[lcrim]

The full digital path needs no DAC.  The amplifier is, in effect, the DAC.

[JohnnyLightOn]

It has to have a DAC, otherwise all you'd hear is a bunch of noise like a computer modem.  Something has to turn that digital signal into analog sound, and in this case it's the receiver's internal DAC.

And typically, this internal DAC is a cheap one.  If you have a home theater/audio combo system, the internal DAC in a reciever might be good enough, but if you're building a 2-channel music system, you might want something better.

Think about it: this DAC is your source.  Just like a turntable or CD player, the DAC circuit in the receiver is what you're listening to.  People spend thousands to get a good CD player, half of which is the transport and half of which is the DAC.  The DAC circuit in a home theater receiver probably costs $10.

I admit that DAC chips are getting better all the time, and maybe sometime soon the internal DACs in receivers might be as good as an audiophile DAC or CD player.  But in the meantime, people are getting something for the money they spend on their sources.  Otherwise, everyone would just use a HT receiver with its internal DAC.

[mcgsxr]

Johnny, I know why you say that is HAS to have a DAC, but in this case, that is not the way it is.

The Panny receivers, when fed a digital signal, convert that not to analog, but PCM, or is it PWM, in any case, it is digital right out to the speaker connectors.

There are some threads around here on this, that likely do a MUCH better job describing the reality of how it works, but the Panny is absolutely a digital signal, all the way through.

[JohnnyLightOn]

If what this means is that the Panny does all its manipulation of the signal purely in the digital domain, then at the very last moment converts it to analog with a DAC so the speakers can play it, I understand.

But if it means that it never does a d/a conversion, even at the speaker terminals, then please explain to me how this works.    

[mcgsxr]

Dude, there is no way I can explain this, but here is what Wayne at Bolder mentioned, in a thread about a year ago...

There is no D/A convertor. The Equibit chip changes the PCM signal from the CD player into a PWM signal. The signal is kept "digital" all the way through the amplifier. Right before the speaker connectors are second order passive low pass filters that remove the switching frequency from the signal.

Here is a link to a .pdf file from TI that explains how the Equibit chipset works:
http://focus.ti.com/lit/an/slaa117a/slaa117a.pdf

Hope that helps...

[JnC]

I googled for "TI Purepath" and found some stuff off their website. I'm sure you can find a better explaination if you dig around.

"Q: How are digital amplifiers different?

A: A digital amplifier incorporates a switching output stage that operates according to a principle known as pulse width modulation (PWM). In contrast to the low-frequency control signal used in a conventional analog amplifier output stage, the switching output stage of a TDAA is controlled by a high-frequency digital signal. The high-frequency digital signal is a PWM signal, in which the music is modulated into a fixed-frequency carrier signal. In a TDAA, the modulation process is based on a digital pulse code modulated (PCM) representation of the music signal (or other signal that needs amplification) from a CD player, a DVD player, or some other device.

Q: What is a true digital audio amplifier?

A: A TDAA is the combination of (i) a very high performance algorithm that enables artifact free PCM to PWM conversion, and (ii) a switching output stage (see Figure 1).The digital amplification technology causes the amplifier to have a different out-of-band spectrum compared to conventional amplifiers, i.e., a spectrum that requires attention to produce correct measurements of such audio parameters as dynamic range (DR) and distortion plus noise (THD+N). In principle, a full-bridge TDAA output stage consists of two sets of switches that are controlled on/off by the PWM signal. This way, the small-signal PWM control signal is converted into a power signal with an amplitude corresponding to the output-stage supply voltage. The resulting output is demodulated in a low-pass filter which reconstructs an amplified version of the original input signal waveform, for example, music. The typical demodulation filter is a simple, passive, second-order filter located just prior to the speaker connector.  It is interesting to note that the only analog signal path in a TDAA is the demodulation filter.

Q: What are the features of TI’s proprietary digital amplification technology?

A: •  High power efficiency, i.e., no heat sinks, no fans •  All digital, easy to integrate with digital front-end •  SMD technology •  Low weight •  Small size •  EMC compliant •  High sonic capability

-- Excerpted from: Digital Audio Measurements, TI application report, 1/2001, Claus Neesgaard

[lcrim]

There is no DAC chip involved in receivers w/ the full digital path.  I realize that this concept is difficult to accept at first.  I have been fooling with these for a few years and the value is tremendous.  As an explanation check out this Sony marketing paper, it offers about the easiest to follow explanation I have come across.
http://www.docs.sony.com/release/STRDA3000ES_TWP.pdf

[JohnnyLightOn]

OK - I retract my previous statements.  Thanks for the info.  Sorry!!    

[JeffB]

I am not an amplifier designer so this will be a little off, but you can easily think of the problem this way.
An amplifier accepts two inputs.  One is the signal from the CD player or other audio source.  The other is electric current usually from a wall outlet.  The signal from the source is used to regulate the electric current from the wall outlet.  If the electric current from the wall outlet were not attenuated you would one very loud noise(full amplification).  The signal from the source is utilized to properly attenuate the electric current from the wall.  A digital amplifier rapidly switches the electric current from the wall on and off.  There is no in between.  The ratio of on to off time determines the volume.  If this switching can be controlled using digital logic then there is no need to convert the input signal to analog.

