2. amps-preamps
  3. 140029-80294

Does anyone care to ask an amplifier designer a technical question? My door is open.

I closed the cable and fuse thread because the trolls were making a mess of things. I hope they dont find me here.

I design Tube and Solid State power amps and preamps for Music Reference. I have a degree in Electrical Engineering, have trained my ears keenly to hear frequency response differences, distortion and pretty good at guessing SPL. Ive spent 40 years doing that as a tech, store owner, and designer.
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Perhaps someone would like to ask a question about how one designs a successfull amplifier? What determines damping factor and what damping factor does besides damping the woofer. There is an entirely different, I feel better way to look at damping and call it Regulation , which is 1/damping.

I like to tell true stories of my experience with others in this industry.

I have started a school which you can visit at http://berkeleyhifischool.com/ There you can see some of my presentations.

On YouTube go to the Music Reference channel to see how to design and build your own tube linestage. The series has over 200,000 views. You have to hit the video tab to see all.

I am not here to advertise for MR. Soon I will be making and posting more videos on YouTube. I don’t make any money off the videos, I just want to share knowledge and I hope others will share knowledge. Asking a good question is actually a display of your knowledge because you know enough to formulate a decent question.

Starting in January I plan to make these videos and post them on the HiFi school site and hosted on a new YouTube channel belonging to the school.


128x128ramtubes
ieales's avatar
ieales
1,201 posts
 
@ramtubes
preamp is balanced via electronic buffers. We don’t want to short those.
Depends on the circuit design. A lot of pro gear has IC balanced outputs that can short either leg to Gnd and the output acts single ended, driving no current into the shorted leg.

However, as Roger said, if you don’t know the output is single ended capable, only use one leg.

AND if using balance lines, only connect the screen at the driven end. A shield grounded only at the receiver forms pair of low-pass filters for common-mode noise
atmasphere's avatar
atmasphere
11,861 posts
 
Ralph, couldn't he use a Jensen transformer to make he XLR to RCA change? Would it still offer the proper grounding?

Yes.

Okay, does atmasphere believe that power cables can make huge differences in an amplifier’s sonic performance and why?
I don't use the word 'believe' because I made the measurements which showed that the power cord **without question** can affect the amplifier's performance. The measurement is easy- the voltage drop from one end of the power cord to the other. Its not rocket science and its not mumbo jumbo woo. Anyone with a 3 1/2 digit DVM can do it. After you know what the voltage drop across the cord is, then measure the resulting differences in the amplifier: output power, distortion and output impedance. You will find that they all change. So by this simple means you have a tool to correlate with what you hear.
So in a nutshell, I don't believe it, I **know** it.
jetter
3,037 posts
 
Hi Ralph, please put your statement above into perspective for us non electrical savvy persons.  Would a "normal" power cord supplied with a piece of gear have enough excess power passing capacity so that any drop in voltage due to the cord, is from one satisfactory voltage to a lesser, yet still satisfactory voltage to power the unit?  Or are you saying that the power cords supplied with a piece of gear could be starving the unit for power and maximum performance?
atmasphere's avatar
atmasphere
11,861 posts
 
Would a "normal" power cord supplied with a piece of gear have enough excess power passing capacity so that any drop in voltage due to the cord, is from one satisfactory voltage to a lesser, yet still satisfactory voltage to power the unit? Or are you saying that the power cords supplied with a piece of gear could be starving the unit for power and maximum performance?
Much is depends on the equipment used, so the answer as a generalization is 'both' although I'm uncomfortable with the phrase 'excess power passing capacity'. Power cords like anything else are subject to Ohm's Law.
prof
3,474 posts
 
Teo wrote: 

—-“Prof uses the measurement canard which is as old as it gets and is well proven to be ineffective when it comes to human hearing at it's limits - which is the subject at hand.”

Ah that’s right.  Human hearing is more sensitive than our measuring instruments.
Wait...what did we need those instruments for again?  Oh yes, to extend our detection capabilities beyond the limitations of our senses.   Heard any 26k sounds recently Teo?  That’s ok - instruments can easily detect things you can’t hear. 

Of course instruments can’t detect things you imagine.  They really suck at that, admittedly.

— “Interestingly enough, his entire job rides on doing things that are either unmeasurable or so close to being unmeasurable that it is not worth bothering to try. “

Wha??  I work in film post production sound.  What I’m doing is being measured all day long.  I want to reduce a sound or boost it, or eq, it’s all measurable and measured!   

—“Hoisted by his own petard. (modern translation: he blew himself up)”

You have no idea what you are talking about.  I suggest stepping away from the bong before posting :-)


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