The complaints can only serve to make me be more clear and maybe explain more.... at least being made aware of how other's perceive my comments, helps.
It helps and is like making a revised book better the next time around.... we can point out some need for the next book version but the books author has to do the work and fill in the details himself.
For others wondering what to call the 2-3 SE transistor circuit with FB to the ips emitter..... (topology has been done with tubes before the transistor version)..... it too already has a name referred to as: Compound- Complimentary configuration.
The push-pull variation is a compound-compl push-pull. Now being thought of as a "simplified' CFA.
Thx-RNMarsh
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If you do not do it we, or at least I will encourage the hell out of you to do so..
😀😛😀Even help if that were possible.
Your excellent CFA of mid power into bridged via current-mirrors for high power? BUt still will need to handle lowZ spkr loads, of course.
Or will it be a scaled up amp from existing design?
Will DADOD and OS and ? get into the SIM topology with you..... ?
THx-RNMarsh
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www.audiomasterclass.com/how-much-power-do-you-need-to-fill-a-venue-with-sound
Recommendations are for only 15dB crest factor -- the max found on pop music samples. So, if you think your crest factor music source will be higher... adjust pwr accordingly. Go for 95dB however and not a max of 85dB.
Agree.... big amps do wonderful things for the sound.
THx-RNMarsh
Recommendations are for only 15dB crest factor -- the max found on pop music samples. So, if you think your crest factor music source will be higher... adjust pwr accordingly. Go for 95dB however and not a max of 85dB.
Agree.... big amps do wonderful things for the sound.
THx-RNMarsh
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During analog magnetic tapes professional recording times, sound engineers were using both Vu-meters and peak meters to evaluate the levels.
Vu meters (with inertia of 300ms) are measuring the instant average level, and were set to -8dB for 0Vu.
Peak meters were tuned to + 12db for max allowed level. With an inertia of 1ms. (Shortest signals were not long enough to notice any clipping on them)
In the same times, the tape allowed some +10dB of overload at 10Khz.
As a total limitation, the best professional gear (mixing desks) allows +24dB before clipping.
But cutting rooms used to limit to +10db / +12 dB the musical peaks before cutting the master to avoid the track to touch the previous grove (well there is only one grove ;-). So the margin was around 12dB most of the time.
With digital equipment, we are in some kind of jungle. Professional digital recorders have their 0dB peak level set for -15 to -20dB from clipping level.
In the record industry, all digital recordings are normalized in order to set the highest level of a tape to this max digital level (100%).
But sound engineers uses (carefully) compressors/limiters, to ensure their musical content has enough average "loudness" to be loud enough in radios.
If we are using digital sources, in our home system, it is very easy to ensure that the 100% level will never clip our amplifiers. If the average level is not enough in this situation, we have to ask ourself questions about the efficiency of our speakers and/or the max power of our amplifier.
On my point of view, any enclosure with efficiency under 90db/w is not accurate. (remember we can reach 96 to 110db with good drivers/speakers).
A little remark about impedances. Because it was harder to produce amps than volts, in tube's times, most of the enclosures were normalized at 15Ohms.
With the arrival of solid state, it was easier to produce amps than volts. So, the average impedances of speakers were lowered to 8 Ohms.
There were a time were it was 'on the mood' to use acoustic suspensions closed boxes, with drivers of little surfaces. With a very poor efficiency. In order to get enough level in the auditorias, manufacturers reduced their impedances to 4Ohms. It is a very bad idea, and i will never use a 4Ohms driver in a hifi equipment.
So, on my point of view, an amp has to be able to give its best at 6 Ohms, witch correspond the the lowest impedance of a 8Ohms speaker at its resonance frequency in a bass reflex.
And, to finish, i would like to point that, when you double the power of an amplifier, you just add +3dB of acoustic level. If we remember that +1dB was set to reflect the slightest level difference than a human ear can notice, we can understand that, between a 100W and a 200W amplifier, the perceived difference is very little.
Most of you, i believe, knows all this, but may-be it can help some others... just my two cents.
While i use a 200W amplifier with my 96dB/w enclosures, even a 75 watts amplifier is overkill for my neighbors.
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Hi Richard,
Not sure what #42 and #44 are referring to. Can you elaborate?
I looked at the paper that Pavel kindly linked me to, but it did not contain the CFA pictures that you had posted. Is that what you are referring to?
Cheers,
Bob
96 to 110dB/W of course ;-)
This means we can reach 114db to 134db of acoustic level with a 128Watts amplifier.
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Hi Bob,
I assume Richard speaks about post numbers in this threads, it makes sense.
In his post no. 42
http://www.diyaudio.com/forums/solid-state/240712-cfa-topology-audio-amplifiers-5.html#post3594808
he suggest to us to study a book, he posted a scan of its title page.
Regards,
Pavel
The circuit that Richard has posted is +/- same as the circuit in the top right corner of the attached document.
