Technical question - removing the preamp

Further Forum searching will reveal many here consider the pre-amp is the most important part of their Naim system, myself included. Why remove something that gives so much pleasure? 

Alba1320 posted:

 

I wonder if this means anything other than removal of unwanted HF as has been cited on a number of occasions. Perhaps there’s a subsonic filter? (Naim doesn’t publish a frequency range.) Or limiters to prevent going over the rated level - but that wouldn’t make sense as it  would need to be different for different power amps. 

Regarding the caution against passive preamps in particular, that could be due to designs having impedance altering with setting.

There are some people who have dispensed with their preamp and used a (Chord) DAC direct into a Naim power amp, and others who have tried it, and not liked it. I guess the question is, can the cash you save on a preamp (plus PSU, shelves etc.) be better spent on a higher level source and power amp. For example, if you don't buy a 282/Hicap, that gives you enough cash to go for a 300 instead of a 250, with a couple of grand left over for a Hugo.

Innocent Bystander posted:

Alba1320 posted:

 

I wonder if this means anything other than removal of unwanted HF as has been cited on a number of occasions. Perhaps there’s a subsonic filter? (Naim doesn’t publish a frequency range.) Or limiters to prevent going over the rated level - but that wouldn’t make sense as it  would need to be different for different power amps. 

Regarding the caution against passive preamps in particular, that could be due to designs having impedance altering with setting.

Passive pre-amps:

Source impedance varying with volume setting (this can have numerous deleterious effects dependent on power amp design).

Lack of HF filtering.

Some sources struggle to produce the 750mV RMS required for Naim power amps.

Huge, have you tried one of these passive pre as used by the reviewers?

Chris, that really is the key question. All the technical data in the world does not necessarily mean that the Allegri wouldn’t sound great with Naim. Looking at your profile, I see why you are asking. It’s like the Chord Dac with its million taps: people still prefer ye olde teche in other Dacs. I read in an early review of the 272 that with the 555 it delivers 90% of an NDS - whatever that means of course. And the 272 preamp is not that far behind a 282. So adding a 282 doesn’t really make sense, especially as two more shelves are needed, and two more mains leads. A move to a 552 is £12,000 plus, yet an Allegri is £2,500. Yet it somehow seems ‘wrong’. The only way is to put prejudice aside and try one at home. There don’t seem to be any dealers though. 

Chrissw19 posted:

Huge, have you tried one of these passive pre as used by the reviewers?

Not an Allegri, no.

But I did design and build an amp system specifically designed around using a passive "pre-amp".

Hungryhalibut posted:

Chris, that really is the key question. All the technical data in the world does not necessarily mean that the Allegri wouldn’t sound great with Naim. Looking at your profile, I see why you are asking. It’s like the Chord Dac with its million taps: people still prefer ye olde teche in other Dacs. I read in an early review of the 272 that with the 555 it delivers 90% of an NDS - whatever that means of course. And the 272 preamp is not that far behind a 282. So adding a 282 doesn’t really make sense, especially as two more shelves are needed, and two more mains leads. A move to a 552 is £12,000 plus, yet an Allegri is £2,500. Yet it somehow seems ‘wrong’. The only way is to put prejudice aside and try one at home. There don’t seem to be any dealers though. 

A bit late for me now, as I already have a 282. At the time I thought it was the best sounding Naim option for my budget, and I'm very happy with it. If, at the time, I was aware of the Allegri, or more likely, the Chord DACs as preamps, I might have been tempted to investigate, despite it going against conventional Naim thinking.

Well, this is all puzzling. As HH says, it seems wrong but maybe it is not. After building an excel model using IB formulas, I understand now why the volume knob on my 282 goes barely above 830 before I'm told "its too loud". It does not look like the active gain of the 282 is required at all if used with an NDS. Does it mean the 282 is not working in its optimum range when used that low? Would probably be a good idea for the new 555 streamer to have a lower voltage output or a variable one.

Chrissw19 posted:

Well, this is all puzzling. As HH says, it seems wrong but maybe it is not. After building an excel model using IB formulas, I understand now why the volume knob on my 282 goes barely above 830 before I'm told "its too loud". It does not look like the active gain of the 282 is required at all if used with an NDS. Does it mean the 282 is not working in its optimum range when used that low? Would probably be a good idea for the new 555 streamer to have a lower voltage output or a variable one.

Part 1:

What value were you using for the output of the NDS?

For Classical (and better jazz) recordings you should use 250mV (2V -18dB).

For other stuff:
Older CDs ~350mV.
Newer (more compressed data) ~ 660mV.

2V is the peak recording level for transients not the average signal level.

Part 2:

What were you using as the lower calibration point of the volume pot and how were you calculating the law of the pot (last time it checked one, the ALPS blue used a triple slope log approximation).

Huge, I'm using using 2.1v as indicated by IB. Part 2, do I really have to model these things to realise that its too loud at 0830? 

