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

[SIY]

In your last screenshot, A-weighted THD+N is higher than unweighted. You might want to check the measurement setup.

 

[restorer-john]

In your last screenshot, A-weighted THD+N is higher than unweighted. You might want to check the measurement setup.

I remember scratching my head when VA (Visual Analyzer) software gave similar results, so much so, I scrapped using it, back in the day.

I figured there was a computational error in the coding. Thoughts?

 

[trl]

I've no idea, but I can ask Maxim that own RMAA, if that's the case.

 

[SIY]

I remember scratching my head when VA (Visual Analyzer) software gave similar results, so much so, I scrapped using it, back in the day.

I figured there was a computational error in the coding. Thoughts?

I'm too dumb about coding to know, but I'd certainly think it's probably. I've used RMAA, but when I want to be sure of what I'm getting, Virtins and ARTA are my go-to; I have never had a single issue with weird results from those packages.

 

[trl]

I'm using ARTA as well, but this is only getting the THD, not any other numbers. For CV2 at 1V RMS I got a THD of 0.0066% with ARTA vs. 0.007 with RMAA, so about the same.

 

[trl]

About a week ago I was able to purchase the transport and DAC cards as well. I won't say the price, because @restorer-john will disagree a lot, but I can say that amount paid was a bit less than 1/2 of the original selling price for both cards (less than Topping D50). When playing from the USB or optical inputs, the volume is controlled via the ES9018S now and not from the PGA2310 chip (this only controls the analogue inputs and the preamp itself).

I can't find any flaws to the output sound...there's a tiny little bit of more background noise added when switching to USB input over the analogue input, but I can only hear that when using my sensitive 16 Ohms & 100dB SPL IEMs. However, with CV2+ I mostly listen to the FOSTEX T50-RPmk3 and Hifiman HE-560 and I have no complains...sound is just perfect.

I'll try some ARTA and RMAA tests soon, but from other tests I've seen on the Internet the internal DAC has no bad influence on the output sound (will have the same values for 2nd and 3rd harmonics).

P.S.: I was doing some math now and looks like I paid somewhere around 850 USD for the entire package and I still have 4.3 years warranty for the amplifier (it was used less then 1 year by the former owner, but transport and DAC cards are just purchased, so are brand new). The next setup I'm thinking about now would be Topping D50 + Neurochrome HP-1 because I really like how both devices measure, but the entire combo with shipping included would be almost twice the price I paid for the CV2+, so not sure I deserve such a treat.

 

[trl]

I was able to do some basic measurements on the CV2+ XMOS/ES9018S based transport and DAC, only USB input has been tested for now.

DAC's 2nd and 3rd harmonics are somewhere near -100dB, so in this regard seems to measure better than the headamp itself, where the 3rd harmonic is somewhere around -87...88dB (check this pic: https://www.audiosciencereview.com/forum/index.php?attachments/arta_freq_response_88khz-png.16894/).

However, my thoughts about these harmonics could be found here: https://www.audiosciencereview.com/...can-we-trust-our-ears.3884/page-3#post-125971.

50 Hz graph, pretty low higher harmonics (around -93dB), given we're speaking about 50 Hz signal

Frequency response across audible band is perfectly clear, less than +/-0.05dB

I guess there is the sharp filter used

Stereophile jitter test. Higher harmonics are beyond human's audible hearing, but worth mentioning that the 3rd one is somewhere around -80dB lower than the main signal; not sure it's my ADC (Xonar U7) or the CV2+ DAC

Multisine test with 1KHz difference between the signals (ignore the 8KHz bump, it's my ADC doing that). All the signals are having the same amplitude without any visible skirts, which is great, because it means that signals are not interfering one with each other.

Another multitone test (again, ignore the 8KHz bump caused by my ADC)

Step response

 

[Thomas savage]

Thanks for your work on this and taking a bit of criticism on the chin .

Personally i liked the photos lol

 

[trl]

Might worth mentioning something about the internal power supply. Each rail has 4 BJT transistors, one shunt regulator and one powerful MOSFET (IRG610/IRF9610). DAC and amplifier are sharing the same +/-21V RMS; the +5V is made out of linear LT regulators (one for DAC, one for USB transport). Protection relays, microcontroller and volume control card get the power from separate 9V supplies, delivered from another toroid transformer.

