Why are separates so much more expensive?

[B3Nut]

Riiight. You guys are seriously claiming that there are people who can hear the difference between class A, Class C, etc? That is a DBT I would love to see!

Class C wouldn't need to be double-blind tested for audio...you would VERY quickly hear why Class C is never used for audio! (Hint: the output devices conduct for a good bit less than 50% of the input cycle.) Class C is only used in the RF output stages of radio transmitters, where the chopped-up waveform is reconstructed by a resonant tank circuit in the plate circuit of the final amplifier before going out to the antenna.

Todd in Cheesecurdistan

 

[cbraver]

Given that the Dynaudios have been shown to be a reactive load, they presented the Pioneer with a load that it was unable to drive. A reactive load causes the voltage waveform and current waveform to go out of phase, which results in little power (wattage) being dissipated into the load but the load still has the voltage across it and is asking for a certain amount of current in amperes to be provided, and if the amplifier cannot provide it the amplifier will clip, supply rails will sag, etc. In some cases this the amplifier or receiver can be destroyed if it doesn't go into protection. Such loads usually don't behave this way at all frequencies, but when they do they can give an amplifier hell. These are the loudspeakers that simply won't perform at their best without the big iron behind them

That's interesting. I've heard that before about Dynaudios, Thiels, B&W and M&K. Power has created night and day differences for both my Dynaudios here on campus and my M&Ks back home. I apparently just choose speakers that are hard to drive, but power has made all the difference. I just wish I would have figured that out sooner. Oh well, you live you learn.

To paraphrase what I feel like I'm getting from this discussion:
To achieve sufficient sound pressure levels in moderately sized rooms, relatively little wattage is needed continuously. Headroom, however, allows for peaks and and an amplifiers ability to deal with reactive loads and difficult speakers. Depending on a speakers characteristics is if it will require/benefit from "big iron" (I like your terminology, haha, I'm a weightlifter). We have established that on a standard 20A circuit: 1224 continuous current draws without negligible effects on the circuit can be 3 times the continuous draw limit, 3672 watts, for short peaks. The power supply in the amplifier also has an affect on the amount of power the amplifier can deliver to the speakers. For doubling perceived loudness, rule of thumb is 10x the wattage. Is this about right?

It would be nice if someone more knowledgeable than I could summarize the key points of this topic at some point.

BTW the Crown is an excellent choice, they build a dependable product and stand behind it. Good folks down there in Elkhart.

Yeah, they have made a fan out of me. One day I'd like a rack of their amps for a nicely powered 7.2 system.


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Another possible argument for separation is that in the short term they might cost more money, but in the long term you'd only need to upgrade your preamp. Might actually save money for the future, since you wouldn't have to "re-power" every time you wanted a new format or whatever. Just a thought, not sure how the math actually works on it and it would certainly depend on the brands.

 

[TLS Guy]

Class C wouldn't need to be double-blind tested for audio...you would VERY quickly hear why Class C is never used for audio! (Hint: the output devices conduct for a good bit less than 50% of the input cycle.) Class C is only used in the RF output stages of radio transmitters, where the chopped-up waveform is reconstructed by a resonant tank circuit in the plate circuit of the final amplifier before going out to the antenna.

Todd in Cheesecurdistan

Nonsense! Peter Walker OBE produced class amps for years. The Quad 405 405 II, the 606 and the 909. The 909 is still in production. These are some of the finest sounding amps ever produced. The 909 is 250 watts per channel into four ohms loads and is unconditionally stable into all loads. It has a low output impedance and is comfortable into loads with complex impedance curves and electrostatic capacitative loads.

This class C feed forward design is a Quad patent which is now held by the holding company that now owns Quad, IAG. For anybody that wants a really good two channel amp the Quad 909 should be high on the list. The other amps are snapped up on eBay fast!

Peter's trick was to use a very good low powered class A amp to correct the error of the output stage. He showed and proved the spec was set by the class A amp. The output, the "dumpers", he called them, provide the muscle.

