KEL 84 signal cable and ECF80s

[A.N. Beal]

Dear Folks,
After building a KEL84XL this summer I experimented with various types of internal signal cable and ECF80 valves. Findings about sonic differences are summarised below. I'd be interested to hear how these findings compare with the experience of others. In each case the findings are based on the sound after a reasonable cable run-in period. (My system: metal-bodied Denon DL103 with Esco line contact stylus in Mayware MkV tomearm into a Blackhead transformer and a Graham Slee Genera preamplifier. The KEL84 drives WD25aXL loudspeakers.)
The types of internal signal cables tried in the KEL84 were:
(a) KEL84 standard version blue signal cable,
(b) KEL84XL Soniqs white silver-plated cable,
(c) Maplin 'High Grade Overall Screened Pair' cable (ref. XS40T). (7.3mm diameter blue polythene insulated OFC cable with metallised mylar film and braided OFC, stated to be suitable up to 105 degrees C, capacitance of 112pF/m, cost £2.19/m (inc. VAT).)

Valves tried:
(a) current WD standard issue AEL ECF80,
(b) previous WD standard issue Ei ECF80
(c) NOS RCA ECF80 manufactured by Siemens, sold by Watford Valves.

With the standard WD blue signal cable, the general sound quality had a warm balance and the different ECF80 valves gave different sounds:
(a) AEL: good balance, slight colouration, slight treble edge;
(b) Ei: warm and coloured sound - rather like an old valve radio;
(c) RCA/Siemens: clean, smooth, low colouration, slightly recessed treble.

The Soniqs white cable produced a cleaner, brighter, more analytical sound balance and again the different valves sounded different:
(a) AEL: clean, uncolored, analytical but recessed midrange and over-prominent treble;
(b) Ei: nice 'easy listening' balance with stronger midrange and slightly subdued treble but some colouration and some 'old valve radio' sound;
(c) RCA/Siemens: clean and uncoloured, fairly neutral balance (i.e. intermediate between Ei and AEL) but still slight residual brightness.

The Maplin XS40T cable was neutral, open, clear and extended - neither 'warm' nor 'bright and analytical' or bright or edgy - and the sound was sweeter, with better string tone than either of the other cables. Interestingly, although differences between valve types could still be heard, these became more subtle: on one hand the AEL valves lost some of their brightness but on the other hand the Ei valves also lost some of their dull warmth and colouration. However it wasn't a case of cable colouration masking the differences - they all sounded clearer and better: the AELs had lost their bright treble and found string tone, making cello sound like cello and the Ei valves had lost their 'old valve radio' colouration and found treble detail. The RCA/Siemens valves were still best but the differences were now subtle rather than day/night - I could live with the sound from any of the valves without feeling something important was missing.

Overall verdicts?

With the standard KEL84 blue cable, the current standard-issue AEL valves are a good match, the bright sound of the valve and the warm sound of the cable offsetting one another. For those who wish to experiment, better valves such as the NOS RCA/Siemens can give a cleaner sound with a rather restrained treble.

With the KEL84XL Soniqs white silver-plated cable, recommendations are more difficult and will be system-dependent: the white cable with the standard AEL valves is certainly bright analytical sound but the treble was too strong for my taste. To my ears the warmer sound of the Ei valves gave a better compromise, although in the process some of the extra clarity and analysis of the XL was lost. The NOS RCA/Siemens ECF80s gave the best sound, although it was still (for me) a bit on the bright side.

For my ears and in my system the Maplin XS40T cable offers a better long-term solution being less coloured than the standard blue cable but avoiding the brightness of the white Soniqs cable and being more sweet and neutral than either. I don't understand how it managed to make the Ei valves brighter and less coloured and at the same time tame the brightness of the AEL valves. The NOS RCA/Siemens valves were still best but with this cable valve choice is less critical and they were all acceptable. In my system, £4.38 spent on 2 metres of this cable has worked out pretty well.

Does anyone else have similar (or different) experiences to offer?

[bearded fiddler]

The Soniqs signal cable was a bit bright to my taste too. So I went back to the blue signal cable I started with. I got the most balanced result with Mullard white shield logo ecf80s. The (more expensive) yellow shield type was strikingly realistic, but had some midband glare.

Jan

[Mike G]

Hi,

Considering you only built your amp this summer, you have been very busy swapping cables already - was there a reason for this being done so soon? I've generally found and an followed the advice of several on the forum, to build as standard first, and live with it for a while, making one change at a time. Maybe i've had a long weekend, but i'm finding you very comprehensive report rather much of an information overload! From your experiments did you find a sound that you liked? I'd trust your ears, and enjoy the music for a while first!

Regards

[Greg.]

I read Mr Beal's post as a basic option review. Thank you. After testing, you've said what seems to work best for you. That is helpful although other punters have differently set up systems, so your information will need to be considered accordingly.

It's all good stuff and well worth the read. Great

[pre65]

Thanks for the details, I've been looking for some screened cable for my 2A3 (or 6B4-g to be more precise) preamp project so might give Maplins a try.

[John Caswell]

Hi all,
Not going to pass any comment on cables, I know what I like
However ECF 80s are pretty notorious for being very variable (see FAQ) They are primarily an RF valve.
Before you state that such and such a valve is this or that or the other you need to confirm that is is as you say.
Just because it says "Mullard", "Mazda" or "Brimar" on it does not mean it was made by that company, as manufacturers use to buy from each other willy nilly to make sure their stocks were adequate.

John

[A.N. Beal]

Dear Mike,
Why start swapping cables so soon? I did actually do as advised (and it's good advice) to give the standard XL Soniqs cable time to run in before judging it. It did improve with use over several weeks but some aspects which had started as minor gripes became irritating. I found that the sharpness and detail which had seemed so impressive initially also included a brightness and glare that was hard on the ears and wasn't going away.

Noting that others had also found the Soniqs cable rather bright, the obvious move was to try the standard blue cable and Matthew Snell kindly obliged with some. This made a big difference and at first I thought it was the solution. However on longer term listening there was still a slight residual roughness at the top, which led to the experiment with the RCA/Siemens ECF80s which were smooth and clean ... but then my ears found the sound a little dull.
I had been reporting findings to the ever helpful Matthew and he lent me a pair of Ei ECF80s to try ... which were interesting but and offered another set of pros and cons. I then decided to give the Soniqs white cable another go, to see if it worked better with the RCA/Siemens or Ei valves. As can be seen, the answer was 'yes and no'.
In the end my 'hifi itch' was only cured by the Maplin signal cable, which with the RCA/Siemens ECF80s sounds 'just right' for the KEL84 XL in my system. Having gone through all this I thought I might as well complete the exercise by testing the AEL and Ei valves with the Maplin cable and then write up the results for this Forum, in case others find the results useful.

[Mike G]

Thats great you have now found a combination that is right for you. I have an early WAD KEL 84 and know with the small case, and PCB, swapping components and cable is not an easy task!