2. amps-preamps
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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.


ramtubes

Showing 9 responses by mapman

mapman's avatar
mapman
22,693 posts
 
Lifelike SPL for me is that what one might hear at a similar live performance in the good seats, not too close but not too far away.

I want my gear to be able to handle it all including perhaps sitting close to the percussion at the symphony or in small club proximity to a rock band. I want to be able to hear it all. I might not be able to in reality but if I can be convinced its very close in my own unique room then that is good enough.

At the same time I want to preserve my sense of hearing so most of the time I would strive to avoid SPLs higher than the mid 80s or so. But I want my system to do it all and never break a sweat no matter what I may ask of it at any given time. That was a key design goal in putting together the setup I’ve had now for several years.
mapman's avatar
mapman
22,693 posts
 
Not my exact pair but there is a pic of the OHm f5 series 3 speakers on this page and mine are identical. 

http://www.e-bnlcafe.com/audioweb/speakers.htm

mapman's avatar
mapman
22,693 posts
 
Back in the 70s selling most popular receiver lines from Pioneer to sansui to Tandberg the more powerful models in a line (generally up to 120 w/ch or so) ALWAYS sounded better at least at moderate or higher levels.


Clipping is always public enemy #1 to good sound. Avoid at all costs. Better to have overkill than clip on that great sounding full range dynamic recording.

Modern louder recordings are more prone to clip as well being louder overall so that ups the ante even more when it comes to how much clean power might be needed.

Also music not reproduced at lifelike volumes is not accurate reproduction rather a scaled down one. Nothing wrong with listening at lower levels but one is not even attempting to reproduce real music accurately that way.

Class D amps may be the most practical ticket to great sound along these lines for many these days that may have never really had one before. Good ones these days sound great, tend to be smaller and more managable, are often more cost effective per watt especially when more power is called for, and are most efficient which lowers power bills and TCO.
mapman's avatar
mapman
22,693 posts
 
I use the receivers only as a simple demonstration of the benefits of more clean power in a line that otherwise is mostly similar in design.

Just my gut feel but I suspect there are many who have underpowered systems that clip perhaps in often subtle ways and then blame the results on a bad recording and never know it.   Been there, done that myself in the past for sure as well. 

Whereas not taking chances with clipping even in its most subtle form is perhaps the single biggest key to getting the best possible results. That and keeping noise to a minimum which is much harder to do in any high power integrated amp or receiver with more circuit and components in closer proximity to each other compared to separate devices.

mapman's avatar
mapman
22,693 posts
 
"Some" would be right of course. 😉

I often listen to peaks a lot louder. You would have to talk very loudly even sitting next to me to be heard. But it never actually sounds that loud which is usually a good omen that distortion is well under control.

System is OHM F5 series 3 speakers (12" Walsh style drivers in refurbed vintage OHM F cabs), Bel Canto ref1000m amps, 500 w/ch into 8 ohm, 1000 into 4 ohm. Room is 20x30 L shaped with speaks in base of L facing toward the long dimension. I normally sit about 10-12 feet back from speakers but they are quite omnidirectional so my listening location can vary.


Sometimes I sit ~4 feet in front and slightly to the left of the left speaker to get a more up close perspective. You can actually do that and retain a coherent  soundstage from most any perspective with these speakers which is perhaps their most unique feature.

I do not have spl measurements but will give that a shot with my cell phone over the weekend maybe and report back.

mapman's avatar
mapman
22,693 posts
 
OK so here’s some SPL measures using db meter pro app on iphone 6 . Disclaimer: I have no info on how accurate this tool is but the numbers I am reading seem reasonable.

So in a samplling of various "typical quality nothing special" CD resolution recordings over several minutes from my closer listening position, I hit peak spl of 99 db and averaged about 86 db. Very clear and amps never break a sweat which I take as a good sign

I would rarely go louder but can and have. I’ve used amps rated at 60, 120, 180 360 and current 500w/ch into 8 ohms. I view the 500w/ch with the big OHM 5s as my insurance policy against clipping at minimum and the current Bel Canto ref1000m amps are the best sounding overall by far especially at higher SPLs. I also seem to hear the correlation between amps with specs that better double power into 4 ohm and better performance overall meaning better sound at least with the big OHM F5s. Not as much with my other smaller OHMs (8" main driver) and even smaller monitor speakers (Dynaudio contour 1.3mkII) and very small Triangle Titus that I also run off same amps.

mapman's avatar
mapman
22,693 posts
 
Never bought by power. Always purchased by sound.

On several occasions with lackluster sound at higher SPLS, I ended up purchasing more power elsewhere and that has worked.


HI, Roger here with a question.

I would like to hear how each of you figured out how much power you needed to buy in watts?

I would appreciate the following information in your response.

Your listening level LOUD SPL (preferably measured at 1 meter from the speaker with a REAL SPL meter. Your low listening level. If you are using a cell phone app then you have confirmed it?

Your speaker sensitivity?

Listening Distance from speakers?

How many watts at your load is the amp is rated to supply?

I figured it out by listening and trial and error over time and based essentially on those parameters as a guide. However specifications alone seldom tell the whole story. The devil is always in the details much of which is never specified. Detailed measurements like those in Stereophile help a lot but I have found there may still be surprises playing real music even with very comprehensive test measurements at ones finger tips, though if done correctly, measurements certainly help with the decision making process of what to try next or not.







mapman's avatar
mapman
22,693 posts
 

This is consistent, btw, with statements I believe Roger made earlier in the thread to the effect that many listeners require less power than they tend to believe.

Yes Al, in your specific case as indicated.

You have speakers that are significantly more efficient than most AND are also very easy to drive as well if I understand correctly, so relatively less watts needed to do things right.

FWIW I heard the 87 db or so efficient Fritz Carrera speakers to teh amazement of many including me knock it out of the park at fairly decent SPL levels (did not measure) at Capital Audiofest off a 8 watt/ch tube headphone amp. Very impressive! The explanation provided for that was though rated less efficient the Fritz use a "series" crossover approach that helps make them easy to drive allowing a smaller amp to overachieve compared to the norm perhaps.

There are many cases where speakers are not efficient and do not present a near perfect benign load to drive. Expect way more watts needed there, perhaps MORE than people might believe.

It can all happen....

My 60w/ch Bel Canto amp does very well with my more typical load OHM Walsh speakers up to a fairly reasonable SPL in a fairly large area. But my 500w/ch Bel Canto amps knock it out of the park with them at any listenable SPL.

Its like comparing a Toyota which drives perfectly fine within its limits to a Porshe.


mapman's avatar
mapman
22,693 posts
 
For full range speakers in particular, aren’t speaker efficiency ratings only useful for determining power needed if they cover the lower frequencies, which is by far where the most power is needed to deliver flat frequency response and avoid clipping?

Don’t power requirements for flat frequency response increase exponentially with lower frequency?

Also FWIW it has been bandied about that manufacturer published speaker efficiency ratings are often let’s just say not completely accurate. True?

Also for that matter do some otherwise highly regarded amps cheat by not even attempting to deliver flat frequency response down to the traditional benchmark low frequency limit for hifi, ~ 20 hz or so?





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