NEwbee, you may be right.
Here are the specs from the arc site:
OUTPUT IMPEDANCE: 260 ohms Single Ended main; 20K ohms minimum load and 1000 pF maximum capacitance. Outputs (3): 2 main, 1 record (Single Ended RCA connectors).
I'm not sure how to interpret this though if anybody can clarify for certain.
Is 260 ohms the pre-amp output impedance and 20K OHMS the minimum recommended amp input impedance maybe?
BTW, I have seen at least 1 ARC SS amps out there have 150K ohm input impedance specifications. |
Well, that's very different then.
ARC's specs are the most detailed I've seen so far then in this regard, and my original question is a moot issue then I suppose.. |
It does make sense to me optimize the electronic interface between components in a system to whatever extent possible, all other factors aside, to maximize inherent performance.
The input impedance of my current Musical Fidelity A3CR amp is ~31K.
I've seen ARC SS power amps with 150K ohm input impedance. I'm thinking that it might make sense to go with an SS amp like this from a company that has tube pre-amps as a specialty.
Other options I know of to consider are Bel Canto Ref 100m (150K ohm unbalanced input impedance, 300K ohm balanced)and Wyred 4 Sound (~60K ohm input impedance).
Stock ICE power class D amps appear to have only about 20K input impedance which would seem to make them a less desired match with many tube pre-amps.
Any other SS amps with high input impedance to consider? I doubt I would seriously consider a tube power amp for my application at this point with the big current hungry OHM 5s in my system. |
My strategy will be to play it safe and go with a high current SS amp that doubles output into 4 and eve 2 ohms as much as possible and has a higher input impedance, along the lines of those I mention above. That will optimize electronic interfaces both in from pre-amp and out to speakers.
From there, whatever amp used will be in an optimal position to synergize with pre-amp and speakers and deliver its best performance as a result, whatever that may be, I would say. |
Tvad,
Any SS Amp recommendations given all this? |
This is primarily for the OHM 5s which have a somewhat difficult load, are only 87db efficient and the more juice, the merrier.
Power requirement: 250w/ch minimum doubling into 4, high current.
I'd like to stay under $2500 if possible for now.
Also, logistically, I would prefer to stay away from large heavy, hot running monster amps if possible. I know that limits my options.... |
"I don't know why Mapman is reluctant to consider ARC recommendations "
Newbee, what gave you that idea?
I'm not. I would assume ARC to be a most reliable source for recommendations regarding their equipment given their considerable history, experience and reputation, and the fact that their unit has been a home run to-date in my system.
Tvad has been around with a lot of different equipment I believe and has a good attention to sound quality and technical details so I do not discount his observations in this area either.
I agree with your point about validity of apples and apples comparisons between amps based solely on input impedance differences as well, but I do not doubt that higher amp input impedances relative to pre-amp output impedance is one (of several) technically sound measurements that one can attempt to optimize along with but not at the expense of others necessarily as well. |
Al,
c
Thanks for the details.
I can say with confidence that the sp16 sounds very balanced, natural and lively with the MF a3CR I'm using (31K input impedance spec).
There is a larger (>200 w/ch)MF A308CR amp up for sale by a local Agoner. I think the impedance specs are the same as the A3CR but need to confirm. Since I like the current sound an would be happy with more of it, that might be something for me to consider again now that I have a handle on the impedance issues. |
Thanks everyone for sharing your expertise and attention on this. Much appreciated. Impedance matching is one of those things that I know makes senes to look at for optimal "synergy" between components, but I learned a lot regarding the details of what might go right or wrong here.
Just because the IC connectors are physically standardized to connect things doesn't mean any two things all do it together equally well electronically for sure! |
Here are the leading contenders for the position of amp in my main system:
1) Wyred 4 Sound st-1000 or sx1000, best value, 500w/ch Class D offers potentiall best overall dynamics in my price range, 60K ohm input impedance, reported best of class results by OHM guru and fellow agoner Mamboni
2) Musical Fidelity A308CR, similar to what I have, 31K ohm input impedance, 250w/ch local seller, can audition in my system, 60+ amps current deliver (total for both channels I'm assuming
3) Musical FIdelity A5CR, similar to A5CR but significantly higher current delvery based on user guide specs, none available currently but I am not in a rush and could wait.
Is anyone familiar with A308CR versus A5CR that can offer insight on what all is different?
4) Larger ARC SS amp, D400 or 300.2, 150Kohm input impedance, 200 w/ch or so , I would have few reservations trying out other ARC gear that can fit in nicely with my pre-amp and the OHM 5s.
All thoughts welcome!
THanks |
Foster,
Yes, it will be interesting what that device might do in your case. On paper, the VTL and McCormack appear to be a pretty good match. The DNA 500 is the only other (non Class D) 500w/ch amp that I have considered to-date. |
Yes, you can cross all the Ts and dot all the Is and there is still that mysterious place known as ..... The (audio) Twilight Zone....
Ominous music cue........ |
I've continued to research amp options for my system since my last postings here.
The bigger Class Ds that specifically address input impedance matching with tube pre-amps in general are still at the top of my list as a result of cost effectiveness, favorable reviews and commentary, specifications and small footprint and resulting impact on my current system layout and configuration.
The Bel CAnto ref 1000 mkiis (currently going for under $4000 used) would seem to be the holy grail in my case based on what I read and have gathered in lieu of hearing one.
The Wyred st-1000 ($2000 new, under that used) would appear to be the very close next best thing for significantly lower cost.
My impression is that the Wyreds and their ilk are driving down the resale value of the Bel Cantos and their historically pricier ilk (like SPectral and perhaps to a lesser extent Rowland).
Any comments on Wyred st-1000 versus BelCanto ref1000 mkii? I might be tempted to try the Bel Cantos at some point soon if further convinced that the sound differences justifies the cost premium? |
Hello all.
Some closure on this for me finally. I ended up with a used pair of Bel Canto Ref1000 mkiis. They are up and running in my system. Very sweet indeed! I'll post some more impressions or whatever else might come up relating to these back in my system listing.
Thanks for all the feedback you all have provided to help me with this decision both here in this thread and elsewhere. |
Dark,
Not sure about a clear answer to your question.
The BC ref1000 specs indicate Peak Output Current: 45 amperes.
I've seen higher and lower. I suspect the switching nature of the power supply optimizes application of delivered current perhaps in comparison to other types? |
al,
the 45 amp spec is published in the amp's user guide on the bel canto website. |
