BURSON Conductor Virtuoso 2+ (inside pics, technicalities, personal thoughts and some measurements)

[trl]

Hello,

I found recently advertised on an online SH-store an "used, like new" Conductor V2 headphone amplifier at a bargain price (625 USD), purchased 5 months ago, with original invoice and 5-years warranty. I just couldn't resist and I bought it.

Hence, I'll post some internal pics here and in the coming day some technicalities and later some tests (RMAA and scope shots with sines and square waves).

First, I do like the packaging: there are 2 boxes, each one with its own protection foam. This is the first time I see this on an audio equipment; not even my 20 KG German speakers were packaged like this, not my Yamaha amplifier, nor my Mackie audio monitors, nor my SVS sub a.s.o..

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Conductor V2 has an impressive look and feel, a beautiful shiny huge piece of aluminum "heatsink" covering a 2 x 8.2 Watts of pure Class-A discreet amplifier & pre-amplifier as well.

Front side and the remote control​

Notice the 6 mm thick aluminum cover​

Back input & output plugs from the internal pre-amplifier​

Huge caps and separate shielded transformers for the analogue and digital parts​

2SA970/2SC2240 complementary bipolar transistors use in the pre-amplifier section for voltage-gain and Class-A biasing

Same as above, just different view

Top view of the internals and the 2SA1930/2SC5171 in the background (on the bottom aluminum case, actually)

Internals - top view

Impressive full-wave rectifiers for each transformer rail, along with the 8200uF/35V ELNA caps

Powerful rectifier diodes

Headphones plug and the relay

Top view with the entire ~7Kg amplifier

Setup with V2 on my desk ​

 

[restorer-john]

I would consider spending that USD$625 on a better potato, perhaps one with a macro lens and auto focus, before burning it on anything from that Burson crowd.

 

[Veri]

Hey @trl I enjoy these kinds of detailed hardware pictures, thanks a lot for sharing

Long ago I had a Burson Audio HA-160, also bought as-new with great warranty, but I did not have a lot of love for this device. It sounded just "okay" since I had such great expectations, and the clicking sounds when moving its volume potentiometer/knob was just awful for this $500+ range.

I think they have improved a lot since then, though, but still sit too firmly in the premium market for me to consider their stuff.

 

[trl]

I would consider spending that USD$625 on a better potato, perhaps one with a macro lens and auto focus, before burning it on anything from that Burson crowd.

View attachment 16843

I've used 28mm/f2.8 CANON and 105mm/f2.8 SIGMA 1:1 macro lens, hand-held pics, no tripod used even the time was pretty high. Let me know if you think some pics might need to get re-taken/swapped.

Many thanks!

 

[trl]

Hey @trl I enjoy these kinds of detailed hardware pictures, thanks a lot for sharing

Long ago I had a Burson Audio HA-160, also bought as-new with great warranty, but I did not have a lot of love for this device. It sounded just "okay" since I had such great expectations, and the clicking sounds when moving its volume potentiometer/knob was just awful in the $500+ range.

I think they have impreoved a lot since then, though, but still sit too firmly in the premium market for me to consider their stuff.

I was reading about the volume imperfections on the HA-160 and about the oil with alcohol needed to clean-up the pot (old school clean-up method). I remember some called that amp as sounding too warm, however...it was powerful and nice looking pice of gear.

The V2 sounds perfect to me, even with sensitive IEM's. Given the digital volume there's no need for any gain switches, so quite an improvement over the V1 or other headamps still using analogue gain control switches.

 

[Veri]

Digital volume handling is definitely the future ...

 

[trl]

As restorer-john is raising the bar on the macro pics, I accept the challenge.

Below some 1:1 pics, made with my SIGMA 105mm, manual focus, per my liking:

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1:1 @f/2.8 for the 105mm means 2-3mm DOF, so quite tricky to get in focus what I really want to.


However, below are some more close-ups made with the same lens, but with a magnification lower than 1:1.

