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

AD797 Preamp based on stolen trademark
AD797 Preamp based on stolen trademark
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Old 2nd July 2020, 06:25 AM   #101
ginetto61 is offline ginetto61  Italy
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AD797 Preamp based on stolen trademark
Sometimes the secret of great sound is also in the details (i.e. parts selection). For instance if panel sockets were not important there would not be market for high quality panel sockets.
Click the image to open in full size.
One example ... i suspect the volume attenuator used in the real MBL is very very high quality. A precision part.
I am a little obsessed by volume pots lately. I have the feeling that some on ebay are even fake parts.
I would look at a stepped attenuator with a decent mechanism and resistors for good sound.
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Last edited by ginetto61; 2nd July 2020 at 06:32 AM.
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Old 3rd July 2020, 09:27 PM   #102
keilau is offline keilau  United States
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Quote:
Originally Posted by gigigirl View Post
Well I received my built up board last week, with the JRC5534DD (presumably fake) op-amps fitted.
I fitted it to my case that previously had a JC-2 in it. I am still waiting for my AD797 op-amps to arrive so I will not do any serious listening until I get them
Anyway after a couple of days of burning in I decided to give it a listen though my Pass H/P amp & AGK701 cans, How did it sound, well not bad at all, certainly better than the JC-2 that was previously being used.
Will give a further update when the AD797's arrive.

Cheers
If it sounds better than the JC-2 with only the NE5534, it has potential.

Did you consider replacing the regulator circuit with an outboard low noise PSU? You can get this board using 317/337 with an opamp de-noiser for about $10. See this post at the power supply forum.
What is this opamp doing in this power supply schematic?
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Old 3rd July 2020, 11:12 PM   #103
analog_sa is offline analog_sa  Europe
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AD797 Preamp based on stolen trademark
Quote:
Originally Posted by ginetto61 View Post
For instance if panel sockets were not important there would not be market for high quality panel sockets.
And yet your picture shows some very durable but average sounding rhodium sockets
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Old 4th July 2020, 02:36 AM   #104
gigigirl is offline gigigirl
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Default Replacing power supply board

Hi, Yes I have thought about that & also upgrading what would be a fake Alps Pot.
However the board shown, which I had not seen before) outputs DC, So I take it I would need to locate were the DC output from the build in board was. Or can you just wire in a +15 / -15 DC supply to the place where you would normally wire the transformer to?

Cheers
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Old 4th July 2020, 03:21 AM   #105
keilau is offline keilau  United States
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Quote:
Originally Posted by gigigirl View Post
Hi, Yes I have thought about that & also upgrading what would be a fake Alps Pot.
However the board shown, which I had not seen before) outputs DC, So I take it I would need to locate were the DC output from the build in board was. Or can you just wire in a +15 / -15 DC supply to the place where you would normally wire the transformer to?

Cheers
I will take all active components (opamp etc.) off the socket before surgical operation.

Remove the rectifier diodes, main filter caps and anything else between them. Make a red jumper from one of the AC-in (use the rectifier hole) to the positive hole of the positive filter cap and a black jumper from the other AC-in to the negative hole of the negative filter cap. Leave the small caps and other components after of the main filter caps in place.

Check continuity from the new +DC in to the opamp + supply pin. Any of the opamp will do. Check continuity from the new -DC in to the opamp - supply pin. If good, you are ready for action.
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Old 4th July 2020, 03:27 AM   #106
keilau is offline keilau  United States
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Quote:
Originally Posted by analog_sa View Post
And yet your picture shows some very durable but average sounding rhodium sockets
Rhodium is a soft metal meant to improve electrical contact. It needs to be on one side of the plug or the socket. The very, very thin layer of rhodium should not have any sound of its own. It may not be exciting, but it is neutral.
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Old 4th July 2020, 05:18 AM   #107
gigigirl is offline gigigirl
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Hi, Thanks Keilu, But that's way above my pay grade. I have very basic electronical knowledge & Skills. Thanks why I normally buy build up kit's.

Derek Derek
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Old 5th July 2020, 09:16 PM   #108
keilau is offline keilau  United States
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Quote:
Originally Posted by gigigirl View Post
Hi, Thanks Keilu, But that's way above my pay grade. I have very basic electronical knowledge & Skills. Thanks why I normally buy build up kit's.

Derek Derek
I understand. Taking components off an assembled PCB is not my favorite hobby either.

For my line level preamp, I use a clone of the Sugden DAC line output board which is very faithful to the original. I have been using a twin TL1083CP regulator PSU for the past year and am waiting for the opamp servo de-noiser PCB to replace the power supply.
IMG_4874.jpg FET_JCR5534_schematic.jpg FET_JCR5534-5.jpg

LM317-LM337_LF353ServoRectifier.jpg LM317-LM337_LF353ServoRectifier_picture.jpg

On the lineamp board, I replaced the NE5534 with LME49710 which is much cheaper than the LD797 and very good for line level.
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Old 6th July 2020, 01:55 AM   #109
gigigirl is offline gigigirl
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Hi, Just spotted this for under $60, From what I can tell, this may be suitable for the power supply you suggested

HIFI MBL6010D Preamplifier Preamp Board Tone adjust Fit For NE5532 NE5534 OPA 228243292918 | eBay

Cheers
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Old 6th July 2020, 02:01 AM   #110
keilau is offline keilau  United States
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Quote:
Originally Posted by gigigirl View Post
Hi, Just spotted this for under $60, From what I can tell, this may be suitable for the power supply you suggested

HIFI MBL6010D Preamplifier Preamp Board Tone adjust Fit For NE5532 NE5534 OPA 228243292918 | eBay

Cheers
For a simple board with 4 NE5534 and 2 NE5532, the $60 price tab seems way too high. Did you check AliExpress? It seems to be unbalanced in and out only. No balanced port!

What potentiameters and how many does it include for the tone control?

Last edited by keilau; 6th July 2020 at 02:08 AM.
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