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?