Resurrecting the Preamp

[Exeric]

This whole ridiculous thing happened because I mentioned an analog switch on a dac. It was simply to illustrate moving the control from preamplifier to dac. Earlier in the thread, go back and reread if your determined, I had said that you should not move the analog input to the dac because you wanted to isolate analog circuits from the dac. It's true. I said that. I assumed everyone had read that so when I said later about putting the analog inputs on the dac it was just to emphasize THE CONTROL being moved.

 

I get annoyed when I see people who do not know me assuming I'm ignorant. And Chris, maybe Barrows has been polite and courteous to you but he certainly wasn't to me. If he had paid attention to my earlier remark in the thread he would have figured out the second remark about analog switching at the dac was for illustration purposes only - not that I was technically ignorant. That part was 5% of the subject I was talking about. It's the same old thing where someone doesn't like what you say even though it is correct. So they employ the age old strategy of going to the periphery of the argument far from the main argument and attacking a vulnerability there. Finally the main message is attacked by inferring and concluding the messenger can't be reliable because the minor sub argument was in error.

 

Does anyone actually even understand what I was saying about why some power amplifiers can't be driven reliably even from good dacs, like dcs models? Didn't think so. Maybe Jim Smith understands.

 

[PeterSt]

So in all honesty, no, I didn't understand. Well, not this one :

 

Something is not correct here. If that is true, and I have no reason to believe he is prevaricating as he has written a book about getting good sound, then any logical thinking person must believe that it is the amp producer's fault. The reason big amp producers can get away with a situation where a 1 ohm output impedance is insufficient is because they are under engineering the power amp in order to sell preamps.

 

... unless you imply a 5 Ohm input or something, how would the poweramp be under engineered ?

 

Thanks,

Peter

 

[barrows]

sorry, I thought the meaning was pretty clear in my post. I specifically used the word "may" to indicate thay I do not know for sure your level of technical understanding. I did understand that your example of a switch was just a talking point.

But, I do know that you are wrong in your assertion regarding amplifier manufacturers somehow trying to take advantage of consumers by making their amplifiers less compatible with direct source input. As Chris has noted, manufacturers try and produce the products that the market demands. Now the Hi Fi world is slow to change, and quite stubborn, so it takes a long time to adjust to new approaches (hence the continued emphasis on separate amp/preamp which is really a legacy from the days of vinyl). For awhile (PS Audio) built integrated amps, which actually outperformed their separate component versions in the same product line. Trying to convince customers that they actually received better performance, by spending less money and purchasing the integrated was difficult to impossible in most cases, and (PS Audio) abandoned that approach because the market just did not "get" it.

It just is not that difficult for DAC makers to put an output stage in their DACs which would drive amps fine-just use the same output buffer circuit and power supply which works in a good preamp, simple. Whereas changing the input stage of power amplifiers, to make them more sensitive, is generally a bad idea, as it will also make them noisier.

Peter: thanks for your response, it is always interesting to hear details of your approach. I can assure you that I do hear "less smear" by going amp direct, but there is also, definitively, less dynamics, especially micro-which leads me to the conclusion that the amp is not being driven as well as it could. BTW, the corner frequency for my DC filtering is 2 Hz (3.9 uF into 20k per phase), so the phase shift is not quite as bad as you note, but certainly is still a "problem"! The output stage I am using is just about to have a third iteration released, which eliminates the need for output caps when used with a true differential input stage, this will eliminate one "problem" and I look forward to hearing the difference. Of course, there is still filter ringing, I tend to prefer the "slow" rolloff filter setting, as it seems to give better timbre. I wonder if reduced ringing might be the reason, and/or reduced phase shift...

 

[Miska]

the corner frequency for my DC filtering is 2 Hz (3.9 uF into 20k per phase), so the phase shift is not quite as bad as you note, but certainly is still a "problem"! The output stage I am using is just about to have a third iteration released, which eliminates the need for output caps

 

I've been typically using 0.1 Hz value, with or without series capacitors.

 

Naturally there are ways for DC compensation without series caps.

 

And if I'm worried about it and know the electronics, I can easily pre-compensate the phase-shift digitally in the player. That's just normal calibration step.

 

 

[PeterSt]

.

 

[4est]

The whole implication that the amplifier manufacturers are doing this to sell pre amps is paranoid BS. They make what people buy. If we all wanted or needed integrateds, there would be a lot more of them out there. Maybe we should all just start buying AV recievers...

 

[PeterSt]

I must honestly say that it didn't come to my mind for maybe 35 years to get myself some integrated. But why ?

 

Maybe because I thouhgt it was for poor guys.

Maybe I thought PSUs or actually transformers wouldn't fit in one case.

Maybe because I never believed much in "all of the same brand".

Maybe because my father always owned separates.

Maybe because I actually always bi-amped.

Maybe because I never believed in the degradation because of interlinks (but did about LS cables).

Maybe because I never wanted (and owned) an AV receiver as well.

