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 read both links. The first is common knowledge and nothing about RF. The second is long so if there is something in particular you want to me to read please quote it here. Are we playing "Wack A Mole’ here?

Im really tired of RF being the devil for everything. Usually if there is RF sensitivity you will hear an AM radio station. If there aint no radio coming in there aint no RF. Lets get real please.
For the What’s Best forum, just look at JCarr’s posts. No whack a mole- not even sure what that comment is even supposed to mean.

No-one has said RF is the devil for everything except you, just right now. But these two links did point at RFI (or ultrasonic or near ultrasonics, in the case of MM cartridges) being a problem with LOMC cartridge operation... I don’t see how that can be construed as ’everything’.

Ralph has not honored the stated purpose and rather come here to once again to hawk his paradigms and unusual ideas about cartridge loading and RFI. You are into vinyl I see. Do you agree with his loading suggestons? Dont we load a cartridge to change its sound? That last one about loading a cartridge for the sake of the preamp was so out of the world. Most of just a juse a ferrite bead to stop RF from coming in.
This statement is outlandish and false. Please note though that I am not attacking you, just the veracity of this statement, unlike you who sees fit to attack me personally. I have honored the stated purpose, as I am a designer of amps and my door is open.

If you say you looked at both links and came away with the idea that RFI has nothing to do with it, the only conclusion that can be drawn is that you didn’t in fact read the links or failed to comprehend their significance. When we are talking about noise in the MHz range, that’s RFI, especially when it is the result of excitation of a tank circuit.
I do agree, Ralph should have never entered this thread nor should you. I dont see a question and I dont see a contribution. You left, said you wouldnt come back, but you did.
Roger, you seem to appreciate my being courteous when I offer corrections (which you seem unwilling to accept), but you seem unwilling to be civil in return.


Contrary to yours and others impressions, this is not your thread- its a public forum.


As a bit of a hint, I find that keeping decorum in spite of personal attacks (including outright untruths) is a simple tool to maintain credibility. FWIW I have an EE just like you and I don’t engage in pseudo science any more than you. I can prove everything I say. I suspect that you are not *as* acquainted with equipment from the old days- 1960s and before, as I might be. You have said that my talk about the Power Paradigm and the Voltage Paradigm is the pseudo science to which you refer; to me that just suggests that you don’t have a grounding in history. This despite my showing an example of what I was talking about (one that we have discussed prior); in spite of that evidence (the Fisher A-55 I linked, and any amplifier with a ’damping’ control) right in front of your face, yet you still accuse me of pseudo science!


But:
You are getting out of hand here. This entire thread is in violation of Audiogon posting rules, for the simple fact that you primarily use it for promotion.
On occasion I get accused of the very same thing, but those that do so will note that I have yet to start a single thread on this site (despite being active on it since its inception in the 1990s), let alone one that focuses primarily how great I am in tandem with how great my products are, all the while demeaning (in some cases, falsely) others. I do mention my products when asked and also in the context of related questions (such as balanced operation; quite often because there is much misunderstanding about how balanced lines are supposed to work).

This is not your thread! - if that were the case it would be on your website. Instead you are posting on a forum that is open to the public. My presence here has mostly been to keep the record straight when things have gone off the rails. The 6SN7 thing and the cartridge thing are two examples.

I can see that it bothers you as much as it does me when you see things that are untrue. If I can offer a bit of advice:We often go thru live with made up stories. In fact we live as if those stories are true. When life and the stories don’t agree we suffer. At that point, to end the suffering the best thing to do is drop the made up story. You will note that I do not attack the voltage rules as being made up. I regard them as an engineering solution, but one that has some bad applications. I’ve pointed out why earlier and don’t need to repeat myself. The old power rules are one way out of the resulting colorations of the voltage rules, but they come with their own price (limited market, for one, more fiddling and more careful equipment matching for another).


IOW, if you think I made up the idea of the power rules, you are simply not grounded in history.


I am perfectly happy to have that conversation on a different thread. I’ve been having this conversation for the better part of 30 years and its not been debunked by any engineer that listens- only those who don’t and are further unaware of how the voltage rules were developed.

I dont mind any designer coming here if we both understand electrical science in its accepted current form and speak the proper language. If you want to read made up science there are pleanty of other threads on here for that.

I have a a question for Ralph, Why have you not sent an amplifier to Stereophile for review? They have reviewed all of mine and preamps too.

I got my degree at the UofM. I don’t subscribe to anything made up. Enough with the innuendo already- if you don’t get what I’m talking about, just say so, otherwise lay off. John Curl got it, Nelson Pass got it, other engineers on this site got it...

Regarding Stereophile:
We sent a preamp to TAS for review. It did quite well- the reviewer bought it and said so in the review. Then he moved over to Stereophile prior to the publication of the review; it got published there. At that point we knew we were in trouble when we got the news that he had jumped ship to Stereophile, as we had been warned by people from several companies (ARC among them) that if you can’t afford advertising with them, they will treat you as a sacrificial lamb to show how hard hitting their reporting is. Sure enough, some months after the initial review was printed (in which I had to challenge JA’s measurement comments, as the Audio Precision at that time didn’t properly support a balanced input, despite it appearing so- a different conversation), and after being asked if we would advertise in the magazine, the reviewer was later instructed by Stereophile editors to print a followup. Apparently when he was installing defecting tubes in the preamp, it didn’t work right. We tested several of those tubes; one was a Telefunken that was so dead that I thought my tester was at fault as it got no reading at all when the Telefunken was lit up. I had to test some known good tubes to know that I was not going nuts! To date I’ve yet to see another 12AT7 that bad that still had a vacuum. We got blamed in the followup for that failing on the part of the preamp. Do you have amps and preamps that function correctly on bad tubes?

