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Old 16th February 2013, 07:05 PM   #531
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This is encouraging me to try Ale's setup, eat my words and use a 2C22. If I input 2v using the ODAC that Ale uses or Pano's DAC with a slight step-up, there's a theoretical chance that I could get away with 2 stages with my PSE 4P1L outputs. I'd certainly like to hear it!
Pano - how would you get 2v out of your DAC?
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Old 16th February 2013, 07:53 PM   #532
45 is offline 45  Italy
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I might have missed something but don't understand why you would not use the ECC40 and want to use a 2C22 that has pretty poor linearity in comparison.
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Old 16th February 2013, 08:13 PM   #533
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I have no real measuring equipment except for my multimeter which I use constantly, so I can't comment on linearity. I only go by what I hear. I used the ECC40 and 2C22 in a few different projects and I liked the 2C22 a lot at the time - it was my favourite small tube before the 26. I didn't like the sound of the ECC40 quite so much in the projects I used it in. I tried a few different operating points for both. I know that many here will say tubes don't have any distinctive sound, but all my years of experience of working with tubes leads me to believe that tubes have quite distinctive sounds. Or maybe the better ones do, since it's easier to distinguish fine details. I build almost entirely by the sound of what I hear. Obviously I spend a lot of time reading up on the theory, but given that, it all goes by what I hear. I listen very carefully and try to be as methodical as I can when I do A-B comparisons, always looking out for the nul hypothesis - that there is no discernable difference - and grading differences very cautiously.
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Old 16th February 2013, 09:06 PM   #534
45 is offline 45  Italy
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Listening is the most important thing but I think one should check at least basic objective things. Maybe the lower linearity of the 2C22 was canceling some H2 distortion of the output valve. Who knows....
I don't believe in A-B comparisons because it has been proven several times that they are tricky and often give false results. Even a simple switch can be the cause! I have learned to listen one thing per time optimized as well as possible because one can tell if is right or not anyway. The importance of listening is the only point we have in common in this case.
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Old 16th February 2013, 09:52 PM   #535
Pano is offline Pano  United States
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IKO - I'm using speakers. My custom Altec VOTT A5. I don't know if I'll go with the parallel pair. It does not gain me much, but even a little could help.
Andy: Depends on which chip I use for the DAC. Some have 2V out, some are 1.5V. If needed, I can use a 1:2 step-up.

What I will probably do is dedicate this to the midrange 1005 horns, and maybe the tweeters. It sounds soooo good up there. I'll put more power in the bottom end.
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Old 16th February 2013, 09:58 PM   #536
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Quote:
Originally Posted by 45 View Post
Listening is the most important thing but I think one should check at least basic objective things. Maybe the lower linearity of the 2C22 was canceling some H2 distortion of the output valve. Who knows....
I don't believe in A-B comparisons because it has been proven several times that they are tricky and often give false results. Even a simple switch can be the cause! I have learned to listen one thing per time optimized as well as possible because one can tell if is right or not anyway. The importance of listening is the only point we have in common in this case.
No - I quite agree that A-B testing is tricky and can give false results. I'm a psychologist in my day job, so I've done quite a lot of testing of various things and I'm just as wary as you are of coming to the wrong conclusions. That's what I mean about being very careful and always looking for the nul hypothesis. All those hyperbolic "night and day" differences are as foreign to me as they would be to you. I'm expecting to hear small differences or indeed nothing some of the time. But for all its faults, I need A-B comparisons for how I build!

This is all rather OT, but maybe useful by way of explanation. Andy
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Old 16th February 2013, 10:04 PM   #537
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by 45 View Post
I might have missed something but don't understand why you would not use the ECC40 and want to use a 2C22 that has pretty poor linearity in comparison.
7193 is not the most linear valve, agree. However is not that bad. I need to check my notes but distortion at full tilt was very good one samples were picked for such purpose.
I agree with Andy, the sound is really nice. However, I'm more inclined to try a 6e5p or 6e6p in triode mode and shunt cascode (Rod's circuit). You can get all the gain you need and distortion is outstanding at less than 0.2% for 200Vpp. Some strange push pull-ness is coming out when driving it at full tilt as the H3 component increases over H2. Either way is very promising due to gain and also results reported by Rod in terms of sound.
Ale
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Old 2nd March 2013, 04:45 AM   #538
Abszero is offline Abszero  United States
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This is actually a common misconception. For example the hottest high-end headphone right now is an HE-6. It takes a serious 6Watts at 50 ohms. Thats more voltage swing than a 35 watt amplifier. Only a 1000V GM70 SET can deliver that sort of Voltage Swing properly. They are really a ss amp only type of headphone.

For senns they are efficient so you may be able to get away with a 5k:300 preamp OPT. Just watch the secondary DCR, a 300 ohm secodary can kill your damping factor and power transfer.

Even 32 ohm 97db/mw headphones are a problem, I had a pair of custom electraprint 5k:32. Secondary DCR is 12 ohms So I am losing 1/3 of my power down the drain, if I had known that I wouldn't have designed my SET around a we417.



I guess what I am trying to say is make sure you love your headphones cause you have to build the SET amp for the specific model and start with the OPT. Its very difficult to build a one size fits all.

With speakers sometime in the 60's all the manufacturers got together and said "we will make 8 ohms the standard" at the same time headphones were all standardized to a 120 ohm "tap", but the last decade that standard has been thrown out the window. So designing an amp for headphones is really tougher than speakers (if you want the best.)

Main thing is define your scope of work, the beauty of DIY is we can build to match. I definately think the 4P1l would be an ideal output tube for senns, just finding the right OPT will take some legwork, but it should be able to serve double duty as a preamp.
Hi Regal,
I followed the thread that you started SET headphone amp, and I completely understand your frustration. Have you looked at One Electron UBT-1. It is SE 1.6k to 4-8-16. Measured DCR on 16 ohm out and is under 1ohm. I would like to try a PSE 4P1L with this OT and 32-38 ohm load. Could be a decent compromise.
Best,
Radu
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Old 2nd March 2013, 06:08 AM   #539
regal is offline regal  United States
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Radu, I replied on the DHT thread, please join us over there your findings are spot on I think.
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Old 6th March 2013, 02:21 PM   #540
Pano is offline Pano  United States
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Just an update:
I'm running my SET 4P1L full range at the moment and it works very well. Sounds very nice. A single 6SN7GT as the input tube, LED biased, AC heater. The 4P1l outputs are running at about 240V, 35mA on battery bias, triode strapped. The batteries are bypassed with a film cap, if that makes any difference.

4P1L filaments are running at 4.2V DC, with the center point tied to ground via 1R. Supply is from the same 6.3V winding as the input tube, just rectified, filtered and regulated with a simple LT1083V adjustable regulator. Noise is low, lower than my bench supply. HT is vacuum tube rectified, then RCLC filtered.

OPTs are small, vintage 5K:8 units made by Roberts, IIRC. They have decent bandwidth and low distortion thru most of the range.

I'm very happy with it overall. It's a real spaghetti mess at the moment, but some day I'll get it in a proper chassis. Some day. ASAP, I'll switch back to an active crossover using this amp on the midrange horns - and maybe the tweeters. It should be well suited to that use, and will need about 10dB less output when I remove the passive attenuators on the horns.

The 4P1L is a nice tube, fairly easy to use and suites my needs perfectly.
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