My best Marshall ever!

[neikeel]

that's pretty much a stock 67/8 amp in terms of basic circuit

No it's not!

- it is a Superbass with a 500pF cap in tone stack and added split cathode on V1.

[Carbia]

Think about tolerances.

Old parts had high tolerances. A 22nF Mustard can measure from 18nF to 25nF. Resistors have tolerance too. I've been measuring some resistors on my Marshall, and, for instance, 100k can measure from 97 to 105k. Small differences, but if you combine a lot of capacitors and resistors...

Transformers are under that tolerances too. You can take several vintage Marshalls, all of them set to the same wall voltage and probably all of them measure different heater's voltage (just to say a voltage that it is not dependent of resistors or capacitors.

[pleximaster]

Combination of the "right" parts are one ingredient.

A professor from the technical department with a huge hifi interest once tried to explain to me how older resistors and capacitors influence the sound in another way then modern equivalents with the same value when they are cold and out of the amp.

I did´t get it... The thing I got however was that the actual value when mounted in a warm amp various more in the old components under load and they are actually doing so almost instantly depending on the currents they are fed with. Sort of like the sag thing we address transformers, the other old components adjust there nominal value depending on the load compared to modern resistors and capacitors which are "better" to hold there supposed value. This would the reason a lot of older amps sound more organic and musical. The old components "adjust" to the currents and there for don´t sound hard and "digital".

That was of topic a bit ...
Here is an extended version that Johan did with the amp!



It even does a bit of Slash tones...

plexi

[JiMB]

Really great sound there!
All kinds of tones in it just from working the guitar.

[SQUAREHEAD]

Wow! That sounds absolutely massive, even through YouTube you can feel the Compression/sound pressure… What's the main change that has been done to this amp to get there?

[SQUAREHEAD]

Oh, 500 pF cap In tone stack… I should try just reading the thread… LOL

[Dirty Murphy]

@Pleximaster: Sounds amazing! BTW on your layout the slope resistor is 560, should this not be 56k ?

[pleximaster]

The slope is an odd 560 ohm!

I am in the process of doing a replica of this amp for name guitarist. We are doing this with mainly old parts. So far I would say influence on tone comes from the 1.transformers including the choke, 2. the tonestack and other design, 3.capacitor and resistor Mustard piher), 4. the feedback circuitry, 5. tubes

Still testing, very fun project!

plexi

[pleximaster]

Just made a quick sound test of the replica amp that I am working on. I is just an iphone recording a standard les paul in a hotplate -12 db and a set of test tubes (all tubes pulled out of an YJM 100) in case I have messed up some where. In this clip its a 10 h choke.

plexi

[OdgeUK]

Just made a quick sound test of the replica amp that I am working on. I is just an iphone recording a standard les paul in a hotplate -12 db and a set of test tubes (all tubes pulled out of an YJM 100) in case I have messed up some where. In this clip its a 10 h choke.

plexi

Is this finished? Which Transformers did you use? Did you source originals?

[gibsonclassic2001]

I think Johan is selling most of his amps.
He had some serious health issues this summer.

[neikeel]

I think Johan is selling most of his amps.
He had some serious health issues this summer.

Johan is the guitarst who does the demos, the amps belong to Pleximaster. 'Pleximaster' has had some serious health issues and has made a pretty remarkable recovery so far (I do not think that he would mind me telling you that) and is now hard back at work for his university. To my knowledge he is not selling up, in fact he is in the UK sniffing out an original offset - like a bloodhound! I have the pictures of it on my 'phone - not to be shared - yet, just in case!

[gibsonclassic2001]

Great news!

Plexi master must have had an amazing recovery.