I like this approach with the discrete components and shunt regulator, because it offers lower output noise, it's low dropout (when needed, but not in this case) and thanks to the output MOSFET the PSU has a very low ESR too, so less prone to oscillations. Usually, most audio equipment is using LM317/337 or similar solid-state regulators (very good devices actually), but going fully discrete with added shunt regulator is a step further.

Voltage after the big reservoir caps of 6800uF (40mV AC ripple out of the 35V RMS)

AC ripple & noise after the IRF9610+TL431 shunt regulator (less than 840uV RMS, measured without spire around the GND)

Voltage after the big caps is +/-35V

Voltage after the shunt regulator is +/-21V​

 

[trl]

Eh, just realized that using ASIO4ALL gets me better figures for the little ADC from inside my ASUS U7. So, retaking some of the ARTA measurements today provided better results. Also, I moved the U7 one meter away from the DUT, so I got rid of some of the mains hum around 50 Hz.

ASUS U7 noise (noise is below -140 dB)

BURSON Conductor V2+ noise while USB is connected (even the two toroids are shielded some mains hum is still visible, given the 1-2 inches distance till the audio circuitry; however, inaudible at -120 db, not even with my 16 Ohms test IEMs and volume to the max. - not music playing!)

BURSON Conductor V2+ DAC's RCA output (3rd harmonic is around -99 dB, the others are below -100 dB)

BURSON Conductor V2+ headphones output (essentially the same with RCA output, just a higher noise-floor; sinewave was played by the built-in DAC, perhaps with a more accurate signal-generator connected on analogue inputs, the spikes could get even lower).

What I see that got improved with this ASIO4ALL vs. the original ASIO drivers from ASUS was the nasty spikes around 12 KHz, sometimes around 8 KHz and other freqs too. Also, noise-floor is a tad lower and more...constant then it used to be with manufacturer's drivers.

Tone generator was audiocheck.net playing on CV2+. Probably, with a better signal generator, the amp might measure even better, in respect with 2nd and 3rd harmonics.

 

[Veri]

What I see that got improved with this ASIO4ALL vs. the original ASIO drivers from ASUS was the nasty spikes around 12 KHz, sometimes around 8 KHz and other freqs too. Also, noise-floor is a tad lower and more...constant then it used to be with manufacturer's drivers.

Pretty weird though, how did they botch that driver...

 

[maxxevv]

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!

A 45mm tilt-shift might serve you better in this regard.

Or, since you're into Macro, use focus-stacking. Too little information in shallow DOF shots to be useful picts.

 

[trl]

Pretty weird though, how did they botch that driver...

I've no idea, but usually ASUS is not the best drivers-integrator ever, I also have Essence One and the Head-Fi thread is full of issues (especially on Win10 and USB3-related), not mentioning the U7 too.

A 45mm tilt-shift might serve you better in this regard.

Or, since you're into Macro, use focus-stacking. Too little information in shallow DOF shots to be useful picts.

For 1:1 I use my SIGMA 105mm lens which is awesome, but now I used a different lens. Given the shot-time I don't use tripod, so no focus stacking possible, but I will try this out for sure because it's a great technique. Thank you!

 

[JohnYang1997]

Not trying to criticize or anything.
But something i have to say.
First of all. 0.002% is indeed where it should be.
I have that amp too i measured myself as well.
There are some downsides of the design.
1, output impedance is a bit high.
2, it shines at low impedance load but high output impedance is non ideal for low impedance load.
3, output voltage is a bit low for discrete design. so not so fancy for high impedance load either.
4, noise floor is actually very high. anything that's remotely close to sensitive can produce noise.

Then about o2. I modded o2 then it only produce 0.8uV at half point of volume pot and 0.5uv at maximum. THD into 32 ohm 1mw is 0.00006%. 0.0001% at 10mw. How about that, king of mods?

 

[JohnYang1997]

u7 + voltage divider is indeed pretty good thd analyzer especially for the price.

 

[trl]

Not trying to criticize or anything.
But something i have to say.
First of all. 0.002% is indeed where it should be.
I have that amp too i measured myself as well.
There are some downsides of the design.
1, output impedance is a bit high.
2, it shines at low impedance load but high output impedance is non ideal for low impedance load.
3, output voltage is a bit low for discrete design. so not so fancy for high impedance load either.
4, noise floor is actually very high. anything that's remotely close to sensitive can produce noise.

