Schiit KARA Preamp and Headphone Amp Review

[T.M.Noble]

@solderdude @lc6

Not to be a pedant on the whole potentiometer conversation, but this pot is actually a linear taper. There are 128 0.625dB steps.

 

[T.M.Noble]

did not answer the question why Jason chose to use relays (with their quirks when adjusting the volume) instead of IC's.

Ah ... but you did not answer the question why Jason chose to use relays (with their quirks when adjusting the volume) instead of IC's.

cheaper, quieter, no weird behavior when adjusting the volume, takes up less space .... but higher noise and distortion (most at least)

I believe he said it in the paragraph. He finds a relay ladder more transparent. Better measurements and sounds better.

"No volume control chip can boast of the transparency of a relay ladder--hence the Kara's disclaimer that passive mode "exceeds the capability of the APx555 to measure""

 

[CleanSound]

What is the deal with all of these Schiit products having the power on the back of the unit? Gear with power on the back only is designed to be on all the time. Why in the world is it designed like that?

There are some subjectivists who believes in electronic warm up time, so they would keep their gear on all the time. I am going to point the finger to this reason as to why Schiit has their power switch on the back of the unit so to capitalize these audio idiocy believes. Put the damn power switch to the front of the unit and add power on/off to the remote and this will get thumbs up from me.

 

[MRC01]

...
Conclusions
In passive mode, the preamp naturally reflects the superb performance of the Audio Precision analyzer. Note that it will change the loading impedance so may impact performance of other devices connected to it. To avoid this, you want to use the active mode which still produces excellent performance.

Are you talking about input impedance, or output impedance? Some passive attenuators maintain constant input impedance at all settings, though output impedance will vary.
I looked through Schiit's product & spec info, but could not find an answer to this question.

 

[dtaylo1066]

One has to admit that's some pretty good Schiit, and they really had their Schiit together when designing the preamp. And for those who demand it, made in the U.S.A.

 

[JohnnyNG]

And for those who demand it, made in the U.S.A.

'cuz our Schiit don't stink.

 

[SCG]

Not to be a pedant on the whole potentiometer conversation...

Please be a pedant, is the Kara's RCA channel distortion difference of 7.8db within Schiit's spec tolerance? The 9.1db RCA channel distortion difference on the Freya S was considered out of spec and a 2nd unit was sent for retesting.

For reference, posting regarding Freya S 9.1db difference:

This unit looks to be in need of repair as we have never seen these results on any Freya S that leaves the warehouse. We publish our own measurements (see link attached) and we state that if anyone cannot replicate these measurements to contact us.

If within tolerance, where between 7.8db and 9.1db (within that 1.3db window) is the crossover point. Many Thanks in advance!

 

[Sal1950]

Kara is also Supergirl

Damn she's hot !!!

 

[Andrej]

@solderdude @lc6

Not to be a pedant on the whole potentiometer conversation, but this pot is actually a linear taper. There are 128 0.625dB steps.

My understanding is that a linear taper changes resistance by fixed amount for any fixed number of degrees (in the turn). What you are describing is a logarithmic taper where the change is constant in dB (which is inherently exponential/logarithmic).

 

[lc6]

Where do you get that idea from ?.... there is nothing exponential about volume controls . They are semi-log.

Our hearing is "log":
"The ear was constructed to hear both very quiet and very loud sounds of very small and very large frequencies. This is why the ear hears logarithmically."

For further proof, consider that:
"In order to double the perceived volume, you’ll need a tenfold increase in power."

Consequently, for a perception of a linear change of volume for every incremental turn of the control, the voltage has to rise exponentially:
log(exp) = lin

See here:
" To compensate for the ears logarithmic behavior, audio taper pots were developed. While it is called logarithmic, it is actually an exponential curve (the opposite of the logarithmic behavior of the human ear)."

 

[pseudoid]

The following comment was made in the review of RoleAudioSkiff:

[member name omitted!]
"The tilted stickers tells you all you need to know about how much the company cares."

