Equalization via software vs hardware

[Rick Barber]

Re: Equalization

This has been one of the better threads I have read here. Thanks for all the insite. I thought for a minuite there we were gonna see a fight! LOL [img]/ubbthreads/images/graemlins/wink.gif[/img] [img]/ubbthreads/images/graemlins/grin.gif[/img]

[Craig Maier]

Re: Equalization

Doug,

Higher voltage rails provide you with more "headroom" and therefore less possibility of clipping on large signal transients. Also, there is a second order effect to consider. The harder that you "push" a transistor (op amps consist of a bunch of transistors on a common silicon substrate as you pointed out) towards either saturation or cutoff, the greater its intrinsic non-linearity and therefore its distortion (%THD) contribution to the system. Yes, most of this distortion is decreased by the Beta term of the feedback loop, but op amps do not have infinite open loop gain and so this is of some concern. Most op amps have two voltage amplification stages. They are the input differential amp (two transistors and a current source) and then the constant current fed single ended voltage amplifier. The constant current fed voltage amplifer is the transistor most susceptible to this second order effect since it is second in the chain of amplification and goes through the highest degree of dynamic swing on its collector (or drain). The totem pole output transistor circuit adds almost no distortion because their voltage gain is about unity meaning that this stage has 100 percent local voltage feedback. This almost completely cancels out any nonlinear distortion produced by the output stage. I hope this helps. By the way, tube preamplifiers can be made to produce 0.001 percent distortion too. I have done it. But, it takes 8 12AX7 dual triodes in the signal path to acccomplish this for a stereo pre-amplifier. The trick is to demand very little voltage gain out of any one stage by using lots of local feedback (meaning - high values of cathode resistors without the use of capacitor de-coupling - bypassing) and lots of overall feedback as well. At the end of the day, you end up with a pre-amp that also serves as a heater with low distortion that sounds like an op amp preamplifier, except with much more noise and something that is so big that your wife will not let you put it in your living room! But, the things (12AX7's) do glow, I will give you that! [img]/ubbthreads/images/graemlins/confused.gif[/img] My op amps very, very rarely do!!! Maybe that "warm reassuring glow of the vacuum tube cathode" is the emotional crutch that some people need to enjoy their audio "soundstage". [img]/ubbthreads/images/graemlins/smirk.gif[/img]

[Craig Maier]

Re: Equalization

Rick,

Yeah, my blood pressure did rise a bit when Galo was mentioned. He once was sent a pre-amp design of mine (actually the Owl 2) to listen to and evaluate. Upon recept of the unit, he opened the cover, saw the op amps and never even gave it a listen. When I spoke with him on the phone about it, he said that he did not have to listen to it because he knew what it would sound like and that was crap. I asked why and he said because the thing did not have tubes and because the power transformer was too small. Then I realized what I was dealing with. So, I asked him a very simple question. I first asked him what his degree was in and what he did for a living. He stated an answer to that question demonstrating that he has no technical background whatsoever. Then, I asked him to state Ohms Law. You can not get any more basic than that if you are a technical guy. He could not and said to me that it was not important to know that and hung up on me. But, this guy is a well known critic of audio equipment. He writes for all the high end audio magazines. Too bad he is clueless. He later promised a business partner of mine that if we ever introduced the Owl 2 into the market, he would make sure that no one reading any of the publications that he worked for would purchase one. Nice guy. And all based on using his untrained eyes instead of his ears. [img]/ubbthreads/images/graemlins/mad.gif[/img] Guess he has a "glowy thing" fetish! [img]/ubbthreads/images/graemlins/ooo.gif[/img]

[Doug]

Re: Equalization

Let's have a vote:

Who dares Craig to send the Owl 2 back to Galo with a couple of dim incandescent lights randomly placed in the circuit?
You could also hide a couple of "over-driven" flat pack voltage regulators under the printed circuit board for added warmth.
Then see if his perception of the Owl 2 changes [img]/ubbthreads/images/graemlins/wink.gif[/img]

I can't understand why anyone would want to use a valve preamp - try using a 7-12 band equaliser Mr Galo

