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
@Daveyf, thanks for providing the additional info.

Sounds good re the connections of the REL sub. You have NOT made the mistake I’ve seen more than a few members here describe having made, in which the ground wires of REL subs have been connected to a negative output terminal of an amp having balanced or bridged outputs. Which depending on the internal grounding configuration of the sub and the amp may often work ok, but depending on those factors risks the possibility of hum, sonic degradation, or even damage to the sub or the amp.

Given that, I think we can rule out the presence of the sub as contributing to the consequences of the miswire at the speaker terminals.

Also, while I couldn’t find a manual for the Sonus Faber Guarneri Homage speakers, I found a couple of indications that they are suitable for biamping, including this statement by no less than Martin Colloms in a 1994 review in Stereophile:

The filters are nominally 6dB/octave over the crossover range, augmented by additional components to shape the acoustic output. The treble high-pass section thus has three elements: two film capacitors and an air-core shunt inductor. For the woofer’s low-pass section, the primary element is a large series air-core inductor with an RC Zobel network and an additional film capacitor. The multi-way binding posts allow for normal and bi-wiring, or even bi-amping.
I would conclude from this and from user comments I found elsewhere that it is a near certainty that the high and low frequency sections of the speaker are not interconnected in any way.

Given that, I don’t see how the miswire you described could have resulted in damage to anything. I would have expected the result to be that both speakers would have played, but with poor sonics as a result of the high and low frequency sections being driven with opposite polarity signals. I can’t explain at this point why one speaker would have produced no sound, assuming there weren’t any loose connections. But perhaps Ralph or Roger will have some further thoughts as a result of the additional information.

In saying this, btw, I’m interpreting your statement that the misconnection at the speakers that involved "one positive cable on positive, one negative cable on positive, one negative cable on negative, one positive cable on negative" did NOT mean that the positive amp output was connected to both + and - of the SAME section of the speaker, and did NOT mean that the negative amp output was connected to both + and - of the SAME section of the speaker. In that situation no sound would have been heard at all, from any speaker or speakers that would have been connected that way. Although again, even in that case no damage would have resulted to anything.

Best regards,
-- Al

Thanks, Al. I think that given that I had the cables crossed only at the speaker end...the amp end was wired correctly, that it is unlikely that the amp was connected as in your last paragraph. What I don’t understand, is why the right channel was playing and not the left.No signal to the left whatsoever! Only once i corrected the cabling connection error did the sound return to the left speaker...and all seemed fine.
OTOH, perhaps I hadn’t noticed if one speaker ( the left) was hooked up the way you describe in the last paragraph, Hmm.
I realize I'm only on pg 7 of this wonderful blog, but I must chime in.

Dear Mr. Modjeski,

Thank you so much for taking all of this time to provide such great information for all of us.  Your honesty and humility is so refreshing and the graceful way you handled the adversity of some of these comments has been truly amazing.  I have owned a couple of your products in the past and I can only mirror the other comments mentioned here.   

From michaelgreenaudio on 11-29   

"Sigh, in the best way possible. The RM-5, one of my favorite components of all time regardless of price.

Speaking of Harry, I was tuning up two of his systems, one with the CAT and one with the Classe. I had my RM-5 with me and me and Harry listened to it for about two hours.

Man did I ever love that preamp! You could mate the RM-5 with anything and it would transform that amp and speaker combo. When Kenny started dampening his Pre-amp it was all over for me, I kept the RM-5 close by. It tuned better than all of them. I think I toured with the RM-5 for about 3 years.

mg


I too owned the RM-5 (serial #0023) for about 5 years (89-94) and yes - Man, did I ever love that preamp too!  It sounded absolutely amazing with everything I threw at it, all except for one amplifier.   First off, aestethically, in silver with the older graphics, I thought it was beautiful to look at, with a great fit n finish.  It sounded absolutely wonderful with a B&K ST140, McIntosh MC225, B&K EX442 Sonata, Paoli M70 monoblocks and Music Reference RM-9; unfortunately, it didn't seem to mate up at all well with the cj MV50?  I don't know why because I really wanted to like the MV50.  At one point, there was a little problem with the mute circuit, so I sent it back to you in VA and you updated it the current RM-5 MkII.