Here are the current dumping amps powering my system, providing 1.7 KW

http://mdcarter.smugmug.com/gallery/2424008#127077723

 

[Joe Schmoe]

Class C wouldn't need to be double-blind tested for audio...you would VERY quickly hear why Class C is never used for audio! (Hint: the output devices conduct for a good bit less than 50% of the input cycle.) Class C is only used in the RF output stages of radio transmitters, where the chopped-up waveform is reconstructed by a resonant tank circuit in the plate circuit of the final amplifier before going out to the antenna.

Todd in Cheesecurdistan

OK, so I chose a bad example (I know nothing technical about amps.) My point is that if two amps are both well designed, nobody can tell the details of their design by listening, even if they can hear a difference at all.

 

[B3Nut]

Peter's trick was to use a very good low powered class A amp to correct the error of the output stage. He showed and proved the spec was set by the class A amp. The output, the "dumpers", he called them, provide the muscle.

I was not aware of Mr. Walker's ingenious topology, though reading his paper I found it would IMHO be best to consider it a hybrid of A and C rather than a pure Class C since the "dumpers" are there to, as Walker put it, "come to the rescue" of the class A stage. A straight class-C output stage would be unlistenably useless for audio without his method of error-correction. That's a pretty "outside-the-box" design...I wonder why more companies haven't built upon it.

Walker touted the freedom from adjustments and maintenance requirements of this amplifier design. Has this been your experience with them? I notice the absence of any trimpots in the schematic for bias and DC offset. Right clever design...learn something new every day!

TP

 

[TLS Guy]

I was not aware of Mr. Walker's ingenious topology, though reading his paper I found it would IMHO be best to consider it a hybrid of A and C rather than a pure Class C since the "dumpers" are there to, as Walker put it, "come to the rescue" of the class A stage. A straight class-C output stage would be unlistenably useless for audio without his method of error-correction. That's a pretty "outside-the-box" design...I wonder why more companies haven't built upon it.

Walker touted the freedom from adjustments and maintenance requirements of this amplifier design. Has this been your experience with them? I notice the absence of any trimpots in the schematic for bias and DC offset. Right clever design...learn something new every day!
TP

You are correct. However Peter Walker never liked to over state the case, and always specked accordingly. But you are correct, it is class A performance without the high quiescent current of class A. I have had 30 years experience of these amps, and they do not wander out of spec. It is a brilliant design. It is Quad patent, now held by IAG,(International Audio Group).

I would not use any other amp personally. The whole concept was pure genius.

 

[TLS Guy]

I read on-line Bob Carver's SunfireTGA-7400 amp. It states: "Each Current Source output has an in-line fuse to protect your speakers. If one ever opens, there will be no output to that speaker."

I thought fuses alone were not good enough to protect speakers?

Fuses won't. However Bob's circuits are always unique, especially his power supplies. The fuses he talks about are only in the current source mode. This amp appears to have auto shut down. My guess is that this is the speaker protection. I suspect the speaker fuses are to give an extra measure of protection to the amp. They would not likely give any worth while speaker protection.

I also note that the difference in the power consumption quiescent is very small. This indicates some very special features of what he calls this "Tracking power supply". This likely has a big part to play in the whole equation. But I have not seen his circuit. But you can guarantee there will be some unique features.

 

[TLS Guy]

Riiight. You guys are seriously claiming that there are people who can hear the difference between class A, Class C, etc? That is a DBT I would love to see!

You will hear a difference between amps. However it depends on what the amp is driving.

The problem is that speakers are not resistive loads. They are inductive and in some cases capacitive loads. In an inductive circuit voltage leads current by 90 degrees. In a capacitative circuit current leads voltage by 90 degrees. This among other ills, as all at the heart of the problem analog passive crossovers.

Now the speaker designer says to the amplifier designer, make your amp sound as good with any load my speakers produce at any audio frequency.

The speaker designer says to to the speaker designer, your loads are a torture test, and if I have to do a good job covering that eventuality it will be expensive.

We have already had the Dynaudio example above. Now I don't know the current Dynaudio crossover circuits, but that used to publish them and liked a minimalist approach.

Now these speakers use a couple of Dynaudio W17-75 EX with D 28 AF tweeter. The crossover is mine.

http://mdcarter.smugmug.com/gallery/2465549#129315000

Now the impedance drops to almost three ohms, and the phase angle changes from +90 to -90 degrees over the operating range of the bass mids.

