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  1. #1
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    Which amp for Tannoy Dorset T185?

    Hi,

    I've recently bought a pair of used Tannoy Dorset T185 (60W, 8Ohm).
    I like the sound and I'm very pleased with my purchase.
    The speakers are currently plugged to an old Pioneer SA-506.
    I'm not an expert audiophile but I have the feeling that I can get more out of the T185.
    So I'm now looking for an appropriate amplifier to combine with them.
    I have been given a list of Denon amps, can somebody tell me more about them?

    Denon PMA 860 / 1060
    Denon PMA 1080R
    Denon PMA 900V

    Is the PMA 900V an integrated Class A amp?
    What is the difference with a New Class A amps?


    I'm open to take in consideration other models/brands, so any valid alternative is welcome.
    Thank you very much in advance.
    Musical greetings

  2. #2
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    I suspect Denon would not be the best match for the Tannoy, in my opinion the match may be a bit bright. What is your budget? You might look at Jolida or Peachtree on the budget end. The Tannoy wouldn't need much power and tube amps may be a better match. Jolida even has a 100 watt hybrid which I haven't looked at in a while but still should be under $600.00 new. NAD and Cambridge Audio offer very reasonable priced integrated amps, neither are tube but may offer a more musically satisfying sound than Denon.
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  3. #3
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    Aren't they usually rolled off at higher frequency?
    If you are not using a pair of external tweeters and Dorset t185s are free from low impedance, how about OTL tube amps? You might want to research t185's impedance curve.

  4. #4
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    To Mr Peabody & jrhymeammo:

    Actually my budget is quite modest ($250.00).
    I can eventually invest some more money (max $500) if in that price range falls a qualitative product (also second hand is fine) that will do for my need.

    Out of curiosity I've been searching for used Jolida amps an found the following:
    - Jolida JD 1501 (100 watt hybrid) year 2009 for $520.00

    With regards to NAD or Cambridge Audio, are there specific models I can look for? How many Watt are actually sufficient?

    I couldn't find any result on internet about t185's impedance curve, and I'm not that technical to measure it on my own...
    You guys are introducing me into a new world and a new technical language (OTL tube amps?). I find this very interesting and makes my quest for an amp extra exciting.

    Thank you for your time and knowledge.



    PS:
    In the meanwhile I've found an online ads for a used NAD C352 (80 watt per channel).
    What do you think about it?
    Anyway I would appreciate to hear advices on my previous questions.
    Last edited by audio2; 01-07-2011 at 05:32 AM.

  5. #5
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    A Denon should work well

    Quote Originally Posted by audio2
    Hi,

    I've recently bought a pair of used Tannoy Dorset T185 (60W, 8Ohm).
    I like the sound and I'm very pleased with my purchase.
    The speakers are currently plugged to an old Pioneer SA-506.
    I'm not an expert audiophile but I have the feeling that I can get more out of the T185.
    So I'm now looking for an appropriate amplifier to combine with them.
    I have been given a list of Denon amps, can somebody tell me more about them?

    Denon PMA 860 / 1060
    Denon PMA 1080R
    Denon PMA 900V

    Is the PMA 900V an integrated Class A amp?
    What is the difference with a New Class A amps?


    I'm open to take in consideration other models/brands, so any valid alternative is welcome.
    Thank you very much in advance.
    Musical greetings
    Firstly, Congratulations on your new speakers. Choice of amplifier very much depends on the vintage of the speaker in question, word on the street is that most pre-1970s models prefer tubes. However from the 70s onwards, many Tannoy speakers were designed with SS amplification in mind, As the Dorset is a late 70s model, I'll suggest that you experiment with some SS amplifiers before jumping on the tube bandwagon. Tube amplifiers may work, but there is not much quality at the $250 mark, therefore if cash is tight its safer to stay with SS until you have sufficient funds to buy a decent tube amplifier.

    I doubt PMA-900V is a pure Class A amplifier, but given that it was designed in the same era as the loudspeaker there might some synergy there. Denon amplifiers have a good reputation and should work well with your speaker. I only heard newer Denon models, but not with Tannoys, however all have been uniformly good in the setup in which I heard them.

