Amp recommendations for Audeze LCD-2 - Page 109

Out of curiousity, what tubes do you have rolled in the mini torii? Also, I was wondering if you think the yulong d100 would have good synergy with the mini torii for the LCD-2? If anyone else has had time with the mini torii, I would appreciate your recommendations.

Quote:

Originally Posted by Skylab 

I think the Mini-Torii is the slightly better amp for the LCD-2 - it's got a bit more dynamics.  It's also a bit more lush.  But the Trafomatic is a very nice amp with the LCD-2, and I have been using it more and more.

Quote:

Originally Posted by SP Wild 

I've got my eye on the Havana, there is even a true balanced version, very rare to see a balanced tubed NOS dac, the balanced output is tubed as is the SE output.

Yeah, it's truly balanced throughout, not just fresh lipstick on a pig.  I haven't had the opportunity to hear the balanced version yet, but it sure looks impressive and I bet it sounds good!

I'm using Tung-Sol 12BH7 driver tubes, Sylvania 6V6G power tubes, Sylvania 6X4's, RCA OA3's and Raytheon OC2's.  Never tried the Yulong with the MT.

Thanks for the quick reply. What dac do you use for your setup for the LCD-2?

I have been alternating between an RWA iMod with ALO Auricap dock, and an Audio By VanAlstine tube-hybrid DAC.

Thanks for the info again. Have a good one.

Quote:

Originally Posted by oqvist 

Nice to hear it works that well. Head One is the one and only tube amp I have ever listened to. Have you found any tube amp in the same price range or less  that is significantly better for the LCD-2? 

Will we happen to see a full fledged review sometime in the future? :).

Form what I have heard so far, the only tube amps that I personally have heard that performs as well with the LCD-2 in the same price range is the WooAudio WA2 and the Decware Mini-Torii.  But the HeadOne is the more flexible amp, as it will work with a wider variety of headphones.. The WA2 is good with planars and high impedance dynamics, but not so much with low-impedance dynamics. The Mini-Torii is really only good with low-sensitivity, low-impedance planar headphones. The Traformatic's impedance switch I have found to be very effective, and as a transformer-coupled design, it does quite well with even the low-impedance dynamics.  I've enjoyed it with the JVC DX1000 quite a but along with the LCD-2.

Anyone compared the ECBA to the Leben or mini-torii?

Quote:

Originally Posted by Skylab 

Form what I have heard so far, the only tube amps that I personally have heard that performs as well with the LCD-2 in the same price range is the WooAudio WA2 and the Decware Mini-Torii.  But the HeadOne is the more flexible amp, as it will work with a wider variety of headphones.. The WA2 is good with planars and high impedance dynamics, but not so much with low-impedance dynamics.

I absolutely agree with Rob on this too. I still own my MAD Ear+HD (transformer coupled tube amp) and Concerto (SS) amps for my low impedance cans that aren't planars.

Quote:

Originally Posted by mamba315 

 

Now, my question would be whether it is common practice for manufacturers to include a buffer on headphone amps before the gain section.  Is it always done, or is it sometimes done and sometimes not?  Could this be why some amps receive wildly different reviews, or is "synergy" and "taste" still the most likely culprit?

 

This is an interesting question, but requires a little thought about the nature of impedence and AC signals.

Unfortunately, it's not quite as simple as just adding a buffer stage that provides the right impedence on both sides.  Impedence is not really a single number, since it is an AC phenomenon -- most of the time it varies with frequency, especially in output stages.  Transistors and Tubes differ in their linearity and ability to deliver a flat power curve into varying impedence loads.  Different input and output topologies will affect this power transfer to a greater or lesser degree.  Buffers are active devices that cannot be counted on to be entirely linear across a wide range of AC frequencies, plus as you point out, many of them tend to have a sonic imprint they add to the music.

For an alternative, think about transformers.  Any transformer is an impedence matching device which can be used to improve the power transfer across audio frequencies.  Different turns ratios or taps on the transformer can be used to tailor the impedence match to optimize the power transfer.  But transformers that are really flat across the entire audio spectrum are expensive. 

On the input side, some designs couple the headphone amplifier to the source across a capacitor, while others apply the signal though a transformer, or even use a buffer circuit as you suggest.  Each connection approach has tradeoffs.  Usually the designer will tailor the tradeoffs to maximize sound quality (or minimize parts count) -- based on price point and priorities for production.  I personally am partial to dual-differential fully balanced input stages, using transformers to couple.  But I've built amps that used other approaches with excellent SQ.  Anyway, it is not as simple as slapping in a buffer stage to solve all the ills of impedence matching.  Wish it was...

On the output side, transformers can work great as impedence matching mechanisms to link the output devices to the load.  But again, they all vary somewhat in their performance at different frequencies (altho their limits may be well outside audible frequencies).  Or in another case, an OTL (output transformer-Less) design directly couples the power devices to the load.  If the impedence match is good, and the design carefully done, the amplifier will be operating its output devices in the most linear part of their operating range, where every increase or decrease in inputs yields an exactly proportionate output.  But the load can complicate that as its impedence varies with frequency.  So nearly every OTL amp has a fairly narrow range of load impedences where it will sound its best.  Fiddling with the input impedence doesn't solve problems of varying power delivery across different output frequencies.

