Recommend a good stereo amp or integrated under $1000 - Page 4 - AVS Forum
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post #91 of 95 Old 03-29-2013, 10:07 AM
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Easily bought used under $1k and it will give you a lifetime of pleasure

I bought a used quad 33/405 combo used for less than 50$ (including the tuner) and compared it to bryston 4BST on kef 104/2 speakers.
I did not have to blind test to NOT hear a difference. And the quad still does duty once in a while.
The brystons are sold and I run now a 300 euro hypex AS 2.100 with spdif input and internal DAC(which I also have compared to the brytons (4Bst, 4B, 2B) w/o any audible differences.
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post #92 of 95 Old 03-29-2013, 11:13 AM
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Originally Posted by arnyk View Post

...Far larger variations are likely with even the best tubed amplifiers, and if the amplifier is a SET, variations on the order of a half dozen dB are possible. This can be very audible...

Hmm. I see this sort of thing stated a lot, but my experience leads me to believe that the impedance mismatch from amp to speaker has to be a worst case scenario for such extreme frequency response aberrations.
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post #93 of 95 Old 03-31-2013, 05:13 AM
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Originally Posted by Wayne Highwood View Post

Hmm. I see this sort of thing stated a lot, but my experience leads me to believe that the impedance mismatch from amp to speaker has to be a worst case scenario for such extreme frequency response aberrations.
My experience agrees with Arny's after having measured a few (as well as designed and built many tube amplifiers including SETs). Few SETs have any gNFB and will typically have a Zout at about 1/2 tap value giving a DF of about 2. Add in one of the many speakers available with a wildly varying Z curve, and a few dB is not difficult at all.

Don't forget too that SETs lack in primary inductance in the OPT due to (often) large gaps required for the DC, which leads to an increasing distortion profile with decreasing frequency.
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post #94 of 95 Old 03-31-2013, 06:23 AM
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Originally Posted by Wayne Highwood View Post

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Originally Posted by arnyk View Post

...Far larger variations are likely with even the best tubed amplifiers, and if the amplifier is a SET, variations on the order of a half dozen dB are possible. This can be very audible...

Hmm. I see this sort of thing stated a lot, but my experience leads me to believe that the impedance mismatch from amp to speaker has to be a worst case scenario for such extreme frequency response aberrations.

Yes, a half dozen dB would be more extreme than average. But, it happens.

A dB or two error is more typical, but that is still audible since it often covers a range of several octaves.

In contrast a good SS amp is flat within a tenth of a dB or less over the critical range from 100 to 10 KHz, and usually drops no more than 0.25 to 0.5 dB at the frequency extremes.

While a great deal is made over the relatively high nonlinear distortion in SETs, I think that the frequency response variations are what people hear more strongly, more often. They are always there at just about any listening level. At very low levels with efficient speakers, the THD is usually low enough to have questionable audibility.
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post #95 of 95 Old 03-31-2013, 12:44 PM
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Thanks Arny and A9X. Take a look at this for a real life example of just these effects, to contextualize this tangent discussion:



That is a snapshot of a fool's-biamped horn/direct radiator speaker, untreated room, one channel, from about 2 meters. SS on the woofs, SET on the horns. Note the linearity and distortion. In the SET's band, linearity is not bad at all (impedance ranges from ~6 to over 30 ohms, and the relative peak at 1500Hz is indeed audible, producing a slightly forward sound in the upper mids/treble-that proverbial SET midrange presence). The distortion is kind of ridiculous, although primarily 2nd and 3rd harmonics. Down low, distortion measurements are pretty low, but all the damping factor of the ss amp and linear electrical response is futile in the face of room modes. It does smooth out with both channels driven and bass traps.

Now the SETs trying to drive the woofers does indeed result in about a 6 db suckout, for the reasons Arny and A9X menitoned. I know impedance dips into the 3 ohm range down there, and that's getting close to the output impedance of the amp. Sorry, I didn't save a snapshot of that, but just imagine a 6 db hole from 250-400 hz.

I hope this info helps any lurkers. It is meant purely to elucidate a point, and is not an endorsement of any particular approach.
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