    Sonys, Pioneers and Kenwoods of that era should also work well. Note of caution, whatever amplifier you end up with, make sure that its rated for 4 ohms operation or at least comfortable driving a 4 ohm load as the speaker nominal impedance probably belies the speaker's ease of drive and a wimpy amplifier will do the speaker no favours.
    Last edited by theaudiohobby; 01-07-2011 at 09:18 AM. Reason: Incomplete title
    It's a listening test, you do not need to see it to listen to it!

  6. #6
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    Quote Originally Posted by audio2
    To Mr Peabody & jrhymeammo:

    Actually my budget is quite modest ($250.00).
    I can eventually invest some more money (max $500) if in that price range falls a qualitative product (also second hand is fine) that will do for my need.

    Out of curiosity I've been searching for used Jolida amps an found the following:
    - Jolida JD 1501 (100 watt hybrid) year 2009 for $520.00

    With regards to NAD or Cambridge Audio, are there specific models I can look for? How many Watt are actually sufficient?

    I couldn't find any result on internet about t185's impedance curve, and I'm not that technical to measure it on my own...
    You guys are introducing me into a new world and a new technical language (OTL tube amps?). I find this very interesting and makes my quest for an amp extra exciting.

    Thank you for your time and knowledge.



    PS:
    In the meanwhile I've found an online ads for a used NAD C352 (80 watt per channel).
    What do you think about it?
    Anyway I would appreciate to hear advices on my previous questions.
    Output Transformless Tube amplifiers( OTL) are an interesting choice, however I doubt you will find any of reasonable quality at your price point and IMO most of them require a bit more maintenance than usual

    Not familiar with the NADs, is the 352 rated @ 4ohms, 80W is plenty but can the amplifier keep its poise when asked to drive a difficult load? Another decent amplifer brand is Rotel, and most models are rated for 4ohm operation and, there are many used ones floating around at your price point.
    It's a listening test, you do not need to see it to listen to it!

  7. #7
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    Quote Originally Posted by theaudiohobby
    Firstly, Congratulations on your new speakers. Choice of amplifier very much depends on the vintage of the speaker in question, word on the street is that most pre-1970s models prefer tubes. However from the 70s onwards, many Tannoy speakers were designed with SS amplification in mind, As the Dorset is a late 70s model, I'll suggest that you experiment with some SS amplifiers before jumping on the tube bandwagon. Tube amplifiers may work, but there is not much quality at the $250 mark, therefore if cash is tight its safer to stay with SS until you have sufficient funds to buy a decent tube amplifier.
    audio2 says:
    Ok this is clear and makes sense to me.
    Question: what does technically mean SS amp?


    Quote Originally Posted by theaudiohobby
    Sonys, Pioneers and Kenwoods of that era should also work well. Note of caution, whatever amplifier you end up with, make sure that its rated for 4 ohms operation or at least comfortable driving a 4 ohm load as the speaker nominal impedance probably belies the speaker's ease of drive and a wimpy amplifier will do the speaker no favours.
    audio2 says:
    mmm.... the PMA-900V has this rated output (20Hz - 20kHz): 120W (8 Ω) , 200W (4 Ω).
    Is this what you mean with "rated for 4Ω operation or comfortable driving at 4Ω load"?

    I'm all ears...

    cheers

  8. #8
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    Quote Originally Posted by audio2
    audio2 says:
    Ok this is clear and makes sense to me.
    Question: what does technically mean SS amp?
    SS means solid state i.e transistor amplifer. The Denon PMA-900V is a solid-state amp.
    Quote Originally Posted by audio2
    audio2 says:
    mmm.... the PMA-900V has this rated output (20Hz - 20kHz): 120W (8 Ω) , 200W (4 Ω).
    Is this what you mean with "rated for 4Ω operation or comfortable driving at 4Ω load"?
    Yes, that's what I mean
    It's a listening test, you do not need to see it to listen to it!

  9. #9
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    Quote Originally Posted by theaudiohobby
    SS means solid state i.e transistor amplifer. The Denon PMA-900V is a solid-state amp.
    Yes, that's what I mean
    Alright, I'm getting there...
    I'll keep posted about the coming events...

