[little-endian]

Quote:

Originally Posted by olivier /img/forum/go_quote.gif namely, if the output of the benchmark (or any other) is really different from the output of my cd player, dvd player, radio etc, perhaps not all of these should be plugged directly into my amp? so ... would it be the case that the benchmark has the perfect output for my amp, but other sources don't!

Hi olivier,

i don't think the DAC1's output is that different (except for the measurable better signal probably).

From the practical point of view, today, the only use of a preamplifier is to select the source, to control the volume and maybe to adjust loudness/bass/treble. What needs actually preamplification is just the phono source because all other levels are high enough in the first place. Thus many "preamplifiers" even reduce (!) the signal level before it reaches the power amplifier - it depends on the volume setting. In the case your power amp allows you to control the volume or input sensitivity, there is nothing against connecting a cd-player for instance directly to it. In the case of the DAC1, the problem of the volume control is none because of its selectable variable setting.

Your point in regard to match the source's signal to the power amp might be an argument but for me it sounds like a bit voodoo since not even the best pre amp would be able to add any detail which isn't present in the source, leaving it intact at best.

@tubaman

Yeah, it's okay to leave it on all the time. Elias from Benchmark already confirmed this here.

 

[poo]

Quote:

Originally Posted by little-endian /img/forum/go_quote.gif From the practical point of view, today, the only use of a preamplifier is to select the source, to control the volume and maybe to adjust loudness/bass/treble. What needs actually preamplification is just the phono source...

I think you are confusing the use of a pre amp into power amp with integrated amplifiers and receivers.

Pre amps have more uses than phono amplification...

 

[poo]

Quote:

Originally Posted by olivier /img/forum/go_quote.gif ...i don't personally know well what preamps are for, and why one should or not use one, but let me make a wild guess here.

I think you need to research that in another thread before you ask questions about how good the DAC1 is at performing as a pre. Why bother if you don't know its application?

 

[olivier]

Quote:

Originally Posted by little-endian /img/forum/go_quote.gif Hi olivier, From the practical point of view, today, the only use of a preamplifier is to select the source, to control the volume and maybe to adjust loudness/bass/treble. What needs actually preamplification is just the phono source because all other levels are high enough in the first place. Thus many "preamplifiers" even reduce (!) the signal level before it reaches the power amplifier - it depends on the volume setting. In the case your power amp allows you to control the volume or input sensitivity, there is nothing against connecting a cd-player for instance directly to it. In the case of the DAC1, the problem of the volume control is none because of its selectable variable setting.

Thanks for the info little-endian. What you say about preamplification is consistent with what I read on other places. Still, some DAC's offer to bypass the preamp stage, so my guess is that the preamplification stage is never neutral, and there may be some benefit to leave this job to a specialized unit.

This being said, I think that my money can be more wisely spent looking for a great DAC/Preamp instead of looking for two separate units. The main reason for this is that most DACs at a reasonable price range will preamp anyway, and the distortions it introduces cannot be corrected for, no matter how good the preamp it feeds is.

Cheers, Olivier

 

[EliasGwinn]

Quote:

Originally Posted by olivier /img/forum/go_quote.gif hello scritch! that, for one, is an interesting opinion. i don't personally know well what preamps are for, and why one should or not use one...

Olivier,

A pre-amp is not much more then what the name indicates: pre (before) amp (amplifier). A pre-amp can serve several functions, include (but not limited to):

1. Amplitude adjustment/volume control (boost OR attenuation)

2. Driving capability (certain pre-amps drive certain amplifiers better or worse then others)

3. Tone shaping (this can include an EQ section, or adding tube-tone, etc)

4. Source selecting and multiple-outputs

5. Phono-pre (I mention this specifically because phono players require a special pre-amp circuit to operate properly)

If you need these features, then a pre-amp is necessary. If you do not need these features, then adding a pre-amp will do nothing more then add noise, distortion, and cost to your system. Even the best pre-amp in the world will add some small amount of noise and distortion. If its not needed, then you may want to consider omitting it.

