John Curl's Blowtorch preamplifier part II - Page 2148 - diyAudio
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Old 18th March 2012, 04:15 PM   #21471
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Concern about loudness levels aside. The intriguing thing about headphones is that it is much easier to attain concert levels using headphones than loudspeakers. As SY's indicated in the past, I doubt my family and neighbors want to me to replicate the sound of a full orchestra (at concert levels) in the living room. (And I cannot imagine what Nirvana live From the Muddy Banks of the Wishkah might do to the neighborhood.)


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Old 18th March 2012, 04:26 PM   #21472
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Note: for those who may be wondering, and apologies if I missed the specifics earlier, this is the "Solomon" I believe mentioned by JC: http://www.ti.com/lit/an/snoa737/snoa737.pdf


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Old 18th March 2012, 04:33 PM   #21473
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Of course, Johnferrier. We don't want to hurt people's ears, we just want to make sure that the headphone amp doesn't clip. One, 'equalizer' is using a 30 ohm build-out resistor, as I have already suggested. This way, a really sensitive 30 ohm headphone will have its output reduced by 6dB. Not a bad idea. It also keeps the design more class A until voltage clipping is possible, and hopefully not often reached.
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Old 18th March 2012, 04:37 PM   #21474
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Thanks bcarso, yes, that is the article that I keep handy, and have done so for almost 40 years.
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Old 18th March 2012, 04:45 PM   #21475
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John,

Quote:
Originally Posted by john curl View Post
I'm a Class A kind of guy! '-)
My preferred way of making a "low impedance load driver for Op-Amp's" has a similarly low parts cound and is also targeted for 100...200mA Iq.

I like low beta, high Ft Bipolar's as direct follower with a CCS in the tail, an LM317 is surprisingly good (I have seen people use them a anode loads for ECC88, I would not go THAT far).

A total of 3 parts (2SC5171 or 2SA1930 depending if we want to pull the Op-Amp output up or down to put it into SECA, LM317 and one resistor) and we are SE Class A, including the Op-Amp output.

I know it's brutal, basic and simple...

Hang the PNP version of this of pin 5 of a real NE5534 and use a heavily degenerated 2SK/LSK389 with CCS tail and cascode as input stage bypassing the internal one and you will have a surprisingly nice Linestage or headphone Amp using the dreaded NE5534... Or take the degeneration out for a Phono Stage...

Ciao T

Last edited by ThorstenL; 18th March 2012 at 04:48 PM.
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Old 18th March 2012, 04:58 PM   #21476
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OT here, but for anyone else subscribing to or reading the Sound Quality vs Measurements thread, are you experiencing the ads rapidly refreshing at the top of the page and each time returning one to them, and preventing reading new posts? I've PM'd a moderator and as well posted a complaint in the standard place. Maddening! And having donated I understand I'm even supposed to be able to kill ads althogether, although I have no idea how to do this.

This thread at least is unaffected for now
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Old 18th March 2012, 06:27 PM   #21477
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I haven't been able to duplicate the issue; have you tried clearing your cache?
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Old 18th March 2012, 06:50 PM   #21478
bcarso is offline bcarso  United States
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Quote:
Originally Posted by SY View Post
I haven't been able to duplicate the issue; have you tried clearing your cache?
It vanished after about four visits (but persisted for a few before that). The behavior was only on the Sound Quality thread, not this one or others. I have no idea what was going on. However, having donated, where do I go to turn ads off?

Last edited by bcarso; 18th March 2012 at 06:52 PM. Reason: wrong thread referred to
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Old 18th March 2012, 07:06 PM   #21479
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If I can go on, what IC should we use? What do we want to select for? Many IC's have different idle currents, and this effects the Iq. What to do?
For the record, the humble uA741 works pretty good in this amplifier. Amazing isn't it? Why?
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Old 18th March 2012, 08:05 PM   #21480
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JC,

Are you actively building this design in your lab now, are you brainstorming, or is this just a thought experiment for the forum ? FWIW, I thought the OPA627/637 were nice chip op-amps. (Although, as I've posted before, in the end I went with Borbely's design.)


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Last edited by johnferrier; 18th March 2012 at 08:09 PM.
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