Mark III+ C27 Cap Question

[soulchief]

Hi all,

I am attempting to do some III+ mods to my Blue Stripe Mark III and would love some explanation on the C27 cap for the R1 and R2 channels...

Main question: On the C27 Cap, is the "10pf" or the "20pf" brighter sounding for R1 and R2?
Which of the 2 Cap Values gives the more of a Fender Sparkle and vibe on R1/2?


I have read contradicting answers, saying the 10pf is brighter, and then saying the 20pf is brighter.. I have also read both of them being described as "Smoother".. "Smoother" to me means possibly darker? Which is actually sparklier?

I am hoping for a consensus for which of the 2 caps is actually "Brighter and Wider Fender Sounding"?


I'm clear on the C30 & C516 values and and how they affect but the C27 has me unsure...

Thanks in advance for anyone who can help clear this up for me.

 

[DC3 Gridlock]

Love to know this answer also since I am trying to tame the brightness of my new to me Mark III blue stripe.

I did change out the two outer EL34's in my Sumul-Class amp, and to my ears, this change did seem to add some Fender sparkle and tone to the amp.

I did read a Mesa bulletin recommending not to do this power tube change in the Mark III. Though I believe that the bulletin was related to running the amp in Class A mode, which I don't plan to do.

 

[soulchief]

I ended up talking the Mike B about it..

He said 10pf is common for the standard (Fender) clarity and has a resistor next to it running parallel. The standard Fender Sparkle comes from a 3.3m resistor in parallel also common to all the Marks BUT he said on the Blue Stripe (and Green) this C27 10pf cap is in parallel with a "2.2m" resistor which is giving the clean channels less sparkle and bolder (more aggressive) tone.

On the Cap value, the 20pf (vs 10pf) would add more grit and hair staying less clean I assume.
He said it was more about that resistor than the cap on the Blue..

Fender and Most 60/100Mark III have C27 10pf parallel with 3.3m resistor.
Blue and Green have 10pf parallel with 2.2m resistor

SimulClass's have the 20pf C27 from what I understand..


DC3, if you are speaking of the brightness on the "lead' channel then you might be a C30 candidate..
It's empty on the Blue Stripe being very bright.
You can add a 500pf or 1000pf 1 KV cap in the empty C30 slot to tame the Lead brightness.
On a Red (which is loved), it has a 500pf 1KV cap there for more sweetness.
On a III+mod or C+, it has a 1000pf (.001uf) 1KV cap there for the most sweetness and growl.

Blue is very bright and some people who had the 1000pf installed said it lost its stage cut or to dark. There are also tons of people who love the 1000pf. I like some stage cut so I went for a 500pf a-la-Red for a happy medium..

Mike B also said running a switch to toggle the different caps is NOT a good idea (which I have seen people ponder) beacause of B+ voltage.
Just pick one and fine tune with the Graphic EQ.

 

[Joi737]

Hi gents,any advice or experience regarding the c27 mod? should i install 20 pf and 3.3 m resistor?i own a simulclass blues stripe and i am not sure.thanks a lot