Benchmark DAC3 HGC vs. Bryston, Exasound, et al: Output Impedance, Sonic Comparisons

[ajant]

Hi Tom,

Your Benchmark DAC thread was very informative and a pleasure to learn from, even if headphones aren't my thing. https://www.whatsbestforum.com/threads/benchmark-dac3-dx.23831/

For my bedroom TV system, while surely waiting in vain for some LED/OLED brand to issue a ~48" 4:3 panel, I enjoy using my lovely old Toshiba 32" CRT to play vintage 1.33:1 (and widescreen) content, fed by my Oppo BDP-95 BD player. The Oppo's unbalanced stereo outputs directly feed my First Watt F4 power amp which drives my DIY floorstanding speakers. The sealed 4-way speakers with 15" woofers are ~ 84 db/w/m. The input impedance of the F4 amp is 47K ohm but being a source follower amp the voltage gain is -0.3db. This Class A amp runs quite warm but I don't feel too guilty as I only use it for a couple hours or so for a nightly movie.

With ~ 9v input the F4 will output 25wpc into 8 ohms, but even 7 watts would likely blast me out of the ~ 15 x 12 bedroom, and I sit ~ 10.5 ft from the speakers. Even so, depending on BD/DVD audio quality I sometimes have to crank up the Oppo remote's analog output volume, so for this and other reasons I'm hoping this Benchmark DAC will deliver ample output voltage to the F4 amp's unbalanced inputs.

Presumably however, since both the Oppo's and Benchmark's unbalanced outputs are ~ 2 volts RMS, would not output impedance vs. frequency determine the loading effects on the F4 amp's inputs, and thereby it's output power?

While the Oppo 95 manual doesn't cite the output impedance, this engineer measures 100 ohms overall. https://www.jensign.com/bdp95/headphones/index.html​

Another DAC option is the Bryston BDA-3, but where Atkinson's measurements found the unbalanced output impedance changing considerably with frequency.
https://www.stereophile.com/content/bryston-bda-3-da-processor-measurements

Luckily, Atkinson also ran measurements on the DAC3 HGC which remained at 30 ohms across the audible range. https://www.stereophile.com/content...preamplifier-headphone-amplifier-measurements

However, I would still like to know why the Bryston's output impedance, however much audibly relevant, varied so much with frequency, while the Benchmark's didn't.
But it certainly does look like the DAC3 might drive my F4 amp every bit as well as a Pass Labs preamp or line stage.

Connectivity wise, I do hate the fact that the DAC3 (and virtually all DAC brands) still include a TOSlink input, or more so that they don't add an extra SPDIF coax input, even if they couldn't be used simultaneously. I have no optical cable and I've heard horror stories where if you bend the cable however much the signal craps out. So, I'll have no choice but to use TOSlink as I want to use both my Oppo and Pioneer LX500 BD players.

A recommended optical cable makes/models least susceptible to signal loss?

My other A/V source will be my pc's BD drive. The video card will output HDMI video to a Black Box composite video converter for the old CRT, while the pc outputs audio via USB to the DAC3. JRiver and VLC handles transport functionality, menus, et al.

Any issues with using the DAC3's USB audio input this way?

My only other concern is that the audio quality of most DVD/BD movies in my collection range from good to very good to excellent. But however the Oppo's ESS and Pioneer's AKM DAC chips and output stages have characterized what I've long been hearing, how likely will I be dismayed by what the DAC3 may reveal about my sources?

I'd gladly spend ~ $2.5K more than the DAC3's price for a DAC that was clearly better across all performance parameters, but I doubt that would be too easy. And the DAC3 also clobbers intersample overs distortion natively, rather than having to do so via your software player.
https://benchmarkmedia.com/blogs/ap...-in-cd-recordings?_pos=1&_sid=0eeb1f150&_ss=r

https://gearspace.com/board/mastering-forum/1401406-intersample-clipping-audible.html

OTOH, some user comparisons of the Bryston vs. DAC3 had the former sounding "relaxed" and the latter sounding "thin".
https://www.stereophile.com/content/benchmark-dac3-hgc-da-preamplifier-headphone-amplifier

And while the DAC3 won praise for its sound stage size and dimensionality, users here found the Exasound-using the same ESS DAC chip-did that better, and with more "detailed treble". https://audiophilestyle.com/forums/topic/61748-benchmark-dac3-vs-‘higher-end’-dacs/

Perhaps splitting hairs here, if over "subjective" comparisons, but please share experiences and suggestions.

