[fdg]

@ rx79ez08
 
There seems to be a little missunderstanding ...
 
… to make more clear what we are using for volume control inside our Violectric gear:
 
Inside V90 you can find a nice and small potentiometer with two of the above mentioned resistors in one case.
It is the RK14 from Alps and works quite fine.

Inside all other headphone amps and PRE V630 we are using the good reputated ALPS RK 27. Here you can find each variable resistor (2 for stereo) in a separate housing, so crosstalk is very good. Also there is a 41-detent inside.
We are measuring the channel imbalance at 12 o´clock position. If it is higher than 0.3 dB it will be sorted out.
 
The first volume control option on V220, V281 and V630 is the remote option.
Beneath other things the volume can be controlled by pushing a remote button.
To do so, we are using a motorized RK 27 potentiometer.
Here a not so little motor through a gearbox turns the potentiometer, visible by the rotating knob. Of course there is a clutch installed so you can turn or stop the knob by hand even when the motor drive is in action.
 
The second volume control option for V220 and V281 is again made with the motorized RK 27 potentiometer. Same procedure as above. But this time a control voltage is generated and A/D converted to control the 128-step relais attenuator.
 
Yes, I know, there are more simple and cheaper ways to remotely control the volume.
But that´s the way we go …
 
By the way, because the volume is attenuated in the digital domain inside DAC V800 the quality of the potentiometer must not be that good. Here we are using again RK 14 from alps.
When there will be an updated version of V800 there will be also a motorized RK27 inside.
In the moment we are seeking the space inside the case to proceed )
 
Greetz
 
Fried

 

[Megalomaniak]

Wow, 4.75V on a DAC thats a lot, my DAC does 2V and I usually stand from 8 to 12 of the volume knob, and I dont like it loud. Of course gain setting at 0.

 

[rx79ez08]

Thank you Fried, I understand now. A very interesting way to do volume control.
I have been using HD800 and lcd-x in balance output, mostly TH900 in unbalance output. I am pretty sure I set the attenuation right, but I will check when I get home.
The 800 required the most output, but even then I for not go pass 9.

 

[project86]

  Wow, 4.75V on a DAC thats a lot, my DAC does 2V and I usually stand from 8 to 12 of the volume knob, and I dont like it loud. Of course gain setting at 0.

 
 
It's a lot for RCA outputs (which are normally 2V) but not so much for XLR (which is generally 4V).

 

[Zkadoush]

  OK, first some (essential) words about volume control:
 
About different kinds of potentiometers (volume control)
 
Think of a simple potentiometer as an open resistor with its resistance increasing from one end to the other.
One end of the resistor is connected to the analog signal, the other end is connected to ground.
On the surface of this resistors there is a metalic whiper. By moving this whiper on the surface of the resistor different levels of attenuation may be achieved from no attenuation (whiper on the end where the signal comes in) to maximum attenuation (whiper on the end where ground is connected.
 
The increasing resistance of the potentiometer may follow different laws.
A linear law is preferred for balance or tone control.
A positive logarithm law is good for volume control while a negative logarithm law is best for microphone gain.

The above resistor may appear in different shapes.
Most time it is curved with an angele about 300 degrees from on end to the other.
On mixing consoles you will find straight potentiometers.
You can pack several channels (resistors) in an enclosure or pack several enclosures with a single resistor inside together and control them with one or more shafts.
 
But there are several disadvantages to consider when you like to use more than one potentiometer at a time - for stereo you need at least two.
There is ALWAYS a mismatch between two or more potentiometers as these cann´t be manufactured 100% exact. This mismatch can be heard as a channel imbalance, meaning the center may move a bit to the left or the right whilst turning the potentiometer.
Also the crosstalk may suffer during attenuation. Therefore better potentiometers have a chamber for each resistor.

Some potentiometers offer one or more detents to ease operation.
These detents have NOTHING to do with a stepped attenuator !!!
A common feature is a center detent for balance control to exactly determine the middle position.
Other popular detents are 13-detent for tone control,
31- or 41-detent for volume control to ease the repositioning to a specific value / angle.
 
To come across the accuracy- and crosstalk-issue several manufacturers offer real stepped attenuators.
These are realized with 12-step or 24-step turn-switches.
The limitation to max. 24 steps is due to the fact that there are no affordable turn-switches with more than 24 steps in this world.

