigger bottom end. These models are interesting because they combine the SS rectifier and power supply, and EL34's, with the JTM45 type specs.

Some Marshall JTM45's also used 470k mix resistors (as does the re-issue) and higher value bright caps on the treble channal compared to the Tweed.

I've always thought the tweed bassman amps had a very different tone stack, but sure enough it's the same as the JTM-45 (sorry I doubted you, but I had to check because I was pretty certain they were different). I'm beginning to wonder just how different they will sound through the same speakers now sure enough...

 

[SlowGroove]

Re: Fender vs. Marshall - just how diff will they sound ?

I've always thought the tweed bassman amps had a very different tone stack, but sure enough it's the same as the JTM-45 (sorry I doubted you, but I had to check because I was pretty certain they were different). I'm beginning to wonder just how different they will sound through the same speakers now sure enough...

Same here mate - same here !



James



PS Post # 3000.

 

[Lake Placid Blues]

Re: Fender vs. Marshall - just how diff will they sound ?

I had to look it up too.

One thing about 60's Marshalls was there could be variation among amps of the same model and vintage. The componant values and brand was in a state flux depending upon supply and Bran's evolving concepts of the design details. Minor changes in design, componant values, and construction methods could occur at anytime back then.

We still have the differences in NFB described by Bran and Grindrod that should cause a different sound to take into account.

Although Grindrod doesn't seem to think the transformers should make a huge difference, the Fender and the Marshall versions of the circuit use very different transformers.

I would like to point out that neither Fender's nor Marshall's PCB re-issues of these amps are accurate in details to most of their orginals. Scott's take, or Metro's, or Victoria's, or some other's, may be more accurate-or not. Fender's standard re-issue version varies from their original quite a bit in the power supply. Marshall's re-issue is more true, but it still runs considerably more filtering than most originals, probably to prevent ghosting.