DIYHiFi.org

For the sake of audio
It is currently Mon Dec 18, 2017 8:20 pm

All times are UTC




Post new topic Reply to topic  [ 162 posts ]  Go to page Previous  1 ... 7, 8, 9, 10, 11
Author Message
 Post subject: Re: I call "Bullshit!"
PostPosted: Mon Sep 23, 2013 12:44 am 
Offline
Cow

Joined: Mon Dec 20, 2004 11:48 pm
Posts: 408
Jocko, give me a call.


Top
 Profile  
Reply with quote  
 Post subject: Re: I call "Bullshit!"
PostPosted: Mon Sep 23, 2013 6:33 am 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1168
John,

john curl wrote:
T, now that you bring it up, I think you should be a bit easier on the audio magazines.


Maybe, maybe not.

john curl wrote:
However, if you, T, think that you are the sole judge of audio quality,


I am the sole judge of audio quality for my personal use. For anything commercial I tend to rely on others ears (especially customers) by far more than on my own, as I am designing for customers.

I am NOT designing to win Magazine Awards or the like (not that I can complain on that front, not at allactually), because mostly I do not feel that the Magazines/reviewers reflect well what suits most listeners.

We can debate the press more and why it MUST fail at any attempt to be relevant to most Audiphiles another time.

john curl wrote:
The Audio magazines sometimes remind people that not all is progress, and this is important.


Listener used to be like that. Now it is a small column in SP, sad fate.

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
 Post subject: Re: I call "Bullshit!"
PostPosted: Mon Sep 23, 2013 8:46 am 
Offline
Goat

Joined: Mon Nov 28, 2005 1:10 pm
Posts: 545
Kuei Yang Wang wrote:
No, my DAC is too cheap for that chip.

A different Philips 16 Bit chip, which raised much ire and caused much kerfuffle here and elsewhere...


Hi Thorsten,

I believe the datasheet of this chip is not available, right? Being a fan of the philips dacs I am curious about it. Is it cmos like the tda1545, or is it bipolar like the oldschool ones?

-Alex


Top
 Profile  
Reply with quote  
 Post subject: Re: I call "Bullshit!"
PostPosted: Mon Sep 23, 2013 8:56 am 
Offline
Goat

Joined: Mon Nov 28, 2005 1:10 pm
Posts: 545
Kuei Yang Wang wrote:

Nice read, thanks.


Top
 Profile  
Reply with quote  
 Post subject: Re: I call "Bullshit!"
PostPosted: Mon Sep 23, 2013 11:14 am 
Offline
Dog
User avatar

Joined: Tue Dec 14, 2004 12:26 pm
Posts: 4981
Location: Lisbon, Portugal
Yes, great reading, highly recommended.
Thanks, T.

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein


Top
 Profile  
Reply with quote  
 Post subject: Re: I call "Bullshit!"
PostPosted: Fri Sep 27, 2013 6:26 pm 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1168
Folks,

Today was (again) a salutatory experience in Audio.

So, I am working on a new product and there are some bugs, I go fix them, when it finally plays well enough to be listened to it sounds spitty, annoying and gritty.

So, I do a bunch of things that according to Mr. AP2 make no measurable difference (like increasing the gridstoppers on the output tubes control and screen grids by a factor 10) and fine-tune the lead-lag compensation and sh1t l1k3 th4t. I tweak a few other things that also make no measurable difference. I change the tube from one set with one number to another set with a different type number that are electrically close to identical, require an extra jumper set per socket to fit the same socket and cost 4 bucks instead of 20 bucks each, but are a trifle more linear and should give a trifle more power...

The Amp promptly breaks into oscillation shown by a "Phut Phut" noise from the speakers. For some reason tube amp's that actually do VHF oscillation tend to Motorboat, never figured why, but useful to know, if your tube Amp Motorboats, first break out the 150MHz or better 400MHz 'scope.

So I re-do the compensation again and eventually I turn down the positive feedback in the front-end (so, Brüno likes to use as much negative feedback as he can manage - well my attitude is more POSITIVE) by 3dB. Everything is happy now and plays well with either tubes across a good selection.

The super cheap mil-spec "unknown" actually bias (cathode bias RC) within less than +/-4% variation from average, compare to more like +/-20% for the "audio(phile)" tubes. Funnily, it makes no appreciable difference to H2, though I'd have expected that, except in the bass, where the DC imbalance of the Audio Tubes roughs things up.

