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.
.
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
451 posts
 
 @atmasphere 
Ralph, How about a curve. People here cant understand what you said, can anyone?

Can you ever give a simple answer?

From 500 Hz to 2000 Hz the response on the record is lifted at a rate of 6 dB/octave for two octaves. Thats 12 db total. Is this your understanding?
atmasphere's avatar
atmasphere
7,068 posts
 
I'm sure someone can understand my prior answer. I know you can, therefore to your first question, 'yes'.

To the second, also 'yes' but the question you asked didn't have a simple answer- some questions are like that :)


To the third, a correct answer requires a correct question- the **response** is not raised; the **pre-emphasis** is, and by about 5 db (so the simple answer is thus 'no'). Remember that the curve is just that and is the amalgam of three timing constants. The range of frequencies to which you refer is the area where the response is relatively flat compared to the rest of the curve. It isn't flat because of the ordinates of the timing constants. So its a gentle curve in that range, and the **pre-emphasis** is 'lifted' by about 5 db over that range, not 12.


There are plenty of images on the web.  Fig. 2 of the article at the link below is pretty good- you can see the 5 db or so rise in the pre-emphasis in the range of frequencies about which you asked:


https://www.stereophile.com/features/cut_and_thrust_riaa_lp_equalization/index.html



ramtubes's avatar
ramtubes OP
451 posts
 
Ralph

Thanks for the link. It is clear to me that above and below 1 KHZ there is 6 dB of EQ on either side of the red line, making a total of 12 dB as stated before.

To be clear I am not talking about what is fed to the velocity sensitive cutting head but what is actually in the groove and what one must compensate for with a constant amplitude cartridge. It is interesting to note that in the better RCA consoles of the 1950s RCA actually applied this 12 dB shelf to their crystal (amplititude sensitive) cartridges. I dont know anyone else who did. 

The time constants are indeed 2 octaves apart at a rate of 6 dB/octave. Of course the corners are rounded but the eventual preemphasis is 12 dB starting at 500 Hz. 

See figure 2...  https://www.stereophile.com/features/cut_and_thrust_riaa_lp_equalization/index.html

This is also interesting. https://en.wikipedia.org/wiki/RIAA_equalization

Since the readers here dont seem too interested, I am going to sit this one out. 
atmasphere's avatar
atmasphere
7,068 posts
 
Thanks for the link. It is clear to me that above and below 1 KHZ there is 6 dB of EQ on either side of the red line, making a total of 12 dB as stated before.
I think you might be misinterpreting something- The red line is not the EQ curve. If you look at the actual curve, at 500Hz it only rises about 3 dB to 1Khz and then about 2 1/2 dB to 2KHz. The scale on the left is 5 dB per gradient.


I've seen a number of older console and stand-alone components that had networks installed for the ceramic cartridge inputs. Loading of ceramic cartridges is pretty critical if you wan them to work right.


Strain gauge cartridges seem to be the high quality version of a constant amplitude device in that they can track at 'normal' tracking pressures and have decent bandwidth. But its always bothered me (nor am I alone in this by any means) that they are often sold without proper compensation. I went to hear one back when CES was still at the Alexis Park and brought an LP that I knew quite well since I recorded it. You could tell it was the same music but the tonality was definitely off. The manufacturer was claiming that it needed no EQ... I thought about offering to do an equalizer for it but with his remonstrations it seemed an uphill battle. I think your comment about the Win hit the nail on the head- there's a bit of a consistency problem.
ieales's avatar
ieales
297 posts
 
@atmasphere 
µs, not ms
75 µs, 318 µs and 3180 µs
More to discover