17th December 2009, 03:11 PM
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#143 | |
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diyAudio Member
Join Date: Jul 2002
Location: Toronto, Canada
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I didn't measure it, but subjectively it's very quiet. You may check this review of the original circuit (I use different parts and completely different PS): H A L L O F F A M E
Quote:
The offset will depend on a particular OPA637 chip; some chips will produce much less offset.
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www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC |
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17th December 2009, 09:21 PM
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#145 |
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diyAudio Member
Join Date: Jul 2002
Location: Toronto, Canada
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Check the offset with the amp connected for different volume settings (speaker disconnected when testing). If it exceeds 100mV use 2.2 - 4.7uF coupling caps.
__________________
www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC |
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20th December 2009, 03:00 AM
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#146 |
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diyAudio Member
Join Date: Feb 2007
Location: sydney
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Hi Peter, plugged in it today-the transformer humming and vibrating like crazy and feel as though not enough gain( compare with herron audio phonostage-66db)
The tranny was dropped onto the floor the other day!!! Likely to be faulty. Please advise how to wire with dual secondaries toroidal transformer. NOOB question. Thanks. |
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20th December 2009, 05:17 AM
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#147 |
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diyAudio Member
Join Date: Jul 2002
Location: Toronto, Canada
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I'm using 2 x 12V transformer, which unloaded produce approx 14V AC per secondary.
In attached pic, you can see 4 pads (on a left). Those pads are for external transformer connection: first two from the top are for one secondary, the other two for the other secondary. You will need approx 19V after rectification and 15V regulated. If you can get 15V because of too low voltage on secondaries, settle for lower regulated voltage, it will not affect anything (adjust with changing R7 and R8)
__________________
www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC |
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20th December 2009, 03:16 PM
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#149 |
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diyAudio Member
Join Date: Jul 2002
Location: Toronto, Canada
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As both positive and negative regulator circuits are completely independent, the secondaries do not need to be in phase; you can also use two separate transformers with single secondaries.
__________________
www.audiosector.com “Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC |
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