PS. If Galo wants added distortion, give him an over-driven Op-amp or one that has drifted to rail by accident. Either that, or tell him to buy a el-chepo boom box made in china. He could light some candles and sit in his favourite arm chair and listen to the distorted sounds and look at the warm glow. [img]/ubbthreads/images/graemlins/tongue.gif[/img]

Maybe the OWL 2 should have been sent out with a six pack of candles - is that where you went wrong Craig?? [img]/ubbthreads/images/graemlins/grin.gif[/img]

[Craig Maier]

Re: Equalization

Doug,

I think that you are onto something here and I like your thinking. Now I see the error of my ways! Candles under the op amps would have been very pleasing to him and would have added lotsa warmth too! [img]/ubbthreads/images/graemlins/smile.gif[/img]

[tomd]

Re: Equalization

I wasn't aware of the problem with Gary Galo. I was looking for information on the recording characteristic of acoustic 78's, and that's what turned up. I believe in IC's for preamps. Douglas Self uses them and his accounts are convincing because he explains distortion mechanisms and backs his assertions with refined measurements on his Audio Precision test set.

If you imagine the process of playing an RIAA LP with a velocity-responding cartridge, you find that in the LF constant-amplitude band the output of the cartridge rises at 6dB/oct. If the termination itself compensated the velocity response, the signal at the preamp input would not rise and the first part of the RIAA playback curve would not be needed. In the mid-frequency constant-velocity band, if the termination compensated for the cartridge's velocity response, the input to the preamp would fall 6dB/oct, and the flat portion of the RIAA PB curve would not correct the fall. The HF constant-amplitude portion would behave the same as the LF one. At the preamp input, you would see a flat LF portion, a falling mid-freq. portion, and a flat HF portion. This is actually what you get from an amplitude-responding cartridge, for which RIAA EQ only makes things worse. The point is that if the input termination compensated for the rising characteristic of a velocity-responding cartridge, the input to the preamp would be the same as that from an amplitude-responding cartridge with whatever termination was proper to it, and the EQ would have to be not RIAA, but one that was flat at the low and high ends and rising in the middle.

[Craig Maier]

Re: Equalization

A magnetic phono cartridge exhibits aproximately a +1 slope across the audio portion of the spectrum when the influence paramater is a constant velocity and in the absence of a termination network (L/R time constant). The "self resonance" of the coil is usually above the audio spectrum. With a termination network, its response is aproximately flat under the same stimulus conditions. Please see my post number 3279 for the formulae which describes the output open circuit voltage of a magnetic phono cartridge having the above mentioned stimulus and also under an open circuit (non terminated) condition.

[Rick Barber]

Re: Equalization

[ QUOTE ]
Rick,

Yeah, my blood pressure did rise a bit when Galo was mentioned. He once was sent a pre-amp design of mine (actually the Owl 2) to listen to and evaluate. Upon recept of the unit, he opened the cover, saw the op amps and never even gave it a listen. When I spoke with him on the phone about it, he said that he did not have to listen to it because he knew what it would sound like and that was crap. I asked why and he said because the thing did not have tubes and because the power transformer was too small. Then I realized what I was dealing with. So, I asked him a very simple question. I first asked him what his degree was in and what he did for a living. He stated an answer to that question demonstrating that he has no technical background whatsoever. Then, I asked him to state Ohms Law. You can not get any more basic than that if you are a technical guy. He could not and said to me that it was not important to know that and hung up on me. But, this guy is a well known critic of audio equipment. He writes for all the high end audio magazines. Too bad he is clueless. He later promised a business partner of mine that if we ever introduced the Owl 2 into the market, he would make sure that no one reading any of the publications that he worked for would purchase one. Nice guy. And all based on using his untrained eyes instead of his ears. [img]/ubbthreads/images/graemlins/mad.gif[/img] Guess he has a "glowy thing" fetish! [img]/ubbthreads/images/graemlins/ooo.gif[/img]

[/ QUOTE ]Given this history I don't blame you for your hair standing up. I have been there a few times too. A small 3 volte heater my work for Dougs Idea too? LOL

[tomd]