  10. #10
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    Quote Originally Posted by audio2
    Alright, I'm getting there...
    I'll keep posted about the coming events...
    Cheers , looking forward to reading your future posts.
    It's a listening test, you do not need to see it to listen to it!

  11. #11
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    Unless the 1501 is new $525.00 seems a bit high used. The 352 would be a decent amp I'd have to look up the specs to verify if stable at 4 ohms but I'd assume so. Rotel is a good suggestion as well. In my opinion NAD, Rotel or Jolida would be a step up from any of the receivers mentioned.
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  12. #12
    RGA
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    I agree with the others - tubes at the lower prices are not generally as good and frankly I would sooner start out with Solid State amplifiers.

    Do the denon's have tuners(radios) built in? Many audiophiles like to suggest integrated amps(basically a receiver without the radio) because we feel it is clearer and more of the money went to better parts than spreading the cost too thin and thus cheaping out on the actual amplification parts.

    I like all the new Rotel stuff - it's actually quite a lot better than it used to be and it was always pretty good for the money. All their power amps even the cheapest ones are fine with 4 ohms and surprisingly some are good to 2ohms and don't cost a whole pile.

    The Rotel RA-02 is my favorite integrated for cheap - it may have been replaced though as it was some time ago. I don't know if it is 4 ohm capable. http://www.superfi.co.uk/index.cfm/p...roduct_ID/1218

    Interestingly when I directly compared the Rotel RA-02 versus the NAD 320Bee the former sounded so considerably better it actually surprised me because generally cheap integrateds tend to sound a fair bit the same (enough that I would want a blind session). The 320Bee was quite popular but practically sounded broken next to the Rotel. Now if Rotel could make a great sounding CD player they could really lay the boots to the price class.

    If you really want the tuner built in then Denon is probably a fine choice as would be Marantz Yamaha etc. If the tuner isn't needed don't pay for it and go with an integrated. The RA-02 was about $500 new and probably half that now. If you need 4 ohms and it doesn't do it then the RB-1050 power amp is an option.

    Other brands to look at - Cambridge Audio, Arcam (probably more expensive). A second hand Sugden, Creek Audio, Rega, Cyrus, Sim Audio, Audio Refinement, might be found in budget as well.

  13. #13
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    Quote Originally Posted by RGA
    Do the denon's have tuners(radios) built in? Many audiophiles like to suggest integrated amps(basically a receiver without the radio) because we feel it is clearer and more of the money went to better parts than spreading the cost too thin and thus cheaping out on the actual amplification parts.

    I like all the new Rotel stuff - it's actually quite a lot better than it used to be and it was always pretty good for the money. All their power amps even the cheapest ones are fine with 4 ohms and surprisingly some are good to 2ohms and don't cost a whole pile.

    The Rotel RA-02 is my favorite integrated for cheap - it may have been replaced though as it was some time ago. I don't know if it is 4 ohm capable. http://www.superfi.co.uk/index.cfm/p...roduct_ID/1218


    If you really want the tuner built in then Denon is probably a fine choice as would be Marantz Yamaha etc. If the tuner isn't needed don't pay for it and go with an integrated. The RA-02 was about $500 new and probably half that now. If you need 4 ohms and it doesn't do it then the RB-1050 power amp is an option..

    All the denon's the OP mentioned are PMA's, which is denon's "name" for anything integrated
    so all the amps are integrated amplifiers.

    I'm pretty fond of the Rotel's too, especially in their price class. We have a RA-06 here, driving B&W DM604's (from the previous 600 series), sounds pretty good, for the price especially. They pack quite some power for their size too, although they do get pretty hot.

    That said, Rotel would be a good choice with the Tannoy's, but so would the Denon's. look into the 900V or the 1080r, the latter one is "optical class A", probably not true class A, but a class A/B design with a pretty high bias, which is controlled by some chips to get the bias as close to a class A design as possible. Technics did that too a while back, "new class A" I think they called it, they do sound good.

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  14. #14
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    I'm actually not interested in amps with a tuner built in. An easy to use and reliable integrated amp is fine.

