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.
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.
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.
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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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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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.
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
Regards,
Chris
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
Regards,
Chris
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.
I'll second that.
I use SET amps for my 3 front channels and SS for surrounds and sub in my home theater. With your high efficiency speakers, definitely take advantage of SET sound characteristics. Tubelab SE would be my recommendation. There is a section designated for their amps on this forum.
For surrounds, it may be a diminishing return to pour all that money on tube amps. The content in their soundtrack isn't worth it. For subwoofer, SS amp with high damping capability would be good which leads to commercial amps. Most of them have cooling fans and if the noise will be an issue to you, Crown makes / made couple models without fans. Or, you can try something like this.
The center channel is pretty important as well for dialog quality and some 3 channel stereo recordings on SACD so I think it makes sense to use 3 identical amps on the front..
Since you are designing the speakers, the amplifiers should be designed around their requirements as part of the overall system. To produce the most synergistic amplifier design you should at a minimum provide the following information:
A couple of comments on amplifier designs:
The tubelab SE is an excellent recommendation and can be built using either 2A3 or 300B..
An alternative I particularly like is a choke loaded 5842 driving fixed biased 2A3 or 300B. IT coupling is another very practical option since you will not be running these full range. I also like regulated supplies because I feel that they enhance resolution, and tighten up the top and bottom ends of the spectrum. (Neutrality over excessive warmth)
0 FDBK SE amplifiers interact in interesting ways with their speaker loads, so the flatter the impedance curve the better in terms of response flatness and distortion performance.
Very high quality OPTs are required for best performance, and Jack Elliano at Electra-Print is quite good at designing and manufacturing these to order. ($)Other options include Edcor, Lundahl ($$), Bartolucci, Tamura or Isotango ($$$).
I designed and manufactured 0 fdbk PP 300B amps commercially for a time at the beginning of the last decade and also published a design I did for SED in VTV back in 1998 - I do think the 300B is a better choice for bass chores at least, and would argue that the additional headroom using this tube in a good SE design is sonically worthwhile.
Currently available 300B tubes are marginally more expensive than comparable 2A3, but you can get at least 4dB more output power out of them for comparable linearity, and at normal listening levels the 300B should be somewhat more linear than the 2A3 given the power requirements.
Based on some of the comments clearly directed at me in your response to my prior post I should probably just state that over the last 20yrs I have designed all sorts of audio gear commercially from musical instrument amps to powered loudspeaker systems, with a particular emphasis in my own prior business activities on tube amplification, and I do also have a few unpowered speaker systems under my belt. So I am not the guy you referenced in that post...
Good luck with your project.
Since you are designing the speakers, the amplifiers should be designed around their requirements as part of the overall system. To produce the most synergistic amplifier design you should at a minimum provide the following information:
- Speaker Impedance
Assuming you will probably use a series parallel arrangement what is the nominal impedance of your driver array? - Required Amplifier source impedance
Amplifier source impedance affects driver QES and hence QTS - what range of source impedance can your speaker design tolerate, and what would the optimum value be? - Amplifier Bandwidth
You indicate that you will probably cross to the subwoofer at 80Hz, IMHO a very reasonable choice to avoid localization and reduce the amount of work the horns have to do in the LF.
So an amplifier flat down to 50Hz should be sufficient, reducing the cost of the OPT significantly and possibly significantly improving other areas of transformer performance in the tradeoff. (Smaller core, lower losses, leakage inductance, capacitance, etc.)
A couple of comments on amplifier designs:
The tubelab SE is an excellent recommendation and can be built using either 2A3 or 300B..
An alternative I particularly like is a choke loaded 5842 driving fixed biased 2A3 or 300B. IT coupling is another very practical option since you will not be running these full range. I also like regulated supplies because I feel that they enhance resolution, and tighten up the top and bottom ends of the spectrum. (Neutrality over excessive warmth)
0 FDBK SE amplifiers interact in interesting ways with their speaker loads, so the flatter the impedance curve the better in terms of response flatness and distortion performance.
Very high quality OPTs are required for best performance, and Jack Elliano at Electra-Print is quite good at designing and manufacturing these to order. ($)Other options include Edcor, Lundahl ($$), Bartolucci, Tamura or Isotango ($$$).
I designed and manufactured 0 fdbk PP 300B amps commercially for a time at the beginning of the last decade and also published a design I did for SED in VTV back in 1998 - I do think the 300B is a better choice for bass chores at least, and would argue that the additional headroom using this tube in a good SE design is sonically worthwhile.
Currently available 300B tubes are marginally more expensive than comparable 2A3, but you can get at least 4dB more output power out of them for comparable linearity, and at normal listening levels the 300B should be somewhat more linear than the 2A3 given the power requirements.
Based on some of the comments clearly directed at me in your response to my prior post I should probably just state that over the last 20yrs I have designed all sorts of audio gear commercially from musical instrument amps to powered loudspeaker systems, with a particular emphasis in my own prior business activities on tube amplification, and I do also have a few unpowered speaker systems under my belt. So I am not the guy you referenced in that post...
Good luck with your project.
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Are you seriously?
2 watt output for home theater?
He's planning on using extremely high efficiency speakers so 2W might be more than enough. (Read his first post)
Hi, Kevin
Right you are! However, the use of an SE amplifier for home theater is the wrong way, IMHO.
I run speakers with an efficiency of around 100dBSpl/w/m and can attest this is already is a big issue. Compound that with the fact that I also use a fair number of transformers in the audio path and it becomes complex.
Yes, but....
Home Theater sound require more dynamic than the one that can provide single-ended amp. SE Amp sound is neutral and gentle. PP Amp sound is more dynamic, more weightier but... not so natural as SE amp sound.
Try Empire Brass Quintet "Passage 138BC-AD1611" for testing. SE will get into a muddle over the low notes. It requires an amp with exceedingly good transient damping to reveal the low octave timbre and mid wind solos at the same time. Despite the business of the CD player being fully error corrected for this-and-that, I still had to put a brick on it.
richy
richy
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