Re: Equalization

To see the effect of magnetic phono cartridge termination, I recorded the pink noise track from "Hi-Fi News & Record Review Test Record II," using DC Five 5.22 and making one recording with normal cartridge loading and one without. The "Pink.jpg" attachment (82KB) shows two Frequency Spectrum displays. The upper one is with cartridge loading of 47 K-ohms and 210 pF, plus cable capacitance. Through most of the audio range it shows a fair approximation of pink noise's 10 dB per decade (3 dB/octave) falling characteristic. The lower display is with no cartridge termination. A resonant peak has appeared at the high end. Below the resonance the curve is the same as before. Using the Spectrum Analyzer's User Controlled Marker and keeping to frequencies below the unloaded resonance, measured levels to the nearest dB are -24 dB at 43 Hz and -44 dB at 4300 Hz loaded, and -25 dB at 43 Hz and -45 dB at 4300 Hz unloaded. In both cases this is a difference of 20 dB over two decades.

The cartridge was a Stanton 681EE. The preamp was an Audio Technologies, Inc. P100. With no cartridge termination, the preamp load is just the impedance of the non-inverting input of a 5533 op amp (the 14-pin IC, not the 8-pin 5532). There is no input coupling capacitor and the IC draws its input bias current through the cartridge. This is probably a bad idea, but it does allow removing all resistance to ground from the input, which I did. There is still the shunt capacitance of about two feet of cable and tonearm wiring. The sound card for the recording was a Digital Audio Labs CardDeluxe.

[DougMac]

Prior Post

[ QUOTE ]
Be real careful when you cite Gary Galo as a reference in the field of audio. Gary Galo has a degree in teaching and teaches English in High School from what he has told me. He pretends to be the world renowned expert in Audio Engineering and insists that such things as Tube Preamplifiers are the only acceptable way to do that job. Hmmmm. Doesn't something smell here.

[/ QUOTE ]

It smells to high Heaven.

I asked about phase shift in a prior post. I had just read Gary's review. He's the one contending that analog filters are necessary to re-introduce phase shift, canceling out the original. Everything is in perspective now.

Thanks for checking out his credentials and sharing them with us. High end audio seems to be a breeding ground of uninformed silliness. When you're trying to sell $30,000 tube amplifiers and $20,000 turntables you have to resort to something.

This kind of thing drives my son to distraction. He's got a Master's in digital music. He and his friend got tired of the outrageous claims they were reading in chat groups, so they started a thread asking which hard drive sounded better. There were tons of posts, fiercely defending the responder's favorite brand of hard drive as having the best sound!

We also went speaker hunting together. The salesman demo'd some esoteric $5,000 speakers, which sounded terrible. When my son pointed this out, the salesman told him his ears had become acclimated to the sound of cheap speakers so he couldn't appreciate quality. My son also has a Master's in music performance. He explained to the salesman in the bruntest of terms the fallacy of his theory. I then took my turn. We bought speakers elsewhere.

Doug

[Craig Maier]

Re: Prior Post

DougMac,

That is a new and great one on me - - - that is - - - which hard drive sounds the best! I personally like the whirring sound of the ones with bad bearings. They don't have the best beat, but they are great to dance with. Yeah, I have met people who have "the glowy tube thing fetish." I think that it may be some sort of disease, perhaps uncurable. These folks are all nuts and never display any engineering background or education. Poor malcontented souls! They just have very strong opinions and probably need medical help more than anything. Keep in mind that these folks who insist on tube amps and preamps are all listening to stuff that was recorded in a studio though a mixing board that had op amps (lot of 'em) in the signal path. Also, they are listening to CD's that have been digitized and stored on who knows what kind of hard drive! [img]/ubbthreads/images/graemlins/confused.gif[/img] Let's let real science and mathematics prevail in these sorts of discussions.

BTW - I have been thinking of starting up a new line of "Golden Ear Hard Drives." They will sell for $25,000.00 each and are guaranteed to meet all of my own personal standards for exceptional sound quality. I will sign each one personally and install a 14 carrot golden eustacheon plate on its side attesting to that fact. I will also figure out a way to include a 12AX7 in the logic circuit chain. Thanks for the new business plan idea! [img]/ubbthreads/images/graemlins/cool.gif[/img]

[Doug]

Re: Prior Post

Where can I get one?

[Craig Maier]

Re: Prior Post

They will be comming to a Computer Store near you soon. Supplies will be limited, so do not wait to make your purchase!