Just imagine that the above mentioned resistor is devided in small portions of high accuracy with 1% or even 0.1 %.
Instead the whiper the 12-step or 24-step turn-switch acts to come from one resistor to the other.
Also you may position the switches for left and right far from each other to enhance crosstalk.
The disadvantage of this idea is that 24 steps often are not enough to meet your specific needs.
 
The next idea is the electronical attenuation.
There are some older approaches like the VCA (voltage controlled attenuator) which work quite fine as an attenuator but have high amounts of distortion.
The better approach is the DCA (digital controlled attenuator), offering 128 or 256 steps of very exact attenuation with good crosstalk. But unfortunately there is still some negative influence on the signal …
 
 
The final solution is the relay controlled attenuation.
It is as exact as the 24-step turn-switch solution (but with more steps) because of the use of accurate resistors. There is no noisy or distorting active electronic in the signal chain. There is best crosstalk.
Instead of the contacts of a turn-switch, here relays are in charge to switch between the resistors and perform the attenuation of the signal.
We at Violectric voted for a 128-step solution with 0.75 dB per step for a 96 dB attenuation.
 
To control electronic or relay based attenuators, normally up-down-buttons or incrementals (turn switches without a beginning or an end) are used because this is a cheap solution.
We voted for a real potentiometer with a beginning and an end so people can check by a simple look at the knob the amount of attenuation. To do so, we again use a RK27 motor driven potentiometer (which would not be nesseccary at this point) to have the same look and feel compared to our other gear. Instead the analog signal attenuation a control voltage is created by this potentiometer which is fed to an A/D converter to form a digital signal which sets the relays.

There is much light shining on the relay volume control but there is also some shadows:
You will hear the relays working whilst turning the knob, this is some clicking when turning slow or even sounds like some soft noise coming out of the box when turning fast.
The other disadvantage is the power consumption ….
 

Thank you Fried for this detailed info on the volume controls used by Violectric. I had to read it a couple of times and do some wikipedia, because I'm not an engineer, but I believe I have a much better understanding of it now.

Cheers

 

[Zkadoush]

Thanks a ton again, Fried.

 
 
@ Zkadoush


You have also mentioned that transformers and power supply in the V220/V281 are different from V200, would it be to much indiscretion to ask you for some details about those differences?
Inside V200 we are using a 10 W transformer.
Inside V220 we are using a 25 W transformer because there is much additional circuitry to supply.
Additionally there is a 15 W transformer for V281 on the upper amp-PCB.

Will there be some digital specs for the new 24/192 DAC modules in the near future?
There will be some more details when our new site is up ... by now violectric-usa.com is best for competent answers.

I really like the idea of a standalone balanced V281 Amp (or V282), it would be a great option for those looking for the ultimate Balanced Amp.
First we are working on our current line (specially V220 / V281) to get them out as perfect we and our customers expect )

Thanks againg for all your answers, and sorry for all the questions.
You´re always welcome !!

Greetz
 
Fried

Thanks a ton again, Fried.

I greatly appreciate your time and all the technical detail provided regarding Violectric's new flagship Amps. I have to say the more I read and the more info I have, the more confident I feel to make a well informed decision about my final purchase. I have recently visited a dealer here in Auckland who clearly knows about the products he's selling, and he's also a passionate head-fier. He's also prepared to bring in a V281 and that would obviously give me a great chance to compare it directly to a Taurus, and to a Bakoon HPA-01 and HPA-21, as he's shortly bringing in those as well. I also received positive feedback from the Addicted to Audio guys in Melbourne, as I'm traveling there at the end of the year, and they will also have a V281 to audition by then.

Schoene Gruesse

 

[Zkadoush]

  @ rx79ez08
 
There seems to be a little missunderstanding ...
 
… to make more clear what we are using for volume control inside our Violectric gear:
 
Inside V90 you can find a nice and small potentiometer with two of the above mentioned resistors in one case.
It is the RK14 from Alps and works quite fine.

Inside all other headphone amps and PRE V630 we are using the good reputated ALPS RK 27. Here you can find each variable resistor (2 for stereo) in a separate housing, so crosstalk is very good. Also there is a 41-detent inside.
We are measuring the channel imbalance at 12 o´clock position. If it is higher than 0.3 dB it will be sorted out.
 
The first volume control option on V220, V281 and V630 is the remote option.
Beneath other things the volume can be controlled by pushing a remote button.
To do so, we are using a motorized RK 27 potentiometer.
Here a not so little motor through a gearbox turns the potentiometer, visible by the rotating knob. Of course there is a clutch installed so you can turn or stop the knob by hand even when the motor drive is in action.
 