Then about o2. I modded o2 then it only produce 0.8uV at half point of volume pot and 0.5uv at maximum. THD into 32 ohm 1mw is 0.00006%. 0.0001% at 10mw. How about that, king of mods?

Hi there,

Criticising it's all about this forum after all, right? All we care is how the audio equipment is built and how these are measuring, so I do appreciate your posts here.

1. I've seen no resistors or inductors in signal path, I wonder if the 3 Ohms output impedance would come from the internal impedance of the output transistors themselves...but this sounds about impossible (a similar output stage is included inside PLAY and this amp has 0.5 Ohms output impedance). I'd like to find a way to dive deep into lowering the output resistance of the output stage, but honestly I find to much trouble involved into taking out the PCB board...there are just too many screw and hours involved into this. However, I've A/B tested CV2 and O2 and HPA-3B amplifiers with my 16 Ohms IEMs and I got the same extended low-end like a 0.3 Ohms impedance amplifier (volume matched by oscilloscope), so this 3 Ohms output impedance is a lowlight only on the paper, not in real life...so I don't care much about this.
2. I found not an issue with my 600 Ohms Beyers, but I haven't tested with other high impedance cans, so please let us know what cans might be incompatible with this amplifier and in what exact way. Although, given the powerful output stage made with 8 x TO220 transistors and without low-pass filter on the outputs, I see no reasons why not pairing perfectly with high impedance cans at all, but of course...YMMV.
3. About 12V RMS/600 Ohms means almost 0.25 W/channel, that would be 5 times more than my Beyers DT880 600 Ohms can sustain.
4. This amp was simply not designed for IEMs (given the lack of adjustable gain and the max. 12V RMS output voltage), but I personally find the internal noise being pretty low for an amplifier designed without an adjustable gain-stage between voltage-gain and output-stage. It's noise is audible-comparable in A/B tests with the noise produced by my O2 when choosing the gain of 3.5X (volume matched for my 16 Ohms IEMs). In a very low room environment (nightly) I do hear a low amount of noise coming from my 16 Ohms IEMs (100dB/mW), but I don't find it disturbing. However, Objective2 with a gain of 1.5X is my IEM's amplifier anyway...this amp is totally quiet indeed, even with max. volume.

Could you please share something about the O2 mods, please? It might be interesting for others to follow your steps.

The mods I've done to my O2 were mostly related to RCA and 6.3mm jack plugs, swapping opamps, decreasing output DC and adding decoupling caps, but output noise wasn't really improved in any way.

P.S.: I do love amps made with no opamps in output stage, or no opamps at all, and I appreciate a bit of R&D done by manufacturer. This is why I purchased Matrix HPA-3B and Burson CV2+ actually.

 

[JohnYang1997]

Hi there,

Criticising it's all about this forum after all, right? All we care is how the audio equipment is built and how these are measuring, so I do appreciate your posts here.

1. I've seen no resistors or inductors in signal path, I wonder if the 3 Ohms output impedance would come from the internal impedance of the output transistors themselves...but this sounds about impossible (a similar output stage is included inside PLAY and this amp has 0.5 Ohms output impedance). I'd like to find a way to dive deep into lowering the output resistance of the output stage, but honestly I find to much trouble involved into taking out the PCB board...there are just too many screw and hours involved into this. However, I've A/B tested CV2 and O2 and HPA-3B amplifiers with my 16 Ohms IEMs and I got the same extended low-end like a 0.3 Ohms impedance amplifier (volume matched by oscilloscope), so this 3 Ohms output impedance is a lowlight only on the paper, not in real life...so I don't care much about this.
2. I found not an issue with my 600 Ohms Beyers, but I haven't tested with other high impedance cans, so please let us know what cans might be incompatible with this amplifier and in what exact way. Although, given the powerful output stage made with 8 x TO220 transistors and without low-pass filter on the outputs, I see no reasons why not pairing perfectly with high impedance cans at all, but of course...YMMV.
3. About 12V RMS/600 Ohms means almost 0.5 W/channel, that would be 5 times more than my Beyers DT880 600 Ohms can sustain.
4. This amp was simply not designed for IEMs (given the lack of adjustable gain and the max. 12V RMS output voltage), but I personally find the internal noise being pretty low for an amplifier designed without an adjustable gain-stage between voltage-gain and output-stage. It's noise is audible-comparable in A/B tests with the noise produced by my O2 when choosing the gain of 3.5X (volume matched for my 16 Ohms IEMs). In a very low room environment (nightly) I do hear a low amount of noise coming from my 16 Ohms IEMs (100dB/mW), but I don't find it disturbing. However, Objective2 with a gain of 1.5X is my IEM's amplifier anyway...this amp is totally quiet indeed, even with max. volume.