 

[tmallin]

It appears to me that your primary problem is that you are using an amplifier that is considerably underpowered for your speakers. Your sealed DIY speakers with 15-inch woofers are speced at only 84 dB/watt/meter. Your amp's output rating is only 25 wpc. Even if your speakers' sensitivity specs are accurate (most such specs are quite, shall we say, optimistic), your speakers are on the low side of moderate sensitivity, a bit less than Harbeth speakers for example. To sound their best, speakers with this type of sensitivity need about 200 wpc.

First Watt's literature about the F4 amp seems to envision it being used with speakers about 10 dB more sensitive than yours. That 10 dB represents a power level of ten times. Thus, while the F4's 25 wpc output may be plenty for speakers rated at 94 dB/watt/meter, it is seriously underpowered for your speakers.

Further, the First Watt F4, while it may well sound excellent, has no voltage gain. In fact, it is speced to have a bit of negative voltage gain. Sine it has only unbalanced inputs, your Oppo BDP-95 will only output a maximum of 2.1 volts. If you were using the balanced outputs, the Oppo could put out 4.2 volts.

I could not find a spec for the input sensitivity of the F4 amp, but most amps will output full rated power with an input of no more than 2 volts. You should have no qualms about turning up the output volume control on your Oppo. Most volume controls are more transparent when set for higher volume than at low volumes. It is a mistake to believe that you need to keep a lot of the volume range "in reserve." Thus, you still may be able to drive the F4 to its rated output if you turn up the volume of the Oppo to near its maximum. Still, 25 watts is inadequate for best sound from these speakers.

And let's be frank. Your DIY speakers are of ultimately unknown quality. The speaker quality is far, far more important to ultimate sound quality than any small differences between the sound of different DACs. Thus, I wouldn't be too concerned about the ultimate DAC quality once you are at Oppo/Benchmark/Bryston quality levels.

What you need, I think, is a more powerful amplifier and one which can be driven by the balanced analog outputs of your DAC. You could continue to use your Oppo if you want, just use its balanced analog outputs which will give you 4.2 volts out maximum.

One amplifier I can vouch for in this sort of situation is the Audio by Van Alstine DVA M225 which costs about $3,400 for a monoblock pair. Terrific sound, fully balanced, fully regulated circuitry, and some voltage gain.

If you want to "improve" your digital front end, you could go with the Benchmark DAC3 HGC. For more money, you could invest in a Lumin streaming front end and get the best direct drive of amplifiers available, plus full streaming capability. The Lumin Leedh digitally processed volume control is, for me, clearly the best sounding way to directly drive power amps. I use the Lumin X1, but there are other less expensive Lumins with a built-in DAC and the same Leedh volume control.

Another less expensive option would be to pair the Van Alstine amp with the Van Alstine DVA Digital Preamplifier, which is probably a match made in heaven. That unit is $2,500. That unit also gets you two coax digital input, USB input, as well as toslink.

I agree that coax digital connections sound a bit better than toslink, although into the right DAC, such as a Benchmark, the difference is quite small. As long as you don't put sharp bends in the toslink cable, they work well enough. I suggest the toslinks from Blue Jeans Cable which, to me, sound better than any others.

Good luck on your quest and happy listening!

Tom

 

[audiobomber]

Hi Tom,

Your Benchmark DAC thread was very informative and a pleasure to learn from, even if headphones aren't my thing. https://www.whatsbestforum.com/threads/benchmark-dac3-dx.23831/

For my bedroom TV system, while surely waiting in vain for some LED/OLED brand to issue a ~48" 4:3 panel, I enjoy using my lovely old Toshiba 32" CRT to play vintage 1.33:1 (and widescreen) content, fed by my Oppo BDP-95 BD player. The Oppo's unbalanced stereo outputs directly feed my First Watt F4 power amp which drives my DIY floorstanding speakers. The sealed 4-way speakers with 15" woofers are ~ 84 db/w/m. The input impedance of the F4 amp is 47K ohm but being a source follower amp the voltage gain is -0.3db. This Class A amp runs quite warm but I don't feel too guilty as I only use it for a couple hours or so for a nightly movie.

With ~ 9v input the F4 will output 25wpc into 8 ohms, but even 7 watts would likely blast me out of the ~ 15 x 12 bedroom, and I sit ~ 10.5 ft from the speakers. Even so, depending on BD/DVD audio quality I sometimes have to crank up the Oppo remote's analog output volume, so for this and other reasons I'm hoping this Benchmark DAC will deliver ample output voltage to the F4 amp's unbalanced inputs.

Presumably however, since both the Oppo's and Benchmark's unbalanced outputs are ~ 2 volts RMS, would not output impedance vs. frequency determine the loading effects on the F4 amp's inputs, and thereby it's output power?