And with each step the Amp sounds better to me (well, it would, expectation bias and so on, right?), yet AP2 says "It measures so close to identical to the first time you did, you need to zoom in a lot and you need something better than this 2K Monitor if you want to see individual traces, rather than a pixel identical overlay."

So I am optimising the Amplifier's clipping behaviour with a scope on the outputs of the amp, various music, a pair of speaker and my original MK1 Ears (do not ask HOW this is done - this is a "Like Jocko" job). I could teach you, but I'd have to charge...

Actually, use your ears, mess with everything until overload obvious on the 'scope sounds clean and check for burst oscillation or other crazy sh1t on clipping... If you do it a few dozend times with different amp's you get a feel how "nice clipping" looks on a 'scope and what it sounds like.

If your speakers are more efficient than my set or the Amp bigger, a "Power Soak" designed to behave as much as possible like a real speaker (impedance, impedance phase etc) may be needed to avoid hearing damage. You can try to make an Amp clip nicely into "nasty" Speakers, I feel "life's too short" and instead use what a normal customer would use. Then again, it did catch me out a few times %.

Mr. Scope tells me we are doing > 28V Peak-Peak into a 4Ohm Speaker, no visible clipping. From a pair of 12W Anode dissipation Pentodes in high bias Ultralinear Class AB1. Yup, that is equal to 10V or 25W RMS with the first 6W+ in Push Pull Class A...

Supposedly the Amp only does 15WPC in total, 10% THD, 4Ohm resistive load. Mr 'Scope and Mr. AP2 agree. 15W @ 10% THD/4R, sine-waves. Subjectively this thing plays cleanly louder than the LM1875 "Gainclone" which does check out as >> 25W/4R @ 10% THD according to Mr. AP2.

So where does the extra "music power" come from? Must be that "Tube watts are bigger" thing...

Or maybe just that for most of the audio range the speaker is way > 4 Ohm Impedance, it only dips to 4Ohm at few frequencies, selected to be fairly away from "power chords". So it is actually still just 15W or less electrical, but more volts for these 15W and if the SPL is XXdB @ 2.83V, it will be more if more volts... Anyway, nearly 3dB extra dynamic range, undistorted. Put a Bow on it please, I'll have that.

A co-worker who is doing the MCU software walks in and asks "Is that the same amp you were messing with earlier?".

I sez "Yes, why"?".

He sez "Well, earlier it sounded awful, now it sounds like I want to take it home. Very high on 'magic'. What did you do?"

Remember. Mr. AP2 cannot tell this version from the first, except the new tubes have a trifle more power before hitting 10% THD. At 1 Watt, forget it. Speakers for listening are 87dB/1W (not 2.83V), 4.5" full range custom made, no crossover, plus horn loaded 1" soft dome as super tweeter above 8KHz. Will be sold with the Amp.

Listening - midfield (think a bit more distance than meter bridge mounted monitors).

I sez: "Some magic." (I wish it was as easy as Magik)

So I flick one of the switches on the front.

He pricks up his ears and asks "What did you just do? Some of the magic went away."

Me sez: "I flicked the tone control (passive, James type +/-8dB adjustment range) into bypass."

We listen back and forth. Sure enough, with the tone control set flat (AP2 agrees to better than +/-0.25dB 20-20k) but in circuit it sounds a little more spacious, maybe detailed, more magic, I agree. A bypass with a resistive divider only (same resistors as in the tone control) sounded less appealing.

So much for "Tone Controls are not high end - they kill good sound". Measurements between the two settings - I'd call it "reliably inaudible differences if any" on anything like phase, frequency response, THD and so on. Go figger.

Of course the test was sighted.

Maybe we are kidding ourselves. Maybe it actually all sounded the same and we were having a group hallucination.

Or maybe there is something in this assembly of resistors, cap's and potentiometers that somehow subjectively enhances the sound quality over 2 resistors, even if the maximum is a very small lower midrange emphasis (< 0.2dB) and all differences are so subtle, an ABX test would vanish them into nothing...

I then remembered seeing a Preamp, Japanese, Tube, where the builder had applied a passive tone control before the volume control (using really exotic caps and resistors too), but here is the killer, with fixed resistors instead of pots and the resistors selected for "ruler flat".

