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.


128x128ramtubes
atmasphere's avatar
atmasphere
11,595 posts
 
JA measured a low 84dB sensitivity but with a higher/smoother impedance he deemed them "a very easy load for the partnering amplifier to drive."
@prof
Tube amplifier power has traditionally been expensive. Inefficient loudspeakers as mentioned above only became possible in the era of solid state since that power is so much cheaper. Unless you are in a very small room, I'd consider a different speaker as 140 watts isn't a lot of power when dealing with a sensitivity that low, regardless of the 'difficulty' of the speaker.

@clio09

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.

Apparently though Roger sees or saw fit to build his own power cord setup using some pretty heavy gauge wire (see page 12); this suggests (if actions speak louder) that he does think they make a difference, else why go through the bother?

(FWIW a power cord with light gauge but good connectors will not bring home the bacon, generally speaking. I've seen power cords, not just the connectors, heat up.)


I first heard how dramatic a power cord can be at the 1990 CES in George Cardas' room. The impact and nature of the bass was easily heard by all present to be quite different and with more impact when stock power cords were replaced by a pair that George offered. I found it disturbing; at the time I just didn't understand what was happening (and it clearly was not snake oil as it was repeatable) but I also knew enough to not buy the explanations that were offered (which clearly **were** snake oil).


But in time I found out that all you have to do is to simply measure the effects a power cord has on an amplifier. Generally speaking, the more power the amplifier draws, the more you will hear differences between power cables. 
prof
3,449 posts
 
Thanks atmosphere. 


(I'm still interested in ramtube's view as well).

My room is on the smaller side: 15' x 13' wide and I listen at modest volume - typically 70 db to maybe 75, probably 90 at the most if I crank it more to listen from down the hall.

I also wonder how the introduction of a subwoofer alters the load to an amplifier.  So say if you have a powered sub and you crossover to the sub from the mains at maybe 80 or 60 Hz.  Once one has off-loaded much of the low frequencies to the sub, I wonder how much the main amp "sees" and if that, in effect, is like adding a more powerful amp in to the equation. 
twoleftears's avatar
twoleftears
5,313 posts
 
@testpilot  Take a look at the Isotek Synchro EVO3.
clio09
3,345 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.
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