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Old 3rd October 2014, 05:17 PM   #1
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Default P7 Mini Preamp Possible Improvements

I just received a P7 Mini Preamp Kit that I ordered P7 Mini Ver5 By LJM).
P7 Mini Preamplifier Board TOP PRE AMP Headphone DIY KIT FOR MX50 L20 L6 NE5532 | eBay

With respect to the included parts, what can i do to squeeze the best performance out of this kit? I will be replacing the included JRC4580 opamp with an NE5532 as this seems a logical step and is even mentioned by the vendor as a drop in replacement.

Will changing the supplied pot for something like an RK27 also result in an improvement? What about the other components as there really aren't that many and swapping anything out will be an easy task.
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Old 4th October 2014, 04:46 AM   #2
ammel68 is offline ammel68  United States
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What makes you think that the 4580 doesn't sound as good as the 5532...because it just seems logical? In a blind listening test I seriously doubt that you would be able to distinguish between one and the other.
Use a socket and judge for yourself.

The RK27 is a nice pot, but I prefer one of these for about the same cost:
Dact Type 21 Stepped Attenuator Volume 10K for Preamp | eBay

I've tried several and they are excellent for the money. They're available in other values as well.

Also, unless you need quite a bit of gain, I would change the 2.2K ohm resistors to a higher value. The circuit appear to have a gain of 5.5.

Good luck with your project.

Last edited by ammel68; 4th October 2014 at 04:50 AM.
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Old 5th October 2014, 10:15 PM   #3
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Thanks for the quick reply.
I actually found a DACT stepped attenuator 10k rummaging in my parts box last night. I will use it.

With respect to changing the gain via a change in resistor value to a higher one, what would be recommended if I wanted to drop the gain of the circuit in half?

I will be using g the P7 with either an MX50X2 or L12-2 boards until my long delayed and half finished Pass B1 can be finished.
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Old 6th October 2014, 01:05 AM   #4
adason is offline adason  United States
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using socked is great suggestion...
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Old 6th October 2014, 01:06 AM   #5
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I did forget to add that I will be using a socket, already in hand, for the Opamp.
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Old 6th October 2014, 04:35 AM   #6
ammel68 is offline ammel68  United States
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Quote:
Originally Posted by kingnubian View Post
Thanks for the quick reply.
With respect to changing the gain via a change in resistor value to a higher one, what would be recommended if I wanted to drop the gain of the circuit in half?
No problem...glad to help.

Using 5.6K resistors, in place of the 2.2k resistors, will reduce the gain to about half.
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Old 8th September 2015, 02:48 PM   #7
asilker is offline asilker  United States
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I ordered this kit to get my feet wet with amplifier design. Can any of you fellas comment on the sound quality of the finished product?

I intend to use mine between USB DAC and power amp.
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Old 21st September 2015, 02:21 PM   #8
asilker is offline asilker  United States
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Finished my build! If anyone in the future is reading through this thread, I'll answer my own question.

I am very pleased with the sound of this circuit. Very transparent with great resolution on vocals and horns. I've been hearing sax harmonics on Brubeck's "time out" that I've never heard. My comparison is against an NAD 3150's preamp. I'm using an AD8066 op amp in my build.

As for gain, it is a bit hot. I'm considering replacing between the 2.2k and 5.6k resisters as discussed above.

I'm very pleased with this kit and would happily recommend it!
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