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AKSA's Lender Preamp with 40Vpp Output
AKSA's Lender Preamp with 40Vpp Output
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Old 1st January 2018, 10:14 PM   #401
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
Hi Nico,
Thanks, but all the credit for layout goes to JPS64. He does this for a living - so these are perhaps, some of the most professional looking layouts that I have ever seen. The ground planes on the MB are insanely good.

For example, the multiple ground planes follow a star topology with the hub at the main input/output connector. The left and right are separate. The CRC and Cap mx ground planes are separate, etc.

Click the image to open in full size.
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Last edited by xrk971; 1st January 2018 at 10:17 PM.
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Old 2nd January 2018, 07:16 AM   #402
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
Latest test results with MELF SMT board looks pretty good.

4Vpp into 7kohms (45v Vcc):
AKSA's Lender Preamp with 40Vpp Ouput GB-aksa-lender-pre-melf-4vpp-7kohm-fft-png

20Vpp into 7kohms (45v Vcc):
AKSA's Lender Preamp with 40Vpp Ouput GB-aksa-lender-pre-melf-20vpp-7kohm-fft-rt-png

Now, for the thread title namesake, 40Vpp into 7kohms (50v Vcc):
AKSA's Lender Preamp with 40Vpp Ouput GB-aksa-lender-pre-melf-40vpp-7kohm-fft-50vcc-png

And if one raises Vcc to 59v, just before clipping this preamp can drive 51Vpp into 7kohms with 0.013% THD:
AKSA's Lender Preamp with 40Vpp Ouput GB-aksa-lender-pre-melf-51-4vpp-7kohm-fft-59vcc-png

That's good for about 41Wrms into 8ohms if the power amp can handle it.

With Vcc at 59v, the SMT board is a bit hotter - but not excessive. I will let it burn in overnight to see if it can take it long term.
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Last edited by xrk971; 2nd January 2018 at 07:19 AM.
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Old 3rd January 2018, 12:50 AM   #403
e_fortier is online now e_fortier  Canada
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AKSA's Lender Preamp with 40Vpp Output
Hi X

Very good work.

For the +48V power supply would this be ok ?

Same as the one in Millett starving student HA;
CISCO 48V 0.38A AC/DC Adapter Desktop Power Supply PSU 34-2477-01 EADP-18FB B | eBay

Thanks
Eric
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Old 3rd January 2018, 02:56 AM   #404
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
Quote:
Originally Posted by e_fortier View Post
Hi X

Very good work.

For the +48V power supply would this be ok ?

Same as the one in Millett starving student HA;
CISCO 48V 0.38A AC/DC Adapter Desktop Power Supply PSU 34-2477-01 EADP-18FB B | eBay

Thanks
Eric
I have not tried this but it may work fine. I personally like variable DC step up so you can set your Vcc precisely. With this you will be limited to 44v Vcc after cap Mx.
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Old 6th January 2018, 06:18 AM   #405
jwjarch is offline jwjarch  United States
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Quote:
Originally Posted by gtose View Post
I linked to them on eBay in my previous post: AKSA's Lender Preamp with 40Vpp Output.
Took a chance on the $2.66 rca connectors. They can be converted if you are careful. The plastic part of the connector is fairly brittle. Don't ask me how I know. Even so I think I'll go with these for my build. They are really good quality for the money.
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Old 6th January 2018, 05:18 PM   #406
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
Quote:
Originally Posted by jwjarch View Post
Took a chance on the $2.66 rca connectors. They can be converted if you are careful. The plastic part of the connector is fairly brittle. Don't ask me how I know. Even so I think I'll go with these for my build. They are really good quality for the money.
You actually have them in-hand and we’re able to convert them?
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Old 6th January 2018, 10:13 PM   #407
jwjarch is offline jwjarch  United States
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Yes Sir! The large pins pull out of the body with a needle nose pliers and the signal wires bend relatively easy. The trick is putting the large pins back in on the bottom without cracking the plastic body.
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Old 7th January 2018, 06:08 AM   #408
Harry3 is offline Harry3  Australia
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Default C1

What are your thoughts in using one of these caps (Bipolar, 50V, Dia=10mm) from Mouser for C1?

647-UVP1H101MPD
667-ECE-A1HN101U
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Old 7th January 2018, 08:48 AM   #409
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
That’s probably fine Harry3. But there may be a thing as too much capacitance. I installed my favorite 10uF Elna Silmic II there bypassed with 2.2uF 250v film. The FFT had elevated 20dB above -130dB noise floor of infrasonic (sub 40Hz to DC) content. I removed 10uF and infrasonic noise went away. Although +20dB above -130dB is pretty inaudible, it probably means home theater content would be fully represented through this preamp. The F3 with 2.2uF C1 is about 2Hz so even 2 octaves above is 8Hz should be plenty of bass extension. I recommend using at least a film cap there and skip the electrolytic if given a choice.
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Old 7th January 2018, 09:20 AM   #410
Harry3 is offline Harry3  Australia
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Hi X,
I am referring to the capacitor that is in series with a 1K (R11) resistor on the daughter board.

I think you are referring to the input cap C132 on the mother board.

The information that you sent is good.

regards
Harry
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