Maybe it's because I always thought the power amps make the sound (which is not true I know now; the pre-amp really does that).

Maybe because lately I don't want a "pre section" at all.

 

Apart from the latter reason, it really never has been in my mind that an integrated could be any good.

But in all honesty, I'm just making up these reasons because it just never has been a consideration.

 

So I guess I'm amongst those who make manufatures create separates ...

 

Peter

 

[audiozorro]

that direct to amp is superior but very difficult to achieve. And you never know whether the direct connection or a preamp is the best you can achieve in your system until you try it. The elimination of the active line stage is a long-term goal that requires each and every component to be optimized and matched with regards to both sensitivity and impedance (and cables for low capacitance).

 

He clearly states “If there is any noticeable and obvious sonic improvement with the active line stage, then you need an active line stage. It's that easy. All that's left is the most difficult part, choosing the model that you like the most.”

 

The superior sonic advantages of a direct connection are typically:

 

Direct to amp:

Transparency

Microdynamics

Air around instruments

Soundstage

Tonal balance

Transients

Treble extension

Clean bass

Less noise

Less distortion

 

The superior sonic advantages of using a preamplifier are typically:

 

Preamp:

Body weight

Dynamics

Powerful bass

Musicality

 

According to Arthur Salvatore if your audio system is optimized and you hear none of the sonic advantages that a preamp usually brings, then you do not need a preamp that will only lessen the sonic advantages that a direct connection usually brings.

 

 

[Happy]

All

 

I've now added an Ayre KX-R preamp to the system.

 

I avoided pre-amps for a long time - more cost, more parts of the chain. In the end I wanted two things:

 

1. Better electrical isolation from the computer source.

 

2. Removal of the volume control (setting the Alpha DAC gain to unity) - the volume adjust is created by the Ayre VGT.

 

The increase is performance is dramatic - not subtle at all. I considered the system to be excellent before - it is now very high performance.

 

It affords me the opportunity to now A/B different DACs, USB/Firewire etc. As an additional benefit I can now pass-through my 5.1 Surround Sound Processor i.e. integrate 5.1 with 2.0.

 

I support the view above - a real benefit to the next gen DACs will be better pre-amp stages or leave the pre-amp to an external device.

 

The Pre-Amp wasn't cheap BUT unlike most system changes the marginal value dwarfed the marginal cost.

 

/Paul

 

 

 

[Part-Time Audiophile]

I want a KX-R in a big, ugly, unpleasant-to-see-in-public kind of way. That VGT is something special.

 

I suppose Ayre could put a VGT into their QB-9 platform, as well as put the KX-R output stage in there too, but I can't imagine them seriously considering it. Who knows.

 

But that's the kind of thinking and implementation I'd need to see before I'm going to be interested in a preamp-less rig.

 

Then again, I'm also into vinyl. So, adding an analog input to the DAC would be crucial. Of course, this would make it less of a DAC and more of a preamp. Hmm.

 

[NickG]

Scot, is a DAC with an analog input a form of an integrated? Do you think of the Grace m903 as a DAC or a headphone amp with a DAC and volume control? Thinking about the Mcintosh C-50 and Classe CP800, I guess they are being marketed as preamps.

 

Why do you think Ayre won't add VGT to their QB-9 platform? I think that would do it for me, assuming it wasn't priced like the preamp that has it.

 

[barrows]

"Why do you think Ayre won't add VGT to their QB-9 platform? I think that would do it for me, assuming it wasn't priced like the preamp that has it."

 

Well, for one, we do not know that Ayre will not produce a DAC with a VGT stage-it could happen.

Here are the reasons why it might not: The VGT stage circuit design may not be compatible with the DAC chip (or I/V stage) output.

A VGT stage will add a lot to the cost of a DAC, as it requires a significant amount of hardware to implement-so a DAC with a VGT stage would only be marketable to those customers who are totally committed to running amp direct-Ayre may not perceive this group of cutomers as large enough to warrant a product designed/developed only for them.

Ayre, produces a very good phono stage, and distributes a very good turntable with their own power supply set up. Many of Ayre's customers are committed to having a vinyl playback set up, and this requires a preamp for source selection.

The VGT stage will not fit in the QB-9 platform or price structure, remember, Ayre's "9" series is their most affordable series of components. If they were to build a DAC with a VGT style adjustable gain stage, it would have to be in their "5" series, or Reference series level components. In the "5" series they could probably pull it off with FET switches for selecting the resistor values, in the Reference series they would likely use the much more costly approach of motor driven Shallco rotary switches used in the KX-R.

 

Most DACs which offer volume control just utilise the digital volume control which is built in to the DAC chip(s). This allows for the addition of volume control at very little additional cost, and therefore can be considered as optional (for use) to the customer. The expense of adding a really good analog volume control is really significant, and as such would not be considered optional (for use) by the customer as a manufacturer cannot expect a customer to pay for an expensive volume control they do not even plan to use. This is why Aesthetix offers an (good) analog volume control as an option for the Pandora DAC (at considerable additional cost).