[Rob Babcock]

I wouldn't mind replacing the Griffin P-Wave I use with my PC with the JVC, if it now has a USB input.  I love my P-Wave, but I have two PCs connected with a KVM switch.  It would be cool to use the JVC to connect one computer via the USB & the other via an analog input.  Then I could switch them, which would be handy for making discs.  Plus a tad more power than the 15 Watts I  currently have might be nice.

Okay, and it's another peice of gear.

[James Romeyn]

Thanks so much for the almost-clear-even-to-me 'splanations.

Now, to extend this a bit.  Let's say I'm very happy with my '04 (current- version) Sunfire Theater Grand IV pre-pro & Sunfire Cinema Grand 5x200W/400W amp (8-Ohm/4-Ohm).  I am sold on 5.1 & won't return to stereo.  I prefer playing even the best two channel sources back in DPL IIx.  Speakers are nice VMPS RM30 ribbons, Dipole Surrounds, & Sunfire True Subwoofer Sig EQ sub.

But some of the earlier 'splanations don't quite make sense (sorry).  If there is literally no DAC in the JVC F10 receiver, why have I read (I think, correct me if wrong) that it's digital inputs sound worse than the analog inputs?  I'm asking because it would seem nice if I could just replace both my pre-pro & amp with the JVC.  

If it's true that for whatever reason the JVC sounds much better on its analog inputs vs. the worse sounding digital inputs, I suppose I could just replace my amp only with the JVC, & use the JVC as a speaker amp.  Am I right?

Thanks to all for your time.    

PS: the JVC would have to completely blow away the '00-vintage $3500 Soundstream 300WPC digital power amp for me to seriously consider using it.

[TheChairGuy]

Hey Jim,

The JVC's (both ES1sl and F10) do have DAC's...they are just underwhelming.  But, using a high quality outboard DAC (or player) hooked up thru it's analog inputs makes nice music well beyond it's $229.00 delivered price.  Use some good filtering, and it's virtues become even more attractive.

Nice to hear from ya' again, stranger...John

[James Romeyn]

John
If I could find whatever makes you such a nice wonderful person, & put it in the water supply, we could all enjoy a happier life.  Nice to hear from you too stranger.

I think I get it now.  The digital inputs of the JVC apparently introduce an extra DAC (not ADC) stage, that is bypassed when using the analog inputs.  This sounds strange, & exactly the opposite of what you'd expect (see the earlier posts in this thread).  The above is true because the digital JVC circuits simply use the analog signal to modulate the digital circuitry, which is integral with the 120VDC power supply coming from the wall, yes?  Do I have it, or am I in need of more tutoring?  

For someone needing only 5 channels, is one of the JVC models better than the other?  About my earlier question: am I correct that I could probably use the JVC at the analog inputs to replace a 5ch power amp?  Could/might it help to internally bypass (via minor modification) any of the input gain, switching or attenuator circuits?  I bet you're going to say no, because the input circuitry is all part of the package, & it's either impossible to bypass or it would not improve the performance.

Thanks again.

[TheChairGuy]

Hey Jim,

Given that I'm only about 20 miles south of you, we probably drink the same water.  Mine's filtered tho...no nasty cryptosporidium running inside me    

I'm no EE, and I try to keep to what I do know rather than conjecture about something I don't fully understand, so the technical why's of the superiority of the JVC inputs over its digital inputs are lost on me.  On page 5 of the F10 manual JVC states about it's analog discrete output jacks:

This connection is the best connection method for enjoying DVD Audio sounds.  When a DVD Audio disc is played back, the original high-quality sounds can be reproduced only using this connection

As DVD Audio discs are multi-channel arrangements with higher fidelity, higher resolution and lower s/n characteristics  than CD's, plain old 2 channel CD-led stereo also sounds better in this fashion.  It's just a cleaner pathway to connect thru, bypassing all the DSP and other conversion functions that are enabled with a coax or optical digital connection.

Everyone, I think, that has or once owned the JVC found that any good outboard DAC device was superior to JVC's internal DAC.

The JVC's have no preamp outs, so you are stuck with it as a standalone unit for processing your 5 channels.  If your player has has 5 channel outs  (or 5.1), then connecting them with 5.1 pairs of IC's to the JVC is the way to go to enjoy maximum fidelity (and choosing the 'DVD Multi' position on the selector).

I found the earlier (5 channel) ES1sl model to sound better - more tubelike (and I don't like tube gear as a rather long held rule).  It just sounded...well rounded.  The FM sensitivity was leagues better than the F10's.  However, several of us here had quality issues of overheating (not me, however) and it crapped out when playing diffcult loads like my Maggies.  The F10 sounds a bit less involving, more solid state, but it has the nuggets or guyans (for our Italian friends) to drive the Maggies with aplomb.  So, I sold my ES1sl and happily live with the F10 + Maggie combo right now.

