ANOTHER Example of Why I HATE DSD and Why Customers Who Bought Sony's Boloney Are So Annoying

[sandyk]

...and since properly designed power amp has same input impedance as properly designed pre-amp (10 - 100 kOhm), how does that change anything?

 

Most modern amplifiers have far too much gain to be used directly with a DAC unless some kind of attenuation is used.

Also, many DACs don't like relatively long interconnects due to the higher capacitance. Many modern DACs use an opamp in the output with for example, a series 100 ohm output resistor to help reduce the problems of capacitive loading, but that isn't always quite enough. In such cases it may be better to use a preamp to drive the longer cable to the P.A.

My own discrete Class A preamp is capable of correctly driving a 75 ohm load, so longer cable differences are not a problem if the input of the P.A. is also terminated with 75 ohms.

I don't know about how the 'magic' in my pre-amp is done. But compared with several DACs volume control I stay with the pre-amp. I'm talking here about several possible listening levels, and several DACs. And, of course, I tried before a lot of pre-amps.

 

Best,

 

Roch

 

I agree with Roch regarding digital attenuation. With many DACs, more than 10dB attenuation leads to severe SQ degradation with 16/44.1. 24/96 does of course fare a little better.

We need to remember here, that in a typical domestic situation, the typical power level is often no more than 1W,hence even further attenuation is required.

 

Alex

[sandyk]

"No, I mean adjusting gain of the power amp, or if not possible placing a fixed attenuation on the power amp input."

 

 

How are you going to make a LARGE reduction in the gain of an amplifier without getting into a lot of major changes regarding VAS stage compensation etc. ?

 

With players such as the Oppo 981 etc. , 10dB fixed digital attenuation very noticeably degraded the SQ of 16/44.1 yet 24/96 was still quite acceptable. Going further than 10dB attenuation noticeably degraded that too.

This was when going directly into my Class A amplifier from the Oppo. It didn't take long to realise the limitations and revert to using a Class A preamp again.

Many commercial DACs simply use opamps as building blocks based on manufacturers published data.Things are quite different in practicce with devices such as the LME49710 etc.though.

Many sound better with more than 100 ohms resistors at the output.Even the capacitance of FETs such as IRF7905 used to replace the now hard to get special muting transistor 2SC2878, which is an NPN transistor with an unusually high reverse hFE of 150 can degrade the performance of many current op-amps. Perhaps it's time to go back to using relays for muting purposes ?

Regards

Alex

[sandyk]

It is not that major change. Alternatively you could place two resistor attenuation on the input.

These days they typically use large value input capacitors at the input to retain the advantages of the lower output impedance of the preceding stage for lower noise purposes . Using resistor attenuation there will result in a minor degradation, and possibly why the lower output impedance of a good preamp makes a worthwhile improvement for many. That's also why you don't normally see the lower -3dB point of an amplifier set by the capacitance value of the input capacitor these days

You are more likely to see something like a 22uF Blackgate ( if any left!) or a quality electro of a similar or higher value..

 

100 ohm output resistor again increases thermal noise and the sound "improvement" is probably mostly due to filter effect in combination with cable and input capacitance.

 

That's not normally the reason these days, as some designers specify capacitance values as high as 10nF (!!!) at the output in order to claim bragging rights about how good their distortion figures are..

The series resistor is fitted to ensure stability of the opamp into the capacitive load of a cable. This is an old technique dating back many years, even as far back as the old Marantz CD65 etc. where direct connection of the cable to the front HA PCB degraded SQ. One of the other cures back then was to disconnect the headphone amplifier section. This was even recommended in the HiFi magazines of the time.

The LME49710 and LME49720 are particularly touchy as regards working into even a short cable load.

[sandyk]

[series input capacitors? No way, I have servos. Serves two purposes, negates any input offset plus doesn't require any internal offset adjustments either./QUOTE]

 

Miska

Both my Class A preamp and 15W Ch. Class A P.A. are both fully DC coupled with servos. There are no capacitors in the signal path or the feedback networks of either. The front ends of both also use dual metal can , closely matched transistors,(LS313 and LS352) with front end balancing as posted in the DIY Audio Current Mirror thread of Nov.2008.

