Help needed to upgrade Capacitors in a Marshall DSL 40C

[salvarsan]

I tried an A/B test by recording a Tube Screamer pedal with different JRC4558 chips in, comparing Burr Brown, new 4558s and a 4558 I'd pulled from an early 80s Ibanez multi-effect - the one that people seem prepared to kill each other to obtain due to how the incredible 'mojo' of this little IC will bring you so much closer to SRV.

Yeh, bin thar dun thet 2.

The single opamp tweak that made an audible improvement was using one designed to handle a 600 ohm load, examples: the OPA2604 and 4559.

Since those weren't designed for low current consumption, battery life predictably decreased.

The other major tweak was to replace the two 2.0 uF bipolar electrolytics in the signal path with film caps.

By then, it no longer sounded like an SRV toob screemr -- it sounded better, and the vintage 4558 fetishists were outraged.

I concluded that the only way the vintage 4558 will bring you closer to SRV is if you hold onto one while peeing into 100 Watt Marshall head running at full power...

Nothing to add save that I really like seeing that quote.

[DrGonz78]

PS people like the C19 lift mod too.

I remember a friend coming over with a Marshall DSL 40C amp recently and he wanted me to do the C19 mod. Problem was when I looked at C19 on his board version it was not at all the right cap as other versions. Version A at least is C19 but his amp (version D) it was really C12 that was the one to lift. So how many people have plucked out the wrong C19 capacitor by reading about a C19 mod on a bunch of different websites?

[J M Fahey]

So how many people have plucked out the wrong C19 capacitor by reading about a C19 mod on a bunch of different websites?

Certainly a lot, Statistics 101 .
Funny thing is that most were probably happy with the "new/improved" sound
Because that's what they expected.

[Enzo]

You know, I have actually done that test. I have had customers listening, and wanting just a tweak, so when they can't see what I am doing, I pretend to adjust something just to see if they say "Yeah, I think that is a little better."

[J M Fahey]

Naughty naughty Little Enzo

[Chuck H]

You know, I have actually done that test. I have had customers listening, and wanting just a tweak, so when they can't see what I am doing, I pretend to adjust something just to see if they say "Yeah, I think that is a little better."

I've done that in a different industry. I was a "tinter" when I worked in various paint company stores for a while. I made custom colors for designers and matched colors for contractors. It was surprising how often someone could "see" something I didn't do just because they thought I'd implemented their bad idea

[Enzo]

yeah, sometimes I like to see who is thinking. I used to sell Hammond oil for $1.50 a tube. people came to my counter and asked for the oil. I'd tell them they were $1.50 each or three for $5. Amazingly, most people went for the "deal." I never actually sold them that way, I always told them it was a joke. But way too many fell for it.

[sohosteve]

Actually the amp has just come back from Marshall as there was a fault with it - horrible racket in triode mode and kept suddenly switching to total silence.
They put new valves and a new master board in - valves are branded 'Marshall' but no doubt made in China I'd guess
It is actually a great sounding amp for the money (£400 including upgraded speaker and cover) and I can get great tones out of it.
Not too far off my beloved JCM 800 100 Watt 2 x 12 combo that I just had to let go due to it's impossible size and weight and a recurring back injury.
I just wondered if I could squeeze a little more out of it tonally.

I know it's not an late sixties head with a period correct basket weave 4x12 but I ain't got the muscles or two grand to play around with.

The easiest components to change to improve tone are speakers and tubes. You've already got an upgraded speaker, but don't mention what tubes are fitted and how old they are.

[Chuck H]

Not too far off my beloved JCM 800 100 Watt 2 x 12 combo that I just had to let go due to it's impossible size and weight.

Right!?!

I did a 2x12 for a guy and I recently had it back on the bench. It's just 2 EL34's, not even 4, but I did use some big iron since it's his "clean" amp. Damn thing is a bruiser to lug around! And I have ten stairs up to my front door He's a big guy. My personal amp is a 15W 1x12

It's interesting that they chose to replace the tubes. If they were Chinese they were probably Shuguang, like the Ruby tubes. I bought two pair of Ruby EL34's at different times from different vendors and both pairs were unacceptably microphonic for combo amp use. Too bad too, because they sound good and perform well otherwise. I can't say that they're all like that but I'm two for two. One pair had been in that 2X12 and it was having problems with periodic volume drops and distortion after only a few uses. I replaced the Ruby's with JJ's and so far so good. I don't think the JJ's sound as good as the Ruby's but they don't go PFFDT! PFFDT! PFFDT! when you tap on them.

[sohosteve]

There is indeed a hell of a lot of piffle bandied about regarding what does what to up something's game.
I don't take any of it as gospel but I have experienced some great results on occasion as well as nothing whatsoever on others...

yeah, sometimes I like to see who is thinking. I used to sell Hammond oil for $1.50 a tube. people came to my counter and asked for the oil. I'd tell them they were $1.50 each or three for $5. Amazingly, most people went for the "deal." I never actually sold them that way, I always told them it was a joke. But way too many fell for it.

[cvjanick]

Answer to Original Question

Hi there
I have just bought a secondhand Marshall DSL 40c 40 Watt Valve Combo.
It has already had a speaker upgrade and I've performed the C19 mod to balance up the channel switching tones which has worked very well.
Now I'd like to dig a little further to see if I can further improve the tone by replacing some of the main capacitors with Sprague Orange Drop 715P capacitors as per this chap.

https://www.youtube.com/watch?v=WqMSlj4dnPc

I feel that I should mention that I am NOT a trained electronic engineer.
However I have safely carried out quite a few modifications on valve amps (replacing all major caps, tone stack mods, etc etc) working from graphic instructions.
So I know how to safely discharge the caps without electrocuting myself and use an electronic toolkit without stripping tracks or melting components.

What I require is some assistance with identifying the parts that I need to order from Watford Valves so that I can replace the components now in place

The twelve capacitors that I wish to replace are marked as follows


Six x 223J400
Four x 102J1000P
One x 102J630P
One x 333K400

Because I'm not trained I don't know how the equivalent parts are described!

This is where I'll be ordering them from as I'm based in London https://www.watfordvalves.com/products.asp?ID=3&man=72

Thanks

Orange drop codes start with the cap value and the last number before the J stands for the number of zeroes to add for the value in picofarads.

So for 223J400 it would be 22000pf or 0.022uf.

J=5% tolerance

Be careful to get the voltage ratings right also at least 500-630V I would think.

More info can be found here; https://www.amplifiedparts.com/tech_...apacitor_codes