    I've been checking NAD C352 specifications and it is 4 ohm capable.
    Continuous power 80W both at 8 and 4 ohms.
    Dynamic power output range: 8Ω/115W, 4Ω/185W and by 2Ω/240W.
    (I'm mentioning this technical details for the audio gurus out there, but I have no idea about the difference between continuous and dynamic power...I'll take my time to learn about this stuff)

    Newbie question: why is important to verify if the amp is stable at 4 or 2 ohms if my speaker's impedance is 8 ohms?



    So, on my quest for an "affordable price/value4money" amp to pair up with Tannoy Dorset T185 I came down to the following [ please don't boo at me, I swear that I've been carefully reading all of your comments ]:

    Denon PMA-900V
    NAD C352

    From reviews found here and there they're both rated as good and performing integrated amps with a warm and detailed sound. Denon is a vintage item and I like it (I know someone's quote is "It's a listening test, you do not need to see it to listen to it! ") and as suggested by 'theaudiohobby' the Denon amp was designed in the same era as my Tannoy loudspeaker so there might be some synergy there. At least this sounds logical, although is a presupposition....

    On this website the PMA-900V scores higher then NAD (High-performance,Reliability,Ease of use,Value for money), although there are not as many opinions given as for NAD:
    http://home-cinema-amplifier.diplo-b...DENON/PMA-900V
    http://home-cinema-amplifier.diplo-b...eview/NAD/C352

    On this other website the NAD C352 is the winner of a test with other SS amps:
    http://www.avreview.co.uk/news/article/mps/uan/652


    This is it for now, tomorrow I have an appointment to check out a used NAD C352.
    ...to be continued...

  15. #15
    RGA
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    There is nothing wrong with the NAD C352. But these comparisons can be somewhat skewed and it is important not to put all your faith in a review where a product gets 4 out 5 or 9 out of 10 versus something they give 5/5 or 10/10 to.

    Here is why. Plenty of products in those tests that don't win are actually preferred for sound quality. I have read enough instances and reading between the lines that the reviewers actually liked the unit that got 4 stars better than the test winner. The 352 sounds a little more like a brute force amplifier - it is - it is more capable of driving tougher loads but it can sound a little pushy while another amp may not have the overall power and drive but it sounds better on subtlety and fine detail - which to me is more important. Also, at the time of this review you posted the Rotel was at the end of its production run - it has now been replaced by a different model. Further, it is not just the amp but how it reacts with the speaker - Ie which amp is a better match for the Tannoy. It may be that the NAD is but I would try and listen to both. A lot NAD dealers here also seem to carry Rotel so maybe in your area they do as well.

    The specs don't mean very much. An 80watt amp will provide a 3db gain in volume level over a 40watt amp. 3db is virtually inaudible and only when played at the very extreme volume levels would it be differentiated.

    As for your question about 8ohms that is the nominal or average rating. Some speakers can dip down to under 4ohms usually in the bass and or treble. This requires an amp to double it's power (or more than double its power) during passages where content is at those frequencies. Speaker makers usually don't provide the info. Generally though 8ohm speakers rated at 8 ohms won't go below 4ohms so they're pretty easy on amps. But not always. All of those amps will likely be fine with most 87db sensitive 8 ohm speakers. Tannoy is generally pretty benign here as well which makes them desirable for lower powered amps.

  16. #16
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    Quote Originally Posted by RGA
    Tannoy is generally pretty benign here as well which makes them desirable for lower powered amps.
    That statement is not correct, Tannoys are generally sensitive but not necessarily benign loads, an amplifier comfortable driving 4ohms would work best, its also a better quality amplifier.
    The specs don't mean very much. An 80watt amp will provide a 3db gain in volume level over a 40watt amp. 3db is virtually inaudible and only when played at the very extreme volume levels would it be differentiated
    Hmmm....3dB could be all the difference between an amp driven into clipping and one that's not..
    Quote Originally Posted by audio2
    I've been checking NAD C352 specifications and it is 4 ohm capable.
    Continuous power 80W both at 8 and 4 ohms.
    Dynamic power output range: 8Ω/115W, 4Ω/185W and by 2Ω/240W.
    (I'm mentioning this technical details for the audio gurus out there, but I have no idea about the difference between continuous and dynamic power...I'll take my time to learn about this stuff)

