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Old 13th July 2010, 08:22 PM   #1
brsanko is offline brsanko  United States
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Default what 2A3 desgin recommented for home theater

Hello, I'm Brett. I post on the speaker forums alot but I've recently come into some money and want to make my home theater the best the world has seen (probably a slight exageration) I have designed the speakers I wish to build and want some tips on what Amps would be the best. It will be a 7.1 channel surrond system but it will be used for 2 channel stereo 90% of the time. My main and center speakers will be monsterous rear loaded horns consisting of 16 1" Tang Band drivers each. Their clarity, impulse, and sensitivity will be second to none. Hornresp graphs a 1W resoponse at 115db down to 50Hz in a corner loaded congfiguration, and when they reach their xmax at 1.8mm they will putting out 125db down to 45hz and using about 5W. I have the utmost faith in the acuaracy of Hornresp as everything we have built has exceeded our expectations by a mile.
Any way back to the amps I need 7 channels of single ended amplification, and probably a push pull amp for the sub (I haven't decided on a sub design yet) I'm thinking a good single ended 2A3 design should have all the power I need for front 3 speakers. The surround speakers will have 4 drivers each and will be tuned to 80hz. I expect the sensitivity will be down about 6-9db as well, so they may require a little more power, perhaps a 300B S.E.T. or a S.E.P. 2A3. How much power could I get out of 8 2A3s in a push pull configuration? I would like to have at least 50W for my subwoofer. Anyway that's my plan, if anyone has any ideas, questions or constructive critisizms please feel free to comment.
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Old 13th July 2010, 08:24 PM   #2
brsanko is offline brsanko  United States
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Oh yeah and I have a friend who will build them for me I just need some schematics for amps you've actually listened to and can recomend. And I'd like to keep the cost for all 8 channels under $5-$6k if that's possible.
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Old 13th July 2010, 09:08 PM   #3
Matt BH is offline Matt BH  United Kingdom
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Hey Brsanko,
I have been thinking about an all tube 7.1 system. I think a lot of your budget would be gone on output trannys. All those 2A3s would eat the rest, leaving little for the other equally important components eg power trannys, caps etc etc.

For the sub 50W seems about right for a decent design. I would go tetrode for this eg 6L6 and the other variants. 8 2A3s would be crazy but would look nice. Thing is they dont last forever

For the rears you really dont need as much power as you think even though they will have lower sensitivity. Although the idea of identical amps for everything except the sub is appealing.

My idea was to go push pull all round with maybe EL84 or 6V6 for all channels PP with maybe EL34 or 6L6 PPP for sub. You dont need this sort of power for you proposed speakers so think about triode connected pentodes. Cheaper, more available and you will have a fair few of them so replacement has to be considered.

Cheers Matt.
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Old 13th July 2010, 09:35 PM   #4
Bigun is online now Bigun  Canada
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would you consider 6AS7 ?

Atma-Sphere Music Systems - Papers
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Old 13th July 2010, 10:20 PM   #5
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by brsanko View Post
Hello, I'm Brett. I post on the speaker forums alot but I've recently come into some money and want to make my home theater the best the world has seen (probably a slight exageration) I have designed the speakers I wish to build and want some tips on what Amps would be the best. It will be a 7.1 channel surrond system but it will be used for 2 channel stereo 90% of the time. My main and center speakers will be monsterous rear loaded horns consisting of 16 1" Tang Band drivers each. Their clarity, impulse, and sensitivity will be second to none. Hornresp graphs a 1W resoponse at 115db down to 50Hz in a corner loaded congfiguration, and when they reach their xmax at 1.8mm they will putting out 125db down to 45hz and using about 5W. I have the utmost faith in the acuaracy of Hornresp as everything we have built has exceeded our expectations by a mile.
Any way back to the amps I need 7 channels of single ended amplification, and probably a push pull amp for the sub (I haven't decided on a sub design yet) I'm thinking a good single ended 2A3 design should have all the power I need for front 3 speakers. The surround speakers will have 4 drivers each and will be tuned to 80hz. I expect the sensitivity will be down about 6-9db as well, so they may require a little more power, perhaps a 300B S.E.T. or a S.E.P. 2A3. How much power could I get out of 8 2A3s in a push pull configuration? I would like to have at least 50W for my subwoofer. Anyway that's my plan, if anyone has any ideas, questions or constructive critisizms please feel free to comment.
I'm not so confident in your projections of performance with 16 of those little TB drivers, not even close in terms of SD or xmax to a typical single single 15" pro woofer. If you are running these full range you will probably have issues with comb filtering even below 1kHz. Have you actually measured the TS parameters of the driver to see if the assumptions you used in Hornresp are reasonable? And are you sure you can trust those results? Please ping GM or Panomaniac for some real good advice and guidance. (I've done a couple of speaker systems including an ambitious and successful design based on the Jensen Ultraflex/Onken, but am relatively inexperienced.) I'd hate for you to invest large sums of money in something that ends up being a disappointment.

