Amp Trials
Graham Holloway
about a new design of amplifier I have put together. So far I have exhausted
my own limited listening skills and come to a halt on further development. I
want to take the listening tests further, if only to confirm that what I am
doing is generally correct. I live in Ashford, Kent and am happy to travel
to adjacent counties, to demonstrate. Any takers?
Sorry, but please don't ask for technical details.
Regards
Graham Holloway
WPS Electronics
Arny Krueger
news:b8oiop$mqa$1$8302...@news.demon.co.uk
Either your amp is sonically transparent or its garbage.
You can determine whether or not its sonically transparent with a
straight-wire bypass test.
If you are smart enough to design a good amp, you should be smart enough to
know that the final authority on amp sound is a straight wire bypass test
and have done one.
So, how did your amp do in its level-matched, bias-controlled straight-wire
bypass test?
If it passed, then it's at least as good as the amp section of a good ca.
$100 100 wpc stereo receiver. Obviously, it can't be any better than
sonically perfect.
Peter
state amps as some the least accurate I have heard - soft with poor imaging
(many people like them though). A perfect square wave is a start. Early
Quads had a dreadfully poor square wave. If it sounds right it is probably
right or very close. This only applies to classical and jazz with no messing
with the signal.
Ask some musicians to listen. I have ended up with a Threshold amp - I would
not change it for anything. I believe the answer is minimal or no feedback
and operating in Class A with masses of reserve. Try comparing it with a
Sugden for example. Use your ears!
In what way is your amp different?
Best wishes
Peter
"Arny Krueger" <ar...@hotpop.com> wrote in message
news:0mWdnZyo9Y5...@comcast.com...
The Old Fogey
> Quad maintained the straight wire test for years. I would rate Quad solid
> state amps as some the least accurate I have heard - soft with poor imaging
> (many people like them though). A perfect square wave is a start. Early
> Quads had a dreadfully poor square wave. If it sounds right it is probably
> right or very close. This only applies to classical and jazz with no messing
> with the signal.
Didn't Quad have an advert showing a string of many 303 power amplifiers,
with suitable attenuators between one output and the next input,
suggesting that music sounded perfect even after that much processing?
Roger.
Arny Krueger
news:5c404d12.03050...@posting.google.com
> "Peter" <pjmck...@cumnor.freeserve.co.uk> wrote in message
> news:<b8pek0$vom$1...@news8.svr.pol.co.uk>...
>> Quad maintained the straight wire test for years. I would rate Quad
>> solid state amps as some the least accurate I have heard - soft with
>> poor imaging (many people like them though).
Bias-controlled level-matched listening test or urban legend?
>> A perfect square wave > is a start.
Urban legend.
>>Early Quads had a dreadfully poor square wave.
So do CD players, and they can pass straight-wire bypass tests.
>> If it sounds right it is probably right or very close. This only applies
>> to classical and jazz with no messing with the signal.
Sensitivity to coloration is not dependent on musical genre.
> Didn't Quad have an advert showing a string of many 303 power
> amplifiers, with suitable attenuators between one output and the next
> input, suggesting that music sounded perfect even after that much
> processing?
I can't find any documentation on the tests, but they could have suffered
from a reliance on resistive loads instead of loudspeaker or
loudspeaker-like loads.
Mike Coatham
> "Peter" <pjmck...@cumnor.freeserve.co.uk> wrote in message
news:<b8pek0$vom$1...@news8.svr.pol.co.uk>...
>
<snip>
> Didn't Quad have an advert showing a string of many 303 power amplifiers,
> with suitable attenuators between one output and the next input,
> suggesting that music sounded perfect even after that much processing?
>
> Roger.
They did indeed have such an advert. - The copy I'm looking at was in
HFN&RR of May 1974.
The words of the advert. are as follows:
"Given the time, patience & the money, one can connect (*) fifty 303
amplifiers nose to tail so that the programme goes through one after the
other gradually deteriorating along the way.
Deteriorating? The fact is that apart from a very slight background hiss-
akin to a good tape recording - the programme will sound exactly the same at
the end as when it started.
(*) Of course one must fit an attenuator to reduce the signal back to its
original level between each amplifier......"
One must assume that at that time, they actually did try this out.....one
thing is for sure, it would have been pretty hard to challenge the statement
unless you had access to fifty 303 amplifiers :).
Jim Lesurf
<coa...@es.co.nz>
wrote:
> "The Old Fogey" <roger....@sun.com> wrote in message
> news:5c404d12.03050...@posting.google.com...
