• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

EF86 do change tone!

Hi, I have been around listening to music all my life. In the last 10 years I have owned vintage Quad II's. I have been very happy with the sound quality as it is excellent. I am now at the point where vinyl is superior to CD in most cases. I am now experimenting with swopping out valves. There is a definite tonal difference when having removed the Mullard EF86's and replaced them with four new old stock Bentley Acoustic valves (foreign made). I have tested them out on various recordings I have known for a long time, the differences are (with the Bentley's). Slightly reduced bass volume, a more 'spacious' sound, wider stereo response, very detailed and clear tops (incredibly so). On some of the records I have just listened to I heard acoustic guitars, triangles and hand claps for instance far more clearly than ever before. (all settings are flat). It's fascinating to me that such changes make things 'different'. I know I am hearing it differently, it is not an illusion. I am 65 years of age and have owned some of these records before I was 10. To be able to keep on getting more and more out of them is really great. Has anyone out there had/or having a similar experience?
 
Controversial territory:

Are your QUADs original? Have they at least been restored? Someone on the forum had a fit once when I said I'd repurposed some transformers from a (not very good) vintage amp. The offended party accused me of messing with a heritage amplifier. At any rate, have a look at Keith Snook's site. https://keith-snook.info/quad-ii-valve-amplifier-mods.html If you want a real deep dive into QUAD II updating Pat? Turner in Australia had some real hard core mods. His site isn't operational as far as I can see but I have the info from it which I'll send to you if you wish to send me a PM.

S.