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
 
@tomic601 

i have been considering the 60 wpc kits Ralph puts out...thanks also for your participation here also..

The M60 is a nicely laid out amplifier, spacious inside, easy to build for even a first times. Chassis and parts are nice.

One suggestion. Ralph uses all one color wire, blue, I would suggest you get a few colors it makes troubleshooting much easier. Red for B+, black ground, blue plates. This can be looked up as there is a standard. I would also use teflon stranded wire I find his solid wire a little hard to work with. If you nick a solid copper wire it will easily break at the nick.  

You will need a 50+ watt iron for all the terminal strips and there are many. Use low melting 37/63 solder.

Since I dont believe wire has a sound I prefer colors. I use all 9 colors in my amplifiers. With colors you can actually start to see the circuit without a schematic.

If you look carefully you will find some long wires repeated so you could simplify things there. Of course once its built who cares. Just dont bring me an amp with one color wires all bunded up. First thing I do is cut them free.

Also make sure you speaker will be happy with high output impedance (damping is less than 1). Amp loves 16-32 ohms, an Autoformer is a good idea in some cases, no all. 
toddcowles
135 posts
 
@ramtubes,

Thank you for the input and highlighting what’s actually happening in the market.  I’m enjoying the thread and learning a ton.
ramtubes's avatar
ramtubes OP
460 posts
 
@rsf07

 I wish I could tell you more on the specs of the speaker but there's little info. Roger Sanders does use a dbx Venue360 DSP unit he modifies (there are no crossovers or transformers in the speakers that I'm aware of). When you say "direct drive" amps since I'm non-technical what are you referring too? Can you send links to your own direct drive amps?Much appreciated.

I will soon publish something about my amp, but as you can see without your information my specs will do you no good.

I can build up to about 5,000 volts. Beyond that its like building a radio transmitter. 

My speakers work at that peak and 2,500 V polarizing. I contend running the polarizing high for sensitivity causes air gap saturation. Ive heard it!

Once again try to get some info on your speakers. Look at the DIY and ESL forums. Call the manufacturer. 

Here is the essence of direct drive. 

A direct drive amplifier is a bridge where each electrode goes to one side of the bridge. One side goes up while the other goes down. 

The problem with step-up transformers has been covered widely. What is not ever discussed is how much capacitance they have compared to what they are driving. There are very few people designing or making step ups these days and my objection to the Plitron has been covered here in depth. 

The problem is that designing such transformers is close to a lost art. Without some numbers I cannot say if the King transformers are good or not.

I found this link. The minimum is 1.8 ohms at 25 Khz, sensitivity 83 db  http://kingsaudio.com.hk/D001.jpg.

Not horrible, but choose your amp wisely. Its strange that none of their amplifiers will drive this speaker at all. I havent looked at the rest which are rather Martin Logan style. 
noromance's avatar
noromance
9,769 posts
 
@cakyo Use electrolytic capacitors with a 105°C rating over the 85°C versions.
unreceivedogma's avatar
unreceivedogma
979 posts
 
Hi ramtubes,

thank you for that and here’s a followup.

If triodes are low impedance and OTLs like high impedance, what was Jon doing then when he switched the OTLs to triode?

i can tell you that the amps sound better after the conversion, and they are more stable too. The bias and the balance don’t drift anymore.

Jon Specter made the conversion with some guidance from George Kaye of Moscode. Both formerly worked at NY Audiolabs.
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