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The Stax Thread III - Page 194

post #2896 of 3504
Quote:
Originally Posted by Jones Bob View Post

Agree with this 100%.

JRiver, Amarra, Audirvana+ all those volume controls are aweful. If you think they sound good you need to upgrade
your equipment. They kill the sound, and the software makers admit it, they recommend an actual pot if possible.
post #2897 of 3504

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?

post #2898 of 3504

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

http://www.hificollective.co.uk/catalog/glasshouse-ladder-stepped-stereo-charcroft-seiden-p-10088.html

 

and I do have one of these, also crazy expensive

http://www.tkd-corp.com/products/att/pdf/type-cs-e.pdf

 

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...)

post #2899 of 3504
That is very detailed information Kevin. Thank you. This subject is huge and has sonic impacts more than people realise. It might be better under it's own thread. Back my the Khozmo I have just bought one of their Passive 'pre amps', the stereo model with selector. I choose the Takman z foils version. I will post my findings in the next few weeks. It is actually going i my speaker rig, fed by a low output impadance of 10 ohms from my Tubed DAC which has 2v output and transformers on the output.

Short interconnects then the Khozmo 10k passive, feeding my Plinius power amp which is 47k input impedance + an active sub which is 10k input impedance. So I was thinking my DAC source would see a load of around 37K? Is that more or less correct Kevin? If the passive sounds awefull due to impedance mismatch, I will need to revert back to using an active pre-amp. The Plinius can reach it's rated power on .8v input so hopefully there will be enough current.

Any thoughts on this subject Kevin. Sorry, off topic on this thread guys.
post #2900 of 3504

Hello,

 

Here are the latest pics available of the new Energizer AudioValve Verto, who seems wanting to go further in terms of versatility and the sound quality (coupled to the amplifier of the same brand Audiovalve RKV-II or III) than its direct competitor, the Woo-Audio Wee.

 

These photographs, taken this time from inside the case, show only two (big) transformers of the brand Pikatron, as well a series of... (?) participating in the creation of a Self Biasing (SB) from the input source (somewhat after the manner of Energizer Stax SRD-7 SB of yesteryear).

 

The supposed superiority of the Verto compared to the Wee would come from both of the best intrinsic quality of the Pikatron transformers, as well as a lower ratio of amplification of the voltage transformers (ratio 1:5 for the Verto versus 1:50 for the Wee)  (NB: transformers optimized for the RKV-Verto combo), that which would give greater transparency and clarity to the sound, as well as less sound distortion.

 

The Self-Biasing (SB) 580 Volt DC charging time of the Verto (if headphone Stax Pro plugged, taking as a source input Jack of Verto (connected to the RKV)) would be of the order of two minutes.

 

A question: what is the advantage of a Self-Biasing (SB) compared to a transformer directly dedicated as 580 Volt DC bias generator?

 

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?

 

 

 

the high-voltage cascade VERTO produced up to 1.5 kV, and is generated only by the signal voltage. It takes about 2 minutes to the charge for the bias voltage established and stable, you can see this at the white glow of theLED, it only serves to control. To establish the charge an adequate volume is required "

 

 

 

http://www.audiovalve.info/to/verto.php


Edited by eric65 - 8/9/14 at 4:50am
post #2901 of 3504
Quote:
Originally Posted by kevin gilmore View Post
 

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.

 

Hahaha, not enough positions.  OK.

 

Reminds me of a girl I used to date.  

post #2902 of 3504
Quote:
Originally Posted by eric65 View Post
 

 

 

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.

post #2903 of 3504
Quote:
Originally Posted by milosz View Post
 

 

Hahaha, not enough positions.  OK.

 

Reminds me of a girl I used to date.  

 

Good banter. But after using a 41 steps attenuator I would not go back to 24 steps.

post #2904 of 3504

Hi everyone. I was in e-earphone in Osaka yesterday looking to pick up some used headphones and ended up walking away with earspeakers - specifically the SRS-2170 system for 30,000 JPY. One question I have that seems to have contrasting answers - these newer Stax amps, do they need a voltage transformer? Or are they fine with just an adapter? I'll be using them in the UK.

post #2905 of 3504
A proper adapter is fine. look out for the reversed polarity. Try doing a search in the thread on reversed polarity.
post #2906 of 3504

Thanks for the reply David.

 

So from what I gather, it has to be 12V, over 400ma, 2.1mm/5.5mm, reversed polarity, and linear regulated?

 

Is that right?

 

Where do I find such a specific plug...

post #2907 of 3504
post #2908 of 3504

Yep. As told several times, you only need 12V, correct polarity and sufficient current capacity (at least 4W / 12 V = 333 mA).


Ali

post #2909 of 3504
Quote:
Originally Posted by kevin gilmore View Post
 

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.

 

Goldpoint also has a 47 step attenuator; The mono units cost $136 each. The stereo units cost $246 each.  Heck of a bargain compared to some of these other prices.

 

post #2910 of 3504

I've posted before about a 6SN7 DIY tube amp, designed and built by a friend (partly based on the Stax T1, but with many major improvements), that I've been using for the 009s, and how it was sweeter-sounding with those phones than an otherwise more-or-less identical EL34 amp, which however did a better job of driving the 007s. Since then we've done several upgrades, including replacing the 6SN7s and the 6FQ7s in the driver stage with vintage RCAs, which really opened up the sound. But the bass, especially low bass, was still on the light side. However, replacing the coupling caps with 4 Mundorf Supremes, with a total capacitance of .68 microfarads (apparently 10x that of the Stax amps) has made a huge difference. The bass is now present pretty much all the way down, and for the first time feels like it has the right weight. And it's as fast and detailed as the rest of FR. OTOH, the 007s didn't benefit from this, they already had enough bass and the change made them too rich sounding. But, believe it or not, the Lambda Signature Pros are now putting out prodigious bass. I've never heard them sound remotely like this before.


Edited by tonereef - 8/13/14 at 3:46pm
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