Not a fan of the VK500 or The Belles, Threshold S500 .. Yes! |
Well Weseixas, I think we part ways on your appraisal of Class A. More often than not (but not always), I've found the more Class A the better the sound. The only problem is many so called pure Class A amps either don't have enough power for the the speakers I prefer, or the cost is beyond my budget. ...And of course, the issues of size heat, efficiency, etc.. |
Unsound says: Well Weseixas, I think we part ways on your appraisal of Class A. More often than not (but not always), I've found the more Class A the better the sound. The only problem is many so called pure Class A amps either don't have enough power for the the speakers I prefer, or the cost is beyond my budget. ...And of course, the issues of size heat, efficiency, etc..
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Is predictive bias-level adjustment a la Krell and Levinson enough, or must it be pure, brute-force Class A operation only? |
Unsound ,
I won't disagree, i can only express my involvement at many levels and again iterate that I find high Class-A Bias amplifiers not to sound like live music IMO, tending to be soft and laid back ( gentle) and nothing like the recording or live music, of course there are exceptions, but for the most part, , yes, this has been my observation.
Again speaker topology play's a big role here and of course there are those that prefer soft and gentle to
"real " and if you have a speaker which is forward sounding or "bright" it will have an issue on anything but Class-A.
Class- D have what i speak of in spades, unfortunately other issues with that topology leaves it a bit dry making ClassA/AB still the best output stage topology IMO.
regards, |
Irv,
We have taken Krell's and re-biased them to 10% of their original class-a bias after service and recapping and the difference is astronomical.
Anyone with an older Krell KSa 200/300 et al series should give it a try, no more 1400 watts being pulled at Idle .
regards |
I appreciate the discussion of amplifier topology and performance. It's informative for electronics novices (like me).
An amp with high input impedance is important
not "dry" or "lean"
lively with bass weight and clarity.
An issue is my Cary SLP 05 preamp has fairly high output impedance into the lower frequencies. My speakers are Mirage OMD 28 /Impedance 6 Ohms nominal /3.5 Ohms minimum 87db efficient /Crossover Point 550 Hz and 2.5 kHz |
I hate to repeat myself, but a Threshold S500 with new caps and a re bias appears to be just what your looking for. Though Threshold made very well received pres, many used them with tubed Audio Research and some used tube c-j pres. If memory serves me correctly the input impedance was 75 KOhms. 250 Watts per channel 8 Ohms, 500 Watts per channel 4 Ohms. 20% Class A bias into 8 Ohms. Class A bias halving as power doubles into 4 Ohms. |
Assumed you had some kind of passive. The 400 ohm Zout of the Cary should not be a concern even for an amp with 10Kohm Zin.
The 3.5 ohm minimum (4.25 - ultimateavmag) of the speakers isn't that critical either, unless it's coincides with a big phase angle, which it doesn't on those. In fact, they tend to be a little midbass heavy, peaking with the minimum impedance at about 90 Hz. Yes, they benefit from the bass control of a strong amp but, along with the titanium tweeter and some high frequency fluctuations (sibilance?), I think you're going the wrong way. Although, you could do much worse than the ones mentioned. |
Thanks Unsound and Ngjockey. Unsound, at the time you referenced the Threshold it had a Sale Pending- I saw it before and it was Sale Pending for quite a while. I would likely have jumped on it.
Ngjockey:
From Stereophile's mearsurements of the SLP 05:
"The SLP 05's output impedance is specified as a usefully low 400 ohms. However, I got significantly higher values for the unbalanced output of 15001600 ohms in the midrange and treble, rising to 3400 ohms at 20Hz, with similar if slightly lower figures for the balanced output." |
That seems like quite an impedance swing from the Cary. I'm not sure I would want to be married to it. |
I'm not that familiar with your speakers and didn't take the extra time Ngjockey took took to consider system compatibility. My suggestion was merely based upon your posted request. |
@Unsound... That's because I've been laid up and bored to tears after knee arthroscopy. |
I admired your effort. I do wish you a speedy and pain free recovery. |
There's a Marantz SM-11 power amp in the listings right now for $2K even (original list $4600). 110W into 8 ohms, 220W into 4 ohms, 101dB S/N ref 1W into 8 ohms. This seems to meet the OP's requirements. I recently acquired one of these myself, along with the matching preamp, and am very happy with it.
No knowledge of or connection with seller, etc |
Luxman:
http://www.stereophile.com/content/luxman-b-1000f-monoblock-power-amplifier |
Weseixas: Luxman B-1000F monos Price: $55,000/pair- well yes, they are high current and new... I'll give you that. |
Atmasphere, technically there is no such thing as no feedback in an electrical circuit and hence a zero feedback amplifier, can you quantify your statement ? Loop negative feedback is what I was referring to. I have no issues with degenerative feedback as it occurs in real time. Foster_9, with traditional SS amplifiers using feedback and operating class AB, you are not going to find a lot of difference in the sound. So older amplifiers are indeed an option, but making sure the electrolytic caps that occur in the circuitry are actually good will be important. In this regard the HK Citation 11 and 16 were decent amplifiers- sounding very much like many modern amps for a fraction of the cost. But you had better know a technician that can service them out, as their filter caps will be shot by now. Another amp that seems to stand out is the BEL amplifier. It was a well-made amplifier whose designer died too soon. |
