About tube DACs? - Page 17 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Line Level

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th January 2013, 10:05 AM   #161
Julf is offline Julf  Europe
diyAudio Member
 
Join Date: Oct 2011
Location: Amsterdam, The Netherlands
Quote:
Originally Posted by stephensank View Post
When I speak of bad effects of feedback, I refer primarily to what Nelson Pass was addressing in his "stasis" amp designs. Distortion of non-repetitive waveforms caused by feeding back signal to the differential input of a circuit that has been delayed by time it takes the original signal to get through the circuit. The simpler & physically shorter the signal path, the shorter this delay will be, but it nevertheless exists.
But as long as the feedback system has enough phase margin, that delay does not matter at all. I think your views stem from the whole TIM controversy from the 1970's. Yes, TIM (really a special case of SID, slew-induced distortion) was an issue with some badly designed solid state amps back in the day. Once the concept of phase margin was well-enough understood by audio amp designers (and not just industrial, telecommunications and control theory people), it became a non-issue.
  Reply With Quote
Old 27th January 2013, 12:00 PM   #162
5daudio is offline 5daudio  United Kingdom
diyAudio Member
 
Join Date: Aug 2012
Quote:
Originally Posted by AlliumPorrum View Post
...but there is some vinegar in Worcestershire sauce and A1 Steak Sauce, and I'm deadly allergic for it ;=)

Ok, back to topic, please :=)

Does anyone else have any experience on Audio Note or Monarchy...? Or any other comparable product?
never heard a monarchy but i have heard the audionote dac2 in stock form and with a tube rectified choke / black gate filtered psu for the output stage,

my friend has the audiolab m-dac, modified tube output eastern electric, audionote dac2,
4 of us have been listening to them,
in blind listening tests the three of us who had no clue which dac we were listening to picked the audionote dac2 in stock form,

at first i thought he was just playing the audionote and i was having a real hard time hearing any change from what i was used to hearing,
then he switched dacs and i heard something i had not heard on his digital before,
"switch back" i said, "switch back again" "thats weird i like that one a lot",
i opened my eyes and looked across at him, he was grinning, "that's the audionote"
i already knew it must be,

to me it sounds more holographic, its easier to imagine a real person or guitar the skin of a drum real sax etc is in front of you and you are there at the recording venue not sat listening to a hifi in your house, everything in the music seems to be a little more easily defined in space,
its more vibrant, closer to his vinyl setup,
its more tappy, ie i can't keep as still, it makes me tap my foot or fingers more than the other two dacs, it does not bring tears to my eyes like his vinyl can but its very good for digital imho,

of the three dacs the audionote is the one that im less likely to tell my friend to turn it off and put the vinyl on,

im the only one of the three listeners not counting the owner that has heard it with the new psu setup and imho it sounds a little smoother with a wider sound stage, it is now a little wider/deeper than the eastern electric and retains the more vibrant holographic presentation,

yesterday we rolled 3 sets of tubes through the audionote, russian , nos telefunkens and the stock tubes without altering anything to optimise the new output tubes,
me and my friend hear the russians as dry with a narrower stage, the telefunkens came somewhere between the other two,
the stock tubes sound warmer or more lush a little less smooth or is that more textured hmm whatever it is we both prefer the stock tubes,
i know i like them best because my foot refused to keep still,

the solid state m-dac comes last to all the listeners in this system in blind listening tests with or without different software,

for the record i use my ears and that's all i use, i don't give two hoots which measures best,
just telling it how i hear it, ymmv.
.
  Reply With Quote
Old 27th January 2013, 07:50 PM   #163
diyAudio Member
 
Join Date: Oct 2006
Quote:
Originally Posted by Julf View Post
But as long as the feedback system has enough phase margin, that delay does not matter at all. I think your views stem from the whole TIM controversy from the 1970's. Yes, TIM (really a special case of SID, slew-induced distortion) was an issue with some badly designed solid state amps back in the day. Once the concept of phase margin was well-enough understood by audio amp designers (and not just industrial, telecommunications and control theory people), it became a non-issue.
No, sir, I am not confusing anything. If you do a bit of reading about Pass's stasis amp development, you would know that I am not. "Delay does not matter at all" is true with nice, repetitive sine/square/etc.-waves, but think about the very non-repetitive & complex waveforms of actual audio, and suddenly delay does matter. "On paper", the quality of metal & physical arrangement of an audio cable "doesn't matter at all", unless very, very poorly designed, and yet, it does, unless you hold that hundreds of thousands of buyers of cables are all self-delusioned(not impossible, considering that many seem to think Bose makes good speakers).

