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Old 25th December 2002, 10:33 PM   #1
OliverD is offline OliverD  Germany
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Question Who owns a LC Audio "ZAP-Filter mk II"?

Is there anybody out there who owns one of those magic ZAP-Filter mk II?

I think the circuit looks quite interesting, and now I'd really like to know which "ultralinear-many-GHz"-BJT's they are using. They call them "Z-Transistor".

So could one of you please have a look at your ZAP-Filter mk II and tell me what the small transistors are marked with? On the pictures, I can only see the marks on the shunt regulator's devices, then the "4F" and "2F" (BC850, BC860) from the current sources, and the "N2" marked parts (FCX491) from the output stage. The rest ist more interesting, though. Let's see if it is all marketing or if they are really using outstanding high quality parts...

Maybe this way we can figure out if the circuit is any good and maybe use it for our DAC projects... I'd also be interested in comments whether there is an improvement in sound which is worth the money you have to spend on such a unit...

Thank you!

Advertisement and schematics are here (danish):

http://www.lcaudio.dk/opgrmat.pdf

Find a high-res picture of the board here:

http://www.lcaudio.de/Tuning/Analog-...er2_1Kanal.JPG
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Old 26th December 2002, 04:29 AM   #2
nFORCE is offline nFORCE  Japan
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Default Re: Who owns a LC Audio "ZAP-Filter mk II"?

PMMT491A (Philips parts) SOT23 package = FCX491A

You can go Philips web site to search "BISS" you can get more

Regards,
nFORCE


Quote:
Originally posted by AMT-freak
Is there anybody out there who owns one of those magic ZAP-Filter mk II?

I think the circuit looks quite interesting, and now I'd really like to know which "ultralinear-many-GHz"-BJT's they are using. They call them "Z-Transistor".

So could one of you please have a look at your ZAP-Filter mk II and tell me what the small transistors are marked with? On the pictures, I can only see the marks on the shunt regulator's devices, then the "4F" and "2F" (BC850, BC860) from the current sources, and the "N2" marked parts (FCX491) from the output stage. The rest ist more interesting, though. Let's see if it is all marketing or if they are really using outstanding high quality parts...

Maybe this way we can figure out if the circuit is any good and maybe use it for our DAC projects... I'd also be interested in comments whether there is an improvement in sound which is worth the money you have to spend on such a unit...

Thank you!

Advertisement and schematics are here (danish):

http://www.lcaudio.dk/opgrmat.pdf

Find a high-res picture of the board here:

http://www.lcaudio.de/Tuning/Analog-...er2_1Kanal.JPG
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Old 26th December 2002, 11:32 AM   #3
OliverD is offline OliverD  Germany
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Quote:
Originally posted by nFORCE

PMMT491A (Philips parts) SOT23 package = FCX491A
Thank you very much, nFORCE

Hm, according to the datasheet, those Philips parts are called BISS ("Breakthrough In Small Signal")

However, they have a transit frequency of "only" 150 MHz... Their case seems smaller than SOT23 on the pictures... And they should be marked something like "9At" or "9Ap" which is different to what we see on the pictures... Maybe you have the older version, ZAP-Filter mk I?

If they are really using smaller outline versions of the Zetex FCX491A, what about the "ultra linear GHz Z-Transistor" marketing?
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Old 26th December 2002, 05:09 PM   #4
nFORCE is offline nFORCE  Japan
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Hi Sir,

MK1 here:
http://www.lcaudio.dk/zfdia.pdf

Yes, the transistor is limit at 150MHz, I think that enough, the spec = ZETEX spec, i.e. I don't know why the begineer stage need TR=1.5G and the final amp stage only need 150MHz.

Therefore the critical path should not in the 150MHz.

Regards,
nFORCE



QUOTE]Originally posted by AMT-freak


Thank you very much, nFORCE

Hm, according to the datasheet, those Philips parts are called BISS ("Breakthrough In Small Signal")

However, they have a transit frequency of "only" 150 MHz... Their case seems smaller than SOT23 on the pictures... And they should be marked something like "9At" or "9Ap" which is different to what we see on the pictures... Maybe you have the older version, ZAP-Filter mk I?

If they are really using smaller outline versions of the Zetex FCX491A, what about the "ultra linear GHz Z-Transistor" marketing?
[/QUOTE]
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Old 26th December 2002, 05:18 PM   #5
OliverD is offline OliverD  Germany
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The marks I'm talking about look more like "F4", "F0" or "FQ" in the pictures...

Can anyone help?

Thank you very much.
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Old 26th December 2002, 05:29 PM   #6
OliverD is offline OliverD  Germany
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Default Ooops

Saw your reply when I had already posted... Sorry.

