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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@ieales  More than once I've rejuvenated a system by re-plugging ALL connectors, both internal and external.

YES, YES, YES.  Ive fixed so many things just doing that. Flat screen TVs, my Sony ES player many times, Its used up 6 of its 9 lives. 

Its sad how many components, expecially CD players end up on the scrap heap that could be fixed in 10 minutes. Dont forget the ribbon running to the laser head. That one needs the most attention. Use some logic. If the player cant read a CD go for that one. If some of the display is out or buttons dont work go for the one going to the front panel. Its really simple and you have nothing to lose. CD players cannot shock you. Do unplug them however. (I dont). 

When I open a unit with lots of those ribbon connectors inside I know it has limited life. All connectors oxidize. Oxides also form rectifiers in the signal chain and distortion.  
The old Polk Audio Cobra cables were a very high capacitance design, and caused some amps to become unstable.
@ramtubes. 

   It is very likely that what I’m hearing with this preamp vs passive thing is a less than perfect passive, against preamp distortions which “smooth” the sound. I’d like to know more about your suggested solution to this issue, but contact outside of this discussion is probably best.

   I do have technical questions regarding cabling and AC outlet use though! I’m not excited about super expensive cables (I’ve tried many with very little in the way of difference), but there are electrical differences (capacitance, inductance) in wire. Also, there are different metals and connectors used. What should one look for in terms of material (copper, silver, etc), and electrical properties (capacitance, etc) when choosing wire?
 
  Regarding AC outlet use, how does one best work out the unavoidable need to plug various components into a two outlet wall plate? I had an electrician run a dedicated 30A, 10AWG line to the duplex behind my system location to isolate the stereo components, and to provide enough amperage for the amplifier’s initial turn on draw (it was tripping the 20A breaker). I have seven components that need power. I plug my power amp into one of the outlets, and a “high end” six outlet power bar to the other outlet. Is there something special, and necessary about power strips for stereo components? If so, what does one look for when choosing between them?
@twoleftears  Technical question: Do certain electronic components, e.g. capacitors, need to "form" before they operate at their best?


Electrolytic caps do need to form and the form time is related to how long they have been off or stored. This is why smart tech bring up old equipment on a variac, to let the caps form. If power caps are just hit with full voltage they will draw DC leakage current as they form. If they get too hot in the process they explode. The process is regenerative so it goes very fast at the end. Many people destroy otherwise good caps by just turning things on for too long. 

If people want to know there is a lot to be said about these caps and I have studied them in depth. I made a current limited "former" that will prevent the overheating runaway. Sometimes old caps are better than what is being made now. I know because Ive tested them. 

It takes about a day to fully form a 10 year old cap. They often form to much higher voltage than the rating. The old man at Mallory explained it all to me.  In large quantities where we spec what we want, the voltage written on the cap is more often the voltage on the purchase order rather than what the cap was made for. 

For example we ordered 1000 pcs of 150 uf 315 volt caps at Beveridge. I tested them and found them good to over 500 volts, therefore I would say they could have been marked 450 but we ordered 315V. We got more than we paid for, but one has to TEST these things to know. 

He also told me that stored at cool temperatures 10 years takes only a month off the life of a cap. Basically nothing. Its all about the water inside staying inside. 

I am sad to report that modern caps from good makers are having other problems that prevent this kind of testing. Recently I found some good caps flashed over at slightly above rating because the edge margins on the paper had been reduced to shrink the cap's size. Now that is sad. 

My advice, heed this well, If you have old lytics that are working fine, DO NOT REPLACE THEM. The new ones may not last nearly as long. I have 30 year old caps in RM-9s that are doing just fine. I don't think modern caps are going to last 30 years. 

Oh, perhaps I forgot to mention, Im really into finding out why parts fail. One has to care to make long lasting equipment.
@bdp24 The old Polk Audio Cobra cables were a very high capacitance design, and caused some amps to become unstable
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We briefly sold those cables till we found out if you step on them they short out. Weaving magnet wire into a snake skin is a really bad idea.