As for testing, I do not trust just my own ears, as I'm now 50, male, and have tinnitus. I use the ears of much younger friends, male & femaie, some of them musicians and/or recording engineers(of which I know many, as ribbon microphones are my primary field). So, I have more than independently verified to my own satisfaction that feedback in at least a dac i/v stage is audibly degrading to sound, regardless of what opamp or discrete circuit is used, and removing feedback not only reveals hidden layers of tone & clarity, regardless of whether tube or ss, but also reduces the audibility of jitter artifacts by a huge margin.
  Reply With Quote
Old 27th January 2013, 08:21 PM   #164
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Quote:
Originally Posted by stephensank
No, sir, I am not confusing anything. If you do a bit of reading about Pass's stasis amp development, you would know that I am not. "Delay does not matter at all" is true with nice, repetitive sine/square/etc.-waves, but think about the very non-repetitive & complex waveforms of actual audio, and suddenly delay does matter.
An amplifier does not know the difference between a sine wave and a music waveform. It just has a varying input voltage, a varying output voltage, and feedback to get the latter to track the former. "Delay does not matter" just happens to be true, because the delay is far too small to do anything. As I said, people often confuse delay with filtering. People often say that delay affects feedback: they are just wrong (whoever they are). Delay would affect feedback, which is why feedback cannot be used effectively for UHF and microwave amplifier but delay is entirely negligible for audio. Filtering can affect feedback, and may require careful design of the part of the circuit before the dominant pole to avoid slew rate limiting (or an approach to slew rate limiting) - but this is not delay.

Quote:
"On paper", the quality of metal & physical arrangement of an audio cable "doesn't matter at all", unless very, very poorly designed, and yet, it does, unless you hold that hundreds of thousands of buyers of cables are all self-delusioned(not impossible, considering that many seem to think Bose makes good speakers).
"Self-delusioned" - yes, that is how I would put it. Some expensive (and DIY) cables will affect the sound, by degrading it. Most will make no difference, as tests have shown.
  Reply With Quote
Old 28th January 2013, 01:40 AM   #165
diyAudio Member
 
abraxalito's Avatar
 
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Blog Entries: 109
Send a message via MSN to abraxalito Send a message via Yahoo to abraxalito Send a message via Skype™ to abraxalito
Quote:
Originally Posted by stephensank View Post
So, I have more than independently verified to my own satisfaction that feedback in at least a dac i/v stage is audibly degrading to sound, regardless of what opamp or discrete circuit is used, and removing feedback not only reveals hidden layers of tone & clarity, regardless of whether tube or ss, but also reduces the audibility of jitter artifacts by a huge margin.
Curious here Stephen how you manage to change only feedback in your comparisons? I haven't so far seen a circuit where just the feedback can be removed and no other salient circuit details get altered as a result. Care to share two example schematics?
__________________
Seek not the favour of the multitude...rather the testimony of few. And number not voices, but weigh them. - Kant
The capacity for impartial observation is commonly called 'cynicism' by those who lack it.
  Reply With Quote
Old 28th January 2013, 02:26 AM   #166
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
yet another person who fools himself that he has no feedback in a circuit. I really wish people would say what they mean here of all places; perhaps no/low global feedback? the dac chip itself of course will have plenty of feedback and there wil be local feedback on tubes, discrete SS whatever.

good chance lowering feedback reduces the audibility of jitter by masking it with harmonic/frequency based distortion products.

Last edited by qusp; 28th January 2013 at 02:31 AM.
  Reply With Quote
Old 28th January 2013, 06:35 AM   #167
diyAudio Member
 
Join Date: Oct 2006
Obviously, yes, when I refer to feedback, I mean feedback around more than one single semiconductor or tube.
I'm done being insulted on this thread. And I apologise if anyone has felt insulted by me. I've simply been attempting to help the OP with his decisions, not get into a formal debate.
  Reply With Quote
Old 28th January 2013, 07:49 AM   #168
diyAudio Member
 
Join Date: Jul 2011
Thank you Stephensank, you really helped me a lot with your comments and suggestion. All the best for you!
  Reply With Quote
Old 28th January 2013, 08:21 AM   #169
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
OK stephensank: its a pet peeve of mine the 'no feedback' thing, many like yourself use it to mean something else and it leads the less informed to believe there is such a thing. feedback can be overused, but it can just as easily be under utilized; thinking that lower is always better is IMO fallacy.
  Reply With Quote
Old 28th January 2013, 11:24 AM   #170
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Quote:
Originally Posted by stephensank
Obviously, yes, when I refer to feedback, I mean feedback around more than one single semiconductor or tube.
A common mistake, sadly, but not obvious. I assume that when someone says "no feedback" that is what they mean. It sometimes turns out that they actually mean something else.

Quote:
I'm done being insulted on this thread.
People have disagreed with what you said. It seems that in some cases what you said is not what you meant. If you regard disagreement as a form of insult then debating is not for you.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Another Tube I/V converter/preamp for balanced DACs with SE output:build thread pauldune Tubes / Valves 4 31st May 2013 03:50 PM
DACs Jerseydevildog Digital Source 1 25th November 2007 07:24 PM
DACs? MashBill Pass Labs 3 28th February 2007 10:43 AM
Parallel different DACs roibm Digital Source 1 4th November 2004 11:54 AM
Audio DACs, Instrumentation DACs. Brian Guralnick Digital Source 10 3rd November 2002 05:56 PM


New To Site? Need Help?

All times are GMT. The time now is 11:30 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2