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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

AKSA's Lender Preamp with 40Vpp Output
AKSA's Lender Preamp with 40Vpp Output
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Old 13th July 2018, 05:49 PM   #711
JPS64 is offline JPS64  Germany
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AKSA's Lender Preamp with 40Vpp Output
@Carl Huff


I donīt personally like signal traces who see each other (green/red layers).


Using this parts allows to put potentiometer directly on entry:
- ACHSKUPPLUNG 2: Shaft coupler from 6mm to 6 mm at reichelt elektronik
- P6 ACHSE: Extension shaft 6 mm at reichelt elektronik


KSA and DN needs heatsinking.


JP
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Old 13th July 2018, 06:25 PM   #712
Carl_Huff is offline Carl_Huff  United States
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Quote:
Originally Posted by JPS64 View Post
...

I donīt personally like signal traces who see each other (green/red layers)...

JP
I am describing layers on a bog standard 2 layer PCB. I don't understand what you mean by 'seeing each other'. Could you please elaborate??

Quote:
Originally Posted by JPS64 View Post
...

... KSA and DN needs heatsinking.

JP
Yea, in this first pass I have done little beyond adapt an existing layout.

The PCB as shown is intended to be attached to the front panel. No pot extensions are required. The ribbon cable to the IO board allows for depth differences in enclosures.
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Old 13th July 2018, 06:51 PM   #713
JPS64 is offline JPS64  Germany
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AKSA's Lender Preamp with 40Vpp Output
Avoid, as possible, crossing red layer and green layer routed signals.

Well, yes, I‘m coming from HF development.

JP
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Old 13th July 2018, 07:14 PM   #714
Carl_Huff is offline Carl_Huff  United States
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Originally Posted by JPS64 View Post
Avoid, as possible, crossing red layer and green layer routed signals.

Well, yes, I‘m coming from HF development.

JP
Aah, Okay. Please note that 90+ percent of the topside 'red' signal traces are positioned above ground on the bottom side of the PCB.
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Old 13th July 2018, 11:03 PM   #715
Kokanee is offline Kokanee  Canada
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AKSA's Lender Preamp with 40Vpp Output
Thanks for the help with the copper heat sinks. I have some chip amps and a few others to hone my copper skills on before building discretes. I am going to save some copper for the Alpha's to maybe beef up the heat sinks on the cpu coolers. Love to experiment!!!

Cheers

McD
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Old 17th July 2018, 07:00 AM   #716
patriz is offline patriz
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Hi X What is it your suggestion for a 3,3k load and an amp with 15dB gain?
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Old 20th July 2018, 07:27 PM   #717
GASCo is offline GASCo  United States
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AKSA's Lender Preamp with 40Vpp Output
Quote:
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Hi X What is it your suggestion for a 3,3k load and an amp with 15dB gain?
Have you figured it out? It would be awesome if somebody explained the math behind this, or pointed in the direction of a post/video doing so.
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Old 20th July 2018, 08:04 PM   #718
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Output
Click the image to open in full size.

The gain is controlled by R10 and R11 through the relationship:

G = (R10+R11)/R11

If we set R10 as 10k and R11 as 2k2, we get G=5.55x

Gain in dB = 20 log10(Vout/Vin) = 20 log10(5.55x) = 14.8dB

A load of 3k3 is not hard for this preamp to drive. maybe increase bias current a bit by lowering R15 to 39R, and maybe R14 to 8R2 (or leave at 10R). R15 is the critical controller of the bias setpoint. Make sure the bias does not exceed 75% of the max for KSA1381 (Q4).
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Last edited by xrk971; 20th July 2018 at 08:08 PM.
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Old 21st July 2018, 06:59 AM   #719
twocents is offline twocents  South Africa
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AKSA's Lender Preamp with 40Vpp Output
Awesome info - thank you X!
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Old 24th July 2018, 04:16 PM   #720
GASCo is offline GASCo  United States
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AKSA's Lender Preamp with 40Vpp Output
Thanks X!

I started populating the board yesterday. It's my first soldering job so I wanted to show here and please let me know if anything is too bad!

I am still missing a few things on the MB but soldered all I had.

A few questions:

1- Mouser didn't have the SMD 2W R161. Is it OK to put TH there?

2- My delivery was missing C121 and C131 (220pF 100V). I will complain, but I have a couple 220uF 100V I bought too many, would that be too large?

3- I forgot to order R141 and R142. Will 0.5W resistors work in these positions? If not I can get them locally.

4- L161 I got at mouser is way too big (15A version) and didn't fit. I will get a smaller one locally.

5- Mouser also delivered the molex 90 degrees wrong. I got 3 pin connectors instead of 10 pins connectors, so I don't have enough..

6- My bad on C134. I forgot it doesn't fit there. Will need to relocate so the DB fits.....
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Last edited by GASCo; 24th July 2018 at 04:24 PM.
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