[G-U-E-S-T]

Elias, did you miss my last post to you, about the Jensen transformer? I would sure appreciate your feedback. If I am incorrect about any of it, don't worry about being "tactful" - I am here to learn! Thanks in advance.

 

[John Reeves]

Hi,

I have been utilizing a Benchmark DAC to run into a Naim pre-amp and power amplifier. I have had this equipment from new and it is about 22 years old. The improvement from running out of the Juli@ was a definite step forward.

However, I decided that since I was not using any analogue sources, then I would run the Benchmark straight into the Naim 250 amp.

This was a big mistake. The improvement was unbelievable, and I do not exaggerate. I don't believe in snake oil, so I can assure you that this is correct. I had friends around and the improvement was so obvious it would have been pointless to carry out blind listening tests. So it was obvious that over the years of good service the Naim equipment was probably a bit tired and needed capacitors etc replaced.

So, the mistake was showing up the deficiencies of my existing system, which had degraded gradually over the course of years, so giving me the dreadful disease UPGRADITUS.

OK the lots being changed. I'm selling the Naim stuff and replacing it with simply a new power amp. I'm going to keep the Isobariks in the short term, but will be looking to possibly replace them- short term, who am I kidding, even my wife doesn't believe me since she has recognized the symptoms of UPGRADITUS.

So, fellow Headfiers beware, buying a Benchmark can easily lead to you catching this dreadful disease whose side effects include an empty wallet and phone calls from the bank manager.

Cheers

John

 

[EliasGwinn]

Quote:

Originally Posted by infinitesymphony /img/forum/go_quote.gif Have there been any contenders to the Analog Devices AD1853

Hey! Sorry I've been MIA...our sales person, Rory, has been out of the office this week, so I've been on full-time phone and email tech-support and sales duty. And, I'll tell you what, I have a new level of respect for Rory after this week!!

RE: Dac chips... The AD1853 is still our chip of choice. AD has another chip (AD1955) that has 3 dB less noise then the 1853, but it has functionality issues that make its use questionable.

As for other dac makers, we've found that Cirrus chips have issues with their low-pass filters, Burr Brown dacs have linearity issues, and AKM dacs have poor stop-band limitations which will cause aliasing.

Another nice thing about the 1853 is that it has a current output, which allows us to build our own I-V converter with much lower distortion then most built-in IV converters.

Thanks,
Elias

 

[EliasGwinn]

Quote:

Originally Posted by G-U-E-S-T /img/forum/go_quote.gif ...about the Jensen transformer...

G-U-E-S-T,

I haven't really looked at the spec sheet for that Jensen transformer, but the spec you mentioned (0.015% @ 20Hz) is rather detrimental. That equates to -76.5 dB, or about 30 dB more then the DAC1. Try one and hear it for yourself...it won't be subtle.

Transformers are used in pro audio for a few reasons: 1. they are a great tool for providing common-mode rejection, when that is an issue 2. sometimes they are needed to provide electrical isolation and/or impedance conversion 3. some people actually enjoy the distortion of transformers on certain instruments, just like some people enjoy tube distortion.

As Crowbar mentioned, using a transformer would really reduce the transparency of the audio. Sometimes they're necessary, sometimes they are desired, but they are never transparent.

Thanks,
Elias

 

[ted betley]

Congrats to all the staff @ Benchmark for the 'shoot the lights out' review at Absolute Sound.

 

[Matias]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif The HPA-2 in the DAC1 is our top-of-the-line, studio reference quality headphone amp. We didn't skimp at all when building into the DAC1.

Hi Elias,

If it could only have a better attenuator, say Alps or DACT, then it would be really top. If it only had more room, I would mod it myself...

Thanks,
Matias

 

[Covenant]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif I don't think there is anything to gain from adding an external headphone amplifier. The HPA-2 in the DAC1 is our top-of-the-line, studio reference quality headphone amp.

Hi Elias,

I'm curious, does the HPA-2 drive the balanced outputs of the DAC1 as well? I've been hearing for ages that the HD650 scales extremely well with balanced operation, and having a reference-grade USB DAC with true balanced outputs and a high quality inbuilt balanced amplifier all in one unit would be very attractive.

Also, is the HPA-2 a discrete circuit, or opamp based? Just asking because I'm not familiar with the HPA-2 at all.

 

[NewMexiCat]

+1 for Covenant's fine questions.