Now most amps will just not do a decent job of powering those speakers. However my current dumping amps do. I have run into numerous situations were changing amps can be quite dramatic.

Now the other issue is that the industry tends to be geared to a price range. For speakers at the lower price breaks, I'm sure the designers try and avoid over complex loads, and sacrifice items like total diffraction compensation in many instances.

The other issue is crossover distortion in amps. Now this can be hidden by manufacturers in their spec sheets, as it is an atypical form of distortion. This is the hall mark of the ubiquitous class AB amps. You can see it on the scope best. I personally have become highly sensitized to even small amounts of crossover distortion and I hate it. It is hard to describe audio aberrations in words. However the word that comes to mind is gritty. Amps that don't have it sound much more relaxed, and provide me at least with a fatigue free listening experience.

And it goes without saying that the more accurate the speaker system the more these type of issues are discernible.

 

[Joe Schmoe]

Reading the above response (too long to quote), I can only conclude that the ideal arrangement would be an amp designed for a specific pair of speakers. This suggests that powered speakers (eg studio monitors) may give the best possible sound.

 

[TLS Guy]

Reading the above response (too long to quote), I can only conclude that the ideal arrangement would be an amp designed for a specific pair of speakers. This suggests that powered speakers (eg studio monitors) may give the best possible sound.

Bingo! Yes, that is true, and it will be more true, as class D amps become more prevalent to keep gear at a low price point. Now it happens that class D amps are much more troubled by the impedance curve of the speaker. Class D amps are in receivers now and expected to take over that end of the market. I think there is likely to be a lot of grief over this issue, with people being puzzled as to the differences in a different combinations of receivers and speakers.

In my opinion, the driver and amp will need to be thought of as a unit. One amp per pass of the crossover. As I have said many times, the place for the amps is in the speakers. Combine this with digital crossovers and I think the price points can be maintained with improved results. I think if class D amps are going to be the only solution to the maintaining affordable price points, then it is time to retire the receiver.

 

[B3Nut]

Possibly as powered speakers become more prevalent (even in the DIY world there is some interest in building powered speakers using the popular National Semiconductor power-amplifier chips, I think they'd be great in such an application...heck, if they're good enough for Siegfried Linkwitz... ) we'll see pre-pros becoming more mainstream. Even midline receivers are sporting preamp outputs (the Yamaha RX-V661 being an example) so such receivers are "powered-speaker ready" if I may coin a bad marketing buzzword.

Look for this to confuse big-box clerks even more than they already are, and completely confuse the corporate suits who crank out retail plan-o-grams without much thought to what they're selling (to a suit, a speaker is a bar of soap is a can of coffee is a vacuum cleaner.) Just look at how our Best Buy displays speakers...just lined up hither and yon on shelves like jugs of laundry detergent that happen to make noise...not that you'd actually want to listen to them at that store, given the only source is our city's most annoying teen-pop FM station...yech. No CD player, and the antenna system prevents the receivers from picking up anything remotely listenable.

Todd in Cheesecurdistan

 

[TLS Guy]

Possibly as powered speakers become more prevalent (even in the DIY world there is some interest in building powered speakers using the popular National Semiconductor power-amplifier chips, I think they'd be great in such an application...heck, if they're good enough for Siegfried Linkwitz... ) we'll see pre-pros becoming more mainstream. Even midline receivers are sporting preamp outputs (the Yamaha RX-V661 being an example) so such receivers are "powered-speaker ready" if I may coin a bad marketing buzzword.

Look for this to confuse big-box clerks even more than they already are, and completely confuse the corporate suits who crank out retail plan-o-grams without much thought to what they're selling (to a suit, a speaker is a bar of soap is a can of coffee is a vacuum cleaner.) Just look at how our Best Buy displays speakers...just lined up hither and yon on shelves like jugs of laundry detergent that happen to make noise...not that you'd actually want to listen to them at that store, given the only source is our city's most annoying teen-pop FM station...yech. No CD player, and the antenna system prevents the receivers from picking up anything remotely listenable.

Todd in Cheesecurdistan

You've hit a few nails on the head there!

