Screened cable for rewiring valve amp

[Barbieboy]

Hello,
I wish to upgrade the signal cable inside my Yaquin MC-10L tube amp. Contacted Chord Co who said they don't supply cable off the reel, but recommended:

"silver-plated cable with PTFE insulation and ideally a two layer foil and braid shield"

Any cable suggestions welcome, want this to make a worthwhile sonic improvement 🙂

Thanks

 

[SY]

That's a nice recommendation if you like risking triboelectric noise.

What is the deficiency in the wire that's in there already? Is this wire already contained within a grounded metal chassis?

 

[Barbieboy]

Hello and thanks for your message,

Here is a pic of the input wire (Black 2 core) on the right going to the preamp board and the yellow arrows pointing where it changes to 3 core when feeds the EL34s

 

[SY]

But how have you determined that the wire is limiting the performance and in what way is it causing problems? If you don't have a clear idea of what you're trying to fix, it's unlikely that throwing random solutions (especially recommendations by salesmen) at the problem will solve it. 😀

If you want to make sonic improvements to the amp, it's best to figure out what the deficiencies are, then attack the root causes- usually design, layout, and grounding issues for Chinese amps. Wire is generally pretty far down the list.

 

[Barbieboy]

I've changed the amp's caps to wonderful effect, little in outlay and catapults the amp into a different league. Rolled the valves too which made a subtle but nice improvement. Tried a few different interconnects and this made me think the internal signal wire maybe sonically crap ?

 

[SY]

Post a schematic and then let's talk. 😀 If changing caps made a huge difference, that suggests that there are some serious design flaws.

 

[Barbieboy]

Ok thanks, interesting 🙂 Will try and get a schematic. there is a group here for the amp:

http://www.diyaudio.com/forums/tubes-valves/110483-yaqin-mc10l-23.html#post3348921

 

[Barbieboy]

Also plan to bypass the input selector as don't need it and replace the vol pot with a stepped one

 

[Eli Duttman]

Here is a pic of the input wire (Black 2 core) on the right going to the preamp board and the yellow arrows pointing where it changes to 3 core when feeds the EL34s

Connecting a shield (screen) at only 1 end is correct technique. The idea is to dump noise into the chassis. The 2 conductors inside the cable carry the signal.

Discriminate between signal ground (earth) and chassis ground.

 

[Barbieboy]

Thanks Eli D 🙂

The schematic:

 

[SY]

See my comments in the other thread on this. The heater to cathode potentials are way too high (and unfiltered); you're likely to be injecting mains and diode switching noise via the heater-cathode capacitance. As well, the reliability is suspect. The phase splitter has bad balance and the input stage is compromised for linearity. Pretty chrome, though.

The input wiring is pretty much a non-issue in comparison with these serious problems. I would start with the heaters- you'll want common-mode filtering and they need to be referenced to a DC potential, perhaps 70V or so, well bypassed to AC ground. You'll then want to carefully examine the grounding scheme overall to see whether or not it was done properly. At that point, if you're not satisfied, the input stage and phase splitter can be optimized to give better linearity and balance, but the reliability and noise issues should be the first ones addressed.

This is all covered in great detail in Morgan Jones's "Valve Amplifiers," which you ought to read and understand before digging into the guts of your amp and spending money on useless "modifications."

 

[Barbieboy]

Ok got you. You probably guessed that I am no expert moder and just tackle the simple stuff 😉 Be interesting to see what feedback we get from this on the other thread. Oh and I did google what the salesman recommend the other day and only his cables fitted that criteria....

 

[SY]

You probably guessed that I am no expert moder and just tackle the simple stuff 😉

Yes, I did. 😀 That's one reason I suggested Morgan's book- a nice amp is a good thing to have, but a nice amp and a lot more knowledge of what makes it tick and why is even better.

 

[Barbieboy]

Sadly I am a complete nonce when it comes to electronics and struggle understanding even basic schematics 🙁 but what I do have is a pair of ears which are my tools 🙂

 

[SY]

Even better reason to come up to speed. If you want to improve a car, you need to be something other than a good driver, you need to learn the basics of being a mechanic and get some basic tools. Otherwise, you end up adding a lot of flashy chrome and convincing yourself that you've got the fastest car, but the quarter mile time hasn't budged. The book I recommended is very accessible and practical, and doesn't use advanced math (basic algebra, no calculus).

 

[Barbieboy]

Haha ok, I will give the book a shot. I did come at the bottom of the class in science and maths at school. But grade A in woodwork, so speaker building no probs 🙂

 

[SY]

Wish you lived near me- I'm **** with woodworking and would trade you some labor. 😀

 

[Barbieboy]

hehe a deal, but big big water in the way sadly

 

[Barbieboy]

But how have you determined that the wire is limiting the performance and in what way is it causing problems? If you don't have a clear idea of what you're trying to fix, it's unlikely that throwing random solutions (especially recommendations by salesmen) at the problem will solve it. 😀 Wire is generally pretty far down the list.

I thought as interconnects made a difference then surely changing the wire inside would too ?

 

[SY]

Worry about the aerodynamics of your hood ornament after you've replaced the bald tires, leaky muffler, and clogged air filter. 😀