I remember having very derogatory thoughts (like "What a moron, if you want to loose 20dB of gain, why not just loose that 20dB tube stage in front of the Tone/Volume stack and cut all the crap out") upon encountering this for the first time.

I guess I just found out the why he did that.

Welcome to reality. Welcome to the next level...

Seriously, you cannot make this shit up, reality is way stranger than fiction.

“There are more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy.”

Well, anyway, I call that "A day at the office"...

Ciao T

% Here is one for you.

Some people like to flatten their drivers impedance profile at LF with parallel LCR Traps, figuring that "the more a speaker is like a resistor the better.".

What they forget is that fundamental and/or Thiele/Small Parameters are highly level dependent and given the values of the chokes needed they invariably go for some ferrite cored sh1t.

As long as we play "girl +geetur" music all is fine. Play some big stuff at realistic levels and the drivers resonance frequency and DCR changes (up) while the chokes start to saturate and become near shorts. Seeing all sorts of craziness the Amp goes self protective (or blows up).

So, beware if you see speakers advertised as "easy to drive" because their impedance has been made like a resistor... At high levelsit may be WAY WORSE than a decent uncompensated speaker.

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
 Post subject: Re: I call "Bullshit!"
PostPosted: Fri Sep 27, 2013 7:00 pm 
Offline
Dog
User avatar

Joined: Tue Dec 14, 2004 12:26 pm
Posts: 4981
Location: Lisbon, Portugal
Thorsten, I don't know your amp but on most the tone control bypass switch doesn't do much.
Years ago I've removed all that tone control stuff and direct switch out of the way on a Vincent integrated amp.
Magic happened.
THAT was direct. 1 meter shorter signal path, wires, connectors, switch.
Then I bypassed the tube pre and yet again magic happened. At this point, it was sounding great - finally.
Then I removed the tubes from the pre (were doing nothing anymore) and it had no effect. :blush:

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein


Top
 Profile  
Reply with quote  
 Post subject: Re: I call "Bullshit!"
PostPosted: Fri Sep 27, 2013 7:43 pm 
Offline
Pig

Joined: Wed Jun 29, 2005 6:34 pm
Posts: 1068
Location: East Coast USA
Well...

Ever look really closely at what grid/gate/base stoppers do or are supposed to do? And, why you might want them? It may not be in the audio band. You can even find this out by reading a Dennis Feucht article or looking in the right places when using LTSpice. (General comment - not directed at T...)

But, everybody doesn't have the same sonic priorities.

One more point. I again measured how much power I/we ever drive the power amplifier to.

The maximum RMS output of the DAC is 1 Vrms. Can't go beyond this, for the obvious reasons.

The preamp volume never gets set even to unity gain.

The power amplifier voltage gain stays 17, shine or rain.

That gives a maximum of 17 Vrms at the speaker terminals. If we turn it up. Which we don't. And, if the recording is recorded full scale (sadly, it often is...).

That's 36 watts into 8 Ohms. Or, about 16 dBw.

These speakers are pretty inefficient as speakers go, too - maybe 87 dB for 2.8 Vrms. The room isn't giant, but isn't small. (20' X 15') Maybe kind of standard. Maybe.

So, except for people hoping to be deaf sooner rather than later and those with really large rooms, why do you need really high power amplifiers? Do you? Or, is it something else?


Last edited by CG on Fri Sep 27, 2013 7:58 pm, edited 1 time in total.

Top
 Profile  
Reply with quote  
 Post subject: Re: I call "Bullshit!"
PostPosted: Fri Sep 27, 2013 7:54 pm 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1168
C,

carlosfm wrote:
Thorsten, I don't know your amp but on most the tone control bypass switch doesn't do much.


My amp is deceptively simple.

Input selector (well, there is a DAC with USB, SPDIF and Optical inputs build in, but has little to do with the story and is just boilerplating from prior designs of mine, as is the Phono)

->

Tone Control or Resistor Divider entirely passive.

The component quality standards are what I would use for EQ/Signal Path in my gear (eg. same type of cap's as in my RIAA EQ, pots are < 2dB tracking and made/designed by people who used to work for Noble US).

->

Tone bypass switch (C&K silver plated self cleaning toggle) selects either Tone Control or Resistor Divider output

->

Volume Pot

->

Amplifier (Gainstage DC coupled to Phase Inverter, capacitor coupled to Push Pull Ultralinear Pentode Output Stage)

As the powersupply works at very high frequencies I have no appreciable audio band noise from the PSU.