 

[AcuDefTechGuy]

Possibly as powered speakers become more prevalent...we'll see pre-pros becoming more mainstream...

Why do we even need pre-pros?

Can't we just hook up the 5.1 Analog output of a HD/BD/DVD/CD/SACD/DVDA Universal player directly to the powered speakers and be done with it?

 

[B3Nut]

Well, they'll have to implement bass management, and this minor little detail called a volume control.... I know a lot of players have the bass-management thing onboard if needed, but not sure about volume...

 

[TLS Guy]

Why do we even need pre-pros?

Can't we just hook up the 5.1 Analog output of a HD/BD/DVD/CD/SACD/DVDA Universal player directly to the powered speakers and be done with it?

That would be a complicated hookup. The control and processing has to be done somewhere. The speaker would not be a good location for that.

The most logical sequence is for a preamp connected to the speakers via balanced audio cables. You could develop an digital standard, but I fear DRM ruining it. Also I think ground loops will become a bigger problem as you have eight power supplies around the room. Balanced audio cables would help deal with that. The big advantage of a digital link to the speakers would be doing the final DAC at the speaker. I suppose HDMI could be put for that, but it would add a lot to the cost in all the licensing fees.

 

[AcuDefTechGuy]

Well, they'll have to implement bass management, and this minor little detail called a volume control.... I know a lot of players have the bass-management thing onboard if needed, but not sure about volume...

You don't think they could just add volume controls to each speaker?
I mean if they can add amps and DSPs to the speakers already (i.e. Bang Olufsen BeoLab 5), how hard is adding volume controls?

 

[AcuDefTechGuy]

That would be a complicated hookup. The control and processing has to be done somewhere. The speaker would not be a good location for that.

All the processing (TrueHD, DTS-MA, etc.) & bass management would be done by the HD/Universal player. The speakers (with it's internal amps) would just control the volume.

 

[avaserfi]

You don't think they could just add volume controls to each speaker?
I mean if they can add amps and DSPs to the speakers already (i.e. Bang Olufsen BeoLab 5), how hard is adding volume controls?

All the processing (TrueHD, DTS-MA, etc.) & bass management would be done by the HD/Universal player. The speakers (with it's internal amps) would just control the volume.

Gain (volume) control wouldn't be the issue it would be the loss of all abilities allowed from a processor: audio/video switching, automatic equalization and digital outputs etc...

Processors are around for convenience in many cases not necessarily need. It would take an extremely complicated and full featured Universal player to do such a thing that would eventually become a processor with a player integrated.

 

[AcuDefTechGuy]

Gain (volume) control wouldn't be the issue it would be the loss of all abilities allowed from a processor: audio/video switching, automatic equalization and digital outputs etc...

Processors are around for convenience in many cases not necessarily need. It would take an extremely complicated and full featured Universal player to do such a thing that would eventually become a processor with a player integrated.

Oh, come on, Andrew!

Aren't you going to put amps and gain controls in your DIY speakers?

Be the first!

Patent it!

There's gotta be some hardcore audiophiles out there who don't even like HDMIs and video processing, right?

True, most people would be afraid of such an animal. It would give most people a severe migraine.

But look at the Bang & Olufsen BeoLab 5 speakers!

It has 4 amps & DSPs in each speaker! I think the only thing it does not have is a preamp/gain control.

Okay, please tell me I'm not the ONLY person in the whole wide world that uses solely analog stereo preamps, instead of a processor?

Please, somebody tell me I'm not nuts!

 

[avaserfi]

You probably aren't the only one, but all of you guys are crazy .

There will be absolutely no internal amplification or crossover components in my DIY speakers. They will already weigh enough as is since I am looking at a minimum of 350lbs per tower alone. Add in the nearly 100lbs of amplification and crossover/EQ work needed to power the suckers perhaps more if an idea pans out...Although these units will not be connected directly the speakers will not function properly without the DCX units and amps so in a way they are one and built "together" if that is any consolation .

The real key is picking proper amplification for each driver and that will be done - I will have somewhere in the range of 800-1000W per speaker in the active setup. Does that make you jealous AcuDefTechGuy??! even if they are about a year to a year and a half from completion .