The DAC1 has the 1st, 2nd and 4th features on this list. Therefore, if you don't have analog sources (tape, phono), and if you want the audio to be as transparent and uncolored as possible (i.e., no EQ or tubes), then the DAC1 will serve as the pre-amp, and it will perform this function as good or better then any other pre-amp. However, if you want to use another pre-amp to utilize those other features, the calibrated RCA outputs of the DAC1 will output the same levels as a CD transport. The DAC1 sound quality will remain, but the signal amplitude will be consistent with other typical devices.

Thanks,
Elias

 

[olivier]

Elias,

Thank you so much for your thorough explanation. I guess the only point that I still need to understand is ... is there any more distortion from the benchmark in dac/preamp mode as compared to dac mode? My first guess would be that raising the signal to a higher gain can introduce more noise, but I can't be sure of that.

Of course, the same question applies to other brands of DAC/preamps as well, although I don't necessarily expect an answer from you on them.

Cheers, and thanks again!

Olivier

 

[EliasGwinn]

Quote:

Originally Posted by olivier /img/forum/go_quote.gif ... is there any more distortion from the benchmark in dac/preamp mode as compared to dac mode?

Olivier,

The distortion does not increase with higher output levels with the DAC1. The DAC1 is designed to operate completely in its linear region at all output levels. In fact, if your amp was able to accept +29dBu input (most can't), it would be advantageous to keep the DAC1's output level as high as possible to obtain optimal signal-to-noise ratio.

Also, amplifiers are more subject to distortion vs. gain, so minimizing the amplifiers gain would be an added benefit of a high output level from the DAC1.

Thanks,
Elias

 

[EliasGwinn]

Quote:

Originally Posted by euclid /img/forum/go_quote.gif i received the DAC1 USB last week. in comparison to the standad DAC1 the usable range on the headphone amp has improved enough for me. now the Senn HD650 can take the volume dial to around 1:00-2:00, the Audio Technica W5000 now have a usable volume range at 10:00-11:00 on the volume knob. with the standard DAC1 the W5000 were really maxed by 9:00 and there was noticable inconsistency in the volume steps, sometimes i would take it one notch further and the volume would raise too much, then i would back it off, raise it agian and the volume was differet. the USB doesnt have that problem with the -10db jumper installed the dial goes high enough to overcome the tracking problems of the pot at low level.

Euclid,

I just noticed this post (sorry, I've been in NYC for the past 5 days).

I'm glad to hear that the -10dB worked for you. I know that the HD650's are high-Z, low sensitivity headphones, but what about the W5000? Are they particularly sensitive? How do they compare with other common headphones?

Thanks,
Elias

 

[euclid]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif Euclid, I just noticed this post (sorry, I've been in NYC for the past 5 days). I'm glad to hear that the -10dB worked for you. I know that the HD650's are high-Z, low sensitivity headphones, but what about the W5000? Are they particularly sensitive? How do they compare with other common headphones? Thanks, Elias

no problem i wasnt expecting a response anyway

the W5000 are 42ohm 102db/w which is comparable in sensitivity to the Senn HD-650 at 103db/w the difference there is impedance.

suprisingly i have about the same usable range on my Shure E4c IEM as well which are 29ohm 109db/w, but IEMs use balanced armature drivers which have natural high frequency rolloff, the w5000 is a fairly bright sounding headphone with exceptional high frequency extension, all other things equal i think the Shures(or any IEM) could be driven to a higher volume without becoming uncomfortable just based on their sound signature.

i also wanted to mention that attenuating the headphone amp on the DAC1 USB any further might affect the HD-650, they get loud enough now with the -10db jumper but past that 2:00 point i can basically take the volume all the way up without them really screaming. the standard DAC1 gain can [over]drive the HD-650 to ridiculous levels but the USB doesnt have that much headroom.

thanks again for the help

 

[EliasGwinn]

Quote:

Originally Posted by euclid /img/forum/go_quote.gif the W5000 are 42ohm 102db/w which is comparable in sensitivity to the Senn HD-650 at 103db/w the difference there is impedance. suprisingly i have about the same usable range on my Shure E4c IEM as well which are 29ohm 109db/w, but IEMs use balanced armature drivers which have natural high frequency rolloff, the w5000 is a fairly bright sounding headphone with exceptional high frequency extension, all other things equal i think the Shures(or any IEM) could be driven to a higher volume without becoming uncomfortable just based on their sound signature. i also wanted to mention that attenuating the headphone amp on the DAC1 USB any further might affect the HD-650, they get loud enough now with the -10db jumper but past that 2:00 point i can basically take the volume all the way up without them really screaming. the standard DAC1 gain can [over]drive the HD-650 to ridiculous levels but the USB doesnt have that much headroom.

