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Class D Switching Power Amplifiers and Power D/A conversion

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Old 13th January 2008, 10:19 PM   #21
Daveis is offline Daveis  United States
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I was using 3 Panasonic SA-XR7-'s in a tri amplified 3-way system.
My crossover was purely digital. So the sound was digital from source PC all the way to the Panasonic's.

I was also using only digital toslink inputs.

The headphone amp on them is quite good considering the cost.

I've also used the same amp in a Home Theater system with NHT ST4 speakers.

I admit to being a person who was hyping the sound of these amps along with the crowd on htguide.

They seem to do well on simple lower order crossover 2-ways.

And they don't drive larger speakers and subwoofers with much authority.

UCD amps on the other hand sound as good as good Class A/B with small size and high power.

In order I prefer from higher preference to lower I prefer...

Threshold T-200 Class A
UCD 180
Aleph30
Rotel multichannel
Tripath (would be higher but I was using 15-watt variety)
Panasonic

The Panasonic does have small size, almost zero DC offset, no turn on or turn off thumps going for it.

DA conversion has to happen somewhere. That the Panasonic does it in the amplifier section doesn't give it any advantage over other quality amplifiers. I used to think that it would magically have better sound because of this.
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Old 13th January 2008, 11:06 PM   #22
jkeny is offline jkeny  Ireland
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Thanks Daveis for your analysis,

My speakers will be crossover free full range Jordan JX92S, the same as t-head, so when you say they "do well on simple lower order crossover 2-ways" would this mean they are even better on above speakers?

Would this fact change your preference order? Is this order based on speakers with higher order crossovers?

What speakers & DAC are you using with your preferred stereo system?
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Old 14th January 2008, 02:20 AM   #23
john65b is offline john65b  United States
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Quote:
I'm guessing your take on the sound of the panny amp with the Magnepan MGIIIa speakers was based on using the analogue in rather than digital in? Was it also based on single channel rather than bi-amping?
Nope - I never even tried the analog in on any of the XR's - always used Digital inputs - and never tried the XR45 "Party" mode for biamping the maggies

I am currently building a Krell KSA-50 Clone, and an Aleph 60 and expect either one of these to best my current "reference fav - UCD

My preference -

UCD400AD - ESP P-101 (biased into Class A) very close tie
P to P Gainclone (but not on maggies)
Homebuilt 6L6/6SL7 Tubeamp
Tripath TA3020
XR45
XR50
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Old 14th January 2008, 12:04 PM   #24
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Hi.

@ DAVEIS: AFAIK the Panas are full digital PCM2PWM converters.
There is no DA conversion in the chain before the signal hits the output filter.

The Panas are using the same chips as they are used in TACT
and Lyngdorf amps. Though AFAIK TACT is getting selected quality chips.

The key is to drive them digital on the input and bridged on the ouput. As far as I read they need the PS to be tweaked.

As we all know - the key for a digital amp to deliver best performance is the power supply, which can't be high quality
at the price the Panas sell.

Of course you'd better make sure that you got low jitter digtial source.

I believe full digital amps are the (near) future. I don't think that
many of the players in the industry will be happy about it.
Think about it - All the traditional DACs and Amps would be obsolete!

For the time being my choice of amps are battery-powered Triptah 2020modules on a 100db SP speaker and ICE-Power for the subs.

Cheers
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Old 14th January 2008, 02:37 PM   #25
jkeny is offline jkeny  Ireland
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Hi soundcheck,
Quote:
As we all know - the key for a digital amp to deliver best performance is the power supply, which can't be high quality
That's why I wondered if running this amp off batteries might work - don't know how PS vol control would work with this? - This mightn't be a problem though as I could control vol outside of unit!

I wondered if there is anybody who modded one & can relate experiences!
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Old 14th January 2008, 03:37 PM   #26
zacster is offline zacster  United States
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I've been looking at this one as well, but for my purposes the price alone is a clincher. I'm building a second HT room in my house and wanted it to be low budget. Combine the price with a decent sound, if not universally praised, it has to be a winner. It would be driving my old Spica TC-50s, very inefficient IIRC.

