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Old 12th December 2011, 09:58 AM   #11
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by dildel View Post
Greetings,
Has anyone compared TDA7293 and LM3886 side-by-side with a pair of audiophile grade speakers? I am asking because LM3886 supposedly has lower levels of distortion. Is it really audible?
Mosfet versus bipolar at this level is very audible (not the distortion). Most people will prefer bipolar I believe. With big transformer and woofer, the TDA7293 will be a poor man's mini crescendo.
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Old 15th December 2011, 01:30 PM   #12
dildel is offline dildel  India
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I didn't understand that. Are you saying that TDA7293 will not perform as well with a large transformer and a large woofer? What does transformer and woofer size have to do with MOSFET versus Bipolar?


Quote:
Originally Posted by Jay View Post
Mosfet versus bipolar at this level is very audible (not the distortion). Most people will prefer bipolar I believe. With big transformer and woofer, the TDA7293 will be a poor man's mini crescendo.
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Old 15th December 2011, 02:37 PM   #13
AndrewT is offline AndrewT  Scotland
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Well spotted.
Use your own judgment to determine whether all the information you read is reliable.
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Old 19th December 2011, 01:32 PM   #14
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by dildel View Post
I didn't understand that. Are you saying that TDA7293 will not perform as well with a large transformer and a large woofer? What does transformer and woofer size have to do with MOSFET versus Bipolar?
I said with big woofer and transformer, the TDA7293 will rival the mini-crescendo. Both amps have mosfet output stage.

Any amp will benefit from large transformer. It seems to me that mosfet requires more free current to charge the capacitance.

Mosfet amps have unique quality that is usually displayed when using big woofer.
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Old 19th December 2011, 03:04 PM   #15
AndrewT is offline AndrewT  Scotland
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And I don't understand the post14 explanation.
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Old 19th December 2011, 03:46 PM   #16
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BJTs have better transconductance especially NPN ones and single LM3886 can deliver more current then single TDA and most likely will provide better control over an average speaker.

For a discreet DIY output stage I would bet on lateral MOSFETs. But in case of IC and FAB on BJTs.
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Old 20th December 2011, 01:14 AM   #17
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by dildel View Post
Greetings,
Has anyone compared TDA7293 and LM3886 side-by-side with a pair of audiophile grade speakers? I am asking because LM3886 supposedly has lower levels of distortion. Is it really audible?

Design and implementation complexity of both is about the same and has been compared in earlier threads.
Thanks.
Quote:
Originally Posted by Jay View Post
Mosfet versus bipolar at this level is very audible (not the distortion). Most people will prefer bipolar I believe. With big transformer and woofer, the TDA7293 will be a poor man's mini crescendo.

Quote:
Originally Posted by dildel View Post
Has anyone compared TDA7293 and LM3886 side-by-side with a pair of audiophile grade speakers?
Yes, I have. Currently I have a few 3886 amps, one 7293 amp, a few not so audiophile grade speakers such as Dynaudio, JMLabs, and some lower grade speaker designs (Vifa, SilverFlute, etc). Speakers with big diameter woofers were/are Peerless 3-way design and another 3-way design using local drivers.

Quote:
Originally Posted by dildel View Post
I am asking because LM3886 supposedly has lower levels of distortion. Is it really audible?
Difference in THD is rarely audible. If you can hear a difference between 7293 and 3886, I would say it is the difference between mosfet and bipolar in common/most amp designs (they can be designed to sound more similar I believe), where mosfet amp tend to sound "muddy"?

--> Mosfet versus bipolar at this level is very audible (not the distortion).

If you want to know how 7293 will perform in comparison to 3886, you have to know how mosfet amps sound in general, then you could benchmark the 7293 with another mosfet amp (where they have similar characteristics in sound). I'll bet 80% at least will prefer 3886.

---> Most people will prefer bipolar I believe.

If "mosfet sound" is not a problem to you (or you are a mosfet fan), or you have heard mosfet amp before, or you have heard review about another mosfet amp, may be you should know how the 7293 would compete against the 50W mini-crescendo.

They have similar sound character. The mini-crescendo has more "full sound". The Hitachi K135/J50 has unique good character but the 7293 that I tried was at least as listenable as the mini-crescendo.

I had to do "everything" to beat the mini-crescendo with 7293, so I used big transformer, especially because the mini-crescendo had a "fuller sound" and used big trafo. Big transformer will for sure improve the characteristics of the amp in bass region and "power". I only asked one experienced man for his opinion about the two amps. He didn't explicitly say which one was better, only that the mini-crescendo had more body and fuller sound.

Speaker is more important than amp. The better the speaker, the less difference you can expect from amps. Sometimes, certain amp match better with certain speaker. In my case, I always found mosfet amps to sound great with big speakers.

So I think that with good implementation (I didn't even use the "best" schematic or matched preamp) such as using big transformer, high quality capacitors, and using suitably high end (big) speakers, the 7293 will be "comparable" to the mini-crescendo.

--> With big transformer and woofer, the TDA7293 will be a poor man's mini crescendo.

Of course, I have found many people prefer the 3886 than a better mosfet amp than mini-crescendo!!
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Old 20th December 2011, 08:48 AM   #18
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by suntechnik View Post
BJTs have better transconductance especially NPN ones and single LM3886 can deliver more current then single TDA and most likely will provide better control over an average speaker.

For a discreet DIY output stage I would bet on lateral MOSFETs. But in case of IC and FAB on BJTs.
Quote:
Originally Posted by Jay View Post
Of course, I have found many people prefer the 3886 than a better mosfet amp than mini-crescendo!!
You may be a lateral mosfet fan like me, or you might be surprised that many people had preferred a 3886 based amp compared to a sophisticated discrete lateral fet amp. That's why I have always emphasized this "taste/preference" issue.

Yes, bipolars have better transconductance. It is this parameter that I think is responsible for the better sonic in bipolar amps. And it is this sonic that will bring more objective enjoyment, not just subjective taste.

That's why I think that in designing a lateral fet amp, this weakness should be taken into account. I'm not an electronics educated person, but I always choose a design and build my amps in a way that I think will solve this issue. Assume for example that a lateral fet transistor is a load for the VAS, you sure want a low output impedance VAS stage. Designers should know how to do it and will do it if they have good ears.

Furthermore, I think that this issue with lateral fet amps is a bottleneck, so it should be solved with every available ways, even with increasing the supply rail and using big power transformer.
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Old 20th December 2011, 09:21 AM   #19
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Can we express this in more scientific terms? Say damping factor and harmonic distortion.

Both bipolar and MOSFETs can be designed to keep harmonic distortion below audible levels.

Damping factor expresses the amount of control an amplifier has over a speaker - TDA7293's damping factor is 180 for an 8Ohm speaker. Does anyone know what the damping factor for LM3886 is?

Quote:
Originally Posted by Jay View Post
Yes, bipolars have better transconductance. It is this parameter that I think is responsible for the better sonic in bipolar amps. And it is this sonic that will bring more objective enjoyment, not just subjective taste.
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Old 20th December 2011, 10:41 AM   #20
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I'm sure that most of us are familiar with the popular workarounds to dodge the harsh noise of the NatSemi spike system current limiter; however, there is little information on ST's limiter and their datasheets are seriously misleading.
For lack of anything else, try this post: TDA7293 capacitors
That also gives some tuning ideas to bring the TDA7293/4 up to approximately the same clarity and low bass performance as LM3886. Anyway, click the link and hear what you're missing.

I just think that we have to come a lot closer to individually optimized applications before it could be possible to compare audio quality of the chips.
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