In general, the term pre-amplifier is a bit of a misnomer. What it actually does is attenuate the signal to a usable level: not amplify it. I use a naim NDS into an Allegri pre-amp, but my power amp is not a naim amp. I like the allegri because it does not need a power supply, or decent mains, or an expensive mains cord, and takes up little space on the rack.

My understanding is that you can try an allegri on a sale or return basis, but I did that some time ago. Max does not expect them to come back!

Chrissw19 posted:

Huge, I'm using using 2.1v as indicated by IB. Part 2, do I really have to model these things to realise that its too loud at 0830? 

I think I had made clear that the figures I had calculated were maximum peak levels, therefore average would be less,  and Huge’s indication with classical music average being maybe about 18dB (and I did mention a version of 1812 where the average would be a lot less because of its high dynamic range and high level of the canons). 

The wider the dynamic range, the lower the average level needs to be to fit in the peaks without clipping them, and vice versa. I am not sure if there used to be a standard average level, subject to reduction if the music had very high peaks, bit it used to be the case that most CDs seemed to be about the same average level, rarely needing the volume control adjusting between CDs. However. In recent years there has been the so-called ‘loudness war’ with CD releases, of pop music at least, where dynamic range has been increasingly compressed in order to allow the average level to be higher. So with a piece having a compressed dynamic range it is possible that the average level might be only 12 dB below the peak level, and Understand they can be found with an average level at least as high as just 8 dB below maximum.

IN TODAYS market most , will have no vinyl  and therefore dont need an expensive front   .  The dac has become  the pre amp , even naim   use ADC  for the line inputs , linn are going that way too.  good for most it brings the cost down and shelf count down too        .       

The number of people using a vinyl front end is increasing not decreasing.

Even with a DAC / preamp, for the higher audio quality units, an analogue preamp and volume control is still preferred (compare the 272 to the Nova).  Even with a DAC that doesn't even have volume control, guess what type of circuit follows the DAC itself...  yes, an analogue preamp!

So inputting analogue signals through an ADC doesn't remove the need for a preamp; it may however remove the need for an analogue volume control - provided you're willing to accept non-bit perfect playback!

audio1946 posted:

IN TODAYS market most , will have no vinyl  and therefore dont need an expensive front   .  The dac has become  the pre amp , even naim   use ADC  for the line inputs , linn are going that way too.  good for most it brings the cost down and shelf count down too        .       

Is the Naim DAC-V1 a Digital Analogue Converter (DAC) or a digital pre-amp.

Answers on a postcard.

Dave

It can't be a digital pre-amp as its volume control is analogue (it uses CMOS transmission gates in the 'linear' part of their operating envelope).

Huge posted:

It can't be a digital pre-amp as its volume control is analogue (it uses CMOS transmission gates in the 'linear' part of their operating envelope).

We all know a conventional pre-amp is required when connecting analogue sources to a power amp, e.g. turntable, tuner or cassette deck plus CD players without a digital output.

Manufacturers such as Meridian, NAD and Cambridge are now marketing products termed a “Digital Pre-amp” which, essentially, allow source components with digital outputs, e.g. coaxial SPDIF, optical TOSLink, USB, HDMI, to interface with a power amp. There is no provision for analogue components.

Essentially a pre-amp require a volume control but why is the implementation a factor?

Dave

That is the different between a "digital pre-amp" (as used in your first post here) and a "Digital Pre-amp" (as used in your second post here), the difference being that the latter is a proper noun (i.e. a name rather than a generalised description by form and/or function).

dave4jazz posted:

Manufacturers such as Meridian, NAD and Cambridge are now marketing products termed a “Digital Pre-amp” which, essentially, allow source components with digital outputs, e.g. coaxial SPDIF, optical TOSLink, USB, HDMI, to interface with a power amp. There is no provision for analogue components. 

But then, to confuse the categories further, some of those DACs with built in pre-amps also have analogue inputs.  Look at Benchmark, Mytek as well as the aforementioned NAD. Even Linn's DSM would come in this category.  NAD and Lyngdorf (and a few others) blur the line even further but amplifying directly a digital signal without first converting to analogue.

Essentially a pre-amp require a volume control but why is the implementation a factor?

Implementation is important and its important to understand what limitations each implementation has.

A digital volume control for example, attenuates the signal without attenuating the noise, so if used at extreme levels then any noise produced by the DAC can overwhelm the required signal.  On the other hand even the best analogue volume controls have an element of noise and distortion inherent in their design; but when used the analogue volume attenuates noise as well as signal.

And talking about digital pre-amps which have analogue inputs, do those inputs go through an ADC and then are treated as digital sources, or do the digital signals get converted to analogue before all going through analogue pre-amps.  While I would always argue you need to judge a product based on what the end result sounds like; there is differences and those can be important.