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Old 26th August 2005, 02:06 AM   #11
BHD is offline BHD  United States
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I can't believe this spammer troll actually got this thread off the ground.

SET or PP? Listen to both and make your own decision. It's not as if someone else's opinion could be a substitute for your own experience.

Sheesh.

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Old 26th August 2005, 02:59 AM   #12
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I read this earlier and ignored it, but now I decided to add my 2 cents. Yes this is largely a matter of personal preference, but it is also greatly influenced by the type of music that you prefer. It is also influenced by the type of speakers that you own. I have several tube amplifiers. I currently have three set up so that I can easilly change between them. I use a SE with 45's (or 300B's), a SE with 845's (or 211's) and a Push Pull with 300B's (no feedback). The 45 excels at the subtle details in most music, but with my 87db speakers, it won't get loud. The 845 SE gives up some detail in exchange for lots more power (40WPC). The 300B push pull (30WPC) has punch and dynamics, even though it has less power, that the SE amps don't have. This amp positively excels for Dance, Techno and some rock music.
My Yamaha NS-10 speakers like the SE amps, but my old AR-4x's like the PP amps. The AR's also like PP pentode amps with feedback.

I have built at least a dozen different types of amplifiers in search of that magic amp that combines the best of all of these without the shortcomings. I have not found it yet. The 833 SE may do it though.

Just because I like SE amps, doesn't mean you will. Everyone has different ears and preferences. Listen and make up your own mind.
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Old 26th August 2005, 03:27 AM   #13
SY is offline SY  United States
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BHD, seriously, if you see something that looks like spam, hit the "report" button. Moderators can't be everywhere at once, so member reports are really, really helpful to us.

/mod hat off

Johan, with all the tomatoes thrown at me over the years, a few more won't be a bother. Some might even prove entertaining.
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Old 26th August 2005, 03:44 AM   #14
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However since the days of ultra-linear (rendering largely triode type distortion) I cannot see anyone using straight pentodes any more.
I tend to agree with you and that's what I would try if I had suitable OPTs. The other form of distributed load, cathode coupling, might be even better. However, my OPTs don't have UL taps or an extra winding, so I'm stuck with either triode or pentode mode (currently using triode mode). Maybe one day I'll get to Singapore and treat myself to a pair of good quality trannies, but I don't have the spare cash yet.

A problem with straight pentodes, quite apart from their inclination to produce odd harmonic distortion, is their very high internal plate impedance (15k ohms for EL34, compared with 910 ohms triode-strapped; UL would be somewhere in between, maybe around 2k?), requiring at least 26dB of NFB to get a damping factor comparable with triodes using no NFB and 30dB or more would be better. That's not to say it can't be done but you need a very high open loop gain to start with and the risk of instability is high. With UL, 10-20dB of NFB would be ample.
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Old 26th August 2005, 03:56 AM   #15
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Quote:
HD, seriously, if you see something that looks like spam, hit the "report" button. Moderators can't be everywhere at once, so member reports are really, really helpful to us.
Sorry SY. I didn't actually click on the link in the first post earlier today because I just assumed the guy was an idiot trying to stir things up (in a very unimaginative way). I think the same guy started another account and has a thread here:

Is 845 better than 211 tube amplifier?

FWIW.
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Old 26th August 2005, 03:59 AM   #16
SY is offline SY  United States
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Thanks! Good instincts you have.
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Old 26th August 2005, 04:01 AM   #17
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SY, i would be interested in your preference other than SET. what are the SET characteristics that you don't like, or the PP characteristics that you like, and so on. If these have been posted before, I'd be interested to know the URL and read about them.

And no I'm not a troll but just a SET guy wanting to understand the preferences of a PP (or NON-SET) guy.

I'm definitely not closing my ears on a specific topology so I'm interested to know what I might be missing.

If you think it is more appropriate to be a private mail, you can send me one, and if you feel you don't want to talk about it, that's also fine with me. I respect whatever decision you come up with.

Cheers.
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Old 26th August 2005, 04:20 AM   #18
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Don't worry, I've been quite upfront in the past about my reasons for disliking SETs, so I'm unlikely to set anyone off that I haven't already set off. Distortion and source impedance lead the list of my objections, followed closely by ridiculous sensitivity to power supply, output load, and sometimes even the source impedance to the input. My response to EC was figurative, but does reflect my impressions; I've always compared using a tube amp to driving a '57 T-Bird, which would be a blast on the freeway, but a Model T doesn't belong out there.

The inefficiency is just irresponsible. Might as well get the biggest damn SUV money will buy.

One more thing: I strongly believe that if you're going to do something irrational like use a tube amp, it ought to at least be well-engineered.
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Old 26th August 2005, 04:34 AM   #19
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Thank you SY, that's fair enough.

Is there a well-engineer DIY PP amp you can recommend I look at? (as a next project, instead of the Bevois Valley EL84)
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Old 26th August 2005, 04:36 AM   #20
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Power range?
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