I think you mean sensitivity not efficiency and your magic 8 ohm speaker is not a resistor so its never 8 ohms and less not forget them nasty phase angles. As to current , for some reason low freq Bass notes love them , a 4 or 2 ohm bass driver sounds different (from 16/8 ohm drivers) and even with high sensitivity speakers the dynamic headroom allowed by the additional power adds life ..!!!
Just saying ...
Hi, a.wayne.
My 'magic' speaker is made of a very ordinary 98dB/W, 12", 8 Ohms bass driver in a bass reflex + horn with a 1" compression 16 Ohms driver from JBL(>110db/W) + a 18", 8 Ohms JBL sub bass driver (99dB). The overall impedance curve is 6 Ohms, flat at -0, +0.5 Ohms from DC to 50KHz and the global efficiency (sensitivity ?) with passive filters is 96dB/W.
Indeed, a 2 Ohm charge at low frequency will sound different, as my 1200W power supply is not unlimited. In this particular case, different means worse ;-)
The result is powerful enough to make-me unable to push this system to its limits without serious damage to my ears and the glasses of my windows ;-)
My course was not for power, but for dynamic, little details, no distortion and transparency. But this is out of topic, i just wanted to point that the best way to reproduce high levels is speaker side, not monstrous amplifiers. I believe the best compromise power/ transparency/micro dynamic is somewhere around and under 200W for a large band amplifier. With my speakers, the Lazy Cat VSSA was powerful enough to drive my system at outrageous levels without clipping. Anyway, my protection system don't allow them.
Not to forget that, if we want to benefit from the advantages of bridged amps, this 6 Ohms impedance will charge each amp with 3 Ohms, i would not like half of this, i remember my 'Orthophase' attempts ;-)
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Looking for a number to use?
That phase angle which the amp has to contend with raises the current requirements in the OPS a lot (eg higher power amp).
60 degrees might be a good number to use.
We should aim for the effec of typical home speakers. I have settled on a conservatively rated 250W/channel. But double that if my high-ish effic or sensitivity speakers are 3dB less (for my listening room size/volume and distance and average room reverb time).
[musicians amps use very high effec speakers - Celest... is perhaps the highest....so the typical 50-100W amps will put out the most spl possible.]
THx-RNMarsh
That phase angle which the amp has to contend with raises the current requirements in the OPS a lot (eg higher power amp).
60 degrees might be a good number to use.
We should aim for the effec of typical home speakers. I have settled on a conservatively rated 250W/channel. But double that if my high-ish effic or sensitivity speakers are 3dB less (for my listening room size/volume and distance and average room reverb time).
[musicians amps use very high effec speakers - Celest... is perhaps the highest....so the typical 50-100W amps will put out the most spl possible.]
THx-RNMarsh
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Old games around CFA -
And, one I liked for the topology.... never tried it though.... not optimized. The values are now probably wrong for the change I made to it. Still in my Micro-Cap files on an older computer. Maybe a SIM guru here could check it out and finish it using best devices and their models.
THx-RNMarsh
And, one I liked for the topology.... never tried it though.... not optimized. The values are now probably wrong for the change I made to it. Still in my Micro-Cap files on an older computer. Maybe a SIM guru here could check it out and finish it using best devices and their models.
THx-RNMarsh
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Though I appreciate that in this forum and with high efficiency speakers lower power amps can be used, in consumer devices this is just not the case. Today I would like to see how many homes have large 15" cone drivers or even 10" drivers that are not made as subwoofers only. The majority of even the best home speakers are now tiny, women have bought into the notion that we don't have to have our large speakers in their living rooms, and many men also, and now we are having to deal with very small sized speakers. So the paradigm of the high efficiency large format bass speaker and a compression driver on a horn is only for very few people. What are those who have to deal with this scenario to do?
I for one am working on small format speakers that just so happen to need the high power output that some of these CFA or VFA amplifiers are capable to output. It takes power to drive these speakers to the higher spl levels that people may still want when listening to music, there is no way to make a small speaker put out the levels required without excursion and the power that takes. Still not being convinced that "most" class D amplifiers are up to the task and not finding much in the way of high fidelity high power with monolithic chip amps this seems the last resort, discrete amplifier circuits with large voltage and current capabilities.
Anyone want to show me how I am missing the boat here? I do still have 15" bass speakers and compression drivers in the house but that is more than rare these days, they are looked at as dinosaurs today by anyone who notices them.
I for one am working on small format speakers that just so happen to need the high power output that some of these CFA or VFA amplifiers are capable to output. It takes power to drive these speakers to the higher spl levels that people may still want when listening to music, there is no way to make a small speaker put out the levels required without excursion and the power that takes. Still not being convinced that "most" class D amplifiers are up to the task and not finding much in the way of high fidelity high power with monolithic chip amps this seems the last resort, discrete amplifier circuits with large voltage and current capabilities.
Anyone want to show me how I am missing the boat here? I do still have 15" bass speakers and compression drivers in the house but that is more than rare these days, they are looked at as dinosaurs today by anyone who notices them.