So I think we are talking about different circuits... The ZAP-Filter circuit has changed completely from mk I to mk II... The new schematic is in the brochure I posted above - without transistor types, though.

Thank you again nFORCE.
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Old 26th December 2002, 09:43 PM   #7
Pan is offline Pan  Sweden
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AMT freak,

I havenīt had time to check what those BJTīs are marked with, however I I think we can assume that if you read something at the LC Audio site itīs true. These guys know what they are doing and are certainly not into false marketing.

As I mentioned in the other thread, I use the Zapfilter mk2 together with LClockXO2 in my SCD-XB940.
The improvements with these upgrades where nothing short of shocking.

So the answer on your question;

"Maybe this way we can figure out if the circuit is any good and maybe use it for our DAC projects... I'd also be interested in comments whether there is an improvement in sound which is worth the money you have to spend on such a unit"

You bet! :-)

LC Audios stuff are right up there with the best IMO. And since they use no signal caps and no feedback, the resolution is better than anything I have heard. (talking ībout amps now).
The Aleph5, Gammut D200 and ARCVT100 was not good enough to replace my Zapsolutes. Therefore Iīm very curious on the new XA amps from mr Pass. Maybe this is what I need to better my amps. Or I simply have to go with the latest Zapsoutes mk4.1.

/Peter
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Old 28th December 2002, 02:26 AM   #8
OliverD is offline OliverD  Germany
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Quote:
Originally posted by Pan
I havenīt had time to check what those BJTīs are marked with, however I I think we can assume that if you read something at the LC Audio site itīs true. These guys know what they are doing and are certainly not into false marketing.
The ZAP Filter mk II is around 275$, pretty much for such a circuit... Ok ok, they have to pay the engineer and probably won't be selling 100.000's of those boards, but still...

LCAudio products have been discussed at length here already, not all of us seem to like their sound.

What the LCAudio clock is concerned, it's is also quite expensive, yet only a more or less standard circuit with a BFR92A and some high speed logic. The famous KWAK-clock can be built for... say 10 to 20$ ... and seems to be better. At least this is what people say, I haven't yet had an opportunity to compare them.

This of course doesn't mean I contradict you, I just say I haven't heard it yet and want to be sure... Understand the circuit... Check if there is something behind their marketing... Maybe I'll buy a ZAP-Filter, maybe I'll tweak it, or maybe I'll try building a similar circuit myself... Don't know yet. Just don't want to risk much, since I don't have the money to try many different output stages.

So if you have time one day to have a quick look at your board and tell me about the markings on the SMD transistors, I'd be very happy... Of course I understand if you don't want to open a carefully tweaked CD-Player again, but maybe someone else can help..?

Thank you all.
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Old 28th December 2002, 11:34 AM   #9
Pan is offline Pan  Sweden
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AMT,

If anyone can build something better than the Zapfilter2 for lesss money I say congrats, I would also do that in such case.
The other readily made boards (of similar quality) on the market cost more as far as I know. So for someone who wants to put down about $400 for Zapfilter + LClock and mod a CDP that can compete (and beat) all or most players out there, IMO itīs a ******* bargain :-)

About the clock. If someone can build a similar or better clock for $20, then go for it. I donīt think everyone can though. So if you want a solution that can be fit in the machine in a lunchbreak that lift your player enormously, then LClcok is a very worthwile investment, and in audiophileterms ($) peanuts. I have read about several people make coments on LClock being as good as or better, then the competition. I have not tried any other clock than LCclock, but I can assure you my jaw dropped the night I installed it.

No problem with open the machine as I did the mods myself, but there is the time issue, and I believe that all I can see is what you can see on the high-rez picture on the LC site.

I bought a SCD-XB940 unheard, knowing I would upgrade it, so the sound of the machine itself was of little interest. Of course I listened to it after I bought it, but it sounded like crap, so I didnīt use it for months until I did the modifications. After the mods it produces (in my set up) the best sound Iīve ever heard. Nothing I have heard comes close to the natural high resolution of the Zapfilter feeding my Zapsolute class A amps, really. I have good speakers also.

The easy way is to send Lars Claussen (LC...) a mail and ask anything you want to know.

Oh.. and if you find a way to mod and better the Zapfilter, please tell me, as if this amazing piece of board can be made better, Iīm in :-)

/Peter
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Old 22nd September 2003, 01:35 PM   #10
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AMT freak I have most of the circuit figured out and I am making some simulations right now.

Do you have a high resolution picture of the board from under?

I am trying to figure out the exact values of the Zener diode that biases the input pair and how the connection really is in the input for non balanced current input. what happens to ground when 4 is shorted?

There is an npn transistor that gives a voltage to the bases of the input pair when the current inputs are into them as common base.

Any ideas are welcome. A version of this circuit with normal parts would be cool. O donīt really like SMD parts.
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