So, I'm not sure if I answered your questions, but that's my take on the situation.

[James Romeyn]

So, people who need high quality 5.1 digital decoding need a good pre-pro ifo the JVC.  

For people who need low-level variable preamp-outputs from any speaker output source: I've had great results, surprising good results, worth trying results, by utilizing a "bridging circuit" common in past studio enviornments: a 10k Ohm series resistor on the speaker output side (source), followed by a 1k Ohm parallel resistor on the load side.  Try it.  If it works with cheap resistors you can buy some expensive ones for best sound quality.  Regardless of the amp's power you should be OK with little 1/4w power ratings, because the impedance minimizes the current flow.

Cheers.

[lcrim]

To clarify for RibbonSpeakers.net:
Earlier in the thread, I pointed out that certain receivers do not require an onboard DAC for stereo (PCM) reproduction-sometimes described as the full digital path.
The JVC receivers are not among those that offer this so-called full digital path.
The Panasonic XR series and many of the Sony ES series maintain the signal in the digital domain until just before it is sent to the speakers.  They are in effect the DAC for stereo sound at least.
My point, taken in context,  was that this is a pretty cool thing because the sound quality resulting was out of proportion to the cost.
The JVC units, while not being capable of this trick have other virtues such as the ability to drive difficult speaker loads.  
 
Multi-channel digital is another beast altogether.  Most of the "popularly priced" players for multi-channel music such as SACD and DVD-A, do convert the format to analog before it is sent to the next stage.  There are, of course many variations on this.  
Many of the popular sound formats associated with DVD video are sent digitally to just about any recent mainstream receiver which can then do the conversion to the format necessary for the amplifiers.  
There are even some players that send multichannel sound formats like SACD and DVD-A digitally w/o an additional d/a conversion, thereby removing a lossy conversion from the chain.  Meridian, Pioneer and Sony have equipment which is capable of this last but at a significant premium in cost.

Hope this helps

[conorj]

From what I've read...it seems like the weak points of most of these lower cost digital receivers are the DACs, ADCs and power supplies.  Given the price point these recievers occupy these weaknesses are understandable.  It would be nice if one of these manufacturers made a no frills affordable two channel amp with a  few inputs and a decent power supply...no dsp, dacs, adcs.  I guess they don't believe there's a market for 2-channel gear anymore though.

[TheChairGuy]

From what I've read...it seems like the weak points of most of these lower cost digital receivers are the DACs, ADCs and power supplies.  Given the price point these recievers occupy these weaknesses are understandable.  It would be nice if one of these manufacturers made a no frills affordable two channel amp with a  few inputs and a decent power supply...no dsp, dacs, adcs.  I guess they don't believe there's a market for 2-channel gear anymore though.

conorj,

If you had a listen to the JVC's, you'd swear their engineers cared about 2 channel.  It sounds plain old good...I'm not sure what level you need to spend to obtain better, but it would take a surprising amount to better this little feller'.

The power supply is linear, according to Wayne/Bolder Cables...a tiny toroid it has and it's sufficient for it.  JVC's claims of 100 watts seems overdone, but it's a dang nice 40+ or so it seems.  That's more than enough to get me decent spl's on 4 ohm Maggies in a 12 x 15 x 8-12' listening room.

The attention to detail on the F10 is really admirable...the receiver has (non-ferrous) copper screws throughout.  That's something I've only seen on Sony ES components....all a whole more than $229.00.

[James Romeyn]

I'm a power glutton.  I like being completely unconcerned with the amp-spkr interface regarding SPL & quantity of power, even with a lot of people over (the almost 100% gelatinous nature of human flesh sucks up power like crazy...have someone of moderate stature stand IFO one speaker channel while you are seated in the sweet spot & see what happens.  Hint: nothing happens, that channel's dead except for reflected sound.  In fact it's a great test to measure purely reflected sound).  

I can have several people over in this 3200 cu ft room & raise the hair on the backs of the their necks.  Not just high average spl, but live-level SPL with absolutely no audible distortion (including room distortion) even on huge peaks of music with high peak to average ratios.  This is wild on well recorded live music.  This kind of power is very addictive & comforting somehow, just knowing it's always there if required.

For the above reasons, I'm quite sure a 40+WRMS receiver would fall flat on its face compared to my 400WRMS@4-Ohm Sunfire sledgehammer.  Maybe not all the time, but it would, sooner or later.  Sound quality wise I'd put Bob Carver's amp somewhere between Ampzilla's original monos & the better sounding Son Of Ampzilla.  

But should this not be the case considering the Sunfire is around $2500 vs. $250 for the JVC?

[TheChairGuy]

The JVC isn't right for everybody and/or situation, but it works well for most....at a most attractive price. For me, it works nicely (super, actually).....for you, I'd say it would be a waste based on your room and power needs.