Regards

Alex

[sandyk]

Sorry to digress Charles

 

Miska

I have used SSM2220 in earlier preamp and RIAA phono preamp designs. Most LS313 appear to have very high HFE (>700 !) as well as being closely matched. Although the voltage ratings are low , they are fine in a typical Current Mirror as described in various Douglas Self books.

The LS352 is a modern replacement for the Motorola 2N3811A,which was used in many designs in the 90s by Erno Borbely.

You can still obtain 2N3811A on eBay.

 

Regards

Alex

[sandyk]

Charles

I am fully aware of their specifications. I also suspect that Douglas Self and Erno Borbely know a little more than you do in this area. My own gear is very much based around the works of Douglas Self and Silicon Chip magazine. Distortion figures would likely be below the typical .0006% from 20Hz to 20kHz as in the Silicon Chip P.A. design, due to careful matching of devices and close tolerances of resistors in the front end especially.

I use these devices on the most linear parts of their curves, and mainly because I am able to completely balance the collector currents of both halves of the LTP. I bet that you don't even believe that anything more than a 1% match will give a further improvement ? BTW, Nelson Pass was also a participant in the Nov. 2008 DIY Audio Current Mirror thread where my claims were verified. Can YOU get quite good surround sound from just 2 stereo speakers on DTV with well recorded material, or room filling surround from just the stereo soundtrack of the BluRay of Ävatar., or from DVD-As such as "The Eagles-Hotel California" etc. as well as with many well recorded CDs and high res. material ? My preamp for example has been judged to outperform $14K retail Marantz preamp and Power Amp combo, as has a friend's 100W Ch/8 ohms using similar devices and similar front end balancing in his preamp and P.A. We also regularly compare our gear against loaned top stuff from Len Wallis Audio in Sydney. at our regular listening sessions with Infinity speakers plus Raal 100kHz tweeters, and now with B&W 802s.

 

.Regards

Alex

 

Current Mirror Discussion - Page 15 - diyAudio

 

P.S.

I find your recent aggressive and arrogant dismissal of other peoples viewpoints, on almost every subject, quite interesting.

Even the very title of this thread makes one wonder.

Are you under the affluence of incahol ? (grin)

[sandyk]

On ‎3‎/‎8‎/‎2020 at 11:55 AM, One and a half said:

DSD has at least some technical lossless advantage as well as multi channel capability.

 So did DVD-A , yet it wasn't enough to make the General Public want it . DSD is likely to remain a niche product and possibly eventually die out as the younger generation in general, doesn't appear to be greatly interested in any more than Audio from a Mobile phone.

 The only thing that appears likely to survive is the Loudness Wars.

[sandyk]

5 minutes ago, beerandmusic said:

Are there any statistics published anywhere that suggest there are less "audiophiles' in the "younger generation" today than there were in the 70s-80s? I would guess that there will always be a good amount of audiophiles to keep dsd alive for many years to come.

 

Outside of forums like this, and readers of the Hi Fi printed media, most members of the General Public wouldn't even know what DSD was . Even BluRay appears to be struggling these days.

[sandyk]

23 minutes ago, jabbr said:

The same could be said for linear power supplies, more so when applied to computers  

 And your OFF TOPIC point is ?

Incidentally, I don't use a Linear PSU in my W10/64 PC.

[sandyk]

1 hour ago, jabbr said:

For me HATING DSD is like hating logarithms, or the Hilbert space, for example

 I haven't said that I hate it. I have merely said that I don't feel the need for conversion to it from the original format ,

 to play in a special (later model) DAC , just as probably 99.99% (or more) of the population don't feel the need for it, or for that matter have any knowledge about it whatsoever. The same applies to USB Audio as well .

 In any case many DSD releases were edited or mixed using PCM anyway.

Quote

The average cares nothing about an R2R DAC nor an SACD

That we can agree on. R2R reminds me of Michael J Fox

[sandyk]

7 minutes ago, opus101 said:

 

Does anyone actively market logarithms?

 

Are you looking for a business opportunity ?

 Perhaps you can get a few tips from the MQA mob ?