Front side with the volume rotary knob, input source selector button and the remote control sensor
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Combating AC ripple with powerful fast diodes and big ELNA caps
The're also 2 x IRF610 to regulate the power rails even further. Seems that the Burson techs really love to go fully discrete for the analogue part, although I've seen several LT1085 across the mainboard, most likely used for the digital parts.
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A970/C2240 transistors with ELNA caps around
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Headphones and output stage protection (the relay is open if there're no headphones connected or if there's DC on outputs)

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The STC15W404AS micro-controller that takes care of V2's correct operation (relays, protections, source selection, front display)

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On the right, PGA2310 digital volume control (-120dB dynamic, adjustable between -99.5dB to +31.5dB)
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[trl]

I was able to grab some "domestic" measurements with my old Xonar U7 ADC/DAC (-110dB dynamic), latest RMAA PRO (paid) version and ARTA free (unregistered). Most likely, with a better ADC, the below numbers will be improved a little bit.

RMAA - All windows stacked, for a better view of the final numbers (24bit/192KHz signals)​

Frequency response (20-200000 Hz): +0.09, -0.01 dB
THD: 0.007%
Noise (A-weighted): -100 dB
Dynamic range: 100 dB
IMD + noise (A-weighted): 0.006%
Crosstalk (left/right) @ 100 Hz: -85.3/-95.3 dB
Crosstalk (left/right) @ 1 KHz: -88.8/-88.1 dB
Crosstalk (left/right) @ 10 KHz: -69.0/-68.3 dB

RMAA - Frequency response (0.1 dB channel imbalance, 0.1 dB frequency deviation)

ARTA - Frequency response (virtually flat)

RMAA - Noise level (most noise-floor is kept below -132 dB, just the mains hum is visible, but still inaudible at its -106 db)

ARTA - Spectrum analyzer (noise level, all 4 mains-hum spikes are way below -100 dB)

RMAA - THD (1 KHz sine, 2nd harmonic is around -107 dB, 3rd harmonic is around -88 dB)

ARTA - THD (1 KHz sine, THD=0.0066%)

RMAA - Dynamic range

RMAA - Crosstalk (~90 dB @ 1 KHz)

ARTA - Jitter (11 KHz sine, no skirt, no harmonics)
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I like how it measures, its crosstalk is very good, dynamics of 100dB and noise lower than -100dB make this amplifier compatible with all headphones I have, from sensitive 16 Ohms IEMs to power-hungry planars and high impedance 600 Ohms Beyers.

I'm not in love with it's 3rd harmonic, but as long as it stays around -90 dB than means it's inaudible anyway, so...I'll just ignore it. Also, the mains hum at 50 Hz and it's harmonics (150 Hz, 250 Hz and 350 Hz) are completely inaudible, even at very high levels (with sensitive 16 Ohms IEM's, AKG K550, Beats Solo2 and no audio source connected on inputs there's no audible mains hum). In the past, I was able to hear mains hum from my ASUS Essence One and Matrix M-Stage HPA-3B amplifiers using same sensitive headphones, so not getting any hum with the Conductor V2 makes me think that -106 dB is indeed inaudible for all of us, "humans audiophiles" .

I like the 100% discreet approach, without any opamps in signal path and, of course, without any caps too. Not having caps and opamps in signal path is probably more of a puristic and subjective approach than an objective one, but I do like this for sure. Too bad this means more money invested in manufacturing process, electronic components and also in R&D, then later in my own pocket.

Also, the 70 W shielded transformers combined with the powerful sound provided by the Class-A output stage could represent an "end-game" for most audiophiles. Comparing V2 with my M-Stage HPA-3B every component inside the V2 seems...overkill and definitely of a higher quality. all is overkill for the Conductor V2, from it's 7 KG aluminum case and huge transformers and powerful bipolar transistors, till the 1 W metallic resistors.