    Newbie question: why is important to verify if the amp is stable at 4 or 2 ohms if my speaker's impedance is 8 ohms?
    • Continous power - amplifier can deliver the amount of power all day long without suffering any damage.
    • Dynamic power - amplifier can only deliver this amount of power momentarily

    Personally, I would try the vintage Denon before the NAD, I have nothing against the NAD but the Denon has some retro appeal, especially in gold livery. And its been around for a while, which should suggest a certain level of quality.
    Last edited by theaudiohobby; 01-08-2011 at 10:40 PM.
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  17. #17
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    Dear all,

    I'm literally overwhelmed by your knowledge and participation; I'm astonished of such a passionate debate sparked from my post and I really appreciate this.
    I feel the need to make this statement, as I've just approached the audiophile world.
    I can't say right now if this is going to be my hobby. Let's say for now that I enjoy listening to music when I have the time for it.
    The Tannoy speakers I recently bought are the very first serious pair of speakers I ever had in my life!
    Their sound has brought a fresh new perspective to my entire music collection, especially with live recordings.
    Suddenly it's become very interesting to rediscover my music library and be amazed, or disappointed, by the recording sound quality and reproduction.
    That's something I could have never think of before "my Tannoy era" and it has been an unexpected improvement of my audio experience.
    Surely (and positively), the way I enjoy listening to music is radically changed.

    Said that... unfortunately I don't understand yet this technical language and after reading RGA's comment "Tannoy is generally pretty benign here as well which makes them desirable for lower powered amps" I honestly have to say I began to doubt if my old Pioneer SA-506 with its 25W could have been fine...
    (Btw, RGA, I also personally find subtlety and fine detail very important)


    I think that keeping it simple is just fine until I'll have a better understanding of technical terms and operation of audio electronic equipment.
    Step by step it "sounds" wise and affordable.
    Of all the brands mentioned in previous posts, the Denon PMA 900v and the NAD C532 are currently the only (second hand) amps in my targetprice.

    For these two amps I've currently found two online deals and they both seems to be in excellent conditions.
    Denon PMA 900v (y. 1987) 230USD
    NAD c352 (y. ?) 260USD

    This afternoon I'll have a listening at the NAD owner's place, next week by the Denon.

    The quest goes on...

  18. #18
    RGA
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    The simple explanation:

    Basically think of a speaker as bucket and the amplifier as a well. The speaker places a demand on the amplifier. If the amplifier and speaker are both 8ohm nominal(average) and the speaker and amp never changed in their demands then everything is fine. We call that an easy load for the amplifier.

    However amplifiers and speakers are not just their average. When the impedance of the speaker drops it requires a lot more amplifier power to keep the same volume level

    Consider a speaker for example that might be 8ohms in the treble. If in the bass notes the speaker drops to 4ohms, the speaker will now request twice the power from the amplifier to achieve the same volume in the treble. So if in the treble the amplifier is putting out 5 watts and the bass passage comes along the speaker would have to put out 10 watts to hit the same volume level it was doing in the treble. And if the speaker drops to 2 ohms then it would request another doubling of power or 20 watts. for each halving of the ohms requires a doubling of the power. At 1 ohm it would request 40 watts.

    So the term a benign load of a speaker rated at 8ohms to me would be a speaker that does not dip below 3ohms. Most amplifiers can get close to doubling their 8ohm rating. It is not completely necessary to get double. For instance if you have a 40 watt amplifier and you are listening to a 90db sensitive speaker at an average 90db (quite loud) then you are using 1 watt of power. If the speaker hits a bass line and drops to 4ohms then the amp will need to use 2 watts to meet the demand.

    If however you are playing very loud say at 105db - you would be using 32 watts of your 40 watt amplifier. If in that bass passage it drops to 4 ohms the speaker is requesting double the 32 watts or 64 watts. The amp is only rated for 40 watts. Still if the amp is rated for 70 watts into 4ohms it will still meet the demand even if it can't quite double it's rated output. Further even if the speaker demanded say 75 or 80 watts - In short bursts amps can likely handle this but if it is prolonged the amplifier will go into clipping or distortion and will send a high powered distortion to your speaker which could damage the loudspeaker or the amplifier. (if the speaker dropped to 2ohms it would request 128watts and this would be well beyond the amplifier and it would clip and possibly blow the amplifier's on board fuse and shut off to protect the amp and your speakers).

