2. amps-preamps
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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
ramtubes's avatar
ramtubes OP
460 posts
 
@bdp24   Roger, could it be the old 1kHz frequency was chosen in relation to the RIAA equalization curves?


That would have been a better choice resulting in 500 Hz for the low hinge and 2 Khz for the high. I would prefer a larger gap as stated earlier. The single point of 1 KHZ is trying to hit the middle numbers wise but not sound wise.

The RIAA points were chosen by the density of program material. BTW the RIAA curve we are familiar with that is 40 dB of EQ from top to bottom is not the RIAA curve. It is the RIAA plus MM/MC curve.

The RIAA playback curve for a semiconductor cartridge is only 12 dB from 500-2,000 Hz. Thus RIAA boosts the highs 12 db and cuts them 12 dB on playback... Does anyone find this interesting or alarming that we call the RIAA curve the big one and not make much mention that it is for velocity transducers only?
atmasphere's avatar
atmasphere
11,615 posts
 
BTW the RIAA curve we are familiar with that is 40 dB of EQ from top to bottom is not the RIAA curve. It is the RIAA plus MM/MC curve.
Try telling the manufacturers of cutter electronics that.

Does anyone find this interesting or alarming that we call the RIAA curve the big one and not make much mention that it is for velocity transducers only?
No. Its well understood that is the case. There has been some controversy over other types of transducers as you point out, won't be properly equalized. IMO/IME the producers of such cartridges should offer their products with an equalizer to set things right.

mikepowellaudio's avatar
mikepowellaudio
138 posts
 
Hey Roj, Its Verastarr Mikey..

Id like to know when we roll tubes and hear differences that are so different and unique even when its the same exact tube type, how and what exactly are we hearing ? Lets take 2 6sn7GT for instance, that for the purpose of this question have near identical electrical characteristics.
Thanks man !
ramtubes's avatar
ramtubes OP
460 posts
 
@atmasphere 

Try telling the manufacturers of cutter electronics that.


How about telling us about the cutting process? The range of constant velocity cutting and range of constant amplitude cutting. 

I was not discussing cutting, but you appear to have something to say. I simply wanted to inform the readers here that the RIAA curve they generally see is not the RIAA curve but the RIAA plus EQ for velocity cartridges. From what I read the Amplitude cartridge people still have not caught on..
ramtubes's avatar
ramtubes OP
460 posts
 
Hey Roj, Its Verastarr Mikey..

Id like to know when we roll tubes and hear differences that are so different and unique even when its the same exact tube type, how and what exactly are we hearing ? Lets take 2 6sn7GT for instance, that for the purpose of this question have near identical electrical characteristics.
Thanks man !


First how many of the characteristice are near identical. Mu, Gm, Rp and bias point. These vary widely. With 6SN7s microphonics can play a large role.

I cannot comment on what you are hearing. If you want to be sure of what you are hearing it takes two identical circuits for the two tubes, an A/B switch, matched levels. We find with many listeners that the difference we hear rolling tubes are small enough to disappear. One cannot just swap a tube, we have found the sonic memory to be too small.

I did a strict A/B for 50 people in the SFAS. They looked at me and said. Hey these all sound the same, where are the differences.

Given that they want differences, we are repeating the test this saturday and will not A/B. It takes away all their fun when thinigs sound the same Sorry, but good equipment sounds good.

Because I test a lot of tubes, use them in off book applications I get to see some real measurable differences but then the tubes are actually different on the test gear too. A curve tracer will tell you a lot. 

The question I have is why do you want these differences?

If you could design your own preamp wouldnt that be more rewarding than swapping parts?


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