TPA3116 / RuneAudio Project

[skrodahl]

[StivVid]

Nope. Still haven't worked out the grounding issue. Haven't really had a chance to play with it much.

I'll be sure to post the solution if I find one. Would really like to use a single power supply for the whole rig.

[Downunder55]

[skrodahl]

Hope you're recovering from the soldering iron accident. If you keep on soldering, you will realize that it happens quite too often.

I have another omg, omg, omg, omg, OMG!!!! moment going here. The P88 preamp is installed, and it works beautifully. I was a little worried that my small 83 mA dual rail PSU would have trouble driving four OPA2134s. They require 40 mA quiescent current, so it was going to be on the limit. But I'm happy to report that it works great.

IMG_20140930_185313.jpg (614.69 KiB) Viewed 2536 times

I had to mount the preamp on top of the phono stage. It's getting cramped, especially with the cabling making everything hard to move around. I would prefer some of the cables to be even shorter, but I don't think that's physically possible. And, it was inevitable of course, I got a small soldering iron burn on my thumb...

I thought the Audiobah TPA2116 amp delivered a very detailed and clear sound. Playing vinyl was even better than the sound from RuneAudio, which made me suspect that a preamp would be nice.

My suspicions were absolutely correct. The level of details, the highs, the lows, the mids, the "blackness" of the silence, the positioning of every possible sound and instruments. It is just unbelievable. There might come a day when I find something better, but I seriously doubt that right now.

[Downunder55]

[skrodahl]

[skrodahl]

Now that the P88 preamp is installed, I played around with the sound signatures in the settings.

Just when I thought things couldn't possibly get better, I found that switching to Orion V2 improved the sound even further.

Hotel California/Hell Freezes Over has never sounded better.

[ACX]

[skrodahl]

[skrodahl]

I did some matching of the preamp, P88, to the Audiobah board. It will work for most of the other TPA3116 boards as they all seem to have a 26 dB gain.

With the standard P88 board at the lowest gain setting, I had a usable volume control range up to about 10 o'clock before the volume was way too loud.

The second gain stage of the P88 needs to have some gain to avoid oscillation, the lowest setting is at 4.44 dB. So I looked at the first gain stage. It can be set to 0, or unity gain, but I decided to keep a little gain anyway. Changing R3 (left and right) from 10k ohm to 750 ohm gives 0.63 dB gain. A total of just about 5.1 dB for the whole preamp.

The volume/balance setup has a loss of 3 dB, so in total the preamp has just a smidge above 2 dB gain. The volume control is usable over a much wider range again.

A 2V input signal was amplified to ~4.7V in the original preamp setup. It is 2.5 volts with the new setting. Of course, this makes it less like a preamp and more of a buffer. Not surprisingly, it still sounds just as great.

Edit: With lowered input signal, and the amp operating at more reasonable levels, the sound is getting much richer/warmer/fuller. So much in fact that I had to go back to the RuneAudio sound signature. It does offer a very natural and transparent sound.