    As you can see if you play very very loud and the speaker dips down a lot in ohms (impedance) then you can see why people tend to like higher power amplifiers with not so easy to drive speakers.

    Plus many makers play with the numbers - some amps may produce 100 watts at 1khz but not necessarily anything remotely close at other frequencies.

    Some of the better amps actually don't double into lower frequencies. The Sugden A21a at 20 watts into 8ohms only muster about 11 watts at 4ohms. So it's a double whammy. When the speaker dips to 4ohms and wants twice the power the Sugden not only can't double the power it actually halves it's power. This is why it is a bit of an idiosyncratic amplifier and won't just work with any loudspeaker. SET amps typically do this and it is a major drawback when partnering with loudspeakers - they have to be relatively sensitive but more importantly the impedance has to not drop much (hence benign or stable impedance).

    Why you might ask would someone want an A21a if it can't double it's rated output - because many people feel that the sound quality of the single ended class A (no feedback) sounds very much superior to the high current (double it's power) push pull amplifier designs.

    Benefits

    * Simplicity. An audio amplifier cannot be much simpler than a Class A single-ended.
    * Overall low harmonic distortion with small signals. By nature Class A amplifiers do not suffer from crossover distortion.
    * Small roaming of anode bias current does not do anything catastrophic.

    Drawbacks

    * Low efficiency. All Class A amplifiers consume power regardless of the signal amplitude.
    * Second harmonic distortion at high signal level is a normal feature of single-ended amplifiers.
    * Compared to the amplifier's low power the output transformer is heavy and expensive.

    So when buying an amplifier you have to generally know the kind of speaker and at what level you intend to play. At low to moderate levels I have found that lowish powered Single ended amps have sound superior even with tough speaker loads and lowish sensitivity. However at louder levels these amps are not going to cut it. So do you listen louder more often or medium low levels more often.

    With highish high and very high sensitive speakers that present an easy load they can be very comfortable with 2-30 watt amps depending. IME I have found lower watt amps tend to sound better and the systems using them have generally sounded better to me as well. But it also tends to cost more.

    Some speaker makers do not provide the minimum impedance so generally it is safer to go with their minimum recommended power rating which kind of gives you a clue as to what will be powerful enough to still play loud. Both of my speakers can play to deafening levels with my 10 watt amp and I never get past the halfway point on either with very tightly controlled bass.

  19. #19
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    Quote Originally Posted by RGA
    The simple explanation:

    Basically think of a speaker as bucket and the amplifier as a well. The speaker places a demand on the amplifier. If the amplifier and speaker are both 8ohm nominal(average) and the speaker and amp never changed in their demands then everything is fine. We call that an easy load for the amplifier.

    However amplifiers and speakers are not just their average. When the impedance of the speaker drops it requires a lot more amplifier power to keep the same volume level

    Consider a speaker for example that might be 8ohms in the treble. If in the bass notes the speaker drops to 4ohms, the speaker will now request twice the power from the amplifier to achieve the same volume in the treble. So if in the treble the amplifier is putting out 5 watts and the bass passage comes along the speaker would have to put out 10 watts to hit the same volume level it was doing in the treble. And if the speaker drops to 2 ohms then it would request another doubling of power or 20 watts. for each halving of the ohms requires a doubling of the power. At 1 ohm it would request 40 watts.

    So the term a benign load of a speaker rated at 8ohms to me would be a speaker that does not dip below 3ohms. Most amplifiers can get close to doubling their 8ohm rating. It is not completely necessary to get double. For instance if you have a 40 watt amplifier and you are listening to a 90db sensitive speaker at an average 90db (quite loud) then you are using 1 watt of power. If the speaker hits a bass line and drops to 4ohms then the amp will need to use 2 watts to meet the demand.