Thanks so much for this feedback. So, perhaps we shouldn't decrease the gain of the headphone amp beyond that of the DAC1 USB?

I can't stress enough how much this info helps us. You all are my insiders into the 'real-world'. I just noticed that this thread has gone on for 50 pages!! And it is still an incredible resource of communication between you all and us. I can't thank you all enough for the invaluable experience this has been. I hope it goes on for another 50, and beyond!!

Thanks a million!!
-Elias

 

[tubaman]

This seems to be the appropriate thread for my question:

When using the DAC1 (USB) to feed a headphone amp, how should the volume control on DAC1 be set?

I have two choices on this: calibrated or variable (adjustable in the back). According to the manual calibrated is near full volume. I tried near full volume (at about 5 o'clock) and I can barely turn the Prehead's volume control past 6 o'clock.

I have been using the variable setting and the volume control on the DAC1 is at about 11 o'clock, the Prehead at about 9-10 o'clock.

I wonder if there is a correct way (e.g. general principle) to do set the volume control on the units, anyone?

 

[xp9433]

""When using the DAC1 (USB) to feed a headphone amp - Corda Prehead""

Tubaman interesting you are using the Prehead rather than the DAC1 headphone out.

Is this because of the cross feed circuit in the prehead or just overall better sound quality? Please enlighten me.

Frank

 

[EliasGwinn]

Quote:

Originally Posted by tubaman /img/forum/go_quote.gif When using the DAC1 (USB) to feed a headphone amp, how should the volume control on DAC1 be set? I have two choices on this: calibrated or variable (adjustable in the back). According to the manual calibrated is near full volume. I tried near full volume (at about 5 o'clock) and I can barely turn the Prehead's volume control past 6 o'clock. I have been using the variable setting and the volume control on the DAC1 is at about 11 o'clock, the Prehead at about 9-10 o'clock. I wonder if there is a correct way (e.g. general principle) to do set the volume control on the units, anyone?

Tubaman,

Are you using the XLR outputs or the RCA outputs? If you are using the XLR outputs, there are output attenuators you can adjust to accommodate the input sensitivity of your headphone amp. If you are using the RCA outputs, it is perfectly fine to use the volume control to achieve the proper signal level for your headphone amp. In fact, it is fine to use the volume control for this purpose with the XLR outputs as well.

Thanks,
Elias

 

[tubaman]

Quote:

Originally Posted by EliasGwinn /img/forum/go_quote.gif Tubaman, Are you using the XLR outputs or the RCA outputs? If you are using the XLR outputs, there are output attenuators you can adjust to accommodate the input sensitivity of your headphone amp. If you are using the RCA outputs, it is perfectly fine to use the volume control to achieve the proper signal level for your headphone amp. In fact, it is fine to use the volume control for this purpose with the XLR outputs as well. Thanks, Elias

Hi Elias, thanks for the reply. I am using RCA outputs now. What do you mean by "the appropriate signal level" (to be achieved by the volume control)? How do I know when it's appropriate? (E.g. minimum of ___ detents)

 

[infinitesymphony]

Quote:

Originally Posted by tubaman /img/forum/go_quote.gif Hi Elias, thanks for the reply. I am using RCA outputs now. What do you mean by "the appropriate signal level" (to be achieved by the volume control)? How do I know when it's appropriate? (E.g. minimum of ___ detents)

Something that specific might be hard to determine, since it depends on what signal level your amplifier expects. If you have testing equipment, you could measure the variable output of the DAC1 until it matches the level listed in your amplifier's manual (if it's in there).