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Old 29th December 2006, 03:09 AM   #1
TriAmp is offline TriAmp  United States
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Hi,

Is anyone interested in talking about Triamping?

I'm in the middle of a triamp project consisting of 3 identical 200W (Randy Sloan) mirror topologies on a single 8x11 inch PCB, including a Linkwitz/Riley 24dB/octive active crossover using a small handfull of very nice LM4562's.

I've just spent the last 5 days laying it out using express PCB and sent out this morning.

I've been a DIYer all my life with just about everything. But I have a special love for audio and building my own amps and speakers. I purchased Randy Sloan's High Power Audio Amplifier Construction Manual when it first came out and it became the spring board to building my first real amp. I've read this book from cover to cover at least 3 times. I really, really like the mirror image topology for many reasons. I've had good success with this first project and now want to use everything I've learned over the past 7 years and apply it to my current Triamp project.

I'm sticking with the Randy Sloan Mirror amp, with some of my own tweaks because it is proven to me to be the best sounding solid state amp ever, (subjective of course). And I've been listening to it for the past 7 years with absolutely no complaints. I am currently triamping and really would have it no other way, especially with the speakers that I built just for this purpose. I won't get into my speakers now, will save the for another post for another day. I'll just mention that I believe they are the best sounding speakers in the world, (a little bias coming out).

So now onward and upward, striving for perfection (relatively speaking). I've used PCB express to construct the schematic and layout and have already purchased most of the parts. I've had to pick and choose very carefully which parts I would use and identify them mostly through Digikey. This was a long and arduous task, but had to be performed first so as to know what footprints were needed in the layout. The last 5 days were spent perfecting the layout, this was indeed a labour of love.

My attachment to triamping is simply because I believe it is an avenue to get the purist sound, with very, very low IMD. I think IMD is one of the biggest reasons for listener fatigue. One does not usually know that he is annoyed with what he is listening to if in the course of long listening span, only that they know they've had enough at some point and feel relieved when they finally turn their system off.

I know I could of designed each amplifier differently because of the vastly different load requirements between the woofer and tweeter, but in the effort for perfect coherency and flatness I opted this route. I will be tuning the input levels for sound pressure level flatness across the triamp because of the different sensitivities that exist across the three drivers. That along with the Iq adjustment will be it.

I'd be curious to know if anyone has done a project like this and what your goals and results were?

Kind Regards,

Paul
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Old 31st December 2006, 11:40 PM   #2
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Greetings Triamp, A merry "Summer Soltice Situation"* and a "Happy New Year" to you. I can't contribute much other than to say that I think you completely correct in follwowing the IMD path. I read an article in the UK mag' "Electronics World" (a year or two ago) which made interesting/scary reading. It was on IM and while I don't understand all the maths the conclusions seemed to indicate that IM had the potential to leave a carpet of low level residuals/muck (Please excuse the esoteric high tech' jargon!) that could be a major factor in disturbing listening pleasure. I then did a bit of thinking. If a system had a band width of, say, 30c/s to 15k Hz which is not extreme. Then even with that fairly modest goal the ratio of highest to lowest frequency would be 500:1. A similar tri-amped system with divisions at, for example, 400c/s and 3,000c/s would only ask an amp' to handle a spread of about 13:1 for a worst case (Bass) and 5:1 best case (treble). Which in the latter case is two orders of magnitude better than the wideband system.
I think this is really worth pondering. I also note that nearly 30 yrs ago (1978) in Collom's great book on High Performance Loudspeakers he has a section on multi amping. He lists several benefits but it is interesting that reduction of IM in the amps is the first benefit he lists. I think what you say is important. Ben Duncan also speaks of the unexpected or disproportionate subjective improvements that people hear even when a biamp system had a x-over at 3,000.
Mind you I don't think it is the sole answer to listener fatigue. I'm persuaded that good amp' stability indicated by good square wave response, and fast settling time are essential.
I've got a grand multi amp design planned which may get built this year (2007) but I'd like to hear of your results. BTW have you got a passive system built and are going to convert it. If so a comparison of the two systems with one channel active would be worth reporting.

Good luck. Jonathan

* speaking from Australia in the Southern Hemisphere that is!
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Old 1st January 2007, 04:01 AM   #3
Minion is offline Minion  Canada
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I have never heard of "Listener Fatigue" Nor have I ever experienced it but then again I don"t listen to much music as I would rather create my own(I guess I listen when I create but it has never fatigued me, well not the listening ,just the Playing)

I guess when you have never used or even heard a high quality audio system you don"t know what your missing.....

I do have a Pair of Bi-amped studio monitors and I do sure like those so I can imagine tri-amping would be awesome....


