"Harry Lavo" <hlavo@[EMAIL PROTECTED]
> wrote in message
news:fsroub01t7k@[EMAIL PROTECTED]
> "Serge Auckland" <sergeauckland@[EMAIL PROTECTED]
> wrote in message
> news:fsp1hd02u4a@[EMAIL PROTECTED]
>
>>snip<
>
>>
>> The issue of all amplifiers sounding the same is one of thresholds of
>> hearing. All modern electronics, unless specifically designed to be so,
>> will
>> have an essentially flat frequency response, low distortion in all its
>> forms
>> and low noise. As these are well below the threshold of audibility, it
>> follows that all electronics will sound the same once level matched and
>> used
>> within their design parameters. This will apply even more to pre-amps
>> which
>> by their very nature have an easier task than power amps.
>>
>> The sole proviso to the above is the RIAA equalisation and cartridge
>> loading
>> that some pre-amps still provide if they have phono inputs. The RIAA
>> accuracy will determine the overall phono frequency response, and the
>> cartridge loading will determine how the cartridge performs.
>> Consequently,
>> I
>> would expect that if there are any differences when levels are
accurately
>> matched and under suitably blind conditions, then it is most likely due
>> to
>> the RIAA eq or cartridge.
>>
>
> Don't forget the interface.....output impedances of preamps can vary
> widely
> with frequency response and vary greatly from model to model. This
makes
> matching up with the input impedances of power amps iffy in some cases.
I
> have Onkyo preamps, for example, that work fine with most power amps but
> roll off noticeably when mated with Outlaw monoblocks. Yet the preamps
> rated output impedance (at 1000 ohms) is the standard "100 ohms" and the
> input impedance of the amps is the standard "10k ohms".
>
If there is roll-off with the Outlaw monoblocks, then there are several
possibilities:-
1) The roll-off is a subjective impression which is not there when
measured.
By the way, I assume you meant (at 1000 Hz) not 1000 ohms.
2) You are using a very long length of cable between your preamp and
Outlaw
power amp ;-) With an output impedance of 100 ohms into 10k, there should
be
no roll off in the audio band unless the capacitance is pretty high. I
calculate a 3dB drop at 20kHz needs a capacitance of 79nF. With typical
100-150pF/metre capacitance, that's 527-790 metres of cable!
3) The output impedance of the preamp is not 100 ohms, but a great deal
higher.
4) The input of the Outlaw power amp has a very high capacitance. Normally
it would be a few pF, but if Outlaw for whatever reason put, for example,
100nF, then there would indeed be a noticeable roll-off even with short
cables.
If 1) above is not the case, then there's ALWAYS a measurable reason for
any
effect.
S.
--
http://audiopages.googlepages.com
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