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Newbie needs help on Audio Research and DynAudio Quality


Hello all,

 

I am a newbie to high end home audio and need help from all of you audiophiles out there. I was actually into high end car audio back to when I was younger so I kinda understand what sound quality level can be considered at audiophile standard. I bought this set up (2 mono amps Audio Research Classic 120, Audio Research LS22 preamp, Dynaudio Contour 1.8 mkII, Rega Planet CD player) 4 years ago and did not have time and room to put them up to enjoy until recently. After setting them up last week, I was very disappointed at the performance. The sound was harsh and I would get tired after listening to 2-3 songs. I remember when I picked up the speakers, the previous owner played a couple of songs using his turntable and it was warm, clear and enjoyable (I could not remember what equipment he had back then). I have another set of solid state stuff to play around which includes Luxman M-12 amplifier, Sansui CA-2000 preamp, JBL 4311B, and same CD player Rega Planet. The sound quality is much better compared to ARC set. I expect that the ARC set at least has to be at entry level of audiophile but what I got out from it is disappointing. I need help from you experts to point out what is wrong or what I should expect from Audio Research.

Best Regards,

Dan


sqlover
almarg's avatar
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almarg
9,670 posts
 
Almarg how would you reconcile the manual indicating same power into 4 8 and 16 ohm with doubling down power into the same?

Tube amps providing multiple output taps typically have the same or similar **maximum** power rating when a 4 ohm load is connected to the 4 ohm tap as when an 8 ohm load is connected to the 8 ohm tap, and likewise for a 16 ohm tap if one is provided (as it is here).

However as long as the amp is operated within the limits of that maximum power capability, how much power is delivered as a function of the speaker’s impedance vs. frequency variations depends on the relation between the impedance of the speaker at each frequency and the output impedance of the amp. It does NOT depend on the amp’s **maximum** power capability, as long as that capability is not exceeded. That’s a point which is often not recognized. And as I mentioned the output impedance of this amp comes very close to being in solid state territory, and to being almost negligible in relation to the impedance of the speaker at all frequencies.

Best regards,
-- Al
mapman's avatar
mapman
22,172 posts
 
Yes the multiple outputs for various impedance levels does cover that.

The speaker specs indicate bass range impedance down to 3.8 ohm. Not natural turf for a tube amp. The speaker specs are fairly detailed for a product manual but specs still leave grey areas. Plus the current operating condition is not clear. It is very hard to say without actually being able to hear what the op hears. I’d give the Luxman a shot for comparison if not done already. Perhaps the ARC amps just need a tune up. They look pretty beefy like they should be reasonably up to the task. Still 4 ohm and less in the bass region and most tube amps are not a natural match from a low distortion perspective.
mofojo
2,288 posts
 
When I had Dyns they did not sound good at all with tubes. That was with a Cayin A100T with kt120s. They sounded great with high current ss amps. 
mapman's avatar
mapman
22,172 posts
 
Hey Al the way the manual is written the 45 damping factor may only be when used with 16 ohm speakers. The amps input stage is semiconductor based, the output tube. Could this tube amp similarly produce a damping factor of 45 into a 4 ohm load?  Maybe but do you see in the specs where that is indicated?
almarg's avatar
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almarg
9,670 posts
 
Hi Mapman,

I see the statement you are referring to, which says:
Output Regulation:  Approximately 0.2 dB 16 ohm load to open circuit (Damping factor approximately 45)
Like most tube amps, the Classic 120 is presumably designed such that the output tubes see a load that is the same or similar when a 4 ohm load is connected to the 4 ohm tap as when an 8 ohm load is connected to the 8 ohm tap, and as when a 16 ohm load is connected to the 16 ohm tap.

To accomplish that, it can be shown that ideally the output impedance of the 4 ohm tap would be half of what it is for the 8 ohm tap, which in turn would be half of what it is for the 16 ohm tap. Ideally that would result in the damping factor being the same for all of the taps. Various factors will cause some differences between the three damping factors, especially when the output impedance is very low, but they will usually be in a similar ballpark.

And given that a damping factor of 45 for the 16 ohm tap corresponds to an output impedance of 16/45 = 0.36 ohms, and the fact that the output impedance of the 4 ohm tap is almost certainly lower than that, it seems safe to say that interaction of the amp’s output impedance with the impedance variations of a speaker whose minimum impedance at any frequency is 3.8 ohms will not be significant.

Best regards,
--Al
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