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.


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ramtubes's avatar
ramtubes OP
460 posts
 
@bdp24 

Thanks for the compliment and notes on the RM-200.

I was also introduced to the Tympani speakers in 1973-4. At the time this product could only be bought from ARC dealers and was essentially a speaker that Jim made for Bill. Both were just starting out. At the time the largest amp ARC made was 75 watts/ch. Bill also required you buy his electronic crossover for the 3 way system which was a total of 8 panels. Those were the days. Great sound at nothing like today's high prices. Marketing took a back seat to engineering not its the other way round.
ramtubes's avatar
ramtubes OP
460 posts
 
@shkong
I really like the sound of SET over PP.You can see my audio history in the below link.https://forum.audiogon.com/discussions/the-most-musical-sound-in-my-40-year-s-audio-historyThanks again for your kind advice


SE amps are often great with sensitive speakers. The 805 tube is an interesting transmitting tube. These types of tubes often exhibit low distortion over their entire power range. It takes power to drive them hense the 300 B is actually doing some work here. We used a 300B in a single ended amp to drive an 833 output tube. The 833 is a monster of a tube, requiring 10 volts at 10 amps of very clean DC for the heater. That part was quite challenging. I think we went for 100 watts of audio power, all transformer coupled. 
ramtubes's avatar
ramtubes OP
460 posts
 
@unrecievedogma
I think the debate between cone and electrostatic is reminding me of the great cable interconnect debate. Could it be that this is just personal preference? Or even that my ears are just trained and accustomed to whatever cones do to the ears? I’ve listened to my share of electrostatics. Some were very impressive. Some were better than my Altecs in many respects. But none moved me.


All debates with audiophiles come down to personal preference. If you like your system then great. My friend Bruce DePlama used to say. "You go to Roger's house you hear Roger's sound. You come to my house you hear my sound".

The Altecs are loved by many. Nothing wrong with them. No one is overcharging you for them. They are efficient and work well with smaller tube amps. 

I would hope we all agree that speaker differences, speaker/amplifier interactions, are far more obvious than cables.

I hope we all have decent systems, without un-intended peaks, without horrible distortion, without noise. If you have one of those problems lets fix it.
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bdp24
9,874 posts
 

@ramtubes, Roger I happened to make my first visit to a new hi-fi shop just opening in Livermore, CA in 1973, Audio Arts. It was a 1-man shop, that man being Walter Davies, now the maker of the great Last Record Care products. And as luck would have it, that was the same day Bill Johnson was delivering and installing a complete ARC system in his new dealer Walt’s listening room; a Thorens TD-125 MK.2, a Decca Blue mounted on a prototype ARC arm (it never went into production), an ARC SP-3, and Tympani T-I’s (as you said, at the time distributed by ARC) bi-amped with a D75 and D51.

I was just a kid, and spent a couple of hours getting an education in high end hi-fi. A couple of months later I had that exact system (with a Decca arm) in my own room. All set up and connected, I pushed in the power switch on my SP-3, and immediately heard a "poof" and smelled the aroma of something burning, which turned out to be a resistor in the power supply. Welcome to the wonderful world of using under-rated parts! High End? Not by my definition!

ramtubes's avatar
ramtubes OP
460 posts
 
@fleschler   
Funny that the latest ARC amps I've heard sound greyish, muted dynamics, etc. My friend has an ARC 75 which is no match for his Classic 60s or my voltage regulated amps. Worse, his amps, Ref 5 preamp and $10K CD player all have had significant break-downs after only a year or two. Yuk!

That is how I would expect the ARC amps to sound given their measurements. Sometimes there is a correlation. I see we still have reliabiity issues. I feel for ARC and the many people who work there. When Bill was selling the company he had 10 requirements of the buyer. One was to not move the company. Bill did some nice work, however he left a few things undone. He never made a short circit protected power supply. That makes techs and the owners who pay them really unhappy.  He had a thirst for new products which resulted in many mods because the first releases were unfinished designs. When a preamp goes from SP-6 all the way to SP-6E thats a lot of mods.

My question remains, I'd like to know what you opinion is of the VAC IQ (continuous autobias) amplifiers. They sounded great wherever I heard them and they appear to be conventional designs well executed. They must have good impedance outputs to make them adaptable to drive many types of speakers like your own amps.

VAC seems to be doing some good work these days. I have worked on one of their big preamps, it was nice but picked up hum from a power amp 2 feet away. We were surprised. 

Autobias can be done many ways. The problem with many autobias schemes is that they shift bias in the wrong direction when the music gets loud (above the class A region). If Kevin worked it out well Kudos to him. I still prefer a bias pot and meter. My bias is so stable as to be checked only a few times a year. 

However many  are looking at amps that dont need adjustment as my newer RM-10. We have found that many of the new tube generation do not like the though of having to use a meter and adjust something.

I am very happy that I put the LEDs in the RM-9 in 1985.The bias circuit lended itself to them and balancing the DC coupled driver was important. When I did the RM-200 bias LEDs were a complicated option due to the circuit and the driver needed no balancing.

I feel in some ways I'm punished for putting a supermatched pair of transistors at the input and thus entered the "Hybrid" land. As always I choose the parts to do the job best. A tube in the input would have gone back to Driver Balancing pots, CMRR pots, tube selection. Sometimes doing an audiophile a favor does one no good. 

Well, at least "Mikey likes it"
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