In terms of subwoofers, a solid state amplifier is probably going to provide a better solution than 8 PPP 2A3. A pair or quartet of 6550 (70W/150W) will run circles around them too for that matter for the required power levels.
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Old 14th July 2010, 03:51 AM   #6
brsanko is offline brsanko  United States
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I'm doing my own research as far as the speakers are concerned and am not interested in a debate over them. No offense your comment was fine I just don't want to discuss them because every time I discuss an ambitious speaker design on this site some know-it-all who built a pair of speakers for his mom once has to tell me I'm all wrong and I waste page upon page arguing over points I have already established and learn nothing. I will do my own research to design my speakers I have taken into account and made accomadations for all of the issues you've mentioned and do not wish to discuss it further until I've built them. What I do want to discuss though is amplification. I've been doing my reading and I have my heart set on a 2A3 or 300B S.E.T. design. I think that the sensitivity of my design warrants using a 2A3 and I guess after thinking about it the same amp for all 7 speakers really does apeal to me. I was really hoping someone would suggest a particular S.E. 2A3 design or two that they had success with, and let me know the pros and cons of the different designs. I guess my budget isn't set in stone I just put that out there so people wouldn't be suggesting their favorite silver wound trannies or whatever other ridiculously expensive ideas, or be telling me about the latest low budget design that is almost as good. So thank you for your input so far I'm not ripping on anyone just trying to gently nudge the conversation in the right direction.
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Old 14th July 2010, 02:16 PM   #7
chrish is offline chrish  Australia
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You say that using the same 7 amps for all channels appeals to you. Why? I would have thought that a little analysis of the requirements of the various channels would lead to an optimisation of resources that would probably lead to different amps being required.

You state that 70% of your listening would be stereo. I am presuming that this type of listening will also be your most critical listening? I know that I personally could not tell if the explosion or sound effect over my right shoulder is being reproduced with 1% distortion or 0.1%. I would suggest making a nice stereo pair of your chosen design (300B or 2A3) with high quality output transformers. For the surround channels, and even the centre channel, 6V6 or EL84 in PP will give great results (and in that duty probably no audible difference) for significantly less than a 300B or 2A3. For the subwoofer amp: solid state. Even Lynn Olson agrees here. You will find more than a few of the senior tube gurus here that use an old Adcom 555 or similar for sub duty. remember, a tube amp has a transformer on the output. What happens to transformer efficiency with decreasing frequency?

So, my opinion is an optimisation of amps based on design requirements will dictate that more resources are allocated to the stereo pair if you are interested in best overall performance. If, however, you are interested in having something that looks impressive when your buddies come around, you may want to do something different

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Chris
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Old 14th July 2010, 02:33 PM   #8
brsanko is offline brsanko  United States
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I will probably do that, to begin with at least. I'm thinking the 3 front channels probably at first.
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Old 14th July 2010, 02:47 PM   #9
brsanko is offline brsanko  United States
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I was wondering if anyone had any favorite designs they'd like to share. I guess I was looking at push pull 2A3 for the sub because I know everyone raves about how amazingly clear and dynamic the 2A3s are in the bass. BTW I've actually changed my speaker design (gasp! nobody does that) I've decided to use the design I made for the surround speakers all around and cross everything over at 80Hz, making the subwoofer quality a bit more critical I would think. My subwoofer design is right on par with the rest as far as sensitivity though. The only reason I want to try for 50W is to get full volume in that bottom octave.
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Old 14th July 2010, 02:54 PM   #10
fff0 is offline fff0  Singapore
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considered tubelab SE?
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