I was at J&R just yesterday looking at it. The thing that struck me the most was the weight, or lack of weight. I guess without the need for huge heat sinks and transformers the thing doesn't weigh all that much. It also didn't have pre-amp outs, which means it can't be used with a separate power amp. This would be a problem for me in my main HT setup as I have a tube amp connected to my main speakers. My original HT receiver has lost 2 amp channels so I thought of replacing that as well, but the 57 doesn't have the flexibility I want. For $80 plus shipping I can get my Outlaw fixed, but that thing weighs a ton and costs $$$ to ship.
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Old 15th January 2008, 07:22 AM   #27
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Quote:
Originally posted by jkeny
Hi soundcheck,

That's why I wondered if running this amp off batteries might work - don't know how PS vol control would work with this? - This mightn't be a problem though as I could control vol outside of unit!

I wondered if there is anybody who modded one & can relate experiences!
I've choosen a 12 V SLA (Northstar NSB90) - it works great with the Tripath. My Icepowers do sound much worse even though I tweaked the whole mains path heavily.

Most of the normal Class-D amps run with powerrails starting at
+/-36V to +/-60V. I wouldn't recommend to set this up with batteries. That's gonna be quite some effort if you want to cover this with high quality batteries. There are quite some thready around here on great SMPS supplies for these kind of amps.

I am not sure though if a good DC/DC converter would do the job. I'd happy to try e.g. a UCD180 over a DC/DC converter.
Perhaps something like that could even work for the Panas.
I am wondering what kind of DC/DC transformer the guys in the car-audio arena are using.


Cheers
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Old 15th January 2008, 07:45 AM   #28
jkeny is offline jkeny  Ireland
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I picked up the service manual & schematics for SA-XR55 & SA-XR57 today. From a quick glance it looks like the PS board is delivering +/- 15V DC. Could this be so - 7*100W amp from 30V rails?

If so 2-3 * 12V SLA batteries would probably do but I need to study how PS vol control is implemented!
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Old 15th January 2008, 09:11 AM   #29
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Hi jkeny,

I plan to get a XR-55 too but having the same problem as u and not sure how to import from US. The Panny AV amps are not sold here in HK.

I think I'll ask one of my friend to bring it to me from Canada when they come to HK.

But I am really interested in the XR55 service manual. Is there anyway u can take some digital image of the schematics and email to me.

I am using same but older version of the digital chip inside XR55 (Ti eval board), I found the sound to be pretty good but I don't think it is enough (without biamp) to drive my 4 ohm speaker.

BTW, I had the Jordan JX92s in a tall cab, I couldn't get it to sound good, it is a very difficult speaker to drive. I sold it in the end. The Visation B200 is a much much better fullrange IMO. Even my FE103 sound better than the JX92s.
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Old 15th January 2008, 11:12 AM   #30
jkeny is offline jkeny  Ireland
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What no SA-XR's in HK! Yea, Panasonic must have a weird global marketing plan.

I just dropped into a Panasonic retailer looking for the SA-XR55 & it's no longer sold - the 57 he could specially order in for €529 ($786), no home trial given or possibility of auditioning! This was not a massive retailer mark-up price it was the RRP from the panasonic e-biz web-site. When I told him the same model was <$300 in US he said it was all due to cost of European electrical CE approval, some story eh!

This is why he doesn't stock the receivers - they're not competitive at that price!

Hi ChuckT, if you PM me your email I will send on the full service manual.

I got it from Sharefx.com - great site for uploading & downloading service manuals for all electricl gear, amps, Satellite receivers & car service manuals! See my post here: http://www.diyaudio.com/forums/showt...66#post1400966

What amp(s) did you try to drive the Jordan's with? t-head seems to like his with the panny amp!
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