"Rob" wrote in message
...
Trevor Wilson wrote:
"Keith G" wrote in message
...
"Trevor Wilson" wrote in message
.. .
"Keith G" wrote
Arcam? No idea - I've just bought a brand new Denon PMA-655R amp in my
'SS revisited' quest for best sound from the smaller of the Firewood
Horns!! (Bloody SS seems to grip the smaller, less sensitive drive
units better!!) I am under the impresion that it's an OK amp with a
particularly good Phono Stage - anyone care to confirm or shoot that
down?
**Personally, I would spend the same Bucks (Squid) on a Rotel, as your
Denon fairly 'screams' in the HF. IOW: It's just another Asian amp,
with a pretty face. Now, if you'd dropped a few more Squid for the
PMA1500AE, then THAT is a whole 'nuther cricket match. It is a very
bloody good amp, with an excellent phono stage. And I'm here to tell
you that I am not a lover of MOSFET amps, but the PMA1500AE is pretty
damned good. As usual, with all the recent generation Denon tuners,
it's matching partner is an absolute gem. In fact, the new Denon tuners
make some of the old stalwarts (Yamaha T2, Tandberg, et al) sound
pretty damned ordinary. And they don't cost the Earth either.
So, in short, you should have spent a few more Squid for something
really nice, instead of another (ho-hum) Asian amp.
OK Trevor, thanks for that - most interesing, but 'few more'..? Bugger,
the 1500AE is over *double* what I paid for the 655!!
**It's well worth it. In fact, you might find yourself selling off some
of your glass things to pay for it. It is a very good amp.
I don't follow this, and remain pretty confused about the whole SS
pantomime. Apart from build quality (that 7-odd kg has to go somewhere)
what has that amp got that improves the way it amplifies, and hence sound?
**Quite a bit, actually. It is not all that difficult to coax bad behaviour
from an amplifier which performs perfectly into a perfectly resistive load.
Since few loudspeakers act like resistors, you can readily appreciate why
amplifier can sound different, yet measure similarly.
On the one hand, I gather from technical people on this ng that all amps
which 1) drive a 2 ohm load at 3 times the maximum 8 ohm power (100W 8
ohm, 300W 2 ohm at 1% THD for 3 seconds for example); *and* 2) are
properly designed and manufactured (nearly all of the big name stuff
nowadays), will sound identical. I doubt any Denon achieves (1) btw.
**The magic words in this statement a "...are properly designed and
manufactured.."
On the other hand, it's not hard to find plenty of reviews and anecdotes
that suggest amplifiers at a given spec do sound different.
Curious - is there any defining factor in your opinion?!
**Sure. Measuring speakers into actual loudspeakers can reveal differences
which may be quite audible.
My curiosity here was to compare the Denon with the Argos POS I have
been using (having compared CDPs) and I have reduced this stack:
http://www.apah69.dsl.pipex.com/show/cdpcompare.JPG
To this:
http://www.apah69.dsl.pipex.com/show/denonstack.JPG
(See how the 'spares' are created!!?? :-)
And I tell you summat - listening askance, with my back turned and eyes
shut at midnight on a foggy day and somebody else working the throttle,
I couldn't tell 'em apart!! The '30W' Argos amp weighs 5.3 kg and costs
60 quid, the '50W' Denon weighs 7.0 kg and costs 250 quid (list)!!
(Where do they get these bloody power output figures from? - I got an 8
watt 300B SET that will blow *both* of them into the weeds!!)
**Yeah, sure.
Well, possibly! Comparing a 100W valve amp and a 140W SS - the valve amp
is simply louder.
**Sometimes, yes. But Keith was talking about an EIGHT WATT amp vs a 50 Watt
amp. BIG difference. The reality is that the SPL difference between two,
otherwise identical, 100 Watt and 140 Watt amps will be barely audible. The
differences you refer to, with valve amps are mostly as follows:
1) Valve amps tend to clip (Voltage limit) rather gracefully. Thus they can
be driven further into clipping, without obvious 'nastiness' and an increase
in average SPL.
2) Valve amps tend to possess a more benign current limit characteristic,
due to the abscence of current limit systems, which are normally used in
(BJT) transistor amps.
3) Valve amps, by virtue of their higher Voltages, tend to have quite large
energy storage systems (the equation is: 1/2CV^2), though the actual
capacitance seems to be quite small. Additionally, the capacitors used in
valve amps tend to possess lower ESL figures.
4) Valve amps require the use of large power transformers, in order to
supply filament supplies. This means more iron and thus energy storage in
the power transformer itself.
1) Can be compensated for with transistor amps, via several mechanisms, but
rarely is.
2) Can be compensated for, but it rarely done in transistor amps.
3) Can be compensated for, by adding more, small value capacitors.
4) Can be compensated for by using larger transformers.
It's not that difficult. The manufacturer needs to spend a little money on
the design. IOW: In general terms, if the manufacturer has performed the
above and the consumer is willing to spend more money, a 100 Watt transistor
amp will sound just as loud as a 100 Watt valve amp. It's all about money.
Valve amp owners seem prepared to spend more on big valve amps than they do
on equivalent transistor amps. They then proclaim that the transistor amp
sounds worse, even though it was half the price. Sheesh!
Go figure (as they say)...!!
(OK, The Denon sits at 50% volume while the Argos amp is at 90% into the
stubborn little horns....)
Incidentally, I can see why SS users might not like horns - there is a
tendancy to a little 'honkiness' with them that you don't get with
valves...??!! But, contrary to what one or two here would have you
believe, us 'valvies' are not so bigotted - I love these amps and for a
few weeks in every year, it's nice to run an SS amp and soft top car!!
(Well, the days of me having a nice little soft top in the barn are long
gone, but I can still afford an SS amp or two!! :-)
**Then choose a decent SS amp.
Here's my last bit of Show N Tell for the day - the kid (my oldest) in
this car is 30 now!!
http://www.apah69.dsl.pipex.com/show/softtop.JPG
**Oh dear. I was hoping for a Morgan, at least. MGs are so passe'. They
always sounded better than they went. Back in the day, one of my mates
owned and MGB and the other a Datsun Princess. The Datsun could easily
pull 120MPH and the MG, well...... Not so fast. Let's not even get
started on oil leaks. Did Pommy car builders ever manage to build oil
seals which, well, sealed? And this is from one who has owned four
Escorts. Not one of them could keep the oil where it belonged.
Now back to earth with a bump - I gotta go and make a start on the
fascia boards and guttering now!! :-(
**Don't get me started. I just moved to a new home and we now live the
most beautiful part of Sydney. Lots of trees (and possums, Magpies,
Cockatoos, et al). The gutters glog every fime mins or so. Since it is a
two story place and I don't espically enjoy crawling around the roof 5
Metres off the ground, I got a quote for this fancy new non-clog
guttering (it really is very clever stuff).
http://www.easyflow.com.au/
Better than clever, actually. It's brilliant. FIFTEEN GRAND!!!! Yikes!
Nice product, but jeez. Maybe I'll keep climbing ladders for a bit
longer.
Leaf blockage?
**Yup.
--
Trevor Wilson
www.rageaudio.com.au
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