> > Didn't Quad have an advert showing a string of many 303 power
> > amplifiers, with suitable attenuators between one output and the next
> > input, suggesting that music sounded perfect even after that much
> > processing?
> They did indeed have such an advert. - The copy I'm looking at was in
> HFN&RR of May 1974. The words of the advert. are as follows: "Given the
> time, patience & the money, one can connect (*) fifty 303 amplifiers
> nose to tail so that the programme goes through one after the other
> gradually deteriorating along the way. Deteriorating? The fact is that
> apart from a very slight background hiss- akin to a good tape recording
> - the programme will sound exactly the same at the end as when it
> started. (*) Of course one must fit an attenuator to reduce the signal
> back to its original level between each amplifier......"
It occurs to me to wonder what the frequency response of the final output
would have been like. At a guess, the -3dB points would have roughly been
at the frequencies where the output of a single 303 is down by 3/50'ths of
a dB. What is the bandwidth of a 303 when we set -0.06dB limits? :-)
Slainte,
Jim
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Arny Krueger
news:4bed395...@st-and.demon.co.uk
> In article <b91g7k$aac$1...@lust.ihug.co.nz>, Mike Coatham
> <coa...@es.co.nz>
> wrote:
>
>> "The Old Fogey" <roger....@sun.com> wrote in message
>> news:5c404d12.03050...@posting.google.com...
>
>>> Didn't Quad have an advert showing a string of many 303 power
>>> amplifiers, with suitable attenuators between one output and the
>>> next input, suggesting that music sounded perfect even after that
>>> much processing?
>
>> They did indeed have such an advert. - The copy I'm looking at was
>> in HFN&RR of May 1974. The words of the advert. are as follows:
>> "Given the time, patience & the money, one can connect (*) fifty 303
>> amplifiers nose to tail so that the programme goes through one after
>> the other gradually deteriorating along the way. Deteriorating? The
>> fact is that apart from a very slight background hiss- akin to a
>> good tape recording
>> - the programme will sound exactly the same at the end as when it
>> started. (*) Of course one must fit an attenuator to reduce the
>> signal back to its original level between each amplifier......"
> It occurs to me to wonder what the frequency response of the final
> output would have been like. At a guess, the -3dB points would have
> roughly been at the frequencies where the output of a single 303 is
> down by 3/50'ths of a dB. What is the bandwidth of a 303 when we set
> -0.06dB limits? :-)
Whatever they are, they generally get appreciably worse when typical
loudspeaker loads are used.
You can see this happen even for a fairly modern, low output Z amplifier, by
comparing
http://www.pcavtech.com/pwramp/macrot-5000VZ/index.htm#FR_100R
to http://www.pcavtech.com/pwramp/macrot-5000VZ/index.htm#FR_100S .
The difference appears to largely be due to interactions with the amp's
series output inductor.
As I recall, the 303 also has an series output inductor. These parts make
amps more durable under taxing circumstances. From an amp longetivity
standpoint, the larger (within reason) the better. The part is usually sized
for response within tolerance with a resistive load.
Mike Coatham
>
> > They did indeed have such an advert. - The copy I'm looking at was in
> > HFN&RR of May 1974. The words of the advert. are as follows: "Given the
> > time, patience & the money, one can connect (*) fifty 303 amplifiers
> > nose to tail so that the programme goes through one after the other
> > gradually deteriorating along the way. Deteriorating? The fact is that
> > apart from a very slight background hiss- akin to a good tape recording
> > - the programme will sound exactly the same at the end as when it
> > started. (*) Of course one must fit an attenuator to reduce the signal
> > back to its original level between each amplifier......"
>
>
> It occurs to me to wonder what the frequency response of the final output
> would have been like. At a guess, the -3dB points would have roughly been
> at the frequencies where the output of a single 303 is down by 3/50'ths of
> a dB. What is the bandwidth of a 303 when we set -0.06dB limits? :-)
Don't know about FR changes but the advert was very carefully worded to say
"the programme....". In those days that would have been vinyl or reel to
reel tape or FM radio. We know that all of those mediums have/had
bandwidths(if that is the right word) which are not as good as those of the
'hardware'.
In the case of the 303, the FR is flatter with 15ohm loads than with 8 ohm
loads - not surprising when you consider which speaker the 303 would have
been partnered with :). So their claim was probably quite valid.
Graham Holloway
to help. I am very pleased with the professional help I received and this
has given me the impetus to complete the project.
Graham Holloway
WPS Electronics