Date: Fri Mar 13 02:59:36 2009 Back to Contents ------------------------------------------------------------------------

Author: Bernard Cleyet

Subject: Re: stereo speakers

Post:

In responce to the portion quoted below from my recent post, my LA
violinist friend* replied:

--------------------------
This is the first time I have heard of this variable ("damping")
called "voltage source and current source".
Also, I have always considered high impedance sources such as tube
amplifiers (low damping) "voltage sources" and transistor amplifiers
(high damping) "current sources" as transistors are themselves called
current amplifiers and tubes are voltage amplifiers.
If one were to put a 1 ohm resistance in an output circuit, it would
not deliver the stated voltage to different loads. The different
loads would show different voltages on their inputs.

Aside from the wording, damping is critical to the proper operation
of equipment. A loudspeaker is DESIGNED for a certain damping factor.
ARs were always designed for low damping, a good high damping
amplifier (high feedback loop) makes an AR-1 sound low in bass. KLH
speakers were designed for high damping amplifiers as that was what
amplifier builders were working toward. Mid range and tweeters have
the same characteristics, but at those frequencies, there is no db
change and hangover is trivial.
The present output impedance of most transistor amplifiers is
somewhere around .1 ohm (dynamic) and so the 4 ohm (modern speakers
are not 8 and certainly not 16 ohms) speakers are restricted in their
damping by the resistance of the speaker wires!

---------------------------------


** In the middle of the last cent. we built speaker systems for his
musician friends, inter alia.

On 2009, Mar 12, , at 00:41, Bernard Cleyet wrote:

cut

>
> more:
>
> The sonic personality of the Sunfire depends on which type of
> output you choose. For those who prefer the crispness of solid
> state amplifiers, there is a voltage source output, and for tube
> sound lovers, there is a current source output. The voltage source
> output sound was characterized by one of our staff as "blue white",
> that is, crisp and clean, without any apparent coloration. The
> current source output, on the other hand, has a warmer
> characteristic to it, similar to (but not identical to, of course)
> a tube amplifier sound. [pic. removed] Bob Carver recommends a bi-
> wiring configuration, in which the current source outputs are
> connected to the mid-range drivers and tweeters, while the voltage
> source outputs are connected to the woofers. In this way, the
> current source outputs, with their moderate impedance (1 Ohm
> resistor placed in series with the output of each channel - see
> photo at right - the long brown cylinder is the resistor) will
> produce a warm sound in the mid and high ranges, and the voltage
> source outputs, with their low impedance (0.01 Ohm) will produce a
> very tight bass that tube amplifiers usually cannot do. Bob also
> suggests using the current source outputs for ribbon and
> electrostatic speakers. This is because these types of speakers
> tend to be very fast in reproducing high frequencies, and thus,
> with some CDs that are a bit edgy, the current source outputs will
> produce a sound that is not overly crisp. However, it all depends
> on your taste, and this unique amplifier gives you a choice not
> available in other amplifier designs.
>
> http://www.sdinfo.com/volume_2_1/productr.html
>
> Note the insertion of one ohm to reduce the damping. As I posted
> previously with some speakers and tube amplifiers a resistor
> inserted improves the sound. This I learned about 50 years ago.
>
> The most common Hi-Fi amplifier circuit during the tube era was the
> Williamson. I have some from the 50's using KT66 / El34s
> Williamson began his designs in the 40's:
>
> http://www.dc-daylight.ltd.uk/Valve-Audio-Interest/Articles-for-the-
> Web/Williamson-Amplifier-1947/Williamson-WW-April-1947.html
>
> Note the output R of half an ohm at the 16 ohm tap.

cut


From tap-l-owner@lists.ncsu.edu Fri Mar 13 02:59:36 2009

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