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Old 1st January 2007, 06:51 AM   #4
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Hi Minion, I hope the season finds you well. Just an historical note:"listener fatigue" is not a recent term employed by the extreme subjectivists. As I understand it the term may go back as much as 40 years or more. I believe it arose when people found early solid state amp's with good spec's didn't sound as good (or were as easy to listen to) as their old valve amps. Again, I'm open to correction, but I think people frist pointed the finger at "cross over" distortion in the output stage and have subsequently looked at other factors such as TID etc. The first reference I have to this sort of observation is in the original paper of John Linsley Hood's Class A amp and I think that dates from '69. I am hesitant in writing in this area as I will illicit a variety of passionate responses!!!!!!!!!!!!!!!!!! And I don't want to get into a fight during the Season of Good Will. Cheers, Jonathan
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Old 1st January 2007, 11:21 PM   #5
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Seasonal greeting Minion,

I am using three way active loudspeakers for about a year an a half. Although there is a marked difference between passive and active operating mode, I am not yet pleased with the outcome.

The problem is that of phase distortion, which I must admit, causes instruments to reveal a different character than in reality.

How do I know. Easy, I am a occassional guitarist in a jazz band and I often use my audio set-up for a few practice lines.

Eventhough I attempted the absolute flat frequency response, the tonal character of the instrument is totally different coming from the speakers than from a set of headphones using a half watt single ended class A amp with wide very bandwidth and high third order intercept.

Although narrow bands does reduce intermodulation products to those falling out of band, phase distortion deteriorates with the number of poles and the filter type.

I agree that phase distortion already manifests itself in the loudspeakers, but adding multipole filters worsens it.

The most satisfying sound I have heard in my 40 years of being an audio fanatic was a KSA100 connected to a set of Tannoy Westministers at my friends place.

I have been trying to accomplish the same performance with multiple drivers and amps but so far without success. My system consists of two 100 watt class A, two 60 watt class A and two 15 watt class A amps connected to B139/B110/T27 KEF horns and still not even close.

There is little possibility of correcting the phase error and my next step will be an attempt to digitally filter the signal. This is not a week-ends work and I assume it will take me most of the week-ends of 2007.

My aim is to digitise the input analog signal and apply filtering and leveling which would allow me to still practice through my set-up. If I can achieve the same on loudspeakers as I can on the class A/headphone system I will already be pleased.

Kind regards

Nico
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Old 28th December 2008, 06:59 PM   #6
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Hi Paul,

Did you finish your tri-amping project? Would like to hear how it came out. You mentioned using G. Randy Slone's mirror topologies. Did you mean his Optimos or TotemPole design or was it design from his book? Would like to hear more about what your overall impressions if you've completed this.

rgds,

--firdaus
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Old 29th December 2008, 02:07 PM   #7
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Quote:
Originally posted by Minion
I have never heard of "Listener Fatigue" Nor have I ever experienced it but then again I don"t listen to much music as I would rather create my own(I guess I listen when I create but it has never fatigued me, well not the listening ,just the Playing)

I guess when you have never used or even heard a high quality audio system you don"t know what your missing.....

I do have a Pair of Bi-amped studio monitors and I do sure like those so I can imagine tri-amping would be awesome....



I get listener fatigue when the music is too loud or been on too long.
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Old 29th December 2008, 02:43 PM   #8
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by nigelwright7557
I get listener fatigue when the music is too loud
But, there are at least two definitions of too loud.
1.) risking long term damage to one's hearing.
2.) clipping the signal.

I hate 2.) for any period of time.
1.) is just tolerable in very short doses.
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Old 29th December 2008, 04:08 PM   #9
Twaksak is offline Twaksak  South Africa
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Triamping
Hi Triamp,

I have also toyed with the idea of tri-amping for my current home sound system but with a different idea than yourself where the power amps come into play. To my mind the current mirror on the LTP makes for a better midrange (voice) frequency and similarly class A is better for tweeter and higher frequency. The bass driver needs the most power and there I would consider the higher voltage class AB power amplifier.

Feed this arrangement from a single input three output active crossover (circuit available from ESP).

Important factors for me are that this must be stereo music intended as well as the front speaker arrangement of a 5.1 system for movies. A final thought is ensuring all poweramps are non inverting.

Just my silly idea
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Old 29th December 2008, 07:57 PM   #10
latala is offline latala  United Kingdom
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Interesting re listener fatique
What kind of active cross overs are you using I have built a no of such systems and found that area the the crossover to be of paramount importance A no of Op amps designs that measured well did not deliver the results when I went to a discrete design with passive xover elements the results were then wonderfull
please tell us more re your system
regards Trev
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