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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I’d like to add this: I appreciate the fact that there are two professionals contributing here, despite the fact that there is tension that’s been created by disagreement. I’m trying to read through the commentary to the points being made, the examples being given, and the facts. The reality is, there are many ways to arrive at the same destination. I’ve listened to, and owned A LOT of gear in my life, though none, so far, by either of these designers. Some products allow the music to communicate to you, some don’t, and a combination of components may speak to me, but not to you. I know this isn’t a technical question, but I felt compelled to write it nevertheless. 
Also, FWIW, I’ll mention that Keith Herron, whose company and products (especially his phono stage) are about as non-controversial and highly regarded as they come, suggests that with his particular phono stage no loading whatsoever will often be found to be preferable with LOMCs, regardless of the cartridge type. (The LOMC input of his phono stage is FET-based, and it applies a load resistance to the cartridge that is nearly infinite when load resistors are not connected externally, to RCA jacks that are provided for that purpose). And I have found that to be the case in my own system, with an AT-ART9 cartridge having a recommended load of "100 ohms minimum."

I am glad this has been brought up. I met Keith at an audio show (IIRC the last THE SHOW Las Vegas held at St. Tropez). He had his phono stage there and because I didn't see any loading capability on it assumed it was MM only. He quickly corrected me by pointing out the cartridge he was using. When I asked him why no loading feature he provided an eloquent response that went over my head, but after my own testing, from that day forward I have never loaded a MC cartridge, regardless of the cartridge manufacturer's recommendation. Keith added a loading feature in the next design iteration and continues to offer it today and we can probably guess why.
@fsonicsmith 

I think you are mistaken. I don't recall ever entering into any debate of any kind let alone some type of trolling-skirmish with you. IMO, you are once again confused.
Let me ask you this Roger; other than one of Ralph's amps, which modern era top-tier tube amps have you actually sat down and listened to with not just your own planar speakers, but also modern coned speakers across a decent spectrum? I ask because as I have said previously in this thread, you keep referencing ancient amplifiers of the remote past which you conveniently choose to piss all over. Others have asked you this same question too and you have not responded. Are you living in a cave?
I re-entered because I could not resist. I saw that your irascible behavior has continued and not just towards me, so I felt better about re-entering. I do respect you and your knowledge base, but it also pays to be a gentleman. Towards the end of his life, Charley Hansen (you misspelled his name a few posts ago-shame on you) was very vocal about MQA and his debate with JA on another forum became quite heated. Throughout that give and take, both managed to remain polite and civil. You could take a lesson from them.
I brought up Charley Hansen's interview towards the end of his life about his latest iteration of amps finally-in his opinion-capturing the sound of the best modern tube amps. Have you sat down to listen to any of his amps? Have you analyzed why they might sound as they do from an engineering standpoint?
I am into vinyl, thank you. I am the proud owner of a Manley Steelhead, which I bought new. I love it and love Manley. I wish the aesthetics of their amps suited me more. I acknowledge that letting aesthetics get in the way of a purchase decision seems silly. I also acknowledge that Ralph's views on cartridge loading differ from my own. But as you quoted me (accurately), I have 1% of your engineering knowledge and his too. But I have years and years of empirical experience and based upon that, I have chosen to disregard Ralph's views on cartridge loading as simply not applicable to my particular system and experience.


Perhaps I have mistaken you for someone, however your last post was rather heavy handed. But lets shake hands and move on. 

I hope to be brief because this is not on topic. I do not think I have ever mentioned Charley Hansen in any post. Please correct me if I am wrong. I would like to read an interview that you particularly like, could you please provide a link? He made excellent equipment and I can see from JAs measurements he did a good job on the three major characteristics of a good amplifier, one that would drive a wide variety of speakers well. On this I am in complete agreement with Charley. Im not sure why I need to listen to his amps, I am confident they sound find. Charley and I are on the same page with what is important. Though some may take objection to the following here is what I have found:

If you compare several amplifiers that meet the three criterion of damping, low distortion, good current delivery then these are what I call good amplifiers. Good performing amplifiers tend to sound very similar because they are GOOD. Now if we take one of those ampifiers and compare it to amplifiers that do not meet the three criterion (there are more than 3 but the first 3 are the most obvious) in an A/B setup, levels matched, the differences can be quite alarming and immediately obvious on either pink noise or the proper choice of source material. This has been my experience over 45 years of doing this. I invite others to get their opinion. I invite you to come listen, bring any amp you like and lets have a go at it.

In the current setup I am using QUAD 57s and a few cone speakers. I prefer ESLs and find them more revealing. I think everyone knows I moved to Santa Barbara from VIrginia specificaly to work with Harold Beveridge in 1978. As I recall he paid me $500 a month plus royalties on my preamp. I didnt do it for the money I did it to apprentice to a master. 

In the past year I have repaired and listened to a Reference Line SS amp, A big 833 SE amp. Several Single ended 45, 2A3, 300B. Of course I listen to all of mine and aways to the strict A/B. 

As to modern amps, on some we are going backwards. The Cary SLI 150 is an example. While it measured badly it sounded fine to Herb because he played it at the low range of power where the distortion is low. This is a very common occurance at Stereophile. Once a broken EAR amp got a great sonic review and upon test it was discovered to be very distorted about a few watts. However below that level where the reviewer used it there was no appreciable distortion. It is clear to me that most reviewers do not put a high power amp through its paces. Its just not how they listen. 

These days anyone who can get an amp to work at all and has the ability to get it to market ends up doing so. 

Eveanna Manley is a close friend, I have stayed at her home when David was still around. I have sold them EI EL84s. I know the stingray well from the point of supplying tubes. The bias control range is rather narrow, Have you had any trouble getting tubes that will not bias up in the range of the pot? We had do do selecting for some customers. 


Also, while I don’t recall the exact numbers, Ralph has stated in some past threads that he has observed remarkably high levels of energy emanating from LOMC cartridges at ultrasonic or RF frequencies.
@almarg
The Hagerman site shows a 30db(!) peak. I can confirm that.

About 35 years ago I used to subscribe to the cartridge-needing-a-load theory. I set out to build a device that would come up with the correct loading so as to eliminate guesswork on the part of the user, which I was hoping to build and sell.

What I found when ringing the cartridges was that they really didn't ring until you got to some very high frequencies well past audio! This is easy to understand- if you pass a squarewave through one, there isn't much inductance to mess with the squareware at audio frequencies.

So if the brightness of an unloaded cartridge isn't due to ringing, what is doing it? I was lucky- a serendipitous event caused me to realize that the preamp played the bigger role.  At that point it became a simple engineering task to insure that a phono preamp design would be resistant to this sort of problem.
In a way, I did get what I set out to achieve- being able to sort out the correct load, which for all LOMC cartridges is 47K. What is needed is a preamp that is unperturbed by a 30 db peak 100KHz or above into the low MHz.... Not that hard once you know what's afoot.
@ OP. How do you feel about Spectral Audio designing amps with extreme bandwidth? Are there benefits for solid state amps?