Tube noise is low enough, so the 11dB SNR loss does not bother terribly (if it had, I'd have placed the tonecontrol into the main amplifiers feedback loop).

It is very minimalist in design.

The difference in loop area between tone control and bypass are less than 10cm.

I think I know the Vincent Amplifier you speak of, model 250 something?

I had one a while back and instead of simplifying too much before the SS Amp, I fixed the tube circuit (very easy, hard was tracing the circuit) and instead converted the SS Amp into a simple Class AB emitter follower tripple, bootstrapped input biasing, the actual original amp section was converted into a DC servo with no role above 0.01Hz at 20dB/Decade.

Some feedback around this output and the Tube section. Maybe 12dB.

I simplified the wiring a lot by replacing remote switches with long wires to them (J.A. Pan Inc. style) with local relays and simple wires carrying DC from the original switches.

Not halve bad, if I may say so. Kept it in the 3rd system for a good while.

My straight "gainclone" with AB resistors,Alps Blue Volume control and Elna Silmic Capacitors a;; the way with CRC filtering turned out better one day and with a small passive EQ circuit addition wired into another input it could deal with overly lean recordings nearly as well, so I gave the Vincent away...

Now I have a Sheng Ya (aka Vincent) Pre-Power being very slowly (think lazy snail pace) modified when I have time. The Pre approaches acceptable, the Amp is near stock still, PSU re-build is nearly done though... It too has improved by nothing more than better diodes, caps and CLC filtering (18mF/2mH/18mF) instead of parallel cap's and generic bridges.

Ciao T

PS, CLC from CRC is a bigger step up than CRC is from C // C, highish current voltage schottky diodes in series with Stealth/Hexfred etc. diode bridges kill all else. Try it.

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
 Post subject: Re: I call "Bullshit!"
PostPosted: Fri Sep 27, 2013 8:09 pm 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1168
Hi,

CG wrote:
Ever look really closely at what grid/gate/base stoppers do or are supposed to do? And, why you might want them?


Yes. The ones in place were fine for suppressing resonant tank oscillation. And even at 10 times the value the impact on phase margin and/or frequency response was minimal.

What I do find is that these resistors (which are auxiliary or tertiary to the function of the amplifier) have a disturbing degree of influence on sonics. Of course, optimal values seem to follow no easily discernible rule...

Usually the best choice is as low as possible, while everything is stable, but not always. No silver bullet, experiment with values and positions...

Some times (mostly true for beam tetrodes) using voltage drop with minimal dynamic impedance is best (zenner dropper for screens), yet in other cases (mostly true Pentodes with the multiple grids wound correctly) a fair bit of resistance seems to do fine. Yet in other cases (not much pattern) no voltage drop between and grid does best.

Bottom line, be empirical. And take Mr. AP2's word for the measurements, but listen to the sound and give this more weight...

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
 Post subject: Re: I call "Bullshit!"
PostPosted: Sat Sep 28, 2013 12:17 am 
Offline
Dog
User avatar

Joined: Tue Dec 14, 2004 12:26 pm
Posts: 4981
Location: Lisbon, Portugal
Kuei Yang Wang wrote:
I think I know the Vincent Amplifier you speak of, model 250 something?


It's some 10 years old or so, Vincent SV-226.
The power amp section is quite good. The pre, forget it.

_________________
Carlos Filipe

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction." Albert Einstein


Top
 Profile  
Reply with quote  
 Post subject: Re: I call "Bullshit!"
PostPosted: Sat Sep 28, 2013 5:06 am 
Offline
Muriel
User avatar

Joined: Thu Jul 26, 2007 5:45 pm
Posts: 1168
Hi,

carlosfm wrote:
Kuei Yang Wang wrote:
I think I know the Vincent Amplifier you speak of, model 250 something?


It's some 10 years old or so, Vincent SV-226.
The power amp section is quite good. The pre, forget it.


Ahh, that one is much later than my one.

It indeed has a pretty good power amp section, similar to the SP-332 Power Amp I have here, just lower power and not asmany output pairs.

My one was the "Ur-Vincent", visually copied from the Luxman Hybrids, inside a pretty grotty SS Poweramp and decent Tube section with way too much gain.

Ciao T

_________________
"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." Richard Feynman


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 162 posts ]  Go to page Previous  1 ... 7, 8, 9, 10, 11

All times are UTC


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group