    If however you are playing very loud say at 105db - you would be using 32 watts of your 40 watt amplifier. If in that bass passage it drops to 4 ohms the speaker is requesting double the 32 watts or 64 watts. The amp is only rated for 40 watts. Still if the amp is rated for 70 watts into 4ohms it will still meet the demand even if it can't quite double it's rated output. Further even if the speaker demanded say 75 or 80 watts - In short bursts amps can likely handle this but if it is prolonged the amplifier will go into clipping or distortion and will send a high powered distortion to your speaker which could damage the loudspeaker or the amplifier. (if the speaker dropped to 2ohms it would request 128watts and this would be well beyond the amplifier and it would clip and possibly blow the amplifier's on board fuse and shut off to protect the amp and your speakers).

    As you can see if you play very very loud and the speaker dips down a lot in ohms (impedance) then you can see why people tend to like higher power amplifiers with not so easy to drive speakers.

    Plus many makers play with the numbers - some amps may produce 100 watts at 1khz but not necessarily anything remotely close at other frequencies.

    Some of the better amps actually don't double into lower frequencies. The Sugden A21a at 20 watts into 8ohms only muster about 11 watts at 4ohms. So it's a double whammy. When the speaker dips to 4ohms and wants twice the power the Sugden not only can't double the power it actually halves it's power. This is why it is a bit of an idiosyncratic amplifier and won't just work with any loudspeaker. SET amps typically do this and it is a major drawback when partnering with loudspeakers - they have to be relatively sensitive but more importantly the impedance has to not drop much (hence benign or stable impedance).

    Why you might ask would someone want an A21a if it can't double it's rated output - because many people feel that the sound quality of the single ended class A (no feedback) sounds very much superior to the high current (double it's power) push pull amplifier designs.

    Benefits

    * Simplicity. An audio amplifier cannot be much simpler than a Class A single-ended.
    * Overall low harmonic distortion with small signals. By nature Class A amplifiers do not suffer from crossover distortion.
    * Small roaming of anode bias current does not do anything catastrophic.

    Drawbacks

    * Low efficiency. All Class A amplifiers consume power regardless of the signal amplitude.
    * Second harmonic distortion at high signal level is a normal feature of single-ended amplifiers.
    * Compared to the amplifier's low power the output transformer is heavy and expensive.

    So when buying an amplifier you have to generally know the kind of speaker and at what level you intend to play. At low to moderate levels I have found that lowish powered Single ended amps have sound superior even with tough speaker loads and lowish sensitivity. However at louder levels these amps are not going to cut it. So do you listen louder more often or medium low levels more often.

    With highish high and very high sensitive speakers that present an easy load they can be very comfortable with 2-30 watt amps depending. IME I have found lower watt amps tend to sound better and the systems using them have generally sounded better to me as well. But it also tends to cost more.

    Some speaker makers do not provide the minimum impedance so generally it is safer to go with their minimum recommended power rating which kind of gives you a clue as to what will be powerful enough to still play loud. Both of my speakers can play to deafening levels with my 10 watt amp and I never get past the halfway point on either with very tightly controlled bass.
    Thank you RGA, I'm gonna spend some time to digest all of this but I hear you.
    I've been checking out for used (this my only way to try to get some good stuff, new is out of my wallet right now) Rega, Arcam and Rotel amps.
    I'll be back with a report of my "hunting", now I must really go to sleep...
    I must admit that I've been underestimating the importance of time/know how. I couldn't imagine at the beginning of my quest that I would have gone this far.
    Too much hast on my quest, I think...typical me...
    Thing is I got very enthusiastic about this vintage Denon and convinced myself that is a good occasion (or maybe it is, for what it is).
    However I'm glad I'm learning something (a lot) here.

    PS - I've been listening to the NAD today, but I can't say I've been touched. How is it possible to judge when the audio set up is completely different from the one I have at home...it's not realistic.

  20. #20
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    I'm reading this thread over and over and although not all the technical/operational concepts are 100% clear to me, at last/least the picture is finally getting sharp (....eureka!...).
    I now understand why a low powered amp would be more suitable to my speakers.
    Thank you.(!)


