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
ramtubes's avatar
ramtubes OP
460 posts
 
@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.
ramtubes's avatar
ramtubes OP
460 posts
 
@krelldreams

   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?


Not sure what I can do about the passive thing but you can write Tony at tubeaudiostore@gmail and he will forward to me. 

The capacitance and inductance in a power cord is vanishingly small and can be ignored. Some platings are nice. DeOxit is a good cleaner and cleaning may help more than anything. 

I would have had the electrician put in several duplex outlets so no power strip is needed. Power strips vary in cost and quality but the expensive ones with big claims are just marketing. You have nice 10 Ga wire in the wall and then what?

Heres something Ive done. Get a bunch of reasonable power cords, like $20 each of various lengths. Cut off all the male plugs strip and hardwire the cut end directly to the 10 GA wire with a bussbar. Solder good solder lugs to the wires and screw them with a star washer to the bussbar. THe star washers are important. Now you have direct power cords and have eliminated one connection.  Make some extras of course.  The ones you arent using just coil them up.

I had custom power cords made that are 8 ft long, very flexible, supple, drape nicely and wont pull  your smaller devices off the shelf. We have them if you need some. 

Bottom line here. Its not the wire that matters. You have hundreds of feet of ordinary magnet wire in every transformer. What you gonna do bout that? :). All this power cord and power strip is just foolishness. Why do we need powercords that are a pain to run?

Thanks for the question. I hope people can see that throwing dollars at something is not always the best solution. 
ramtubes's avatar
ramtubes OP
460 posts
 
@stargazer   I must admit that I personally in my limited experience of owning new HiFi components I never experienced this marked change of sound during 'burn in process'. When you confirm that in regard solid state amplifiers it is the listener who is becoming accustomed to the change thats quite an assertion when you consider the host of people (professional and non professional) who claim to have actually heard and experienced the change of sound during the claimed burn in process. Its fascinating that such a divide exists among normal music lovers.

It is quite an assertion that I made. We know not what they heard, we know not what posessed them to make such claims. I assert that the change is so subtle as to be entirely imaginary. I have said to many who report such " Wow you have a really good imagination"

Look at it this way. There are professionals and non professionals who assert they have golden ears and they must say these things to support their ears. We dont know what someone is hearing. 

As I have posted previously ive been in a room with some golden ears where the system was "broken" and they didnt hear it. Given that who is really hearing what?
jlhaudio
1 posts
 
Roger, why did you switch the input to the 12AT7 from the 12AX7 on the Ram10 mkll?
ramtubes's avatar
ramtubes OP
460 posts
 
@jlhaudio Roger, why did you switch the input to the 12AT7 from the 12AX7 on the Ram10 mkll?


Along with changing the bias system from fixed to cathode bias and changing the B+ I found the 12AT7 was a better choice. It has a lower saturation voltage than a 12AX7 and higher current. As far as we can determine the amps sound the same. We want them to. 
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