The good news for Audez'e users is that the LCD-2 is mostly resistive in load, barring cable capacitance, etc.  So these cans provide a fairly nice load to most amps that can handle a low impedence, provded they can deliver enough current

Hope this helps!

Frank

I brought my rig over to my parents tonight to show my dad how good the pairing is between the LCD-2 and the Concerto.

And I was also showing off the wood/black granite mini-shelf I made for my my Concerto and StageDAC.

Frank, that was such an awesome explanation I turned it into a wiki!

I hope you don't mind 

Quote:

Originally Posted by DeadEars 

This is an interesting question, but requires a little thought about the nature of impedence and AC signals.

 

Unfortunately, it's not quite as simple as just adding a buffer stage that provides the right impedence on both sides.  Impedence is not really a single number, since it is an AC phenomenon -- most of the time it varies with frequency, especially in output stages.  Transistors and Tubes differ in their linearity and ability to deliver a flat power curve into varying impedence loads.  Different input and output topologies will affect this power transfer to a greater or lesser degree.  Buffers are active devices that cannot be counted on to be entirely linear across a wide range of AC frequencies, plus as you point out, many of them tend to have a sonic imprint they add to the music.

 

For an alternative, think about transformers.  Any transformer is an impedence matching device which can be used to improve the power transfer across audio frequencies.  Different turns ratios or taps on the transformer can be used to tailor the impedence match to optimize the power transfer.  But transformers that are really flat across the entire audio spectrum are expensive. 

 

On the input side, some designs couple the headphone amplifier to the source across a capacitor, while others apply the signal though a transformer, or even use a buffer circuit as you suggest.  Each connection approach has tradeoffs.  Usually the designer will tailor the tradeoffs to maximize sound quality (or minimize parts count) -- based on price point and priorities for production.  I personally am partial to dual-differential fully balanced input stages, using transformers to couple.  But I've built amps that used other approaches with excellent SQ.  Anyway, it is not as simple as slapping in a buffer stage to solve all the ills of impedence matching.  Wish it was...

 

On the output side, transformers can work great as impedence matching mechanisms to link the output devices to the load.  But again, they all vary somewhat in their performance at different frequencies (altho their limits may be well outside audible frequencies).  Or in another case, an OTL (output transformer-Less) design directly couples the power devices to the load.  If the impedence match is good, and the design carefully done, the amplifier will be operating its output devices in the most linear part of their operating range, where every increase or decrease in inputs yields an exactly proportionate output.  But the load can complicate that as its impedence varies with frequency.  So nearly every OTL amp has a fairly narrow range of load impedences where it will sound its best.  Fiddling with the input impedence doesn't solve problems of varying power delivery across different output frequencies.

 

The good news for Audez'e users is that the LCD-2 is mostly resistive in load, barring cable capacitance, etc.  So these cans provide a fairly nice load to most amps that can handle a low impedence, provded they can deliver enough current

 

Hope this helps!

 

Frank

Thanks.

Quote:

Originally Posted by grokit 

Frank, that was such an awesome explanation I turned it into a wiki!

 

I hope you don't mind 

Aw shucks! 

It's better with math, than in English.  I remember the "aha" moment when looking at the output of a curve tracer for several different active devices (transistors & tubes) and seeing how their transfer function varied at different frequencies.  That's when I realized that the amp I was building was operating the same device at different points along the curve with each frequency.  And every device has a different curve at different operating voltages/bias points.  Whew!

Designing this stuff so that it sounds outstanding, rather than merely good, is an art form.  It is not just all-so-simple to make sure all of the possible input frequencies are along the linear portion of the transistor/tube, given ALL of the possible output voltages from the previous stage.  At the same time, the designer is considering the bias voltages being used on each device, feedback, and then coupling to next stage, or to a load.  Remember that the source can output mere millivolts all the way up to 3 volts, or even 5 volts in some instances. The amp needs to be linear across this range of voltage, at every audio frequency.  I am in awe of the great audio designers, like Nelson Pass, John Curl, or Alan Kimmel.  It is quite an accomplishment when it all comes out sounding spectacular:  selecting the right devices and setting up a circuit topology that operates them to best effect, while not overdriving them (for longevity), and not under-driving them (for noise elimination & non-linearities) and avoiding the use of band-aids like negative feedback loops.  I've spent a lot of time looking at circuit diagrams and rebuilding vintage tube amps from the 40's, 50's and 60's.  It is simply amazing all the different solutions and circuit topologies that have been used simply for audio amplification.  While there are many "standard" topologies that are heavily used, there are often really creative solutions that break the mould and accomplish fantastic sonic results (see for instance the way David Berning couples audio signals by piggybacking them on top of RF signals!).

Fun stuff!

Frank