The second volume control option for V220 and V281 is again made with the motorized RK 27 potentiometer. Same procedure as above. But this time a control voltage is generated and A/D converted to control the 128-step relais attenuator.
 
Yes, I know, there are more simple and cheaper ways to remotely control the volume.
But that´s the way we go …
 
By the way, because the volume is attenuated in the digital domain inside DAC V800 the quality of the potentiometer must not be that good. Here we are using again RK 14 from alps.
When there will be an updated version of V800 there will be also a motorized RK27 inside.
In the moment we are seeking the space inside the case to proceed )
 
Greetz
 
Fried

More interesting info, thanks Fried.

 

[Zkadoush]

   
Yes, I'd say the V281 (and V220) are an evolution of the V200 sound, so the general comparison with CMA800R still holds. However, this time around things are more open sounding with the new Violectric. So advantages that formerly went to the Questyle amp, are less of a difference now.
 
 
So far I've been using extremely sensitive IEMs like the UM Merlin, with -6dB pregain setting, and it's very quiet. I suppose I could go to -12dB if I had any trouble but thus far there's no need. It's just like V200 which means extremely good with IEMs - the huge volume knob is great for dialing in a precise setting. I have not tried my balanced IEMs yet. 
 
 
 

Thanks for your answer, project86. Your valuable impressions certainly make the V281 an even more attractive Amp.
I recently had another session with the Taurus (along with a Bryston BHA-1 and a Woo Audio WA2), which was far more positive than the last one. My previous listen was with the VEGA and this time it was with a Bryston BDA-1. I can't really attest to the DAC being responsible for any changes, but my impression was certainly different. I also had a go at the newest LCD-3 along with a LCD-X, and I was far more impressed than with my last experience with them, which clearly were older models. This time over I could really enjoy the LCD-3 from the Taurus' both outputs, but I particularly enjoyed the LCD-X. It is also hard to resist the temptation of getting one as a great alternative to my HD 800s.

The Woo was also an impressive match with the HD 800s, and now I'm pretty much waiting for a the Bakoon HPA-01 and HPA-21 to arrive and give them a comparative listen against the Taurus.

I know the LCD-X is a lot easier to drive than the LCD-2/3s, and that certainly gives it an advantage, as I wouldn't necessarily have to rule out the CMA800R based on the current both the Taurus and V281 can deliver. Have you compared the LCD-X between the CMA800R, Taurus and V281?  

Thanks again for your valueble impressions and response.

Cheers

 

[Armaegis]

Since we're talking about pots, another German amp guy Jan Meier does things slightly differently and uses a pot ADC to control the gain. I know he does this in his portable Stepdance amps, not sure about the desktop ones.

 

[rx79ez08]

 
Are you sure you aren't reading the pregain settings backwards, and setting it to +12dB instead of -12? You wouldn't be the first person to make that mistake. Start with all switches down. Flip the switch marked -12 (on the far left side) upwards, leaving all others down. 

I just checked, the setting is correct. Maybe the M51 just got a high output.

 

[project86]

  I just checked, the setting is correct. Maybe the M51 just got a high output.

 
Wow, that's really odd. Seems too high to me, considering the output voltage involved. But NAD has a really good digital attenuation implementation, so you could always drop the volume on that end and go from there. Start at -1dB and go down as needed, things should stay pretty transparent until you go down by 30 or 40 dB. 

 

[PleasantSounds]

 
 I also received positive feedback from the Addicted to Audio guys in Melbourne, as I'm traveling there at the end of the year, and they will also have a V281 to audition by then.
 

 
Just returned from the A2A store: the V281 is already in stock, minus one in the boot of my car  
 
Listened also to the Auralic Taurus, Luxman p700u and Bryston BHA-1. The Luxman was probably a tad more refined, but it takes too much space (and costs much more). And I don't like the dual XLR headphone sockets. The other two amps failed to really impress me, especially the BHA-1 was not as good a match for the HD800.
 
More on the V281 performance when I have some experience with it.
 
Cheers

 

[madbull]

Has anyone ordered a V281 through Aprhodite Cu29? I have been trying to contact Robert but can't get no answer.

 

[project86]

Has anyone ordered a V281 through Aprhodite Cu29? I have been trying to contact Robert but can't get no answer.

That's the sort of behavior that made Violectric search for a new distributor in the USA. Violectric-USA will respond to emails immediately.

 

[Fegefeuer]

Yep, Arthur rocks.