Re: One a Minute ?



"maxhifi" <no@xxxxxxxx> wrote in message news:483D8E60.E38F3FD1@xxxxxxxxxxx


Phil Allison wrote:

** Hi to all.

Aussie electronics magazine " Silicon Chip " has just published a
technical
review of this amp:

http://www.fountek.com.au/products/a3500-ss/

They verified most of the specs OK - modest though they be (ie 0.63%
THD).

They added one new one, the damping factor was only 1.6 with both 8 and 4
ohm loads - which is typical for guitar amp output stage !!! Even by
early 1950s hi-fi tube amp standards, this is piss poor indeed.

Models sold by Quad and Leak well over 50 years ago delivered THD figures
of
0.1% and DFs of around 10 to 20.

This Chinese made 32wpc power amp retails here for a cool A$1900 .......

Bet they make 'em one a minute, for the legendary market with that same
birth rate.

Lots of new tube amps have a poor damping factor, and lots of makers don't
tell
you what it is, even expensive ones. This is by no means restricted to
Chinese
products. It appears to be the often ignored flip side of the 'negative
feedback
is bad' movement.

Chinese tube amps rarely come with a comprehensive set of test figs.
Often, when tested, they do not meet the published spec. This
is expecially true of bandwidth and distortion at full power.

My 50W tube amp (built in my own workshop) has a Zo
of 0.4 Ohms and so a damping factor of 20. This is good for a tube
amp but modest compared with most SS amplifiers.

Many people think that damping is not too important.

I had lunch just a few days ago with a very interesting chap, a
talented amateur oboe player. He told me that he could not listen
to an amplifier with feedback. Even the 10-15dB found in many tube
amps introduced artifacts which he found disturbing and "smeared
the musical signal" He found listening to SS amplifiers a most
unpleasant experience.

I pointed out the considerable advantages of NFB in tube
amps, lower THD, improved SNR, lower Zo, better
damping. But his reply was that all this was too high a price
to pay for "corruption" of the signal.

Even though I hold the oppositive view, I was interested
to hear what he had to say. I could not state categorically
that he was incorrect, and none of us can put ourselves
in another person's ears:-)

Iain



.

Relevant Pages

  • My recent GAS: Stellar guitar/Peavey Tube Amp
    ... A second guitar will be on its way once I ... watt tube amp form a guy off of Craig's List. ... The weak point of this guitar are the pickups. ... but more about that when I get to the amp portion ...
    (alt.guitar.beginner)
  • Re: Tube Amp Shopping?? .. looking for opinions/clarification
    ... I'm looking at getting a new amp.. ... when buying a tube amp what should I look for? ... It can produce a fairly nice sound, but not a genuine power stage breakup sound. ... However, not even the Epi Valve Junior, at 5 Watts, will produce tube breakup sound at levels you can use at home. ...
    (alt.guitar.amps)
  • Re: Two amps, one set of speakers ...
    ... amp has an output tranny it would hate unloaded outputs too. ... An unloaded transformer is simply a huge inductor. ... This amp still has the death cap installed at the primary but it does ... most every tube amp comes with this warning in the manual. ...
    (rec.audio.tech)
  • Re: Ok, I need serious help!
    ... I had to sell my Fender De ville tube amp as well. ... But that made in mexi Nashville Tele. ... this cause it's been a dream of mine to learn guitar. ...
    (alt.guitar.beginner)
  • Re: general question about audio amplifiers
    ... the transformer required to do the impedance ... transformation from the output of the tube amp into its load would ... mean by 'smoother'. ...
    (sci.electronics.basics)