I noticed that there's absolutely no channel imbalance when volume levels are getting lower, due to the fact that the volume knob (rotary controller) is lowering the volume digitally, so there are no analog potentiometers inside (http://www.firstpr.com.au/rwi/dfish/pot-wear/). My other headamps are having a mildly-audible channel imbalance when volume knobs are lowered somewhere around 9 o'clock or lower (e.g.: Objective2, Essence One, M-Stage HPA-3B). The only amps with perfect channel balance are Conductor V2, PLAY and FUN, of course, all having digital volume.

P.S.: Speaking about digital volume control, I'm not a fan of this, mostly because the pre-amplification stage (voltage gain) is usually located between the volume knob and the headphones (well, Objective2 is the different here, but this is an exception). So, who's lowering the background noise coming from the gain stage? Nobody, of course. So, if the voltage gain is using a mediocre opamp or some noisy resistors in signal path, then this noise will get into the output stage and later to the headphones. This can be usually heard with very sensitive cans only, like IEM's

 

[restorer-john]

US$625 is an awful lot of money for a headphone amplifier, but you can hook up speakers to that 8.2Watts of class A can't you?

 

[trl]

John, you’re right, I paid few bucks less for my 2x160W Yamaha A-S701 (it also includes a cheap DAC inside too). I just saw the advertise and I just bid it...it was the instinct I guess, can’t explain, but honestly...I feel happy somehow, hope I don’t need a shrink yet. BTW, I won’t say I’m looking to purchase the Transport and the DAC cards for the V2 to transform it into V2+.

Now I feel like I need to connect it to my 4 Ohms speakers too.

 

[trl]

[....] but you can hook up speakers to that 8.2Watts of class A can't you?

You really want this amp to get burned, didn't you? Or you're just teasing me?

Starting to clip at 9.05W/channel, 8.458V RMS @ 7.9 Ohms!!!
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So, yes John, I can power speakers out of this baby, and it's all pure Class-A.

L.E.: No smoke, no smell and no brownies after few minutes. Resistors were warm-to-hot, but nothing suspicious at all. Unbelievable, this amp is built like a tank!

 

[trl]

I found something interesting on manufacturer's website: "Frequency response:± 1 dB 0 – 56Khz". It looks that V2 has a fantastic linearity, I'm sorry I can't measure it with my own equipment (my Xonar U7 ADC/DAC is linear from 10 Hz to 35 KHz), but I can at least check this partially:

Perfect linearity: +/-0.1 dB between 10 Hz and 30 KHz and +/-1 dB from 2 Hz to almost 45 KHz!​

Too bad I don't have a better ADC to see if it can go up to 56 KHz @ -1dB, as per manufacturer's specs. However, I do love the linearity for sure, impressive actually.


Moving on to max. output power for 600 Ohms load (same as nothing connected at outputs):

11.9V RMS, just before starting to clip (236 mW/ch. @ 600 Ohms)

9.829 V RMS, just before clipping (3.275 W/ch. @ 29.5 Ohms)
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Also, given the 8 Ohms and the infinite output voltages measured above and based on http://www.sengpielaudio.com/calculator-InputOutputImpedance.htm seems that the output impedance is pretty close to manufacturer's specs of 3 Ohms. Although, I was expecting this to be even lower, but I can definitely live with this, because the lowest impedance cans I have are 16 Ohms IEM's and they pair absolutely perfect with Conductor V2 (these IEM's were not pairing well with my Essence One with it's 10 Ohms output impedance).

 

[trl]

Representation of common sine-waves:

20 Hz sinewave - perfect look, so perfect bass

1 KHz sinewave - perfect again, but most amps are dealing same way with 1 KHz sines

20 KHz sinewave - very good output, almost perfect superimposing of the two sines (input vs. output)

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Representation of common square-waves:

20 Hz squarewave - perfect representation (DC coupled indeed)

1 KHz - both signals are about identical

20 KHz - output (blue) is almost identical with input (red), so very good result
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Given all of my above measurements I can definitely "promote" this headphone amplifier to REFERENCE GRADE among my few others headamps from home.

 

[March Audio]

Reference grade? On what basis?

Plenty of amps that Amir has measured significantly out perform this.