Quote:

Originally Posted by Covenant /img/forum/go_quote.gif Hi Elias, I'm curious, does the HPA-2 drive the balanced outputs of the DAC1 as well? I've been hearing for ages that the HD650 scales extremely well with balanced operation, and having a reference-grade USB DAC with true balanced outputs and a high quality inbuilt balanced amplifier all in one unit would be very attractive. Also, is the HPA-2 a discrete circuit, or opamp based? Just asking because I'm not familiar with the HPA-2 at all.

 

[infinitesymphony]

Those questions were answered earlier in the thread. The headphone and line output sections are different, the DAC1 is not designed to drive headphones out of the balanced outputs (and Elias recommends against it), and the headphone section uses either a NE5532 (regular DAC1) or a LM4562 (DAC1 USB and DAC1 PRE) op-amp for the headphone section. At least, that's what I remember.

 

[EliasGwinn]

Quote:

Originally Posted by Covenant /img/forum/go_quote.gif ...does the HPA-2 drive the balanced outputs of the DAC1 as well?

No, the HPA-2 drives the headphone output only.

Quote:

Originally Posted by Covenant /img/forum/go_quote.gif I've been hearing for ages that the HD650 scales extremely well with balanced operation, and having a reference-grade USB DAC with true balanced outputs and a high quality inbuilt balanced amplifier all in one unit would be very attractive.

The DAC1/USB/PRE does, in fact, have true-balanced outputs. These outputs can drive balanced headphones. However, I strongly advise against this configuration using any balanced headphone amplifier.

I've written about this here and many other places, but I'll quickly summerize for you.

Balanced headphone have many inherent drawbacks, and very little substantial benefits.

Inherent drawbacks include:
- Double output impedance
- 50% reduction of damping factor
- 100% increase in noise
- +/-200% increase in distortion.

Benefits include:
- Increase gain
- Increase slew rate

These 'benefits' (increase in gain and slew rate) are hardly worth the major drawbacks. The gain and slew rate of the Benchmark's HPA-2 are far more then they need to be for the application, so increasing them won't gain any performance increase.

Quote:

Originally Posted by Covenant /img/forum/go_quote.gif Also, is the HPA-2 a discrete circuit, or opamp based? Just asking because I'm not familiar with the HPA-2 at all.

I've addressed this here, but I'll recap for you. The output driver of the HPA-2 is the BUF634, a high-speed buffer amplifier capable of 250 mA output current and 2000 V/uS slew rate.

Thanks,
Elias

 

[Covenant]

Thank you very much for your prompt response, Mr Elias. Its great to see you're still active here and so knowledgeable about your product, I wish more manufacturers would aspire to such support. You're a gentleman and a scholar

I wont pretend to fully understand the link you provided listing the technical reasoning against balanced operation, however this seems to fly in the face of conventional wisdom on these boards. Its been drilled into us like a religious sermon that balanced operation will always exceed unbalanced operation in terms of extrating the last ounces of sound quality from a headphone, especially with the Sennheisers.

The reason touted is normally the elimination of crosstalk and the doubled voltage swing provided to each driver - the Senns are reputedly very voltage-swing dependant, and subjective listening tests seem to have verified this.

I'm not disputing your information, however i'm just curious as to why oppinions are differing so much on this. Even if the balanced line-out stage of the DAC1 USB was somewhat inferior to the headphone amp for the purpose of driving headphones, I would have wagered that a balanced HD650 would still far outperform an unbalanced HD650 with the DAC1 USB as source/amp.

 

[katalyst^]

Is there any difference between the DAC1 and DAC1 USB in terms of the quality of the headphone amp?

 

[applebook]

Quote:

Originally Posted by katalyst^ /img/forum/go_quote.gif Is there any difference between the DAC1 and DAC1 USB in terms of the quality of the headphone amp?

The headphone amp is not affected by the DAC output

 

[luciyuspax]

Hi guys! I am planning to buy benchmark DAC1 USB. I have sometimes the hum problem when I am listening to music with my headphones through headphone output of my onkyo integrated amplifier. I guess I have a ground problem.

Does Benchmark DAC1 suffer from hum problems as well? I will use DAC1 only plugged to my laptop purely for headphone listening. Only DAC1 and laptop will be plugged into the same strip. Also about those surge protectors with power filters(not the big powercenter models in a box), how do they behave with DAC1? I will either buy a monster HTS1000 or belkin pureav surge protector. I heard that they generally improve video quality of plasma TVs etc but that some amplifier really do not like them. Will they improve or decrease sound quality of DAC1 USB?

Have a nice day all!

 

[katalyst^]

*blank stare* I am confused

Someone mentioned above that they use different opamps - I thought the head amp might have been upgraded a little at the same time as the addition of the USB.

Does that mean that if I don't need USB, I can buy an ordinary DAC1 and it'll be otherwise identical?