Preamp based on the Pass 1.7

Love the description:

Sound features:

Voices are mellow and sweet, low frequency elasticity & strong, and high frequency is slim.

 

I definitely hear an improvement when using a preamp or integrated instead of the sabre built in digital attenuation.. even with my oppo sonica which has the newest 9038pro chip. Had great results with my Hattor mini active preamp and the kinki ex-m1 integrated amp volume control

 

I am enjoying it very much, have everything now, cables, attenuators, etc. I just set the volume to around 12 o'clock and use the remote controlled variable volume out from my dac. I have tried a pre amp with a simple stepped attenuator instead of this but the downgrade involved in doing that is very clear.
Plusses: Beautiful sound and flexible connectivity.
Minus: You can hear the internal transformers hum when you are a meter or lesss away from it.

 

I experimented with using the RCA out to drive headphones. Very nice indeed No need for any special headphone amplifier.

 

Currently using it to drive HD600s and it is totally addictive.

 

A couple of years late on this, but whatever. The commercial Pass Aleph P preamp has a pair of gain controls which would have alleviated your problem with too much gain. The diy boards that I have seen (and built) also accommodate this. It uses a pair of 2K linear volume pots. Using this, you should be able to reduce the gain to a level where you no longer would need to use the digital volume on your source.
I liked the diy raw preamp that I built so well that I just bought the commercial Aleph P1.7 after calculating what I would spend for casework, I/O, etc. to finish the diy version to match the commercial one.

 

Hi, I just bought a preamp equal to yours, and if you don't know, I'll give you the configuration of the input gain, with the dip swichs.
the board swiches is to adjust the gain of the amplifier board
The full set is on, the gain is about 7 times, and the input impedance is 3K

The whole set is off, the gain is about 3 times, and the input impedance is 30K

1.4 is on, 2.3 is off, the gain is about 4 times, and the input impedance is 22K

1.4 is off, 2.3 is on, the gain is about 1.5 times, and the input impedance is 15K

The above gains are balanced input and output, and the unbalanced profit is halved.

 

First of all I can advice 3 methods to get the best sound.
1. no need any heatsink for active device, IRF610, 9610 because they need their original threshold when they hot only.
2. source resistor (5K) which connected each phase together need to trim for the best gain and sound stage.
3. original AP 1.7 used low vgs than diy version.

 

@alpefe: Many thanks for sharing the info about adjusting the gain!

I'm in Germany and recently bought the same preamp.
In the beginning I was disappointed because gain was much too high, even when setting it to the lowest at 1,5 / 15K.
The reason for this was that I used the XLR input. As soon as I switched cinch it was fine at 1,5 gain. Now it's hugely enjoyable. It is indeed extraordinary, if you look at the price tag.
Anyway, I wonder whether this really is a symmetrical layout?
I'm using an Atoll DAC 200 Signature and Brocksieper LC807/ 25 mono tube amplifiers with the preamp.

Cheers,
Niko

 

holy thread resurrection batman!

please, if you’re still with us, could you explain a little about your point 2

many thanks
A