 

[trl]

"among my few others headamps from home", although not sure anyone will be able to hear the 3rd harmonic at almost -90dB.
I also love the square-wave tests and the output power, but the low noise too.

 

[March Audio]

With respect It's really not reference grade or low noise. Expensive for that level of performance.

 

[restorer-john]

All the ARTA and RMAA tests are done at what level?

If we are talking sound card level (2V), they prove very little unfortunately.

 

[trl]

For more than 2V I can only use my scope to test, but it has a low granularity and resolution on FFT, so it’s kinda unusable for this scope of work. I could try to use a resistive divider on ADC’s input, but not sure it’s OK to do that (maybe it’s time to get a better ADC).

I’ll re-calculate output impedance for 50% of max. power, my former calculation was done for clipping power @infinte and @8Ohms and it’s probably not OK. BTW, not a fair comparison here, but my Yamaha A-S701 has the 2nd harmonic @-100dB and all the other harmonics hidden inside the noise-floor threshold (<-110dB), but channel separation and output noise when using headphones are a bit worse, as most speakers amps actually.

I’ll measure the other channel from V2 with ARTA to check the FFT spectrum. However, it’s odd that there are no visible harmonics for 11 & 12 KHz sines, but there are for 1 KHz sine.

 

[restorer-john]

For more than 2V I can only use my scope to test, but it has a low granularity and resolution on FFT, so it’s kinda unusable for this scope of work. I could try to use a resistive divider on ADC’s input, but not sure it’s OK to do that (maybe it’s time to get a better ADC).

There are a few options. You could make something up or go with one of these:

Jan Didden's autoranger: https://linearaudio.nl/la-autoranger (thread on diyaudio on this)

Pete Millet's one: https://www.audioxpress.com/article...data-acquisition-in-audio-measurements-part-4
http://www.pmillett.com/ATEST.htm

 

[trl]

I made a resistive divider and I was able to output about 5V RMS from the amplifier:

Conductor V2 @5V RMS (about 1KOhm load)
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Not a game changer, but it's 2.5dB improvement in dynamic and noise. FFT looks about the same, 3rd harmonic is still around -86dB...perhaps a bit higher as number, but still inaudible.

What I like a lot is V2's ability to perfectly represent 20Hz and 20KHz. I care a lot on how sound is represented on my scope because in the past I needed to start modding my amplifiers to be able to sound properly, even if RMAA was showing perfect frequency response (right-click and open-to-new):

https://www.audiosciencereview.com/...-hpa-3b-mods.4344/#lg=attachment15225&slide=0 & https://www.audiosciencereview.com/...-hpa-3b-mods.4344/#lg=attachment15215&slide=0 - bass was too warm and missing some impact.
https://www.audiosciencereview.com/...-hpa-3b-mods.4344/#lg=attachment15218&slide=0 & https://www.audiosciencereview.com/...-hpa-3b-mods.4344/#lg=attachment15217&slide=0 - bass sounds perfect after a simply omd done to the high pass filter (maybe the sound change was from the different input caps, unable to find out).

https://www.audiosciencereview.com/...-hpa-3b-mods.4344/#lg=attachment15220&slide=0 & https://www.audiosciencereview.com/...-hpa-3b-mods.4344/#lg=attachment15221&slide=0 - trebles were shy, distant, my Objective2 amplifier was sounding much clear and resolute.
https://www.audiosciencereview.com/...-hpa-3b-mods.4344/#lg=attachment15222&slide=0 & https://www.audiosciencereview.com/...-hpa-3b-mods.4344/#lg=attachment15223&slide=0 - trebles are now perfectly reproduced, much more clear, much more detailed, even if bandwidth freq. response seems to be identical pre vs. after the modding.

I copy-pasted here the above pics from my modded HPA-3B headamp because I couldn't accept that Objective2 can sound more resolute and detailed than a much expensive headamp. I cold ignore the laid back sound and the dull bass, but not the lack of trebles resolution and it's mains hum. Since then, I do believe that phase-shift in bass or treble is affecting the way amplifier sounds.