A second product, the MA-2, was destined for a nice review in 2004 by Paul Bolin when he was with Stereophile, but a company that was trying to take over my company threatened Stereophile with a lawsuit if they didn’t give the amp back to them. Paul let me know this was happening, and since we owned that amp I went and picked it up. While the lawsuit never went down, JA was sufficiently rattled by that event that he removed Paul from the Stereophile staff.

Regarding the issue of cartridge loading, in a past thread here Jonathan Carr (Lyra cartridge designer, who I believe has also designed some phono stages) stated as follows:

I should now debunk another myth regarding loading, which is that low-impedance MC cartridges are insensitive to capacitive loading. OK, the MC cartridges themselves aren’t particularly sensitive to capacitance, but the inductance of the cartridge coils will resonate with the distributed capacitance of the coils and the capacitance of the tonearm cable to create a high-frequency spike, and this spike certainly is sensitive to capacitance. In general, the less the capacitance the better. Having more capacitance (across the plus and minus cartridge outputs) will increase the magnitude of the high-frequency spike and lower its frequency, neither of which is good news for phono stage stability or phase response.

Generally speaking, the greater the capacitance across the plus and minus cartridge outputs, the heavier the resistive loading needs to be to control the resulting high-frequency spike. Conversely, less capacitance allows the resistive load on the cartridge to be reduced, which will benefit dynamic range, resolution and transient impact.

The relevance of the Hagerman link Ralph provided in his previous post is that it illustrates the high frequency resonant peak (i.e., the "spike") formed by the interaction of the inductance of the cartridge and the load capacitance that it sees.

I am not in a position to say whether or not the **only** relevance of resistive loading of a low output moving coil cartridge is to control that peak, and its potential effects on the particular phono stage. However I certainly wouldn’t consider the possibility that it could often at the very least be an important factor in the performance of a system to be "out of the world," as Roger stated.

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.

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."

Finally, without placing blame (although I have my own thoughts about that) I’ll just say that it’s a shame that an otherwise wonderful thread is compromised by the fact that two long-time designers of highly regarded audio electronics can’t deal with each other in a more respectful and matter-of-fact manner.

Regards,
-- Al
Haha... Nimble Tube-Roller Society! That exchange must have been just before I started buying stereophile (1986). I agree that having the freedom to choose different power tubes for the same amplifier is liberating from an owners standpoint (well, at least THIS owner!). It is also a very good point that buying something designed around a “single source” part is risky. I had an H.H. Scott LK-150 power amp (built in 1961) that I’ve used 6550, KT88, and now KT120 power tubes in. My son is using the amp now. That’s still a great amp (in my opinion). My point is that even though those tubes are from the same “family”, it was great to be able to try different flavors in the same amp. Regarding preamp tubes; I’ve had preamps that were built around different tube types, and they all had their strengths and weaknesses. I didn’t really attribute those differences to tube A vs tube B. But I knew not what made them sound the way they did. That’s why I wanted to take this opportunity to ask someone who has to make a decision about which to use. As you said, how can one compare between tubes used in completely different units?
@fsonicsmith

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?

Other than designing amplifiers Roger has a pretty robust repair business and is an authorized repair shop for Allnic. Lots of vintage and modern equipment, solid state and tubed, crosses his path. I know because for the last 3 years I have been the repair intake person. As he has mentioned previously, Roger also measures anything he can get his hands on and has notebooks full of test notes for equipment that spans the ages. Also, Roger does not design planar speakers, he designs electrostatic speakers, there is a difference, perhaps you might read up on that.

Are you living in a cave?
Actually he has quite a nice house with a very nice system.

When we’re bored we go visit local folks to hear their modern systems (this past weekend we heard Avantgarde horns with their associated electronics) and Roger is pretty active with the SFAS, with the responsibility for running the upcoming phonostage shootout in January. My point is that Roger is very up to speed regarding current designs and design "philosophies," but testing and measurements are still critical to producing quality components and the principles behind these measurements go back in time. Ohms Law is still Ohms Law after all. Unless I missed something it hasn’t been updated or modernized.

Same is true for balanced amplifier design. Today we see all sorts of designers referring to their equipment as balanced. In many cases the design is just balanced at the input, not throughout (then there are the pseudo balanced designs). The only person I know that has been doing true balanced tube designs consistently (and in adherence to the balanced standard) has been Ralph Karsten and he’s been at it for over 40 years. However, the concept is not so modern, in fact it wasn’t developed for home audio use, but rather first utilized by the phone company to drive long cable lines (although I am unclear if the phone company developed the standard which I have heard referred to as the 600 ohm standard).

So Fred Sonic Smith (I assume that’s what your handle references) perhaps you should leave us. You bring zero value, you do not possess the knowledge or credibility to refute anything Roger says and although their opinions greatly differ, at least Ralph has the credentials and reputation to partake in those discussions. Let him do so if he wishes, he needs no help from you.

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.

Actually that was your cue to leave and stay away. You re-entered because you enjoy trolling here.
(although I am unclear if the phone company developed the standard which I have heard referred to as the 600 ohm standard).
The 600 ohm aspect has to do with the spacing of the lines on telephone poles. You've seen them many times - that spacing causes the resulting transmission line to have a characteristic impedance of 600 ohms. This means that if terminated by a 600 ohm load, there will be no reflections at the termination in the transmission line- its not that the impedance of the transmission line is 600 ohms.
So output transformers driving a balanced line were set up to drive a 600 ohm load. When the balanced line system was brought into studio and radio station applications, the 600 ohm became a standard which stood for many years and many pro audio components still support it.