    I've found for an affordable price the following products. Can I have your opinion about them?
    Rega Brio
    Rotel RA-930bx

    Are they more or less equivalent or maybe at this point should I wait until I find a good deal for a Rotel RA-02?

    With much appreciation

  21. #21
    Ajani
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    Just to add my 2 cents to the discussion:

    I owned the NAD C352... It certainly has loads of power (NAD and Rotel are notorious for understating their actual output power)... Also you would be in no danger of it making anything sound harsh...

    My complaint with the 352 is that despite all the great reviews (which is why I bought it back in the day) I found it to be utterly boring... If you have wild speakers then it might be a good choice to tame them, but otherwise I'd look for something else (Rotel would be my choice in that price range)...

    Note: by" wild" I mean excessively bright and lively...

  22. #22
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    Hallo hallo

    On behalf of the extensive explanations I received to my initial question, I've spent some time looking around for an amp suitable with Tannoy T185 speakers.
    I've almost made up my mind and I'm currently interested in one of the following amps:

    Rega Brio (first serie, year 2000)
    Rotel RA-04 SE (can't easily find a used RA-02; btw, does anyone know why a new RA-02 is more expensive then a new RA-04?)

    I would appreciate to hear suggestions/comments before going for it.
    I promise I will post a genuine review soon after I will have tested the "new" amp (hopefully a musically happy match ....)

    I just think it's appropriated and considerate after all this brainstorming.

    Seriously thank you

  23. #23
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    Hi all,

    finally about two months ago I came across a good occasion and bought a Rotel Ra 04.
    Since then I haven't spent much time on long and extensive audio sessions. I mostly played it when I had time as background music.
    Anyway here is my first impression:

    My previous amp was a Pioneer SA-506 from the 70s (25W) which at low playing level could reproduce a warm sound and full bass.
    With the Rotel RA 04(40W) I miss this warmth when playing at low level but as I turn the volume up the power and potential of the audio system come out as a whole.
    It's like giving gas on a fast car and enjoying being push into the seat, that's the feeling (just to make a very expressive comparison!).
    I'm happy with this match (Rotel + Tannoy) and I especially I enjoy it with live recordings.
    Of course the quality of recordings are now playing an important role and this system puts a strong accent on it.
    The room where the audio system is installed it's not very big (approx. 14 square meter) but it doesn't seem to be problematic at higher levels, although I play more often at low/medium levels (I would also like to play louder but I'm considerate to my neighbors).
    I'm now very curios to find out how it would sound a Sugden amp, maybe that's where I will move next, but I will take some time to enjoy and test the Rotel properly.


    At last I would like to quote RGA's comment again as I find it an important consideration one should think about it before/when choosing components for an audio system:

    So when buying an amplifier you have to generally know the kind of speaker and at what level you intend to play. At low to moderate levels I have found that lowish powered Single ended amps have sound superior even with tough speaker loads and lowish sensitivity. However at louder levels these amps are not going to cut it. So do you listen louder more often or medium low levels more often.

    With highish high and very high sensitive speakers that present an easy load they can be very comfortable with 2-30 watt amps depending. IME I have found lower watt amps tend to sound better and the systems using them have generally sounded better to me as well. But it also tends to cost more.

    Some speaker makers do not provide the minimum impedance so generally it is safer to go with their minimum recommended power rating which kind of gives you a clue as to what will be powerful enough to still play loud. Both of my speakers can play to deafening levels with my 10 watt amp and I never get past the halfway point on either with very tightly controlled bass.



    Thank you and happy listening,

    audio2
    Last edited by audio2; 04-23-2011 at 01:33 AM.

  24. #24
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    Consider a Tripath amp

    Often overlooked by people with speakers of good efficiency are Tripath, "Class T", amps. They typically offer very clean sound with moderate power, and compact size -- and compact price. Personally I'd tend to prefer them over low powered NADs, Rotels, Adcoms, etc.

    Here is an example from Parts Express, a Dayton Audio DTA-100a, HERE ...


  25. #25
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    I too prefer the T-amp sound over the NADs, Rotels and Adcoms of the world. Amazing little boogers they are indeed.

    If they cost more, weighed a ton and came in a big chassis perhaps they'd be more popular.

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