DE-Bunked??

 

[T.M.Noble]

My understanding is that a linear taper changes resistance by fixed amount for any fixed number of degrees (in the turn). What you are describing is a logarithmic taper where the change is constant in dB (which is inherently exponential/logarithmic).

That pot is a linear taper as where out pots we use are an audio taper with is logarithmic. I may be completely in the wrong here but I am almost certain logarithmic tapers on pots are most certainly not constant in dB change.

 

[lc6]

That pot is a linear taper as where out pots we use are an audio taper with is logarithmic. I may be completely in the wrong here but I am almost certain logarithmic tapers on pots are most certainly not constant in dB change.

This article provides a pretty good description:
"The dashed lines in the graph below show the "real" logarithmic and inverse log curves. In practice, logarithmic types which are used for audio applications do not provide a true exponential response, but follow the curve stepwise. The blue line shows the actual taper curve of an audio potentiometer. This approximation is done because it simplifies the manufacturing process. Instead of a continuously varying resistance track, two different tracks are used which overlap at the middle position. As audio volume control is a non-critical operation in general, this satisfies for these applications. Tapered potentiometers with real exponential curves are available for specialized applications."

 

[T.M.Noble]

This article provides a pretty good description:
"The dashed lines in the graph below show the "real" logarithmic and inverse log curves. In practice, logarithmic types which are used for audio applications do not provide a true exponential response, but follow the curve stepwise. The blue line shows the actual taper curve of an audio potentiometer. This approximation is done because it simplifies the manufacturing process. Instead of a continuously varying resistance track, two different tracks are used which overlap at the middle position. As audio volume control is a non-critical operation in general, this satisfies for these applications. Tapered potentiometers with real exponential curves are available for specialized applications."

View attachment 313656

Pretty sure this it what I said if you forgive the spelling mistake. The pot on Kara is linear, not an audio taper.

 

[MRC01]

@T.M.Noble will Schiit publish the input and output impedances of the Kara in passive mode?
For example if it's a 10k ladder then input is 10 kOhm at every setting while output varies, with highest worst case being 2.5 kOhm at -6 dB.

 

[Andrej]

That pot is a linear taper as where out pots we use are an audio taper with is logarithmic. I may be completely in the wrong here but I am almost certain logarithmic tapers on pots are most certainly not constant in dB change.

"logarithmic" = "constant in dB change" by definition. For audio there may be a variant where the change is mostly logarithmic, but changing the log base as it goes up/down.
Edit: See post 113 for a more specific explanation

 

[T.M.Noble]

@T.M.Noble will Schiit publish the input and output impedances of the Kara in passive mode?
For example if it's a 10k ladder then input is 10 kOhm at every setting while output varies, with highest worst case being 2.5 kOhm at -6 dB.

10K input impedance, 0-5K output impedance, worst case at midpoint (-40dB)

 

[lc6]

Pretty sure this it what I said if you forgive the spelling mistake. The pot on Kara is linear, not an audio taper.

Linear in terms of dB, which is a logarithmic measure (see formulas). Let me try another explanation: Consider, for example, a fixed angular change of the pot, say by 10 degrees out of the total possible 270 degrees. As you turn a truly linear pot, for every such angular change the signal changes by the same constant amount (in this case 1/27th of the maximum). But as you turn a truly exponential pot (incorrectly called "logarithmic" in audio), for every such angular change the ratio of the next signal to the previous signal is constant. You would only perceive the latter as a linear change in volume.

 

[MRC01]

10K input impedance, 0-5K output impedance, worst case at midpoint (-40dB)

Thanks for the info. That's unexpected, must not be a ladder configuration.
With 5k output impedance, you want short interconnects between the Kara and your power amp, and to maintain 10:1 impedance ratio the power amp should have at least 50 kOhm input impedance.

 

[Pe8er]

Oh my goodness, your dog is gorgeous!!