TPA3116 / RuneAudio Project

[skrodahl]

It's funny you should mention ESP P88, because I just got one:

Did you just buy the board and build it, or did you purchase made up?

A long story.
The short of it is that I bought the board, built it, misplaced it and got it back today.

[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]

I found a great explanation on the web on how transistors work:
http://www.build-electronic-circuits.co ... tors-work/

This was a great simple explanation thankyou !

I still haven't been able to test the preamp, I've been to busy being ecstatic about my phono stage (which in all honesty might be a bit off topic, but it is a part of my amplifier build).

CONGRATULATIONS ...... great when a plan comes together !

The absolutely simplest way of eliminating the POP would be to turn down the volume. That might not always be practical, and you may forget to do so from time to time. Another solution is to install a delay circuit to get rid of the pop.

I get the POP with or without any volume, as you said the turn off pop from the Audiobah is very very low, but with the pre-amp in place is near speaker destroying !.

Thanks for the delay switch idea/link but rather than look at another circuit in the mix just yet, I am going to build another JFET PreAmp with my new found better soldering skills and see if it is a construction error that is causing the POP ..... having said that, in removing some of the components from the old board (seemed quicker than going down to the store) I ended up juggling the soldering iron and rather than let it fall in my lap I grabbed the hot body with my hand Ouch !!!! ...... and now have two lovely burn blisters that will slow me down for a couple of days I think !!!!

If this doesn't eliminate the POP maybe a little ESP P88 project maybe the go !

[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 2383 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]

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

Yes thanks ..... "it's just a flesh wound"

Well I built the second JFET Pre-Amp and while the sound is just great again I still get the POP, but building this has been a great exercise and have really enjoyed it, Skrodahl you are so correct.

Funnily this cheap little preamp has created quite an associated expense trail of it own...... soldering iron, soldering iron holder, brass tip cleaner, pcb holder with magnifying glass, multimeter, Dremel type tool, small suction vice ....... is there no end to the great gadgets .....

I have another omg, omg, omg, omg, OMG!!!! moment going here. The P88 preamp is installed, and it works beautifully

Sensational, congratulations....... you do sound reasonably happy about this !!!

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.

Ok .... I'm convinced a Rob Elliot Project 88 is the next bit of fun, thanks Skrodahl for all the ideas, hope you don't mind me copying your path but, it's great to learn from someone who knows about this stuff !

I really wasn't looking for a balance control, could this be excluded ? .... but suppose I could use a small pot so as not to be too intrusive.

[skrodahl]

Funnily this cheap little preamp has created quite an associated expense trail of it own...... soldering iron, soldering iron holder, brass tip cleaner, pcb holder with magnifying glass, multimeter, Dremel type tool, small suction vice ....... is there no end to the great gadgets .....

Hehe If you're anything like me, there's nothing quite like a good excuse to get more tools.

Sensational, congratulations....... you do sound reasonably happy about this !!!

Yes... Reasonable happy was exactly the emotion I was trying to convey.

Ok .... I'm convinced a Rob Elliot Project 88 is the next bit of fun, thanks Skrodahl for all the ideas, hope you don't mind me copying your path but, it's great to learn from someone who knows about this stuff !

I really wasn't looking for a balance control, could this be excluded ? .... but suppose I could use a small pot so as not to be too intrusive.

The balance control can be omitted, it's all there in the instructions if you buy the PCB. I kept it because it can come in handy for some vinyl records where the balance can be off. It's also the most forgiving balance control I've ever encountered, the center point is really wide.

[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]

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.

If you can finally hear the differences between the profiles, it means that your setup is revealing enough. In other words... congratulations! You built a good system Moreover, the Orion V2 profile usually rewards "tight" setups improving PRaT and detail.

Hotel California/Hell Freezes Over is also one of my favourite test tracks (I wrote it in the dedicated thread).

[skrodahl]

If you can finally hear the differences between the profiles, it means that your setup is revealing enough. In other words... congratulations! You built a good system Moreover, the Orion V2 profile usually rewards "tight" setups improving PRaT and detail.

Hotel California/Hell Freezes Over is also one of my favourite test tracks (I wrote it in the dedicated thread).

The differences between the profiles have been audible all along, and I love that feature. Up until I added the preamp, I switched between the default RuneAudio profile and yours. I even dabbled with a few of my own profiles, but none of them were as good as either of the built-in ones. I guess you have been spending quite some time experimenting with the different parameters.

As for the amp, it is really fantastic. It's been about two and a half months since I started the build, and I had a clear picture of what I wanted. Four inputs, built-in PSU, an amplifier, a RIAA stage, volume and balance.

What took the longest time was figuring out how to power the phono stage. The preamp was an afterthought, but I'm happy that it fit in the enclosure and that the dual rail PSU had just enough juice to power both the RIAA stage and the preamp. I wanted the Raspberry Pi to fit in the enclosure when I started out, but I rather like that it's modular.

Now that it's all come together I couldn't be happier with the result. Off topic, I know, but I am utterly amazed at how good vinyl actually can sound.

I actually took the Hotel California tip from you, thanks for suggesting it.

[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.