The Lavry DA11: For your ears only
Sep 17, 2012 at 12:15 PM Post #183 of 191
From the DA11 manual:
AES/EBU professional analog line levels:
Set to 56 for 24dBu balanced = 34.72V peak to peak = 12.28V rms
Set to 56 for 18dBu un-balanced = 17.36V peak to peak = 6.14V rms
A typical home power amp or powered speaker:
Set to 40 for 8dBu balanced = 5.6V peak to peak = 2V rms
Set to 46 for 8dBu unbalanced = 5.6V peak to peak = 2V rms

For most consumer equipment, I'd think that the 2V rms settings would be more typical. "56" may be more than your headphone amp or preamp wants to see into its inputs.
Sep 17, 2012 at 12:52 PM Post #184 of 191
From the DA11 manual:
For most consumer equipment, I'd think that the 2V rms settings would be more typical. "56" may be more than your headphone amp or preamp wants to see into its inputs.

Cool, got it.. Thanks.
Can you point me to your review on this DAC?
Sep 19, 2012 at 2:14 AM Post #185 of 191
FYI - The built-in volume control on the DA11 is excellent. It is a digitally controlled analog volume control, so there is no loss of resolution, no lowering of the SNR, superior tracking and channel separation than a potentiometer, etc.

To control the volume, I have the pot on my amp set to the point where the Lavry volume is generally around the ideal voltage for fixed output (as indicated in the manual and in Jude's post above) and a typical listening volume for me. Then, when I need to make any volume adjustments I use the Lavry's superior volume control either with the remote or the front panel switch (but usually the remote).
Sep 19, 2012 at 1:08 PM Post #187 of 191
What makes the tha DA11 volume control so superior?

Here is why:

The matching between channels is far better (!) then a dual analog pot,
And it holds its accuracy over the whole range. Say you want 60dB range. That means 1000 to 1 resistance range. Now take 2 pots and mount them on a single shaft (dual pot). The mechanical tolerance plus the resistor matching needs to be at least 10000 to 1 to get 10% matching over the range... The results are way off the mark. I could add fuel on the fire by mentioning that the pot resistance is semi logarithmic curve...

Now, with my scheme, you get .1dB absolute accuracy over the whole range, and the matching between channels is even better then that.

Also, unlike analog potentiometers, when you set the gain with a digital display, you get reliable and predictable level (such as 56 mean 24dBu, 55 means 23dBu...). When you move an analog pot, you lose the calibration. Some people want such accuracy (mastering engineers, hearing tests labs and others)

Digital attenuation also provides accuracy but digital attenuation causes loss of bits (around 1 bit loss for each 6dB attenuation). When attenuating by analog means, you do not truncate digital bits.

Also, the digital controlled analog attenuation does not have the wear and tear of a mechanical pot:
With analog pot, the signal itself passes through the pot contact (friction between a conductor and the resistive material).
With a switch, the contact resistance can deteriorate to 100 Ohms (don't worry it will not happen), and everything still operates like new. The switch does not pass analog, it is just an "up one" or "down one" command.

Rotary encoder is also a friction based device, and while not as bad as a pot, it does pass the signal and it does wear out over time. Doing a rotary for 56 positions at 1dB steps may not be practical. Some analog attenuators use 2 rotaries, such as for 1dB step and the other for 10dB steps. Say your setting is at 20dB and you want to change it to 19dB. You first need to attenuate to 10, then you need to do 9 steps to 19dB... This is not user friendly way... The switch is better - note that the switch controlled volume speeds up when you hold the switch up or down.

The digitally controlled analog attenuation is much costlier then a dual analog pot. I chose that method for the above reasons.

Feb 8, 2013 at 5:38 PM Post #189 of 191

Originally Posted by philodox /img/forum/go_quote.gif
Then again, I'm a stepped attenuator kind of guy, so take that with a grain of salt.

Either way, looks like a good update to the DA10. Nice work.

Hi philodox,

So let’s talk about step attenuators. The advantage is clear, you are using passive parts (resistors), and that enables one to set reasonably precise attenuation levels.