Here's the part that gets interesting and has become the basis for my theory on our aural memory.  When the RM5 was with you getting repaired and updated, the dealer loaned me a Dyna PAS2 preamp to go along with my B&K ST140 and ProAc Studio 1 speakers.  After a short time, I really started enjoying the PAS2 preamp and it sounded wonderful and lush.  After a couple of months the RM5 mkII was returned.  You had mentioned the changes weren't very drastic but when I got it back, my ear had become so accustomed to the PAS2, that I really hated to see it leave and actually thought it sounded better in my set up than the RM5.  I understand its all about system synergy so perhaps the PAS2 added that extra lushness to the ST140; whereas with the MC225, the RM5 balanced out its lushness.  And if I had the opportunity to try the PAS2 with the MC225, it would have probably been like putting too much sugar on top of your already sweet grapefruit.  


Unfortunately, while I do not possess the electrical knowledge to be able to repair or build gear, I have learned an awful lot from reading literally 100's of issues of TAS, Stereophile, HiFi Heretic, HFH & RR, Listener and others over the years.  And what I've realized over the 35+ years of being an audiophile and changing gear sometimes seasonally, sometimes less often (whenever I have solid state gear, I'm wanting to change gear a lot more often, and when I own tube gear I make a lot less changes) is that I believe there is an aural memory that we all have that you get accustomed to.  Whenever I make a change in gear, even if its an upgrade, my mind needs time to get used to that new change in sound.  Sometimes, it takes a week or two, sometimes longer for my ear to adapt to the new change in my system to where I can really enjoy the new piece in my system.


I'm grappling with this very issue now as I've recently sold some classic gear for a friend and in a short term have switched from a McIntosh MC225/MX110/Rauna Tyr II combo to a B&K ST140/Technics SU9070 preamp/Rauna combo to a moded GemTune EL34 SE int/Rauna combo and the differences have been pretty profound, but I'm loving the journey.  These little concrete speakers from Sweden were the first speakers I ever heard when I went into my first real high end store in the mid 80's and my jaw dropped & now I own a rare pair.


I apologize for my very long-winded response here, but if you have a chance, perhaps you can shed some light and your thoughts on this non-technical subject. 


Sincerely,

Louis  



      

   

   

Well ramtubes, we have 100% opposite opinions concerning the necessity for well designed power cords.  I am a beta tester for a boutique manufacturer.  I've sampled at least 50 designs and tested them against all types of high end cables.  When substituted at audio shows, they were the equal of or blew away the comparable high end and expensive cables.  The worst power cables were from High Fidelity with their patented magnet design.  (I've have 8 friends and two high end homeowners who did testing on their equipment as well and the latter two dumped their HF cables).  Two posters have thought HF cables are supreme.  We (10 of us), have found them to be hard, bright, forward sounding and harmonically thin on a wide range of tube Class A, A/B SE and SS amps, pre-amps and phono pre-amps.  

I don't have any electrical engineering degree or knowledge concerning transformer design or household current.  Basically, after auditioning so many PCs on so many high end systems, it appears that you could conclude that all the auditioned equipment was faulty do to poor transformer or power supply designs or implementation.    I disagree.  My own various custom made Class A/B tube equipment are greatly altered based on the power cables and I do not believe they are poorly designed.  They sound magnificent.  The chassis and transformers remain cool to the touch (maybe 80 degrees) after hours of use at sound levels averaging 90 db with challenging impedance speakers (Legacy Focus) with 6 - 12" woofers in a 5,000 cuft room.  The EAR 890 amps Class A chassis and transformers are burning up trying to drive those speakers (no problem with the Signature IIIs at 1 ohm higher impedance and 6-10" woofers).  
Hello Roger,

Years and years ago I re-tubed my ARC SP-10 with your RAM tubes and the phono stage quieted down mighty well.  And then a year or so later I heard your RM200 amp at a dealer in Phoenix and that was a very nice sound as well.  Thirty years later, I have a question that I imagine you or some of the other techie gurus might be able to answer.

I swap between amps with some that only have single-ended inputs and others with only balanced inputs and others with both.  My preamp has outputs for both.  I recently acquired a very nice 4m balanced IC.  For the cases when I want to use the single-ended input only amp, the CAT JL-3 monos, I will need to use an XLR to RCA adapter into the amp.  The adapter I bought has the neg line tied to ground.  But this results in the preamp's neg output line being shorted to ground which does not seem to be a good thing.  Would it make more sense to put a 10k, 50k, 100k, etc., resistor inside the adapter from the the neg pin to ground to more accurately simulate what the cable would otherwise see as the amp's input impedance?

Any thoughts here would be greatly appreciated.

John