Posts by MP1968

    I connected the DAC to CD1, and then played my test tracks again. I kept the RCA clear tops in the Eclipse. The volume on the Eclipse was still around 50%. This time there was no harshness or exaggerated treble response. The sound was clean and well balanced. No sibilance at all.


    So is it the case that the increased treble that I heard on my first test was entirely due to the DAC over-driving the Eclipse? It certainly seems to be the case, and nothing to do with the RCA clear tops at all.

    I have tried two RCA clear top 12AU7 valves in the left hand position, and thought I would post my brief impressions here.


    Certainly the signature is very precise and detailed. My only slight reservation is whether there is perhaps too much treble detail, which is a criticism of these valves on other forums. There is perhaps an emphasis on the higher frequencies with a slight loss of mid range response. Some music tracks can sound quite sibilant.


    Anyway, I'll spend some more time with them. I also have a pair of Siemens 5814A triple mica to try, plus a pair of 6189 tubes which are labelled Philips but which I think were made by RTC. Gerard had good results with these 6189 valves, so I wanted to try them.

    Following on from Gérard's question, I'd like to know whether two E80CC valves could be used in the left hand position.


    According to the Brent Jessee website (http://www.audiotubes.com/12au7.htm) they can be used as ECC82 substitutes, but with a couple of factors to consider:


    'Since this tube has a much higher Gm and Mu factor than a 12AU7, the gain is going to be greater and this tube will give a more forward presentation. Awesome in phase splitter applications. If in doubt, check with your amp or preamp manufacturer to see if this tube will work OK in your application. This tube is also about twice as tall as a 12AU7, so installation space in your chassis is a consideration as well'.


    Marty - any thoughts?


    Best wishes


    Mark

    Hi Martin,


    Many thanks for the information, that's very helpful.


    I have decided to try some tube rolling in the Eclipse. I am going to start with RCA Clear Top 12AU7s. I will also try modern production Psvane 12AU7 TII.


    Can I just clarify one thing? Your post says that 'tube rolling has its merits on the two left tubes'. Hence is it really only the two left tubes which make a difference to the sound quality of the Eclipse? Is there any point at all in changing the two right hand tubes?


    If it's the case that only the two left tubes are worth rolling then that's very important. It means I can put two of the stock Electroharmonix valves (which came with the Eclipse) in the right hand position, and just focus on rolling the two left tubes. This would make it much less expensive, as I will only need to find a matched pair (not a matched quad).


    Incidentally, I collect vintage solid state and valve amplifiers, both integrated and power amps. I have the Sony TA-F7 (V-FET), Sansui AU-111, Sansui AU-907 Alpha Limited, Sansui BA-F1, Pioneer M90a, Sansui AU-X11, Radford STA25 Series 3, Victor JM-S7 (V-FET), Sansui BA1000 (V-FET), and Yamaha B3 (V-FET).


    These are what I use with the Eclipse. The integrated amps can also be used as power amps. Because many of these amps are quite old, they have all been fully serviced and restored (new electrolytics, etc etc) by technical experts in different parts of Europe who I have 'met' through Audiokarma.


    My speakers are Tannoy Eaton Legacy. My DAC is an Aqua La Voce S3 (R2R design).


    I listen to lots of different types of music, but not much classical.


    Best wishes,


    Mark

    Many thanks for your response, particularly the information that the Eclipse does not auto bias.


    After discussing this with audio experts in other forums I've decided not to try other valves in the Eclipse: I do not think it will make any difference to the sound profile.


    In my hi-fi system the sound with the Eclipse is quite mids-focused, and seems to me to lack some precision and definition. In addition, the soundstage is good from left to right, but not so good from top to bottom. This is what I was hoping to fix by trying different valves: a better balanced sound, less mids-centric, a bit more air, an improvement in soundstage, and better placement of vocals. I managed to achieve all of these things when I replaced the Eclipse temporarily with the preamp section of a solid state, neutral signature integrated amp.


    My belief is that if the circuit has been designed correctly around the valve, then it won't matter very much whether you're using a modern production tube or some rare 1950s version with a big price tag. Essentially the circuit as a whole defines the sound signature, and although individual parts do play a role terms of specific characteristics (as they would in a solid state amp), they cannot alter the circuit properties that much. My experience of tube rolling in a headphone amp supports this: there are some very subtle differences between different 6SN7s, for example, but not enough to justify the price that NOS / vintage 6SN7s now sell for. I think there's a lot of hype in some audio forums about the sonic benefits which are claimed for some old production valves: I think a lot of that is just New Toy Syndrome, rather than an actual, significant difference between Tube X and Tube Y.


    Tube rolling comes at a significant cost: a quad of 7316s in the UK will cost at least £300. If they don't give me what I'm looking for then another quad of 5814s (for example) will also be expensive.


    In the last few days I've been trying to weigh up the likelihood of being able to modify the Eclipse signature to what I want by changing valves. But I don't think this will be possible, and perhaps replacing it with a solid state preamp would be a better investment.

    Hello. First question: I have read on the internet that the four tubes put into the Eclipse do not need to be closely matched, as the circuit is self-biasing. Is this correct? Would it be important for the two tubes on the left side (the entry tubes) to be a matched pair, as they are more important than the right hand tubes (exit tubes)?


    I am asking because it is much more difficult to find a matched quad of NOS / vintage tubes. However, it is easier to find either two matched pairs, or four unmatched individual tubes.


    My second question: last year I changed the stock tubes to two Brimar 6067 ECC802S 'T' (the entry tubes), and two Pinnacle 13D5A (the exit tubes). However, I would like to see how much the sonic character of the Eclipse changes with tube rolling. Does the sound of the Eclipse really change very much with different tubes? If so, can anyone suggest which vintage / NOS tubes would be worth trying next? I have read that Amperex 7316 tubes are excellent, but they are very expensive. A less expensive option appears to be the RCA clear top 12AU7A, or the Westinghouse 12AU7 with the carbonised plates from the 1950s.


    Any suggestions would be welcome. Would it be worth moving the two Brimar 6067 ECC802S 'T' tubes to the right hand side (as the exit tubes), and use something different in the left side (entry tubes)?


    Many thanks.