Initially it sounds very appealing because there is no active device in the circuit, but that is an illusion. Sooner or later, you will need to tap the signal with some active circuit, be it a headphone amplifier, an input to a power amp, some mixer or what not.

There are 2 problems with the passive attenuator:

The first one I already mentioned – the signal has to pass through mechanical contacts, thus wear and tear becomes an issue.

The second problem is bigger. The output resistance of a passive attenuator changes from position to position (attenuation setting). In fact in most positions the resistance is very high, it can be many KOhms. That is not a good thing. The output of the attenuator is “connected” to the next device by a cable, and a cable with high impedance at both ends is very susceptible to picking up electromagnetic noise (from ac line to radio station to an electric drill next door….). This is a fact of life, and that is one of the reasons that driving cables is best done with low impedance.

One can solve the issue by using a very short cable between the passive attenuator and the next device (which is typically at least a few KOhms). Alternatively, one can put an active circuit to “tap” the high impedance point and drive the cable via low impedance source resistance (impedance conversion). Typical impedance for driving a cable is less then 100 Ohms, not many KOhms. Of course putting an active circuit makes it into an active, not passive attenuator.

Many passive attenuators are over 10KHm to 20KOhms at the middle position. Again, you will end up needing to do such active impedance conversion anyway (the only question is where), and it is best to do it right next to the resistive attenuator tap.

In addition, having a high output resistance (passive attenuator) driving the destination device can really screw up the frequency response. Say you have an active driver with 10KOhms resistance, and a 10 foot cable with say 100pF per foot (pretty typical value). That will limit the bandwidth to around 15KHz! (3dB loss at 15KHz is terrible) In fact, you are already 1dB down at 8KHz!

But with an output resistance of 100 Ohms, the response of the same cable capaitance is flat to better then .001dB at 20KHz, and .02dB loss at 100KHz. In other words, low source resistance is very important to overcome capacitance. Again, short cable helps a passive attenuator. In fact putting that active stage right at the tap of the passive attenuator is ideal, because you eliminate the cable capacity loading effect.

To summarize, driving a cable with high source resistance with an active circuit at the end of a long cable is real bad practice, it makes for susceptibility to external noise, and it screws up the frequency response (loss of highs). The illusion of less active circuitry is just that, an illusion:

One stage of active circuit is very little in the context of the audio signal path (from recording to playback). The mic pre at the recording space, the analog mixer circuits, the AD analog circuits, the DA analog, the power amp or headphone amps and possibly more circuits amount to dozens or more of active circuits. Saving one stage while asking for the trouble I pointed out is not wise…

Well, my DA11 attenuator is in fact a precision resistive passive circuit, just the way you like it (I also like it), followed by internal impedance converter stage to overcome the issues I pointed out – minimize noise susceptibility and have a good and predictable cable independent and load independent flat frequency response…

And while at it, most passives are single ended (unbalanced outputs). My output stage offers both balanced and unbalanced low impedance output drive.

Dan Lavry

Interesting reading Dans expertise on this. I use the DA11 with a passive Goldpoint SA1X stepped attenuator using 10K resistors, but haven't really noticed any significant difference with or without it. He says typical cable is 100pF per foot, but the cables I use are Van Damme tour grade microphone balanced cables, which have a capacitance of 56pF/m (or about 17pF per foot), 2 meters in length from my SA1X to my monitors. At this length and capacitance any loss is pretty negligable from my experience with it so far. So with short length high quality cables, using an additional good quality passive stepped attenuator is probably 'ok'.
*edit* forgot to add, regarding all the comments about the annoyance of the up/down switch for the volume. Simply go out and buy any cheap-ass phillips type remote control and you can use that. I just grabbed the tv remote from downstairs and i can point it in any random direction in the room and the Lavry picks it up, nice simple smooth volume changing, works a treat!
Dec 24, 2013 at 9:50 PM Post #190 of 191
Love this, but i am now moving towards speaker and portable. I am thinking to sell mine since i just use it occasionally. Thinking to let my baby go for those who can fully utilize its potential. Wondering how much can i sell for a 2 year old DA11

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