Cavalli has a new Liquid Lightning version, the LL2T.
A major change is a digital volume control. Any comments on such a thing? (I think Malvalve has one too.) Thanks.
This sounds interesting. I went to his website a few weeks ago and only saw the old LL2. I have the original LL and I really love it. Looking forward to hear from anyone who ends up getting it...
Sorry, I got the attenuator description wrong.
It's this (quoting):
A Cavalli Audio unique processor-controlled, optically-coupled, photoresistor volume control. This entire assembly lives on a small board that sits at the rear of the amp near the input section.
You can see the cable running to the control pot on the front panel. The control is a small TKD pot that tells the opto controller where to set the volume, but since it is a nice TKD pot it has the same smooth action as all TKD pots. We have tested and listened to this setup. It sounds really good.
There are 2 problems with Light Dependent Resistors.
The first problem is that they drift over time and need calibration.
These guys seem to be the king of in the field recalibration
takes 10 minutes (20 balanced) to do a full calibration.
The other problem with LDR's is that they have significant THD in the range where
you would want to use them. Nelson pass did a fair bit of work testing these things
others have done the same
scroll down to the middle of the page here
constant impedance step attenuators with very high quality resistors are one way to do it right.
The twisted pear thing is NOT constant impedance. The sigma1 by amb IS constant impedance.
The other way it seems is something like the khozmo which is only 2 resistors in the path at
any time. But built with a switch that lasts more than a month.
There is a company in Brittan that makes a really nice one, pretty big and pretty expensive.
analogue devices, 42 steps.
and if you have a bunch of room, the shallco that is also used in the ctc blowtorch, 45 steps
the ayre preamp also uses the shallco I believe, with a motor drive.
Do you know their name?
What's your opinion of Goldpoint attenuators?
What about the stepped attenuators on a chip, are these any good? I believe my Grace Design m903 uses one like that. It has a clicky dial on the front, which operates an analog stepped attenuator on a chip in steps of 0.5 dB. Channel matching is superb on all levels, and it's a joy to use, but I'm wondering if anybody can comment on the relative sound quality of such a device.? What are the trade-offs if you compare it with a high-quality pot?
The goldpoint uses a 23 position switch, the DACT uses a 24 position switch.
Both seem reliable for many years but in my opinion both are too coarse and
do not have enough positions.
For the crazy out there, there is this
and I do have one of these, also crazy expensive
The 48 step khozmo would be great, maybe the newer ones are more reliable.
The 63 step shallco are very VERY nice. Also large.
way back when, Collins radio made 79 step attenuators designed for mixing boards
for radio stations and the like. The most fantastic thing I have ever used. Also large.
Had the best feel of anything else and lived forever. Silver contacts...
The TI pga2320 is a well known and fairly decent chip based thing with a thd of .0003%
but I have never seen a high end preamp use them.
Way back when Levinson had two different solutions both of which evidently people
really liked, and both were expensive. The first one was a 12 bit multiplying dac
(actually 4 of them) where the audio input was the voltage reference. So you can
consider this IC based. The other one was a standard R2R thing that used
datageneral dg501 (now Vishay) cmos switches as the switching elements
all on a Teflon circuit board.
The nelson pass high end preamp does the same R2R attenuator with hand
selected fets used as the switching elements, biased in a way such that they
produce ultra low distortion.
I like my 256 position .25db per step gold crosspoint relay attenuator better
than all the above. (well if I could get the Collins radio things...)
Hahaha, not enough positions. OK.
Reminds me of a girl I used to date.
Another question, related to the first question: Spritzer seemed to say that the generator (transformers) of bias voltage (580 V DC) of the Woo-Audio Wee Energizer was a 'diaphragm killer' (because of the instantaneous voltage of diaphragm implementation?, which would not be the case of loading much more progressive and long provided by a SB device). Is this true?
If this criticism is justified, would it not also the case of all Stax amplifiers when they are plugged and unplugged on Stax headphones on the output (outlet Stax) of the amplifier already lit, same potentiometer to zero from the amplifier?
All stax made amplifiers and in fact most other amplifiers have 5 Megohm series resistors to the diaphrams from the bias supply limiting the charging current
and thus controlling the charging time. Anything that puts any amount of capacitance after this series resistor can damage the headphones.