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.


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ramtubes's avatar
ramtubes OP
460 posts
 
@corby2 Hello, I have a budget system I like. It has a 25 watt Will Vincent Balwin tube amp with Coincident Dynamites. I do not have an audiophile power cord. How much do audiophile power cords help with the amp? I was thinking of getting to Anticable stage 3 power cord. Thanks, Cory in Reno


Hi Corby,

Very few amplifier makers wind their own transformers, but I do. When I wind a transformer for a 25 watt amplifier it is about 150 feet of 24 ga wire. After I am done I really dont see how 12 feet of 18 or 16 or 14 ga wire will make any difference.

If you measure the resistance of the primary circuit of your amplifier it is like likely near 5 ohms given that it is 25 watts.

This is easily done by unplugging the amp, turning it on, putting an ohmmeter across the two prongs of the power plug. Now you will know the total resistance of the primary loop. The total resistance of the secondary loop (reflected to the primary) is similar to that so double what you just measured. Now ask yourself how much a power cord of 0.01 or 0.1 ohm or 0.5 ohm is going to make when added to that number.

The claims about RF shielding are absolute bullshit. Along with any other specious claims.

Just get a cord with good connectors.
ramtubes's avatar
ramtubes OP
460 posts
 
@tomic601 

  RM - took a hiatus from the book, restarted on page 59....junction temps....had a bad experience with ON Semiconductor thermal tracs.....I know you are a tube guy, can you comment about the diamond topology ?


Not sure what you mean by thermal tracs?  ON semi is making the Motorola parts. I dont know if there is anything new. Do you have a part #.
clio09
3,360 posts
 
@atmasphere - this is the power cord he was referring to that does make a difference under certain circumstances:

http://tubeaudiostore.com/pocoyoucanac.html

Otherwise as Roger noted in his last post just get a cord with good connectors.

tomic601's avatar
tomic601
12,951 posts
 
RM - NJL3281D

not exactly sure which Ayre used but they did not prove hyper reliable...
the Twenty series use a derivative of the Diamond circuit and I believe also switched away from the thermaltrak...

ramtubes's avatar
ramtubes OP
460 posts
 
@analogluvr  Over voltage can cause mechanical hum in a transformer


Thanks for pointing that out. The flux (and thus mechanical buzz) of a transformer rises sharply at some voltage. That point is up to the designer. I try to get mine still quiet at 130 Volts but we are getting up to 125 now in our houses so might have to go higher and wind for 125 rather than 120. 

Small amounts of DC on the line make things worse expecially with torroids as they have no gap. 0,5 volts of DC is enough. We make a power cord with a device to block the DC. Ask Clio, or you can make your own. Im not trying to sell anything here or be accused by one who does. 

Power transformers are a pain in the ass. If you make them bigger to reduce the flux they make more noise due to larger size. Ive been around the block several times on this. All our tranformers are silent at 2 feet in a very quiet room. My thought is if you cant hear it at the listening position whats the problem? Who sits next to their power amp? If you want someting lower noise I can make it for you. 

Power transformers can become noisy with age. Spongy feet or a bed of sand helps a lot to decouple from the rack or floor. 
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