Could you please share something about the O2 mods, please? It might be interesting for others to follow your steps.

The mods I've done to my O2 were mostly related to RCA and 6.3mm jack plugs, swapping opamps, decreasing output DC and adding decoupling caps, but output noise wasn't really improved in any way.

P.S.: I do love amps made with no opamps in output stage, or no opamps at all, and I appreciate a bit of R&D done by manufacturer. This is why I purchased Matrix HPA-3B and Burson CV2+ actually.

One burson's website i believe it is 3ohm(my bad). What i believe it's that it's no global feedback. So it's possible to have higher output impedance. And i have measured their v6 opamp which can gondown to 0.0001% thd. So the noise and 0.002% at even low output indicated no global feedback.

About o2. The entire circuit is opamp + resistors and some caps. So i changed to 1k potentiometer and low noise opamp. I bypassed the input gain stage and the input resistor. 2v from dac is really all we need. I see no headphones need over 2vrms. Including he6 and k1000. The dynamic are all limited by the digital domain. So no lost in anyway. I also lowered output resistor to 0.1ohm. The opamp was specifically selected in this situation so less than 100uv output offset is achieved. Completely low noise and distortion and fully capable of any realistic output power.

 

[JohnYang1997]

btw. I still own cv2+. The reason why i bought it was the day in the show none of the amps there were able to power final d8000 (prototype) right. wa33 was sounding like complete shit. 430had was much better but still wasn't music. when plugged into cv2 holy shit it's pure music.
To me it's best pair with low sensitivity ~50ohm planars.
A bit not so smooth with high impedance cans. That's about it.

 

[trl]

I measured CV2's output resistance and it's about 3 Ohms (@1 KHz sines). Given it's low THD I guess it does have NFB after all.

O2 already has a very low noise by default, I see no reason to reduce the noise even further, unless for fun of DIY; see Neurochrome's measurements.
What you've done to your O2 headamp is a dramatically change of the original schematic, you've crippled the design (from what I understand) and not a modding. Loosing the input gain stage make your O2 a simple output buffer and not an amplifier, but maybe I'm wrong...

 

[JohnYang1997]

I measured CV2's output resistance and it's about 3 Ohms (@1 KHz sines). Given it's low THD I guess it does have NFB after all.

O2 already has a very low noise by default, I see no reason to reduce the noise even further, unless for fun of DIY; see Neurochrome's measurements.
What you've done to your O2 headamp is a dramatically change of the original schematic, you've crippled the design (from I understand) and not a modding. Loosing the input gain stage make your O2 a simple output buffer and not an amplifier, but maybe I'm wrong...

Global feedback without output resistors will lower the output impedance to less than 0.5ohm. And the distortion will be lower and become frequency dependent. It sure has local feedback. No circuit doesn't have local feedback.
Yes the o2 is becoming a buffer but still an amplifier, a current amplifier. I didn't rebuild the pcb so technically it's sill modding. I call it heavily modded. About already noise being low and no need to have it lower. Let me put it this way. At regular listening volume. Noise is significantly higher than distortion. thd+n is limited by noise even at a few hundred mw. So what's the meaning of reducing the distortion further? If you think like this you can either, oh shit i don't give a fuck about measurements anymore or yeah reducing noise makes sense.
One thing about hp-1, is that as he published 32ohm load 100mw multitone distortion figure but not for hp-1. I really want to see it. Because i also modded jds el amp(not too much to mod), i also have 1622evm. I think 49600 based circuits' weak point is low impedance load at high frequency. Distortion will rise up after 2khz and become 6 times the distortion at 10khz. Maybe two 1611+49600 complete loop in parallel will solve this but I'm skeptical. I want to see it. Also for true earphone load, output impedance drastically change the distortion in some frequency depending on the headphones. From my experience less than 0.1ohm output impedance or at least 0.16ohm can minimize the effect of real headphones/earphones load. So for two 1611+49600 in parallel under that output resistor, i think the stability is going to suffer. So he chose 1ohm for that.