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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clio09
3,360 posts
 
@atmasphere - I can't seem to find the reference you referred to on page 12. What I did find was this which Roger wrote:
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?

The custom power cords he is referencing in the quote above I believe to be 14 or 16 gauge, I'll have to check. I don't disbelieve your statement on connectors or power cords heating up, but I have never experienced it on any of my components including yours and Roger's amplifiers. As for the reference to light gauge cords not bringing home the bacon, what gauges are we talking about?
ramtubes's avatar
ramtubes OP
460 posts
 
@skiramp Hi there would appreciate some help, I am shipping my Macintosh intergrated amp 200watt plus my def tech bp7000 sc to Thailand to live with me ? Very dodgy mains power !!! I am toying with the idea of ups or stabilizer or whatever , for some protection ? Against voltage drop . The def techs have 1800 watt driven subwoofers x2 of course ? I know that the equipment will never be driven at capacity, as house would fall in , your thoughts on a possible soloution,,, thank you : skiramp


I dont know the specifics of  your equipment as to low voltage. Solid state amps I have designed work fine down to half line voltage. Some do not. Well designed switching supplies are low voltage protected but if not they smoke and burn up. 

Get a power regenerator with wide voltage tollerance and let it deal with it. I do mean regenerator like PS audio makes. IF it fails you can send it back. 

I would also question what you are doing with those big subs. Are you watching Das Bot.

I wish you well in Thailand. Its a lovely and exotic place I visited many years ago.
ramtubes's avatar
ramtubes OP
460 posts
 
@testpilot  How do you block DC.


Connect two diodes back to back in parallel and insert in hot lead of power cord. 
ramtubes's avatar
ramtubes OP
460 posts
 
@stargazer3 For the OP what are the pros and cons in relation to damping for amplifiers; eg Hegel store great reliance for damping in relation to driving difficult speakers.


There is no con to high damping if done properly. However more than 20 will have little effect and may cause the designer to do some bad things to achieve it.  When a designer goes to maximize his favorite parameter he can go too far and other things will suffer. In this case stability from oscillation.  There are many amplifiers out there waiting for the wrong load and their own destruction.

I have seen many amps with very high damping oscillate into a 0.1 uF load which is typical of some speaker cables. Smoke and shorted output transistors was the result. The cause is too much feedback and assuming that if the amp is ok with the standard 2 uF test load it will be stable with smaller capacitive loads. Many well known amps are not. I tested an early ADCOM that took of with 0.1 uF. I did it for one second. A few more seconds would have been the smoke test.

Do you have a link to Hegel, I would like to read it?
atmasphere's avatar
atmasphere
11,901 posts
 
As for the reference to light gauge cords not bringing home the bacon, what gauges are we talking about?
18ga for sure- not suitable for larger current draws. The wire gets warm along its entire length with a big enough amp- that suggests its limiting current, and certainly the voltage at the amp will not be that of the wall.

Connect two diodes back to back in parallel and insert in hot lead of power cord.
The diodes are bypassed by electrolytic capacitors, which conduct only when neither diode is conducting.
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