While the Oppo 95 manual doesn't cite the output impedance, this engineer measures 100 ohms overall. https://www.jensign.com/bdp95/headphones/index.html​

Another DAC option is the Bryston BDA-3, but where Atkinson's measurements found the unbalanced output impedance changing considerably with frequency.
https://www.stereophile.com/content/bryston-bda-3-da-processor-measurements

Luckily, Atkinson also ran measurements on the DAC3 HGC which remained at 30 ohms across the audible range. https://www.stereophile.com/content...preamplifier-headphone-amplifier-measurements

However, I would still like to know why the Bryston's output impedance, however much audibly relevant, varied so much with frequency, while the Benchmark's didn't.
But it certainly does look like the DAC3 might drive my F4 amp every bit as well as a Pass Labs preamp or line stage.

Connectivity wise, I do hate the fact that the DAC3 (and virtually all DAC brands) still include a TOSlink input, or more so that they don't add an extra SPDIF coax input, even if they couldn't be used simultaneously. I have no optical cable and I've heard horror stories where if you bend the cable however much the signal craps out. So, I'll have no choice but to use TOSlink as I want to use both my Oppo and Pioneer LX500 BD players.

A recommended optical cable makes/models least susceptible to signal loss?

My other A/V source will be my pc's BD drive. The video card will output HDMI video to a Black Box composite video converter for the old CRT, while the pc outputs audio via USB to the DAC3. JRiver and VLC handles transport functionality, menus, et al.

Any issues with using the DAC3's USB audio input this way?

My only other concern is that the audio quality of most DVD/BD movies in my collection range from good to very good to excellent. But however the Oppo's ESS and Pioneer's AKM DAC chips and output stages have characterized what I've long been hearing, how likely will I be dismayed by what the DAC3 may reveal about my sources?

I'd gladly spend ~ $2.5K more than the DAC3's price for a DAC that was clearly better across all performance parameters, but I doubt that would be too easy. And the DAC3 also clobbers intersample overs distortion natively, rather than having to do so via your software player.
https://benchmarkmedia.com/blogs/ap...-in-cd-recordings?_pos=1&_sid=0eeb1f150&_ss=r

https://gearspace.com/board/mastering-forum/1401406-intersample-clipping-audible.html

OTOH, some user comparisons of the Bryston vs. DAC3 had the former sounding "relaxed" and the latter sounding "thin".
https://www.stereophile.com/content/benchmark-dac3-hgc-da-preamplifier-headphone-amplifier

And while the DAC3 won praise for its sound stage size and dimensionality, users here found the Exasound-using the same ESS DAC chip-did that better, and with more "detailed treble". https://audiophilestyle.com/forums/topic/61748-benchmark-dac3-vs-‘higher-end’-dacs/

Perhaps splitting hairs here, if over "subjective" comparisons, but please share experiences and suggestions.

I stand by my Audiophile Style description of the DAC3 vs. exaSound e32 Mk-II sound, which you linked above, however I'm embarrassed that I neglected to mention in that thread that I also changed streamers when I changed DAC's. I used the DAC3 L with an sMS-200 and linear power supply, whereas I use the e32 with an exaSound PlayPoint. I don't know how the streamers compare sonically. The e32-II only mates with exaSound, Windows or Mac gear, an issue I believe has been resolved in the replacement e62 DAC. The DAC3 has an analog input, a feature I miss on the e32 and may be beneficial in your setup.

I know you don't care about headphones, but they are a great option when the household is asleep. The headphone amp in the e32 is excellent, every bit the equal of my Hafler HA15 for driving my 250 ohm Beyerdynamic DT 1990 Pro headphones.

My DAC has to simultaneously drive 20kOhm monoblocks for the main speakers and a 6kOhm miniDSP for subs. That is a very tough load, but the e32 handles it brilliantly, I feel absolutely no need for a preamp. I've even used the e32 to feed a 2.5kOhm passive line-level crossover and the 6kOhm minDSP, a ridiculous load, but not a problem for the e32.

In my system, I use a Pioneer multiplayer as a CD transport, connected to the e32 via coax. I connect my Oppo 980H to the TV via HDMI for DVDs. The television outputs to the DAC via Toslink. Note that this is a DDC connection, the DACs in the Oppo and TV are bypassed, the only analog conversion is via the main DAC. For a further improvement in sound, I use an iFi iPurifier SPDIF between the TV and DAC.

When I had the DAC3, I connected my Oppo to it via RCA, which allowed me to play my DVD Audio and SACD discs. I can no longer do so, but I didn't have much of a collection anyway, and I've since ripped them.

PS A DAC will give you cleaner sound, not louder sound. If volume is an issue, you need new speakers on a new amp.