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Old 8th August 2003, 06:00 PM   #21
vuki is offline vuki  Croatia
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Peter,
you don't get it, do you? I suggested you to try TDA7294 because it sounds good to me. My suggestion was based on my experience with various ICs and, sure, my taste. The best way to find out how something sounds is to listen it for yourself, but people like to take shortcuts and sometimes prefere to follow suggestions. That is probably the reason "everybody" is using LM3875. "Everybody" - who? Sakura Gaincard uses it, but Rowland is using LM3886, Linn is using TDA7293 (in Klimax Twin) and there are other amps with various ICs.
It's fine if you prefere TDA1543, but that's just you - it's not universal truth.
Also, I'm really sorry my suggestion costed you 3 days - don't follow advices - DIY.
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Old 8th August 2003, 09:12 PM   #22
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You actually didn't suggest it sounds good to you, I didn't get it like that. You obviously made a statement that TDA 7294 is best chip for a GC amp. You even made a grading of some other chips and LM 3875 wasn't at the first two places. This is obviously misleading. I tried that chip (TDA) and OPA549, and while the last one comes close to LM chip (and may be preffered by some people who are into more accurate sonic reproduction), TDA7294 doesn't even come close to what can be regarded as accurate reproduction. I wouldn't recommend it to anybody.

Who else is using LM3875? Almost everybody on DIY forums. Very few people are into other chips. Is it following suggestions?Probably yes, in most cases, but I've heard comments that people tried other chips and chose LM as best performer. I've noticed some people choosing OPA 549 and I can't blame them, because I had hard choice in deciding between the two. But TDA 7294? I knew from beginning it's no good and spend 3 days trying to improve it somehow, but I simply couldn't.

So next time you say it's good, make it obvious that it's only good for your taste. Who else is using LM3875? I know at least 3 other people whose judgement I can trust more than yours: Scott Nixon, Joe Rasmussen and Fedde ( who really inspired me to try it out).

As to DAC chips, I don't think this is the thread to talk about them here. So what else do I not get?

EDIT:

If you chose TDA7294 as a top performer, I'm not even slightly surprised you fancy buffer so much.
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Old 9th August 2003, 07:07 AM   #23
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peter,

perhaps the tda7294 can be made to sound good......
we know that linn is using it with great succes......
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Old 9th August 2003, 07:15 AM   #24
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Quote:
perhaps the tda7294 can be made to sound good......we know that linn is using it with great succes......
Great success? Have you ever heard a Linn amp? I wouldn't call any of their amps 'great success' sonically.
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Old 9th August 2003, 07:24 AM   #25
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Peter Daniel

While i fully agree with your view on buffering (who would want an extra cap + PS + dubious 627/ECC88 follower in a minimum amp?) you should give a simple filter a listen. I use a 2k followed by 750pF to ground followed by 20k. It will only take you a few minutes to put together and by disconnecting the cap you can listen to filtered against non-filtered sound with minimum intervention. The filter values assume lowish and constant output resistance so it's ideally driven by an active pre.

cheers
peter
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Old 22nd August 2003, 01:09 PM   #26
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Quote:
Originally posted by analog_sa
I use a 2k followed by 750pF to ground followed by 20k. It will only take you a few minutes to put together and by disconnecting the cap you can listen to filtered against non-filtered sound with minimum intervention. The filter values assume lowish and constant output resistance so it's ideally driven by an active pre.

cheers
peter

What is a feedback resistor value that you use with the above setup?
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Old 22nd August 2003, 01:20 PM   #27
Bricolo is offline Bricolo  France
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Quote:
Originally posted by Peter Daniel


If TDA7294 is the best, why everybody's using LM 3875 chips?
Because P2P on the TDA needs so much hours of work (at least for me)
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Old 22nd August 2003, 02:59 PM   #28
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It won't take more than double the time of p2p-ing LM3875
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Old 22nd August 2003, 03:09 PM   #29
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Quote:
Originally posted by analog_sa
While i fully agree with your view on buffering (who would want an extra cap + PS + dubious 627/ECC88 follower in a minimum amp?) you should give a simple filter a listen.

So finally today I gave a simple LPF a listen. I used minimized GC circuit with 10k series and 220k feedback resistors in monoblock chassis. I added a Vishay 1k resistor and Wima 1n8 cap which supposed more or less form a LPF. I connected a cap in such a way that I can switch on and off its connection to ground and effectively have the filter in and out of the circuit. I'm not using any pot in this setup (what you see in a pic is disconnected and Grayhill switch is used only to connect the cap to the ground. The signal is fed directly from TDA1543 non oversampling DAC with passive I/V conversion (1k resistors) using Kimber Silver Streak interconnects.
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Old 22nd August 2003, 03:14 PM   #30
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The speakers used for evaluation are my recent creation. Those are infinite baffle arrangement (in wall separated two rooms in a basement). Tweeter is Raven2 with one series cap used for filtering and 2 PHL units with no crossover at all. While this may not be the crossover choice yet (I'm still working on it), yet the system is very revealing and with proper setup can play amazingly well. I measured freq. response and it's pretty flat especially in crossover region (5k, my estimate). The speaker cables are very short and soldered directly to drivers (Alpha Core copper foil, not insulated).
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