[rhing]

I'm not even using the stock power supply. As I mentioned in my previous post, I'm using my upgraded Astron RS-12A regulated linear power supply. I have modified Klipsch Forte Ii speakers and they are 98dB efficient, so 12VDC is plenty of power for my listening needs.

[dboy]

Wanted to say cheers to the guys who suggested things to try to stop my blue/black board from hissing. I touched up some solder joints, tidied/twisted my wiring, and swapped the stepped attenuator for an old potentiometer. The hissing is almost inaudible now!

Possibly even better is that the turn-on pop seems to have vanished. It was scarily loud before to the point where I was thinking even if I fixed the hiss this amp was not going to get much use. Now I get a small ticking sound on powering down and nothing at all on powering up. No idea why.

Enthused, I swapped the inductors for some aircore ones I took off a Charlize board that I fried a few years ago with too much fiddling. I also swapped the onboard caps for some 100uF Black Gate "N" and put 1500uF Panasonic FC at the power input to the board. These were all preused bits that have been hanging around, not chosen to be ideal. Had to put the BG's on the underside of the board 'cos the leads were too short and couldn't get the iron round them on top.

Sounds OK so far, alhough the hissing has come back a tiny bit (nowhere near so bad). I suspect this may be because I snaked a bare wire around the board to connect the inductor shields to the ground input. I guess these amps are just hugely susceptible to RFI (or to hamfisted modders who don't really know what they are doing!).

[Markvdv]

What is the function of the extra contact on the inductors?

[dboy]

The extra contact on the inductors goes to a piece of copper foil that surrounds the coil on the inside of the heatshrink. If I remember the thinking correctly then aircores need this shielding more than other types. I believe it is intended to connect to ground.

Keeps garbage in or keeps garbage out? I can't quite remember but probably both. I may have used it incorrectly and am open to being put right. Just fancied joining the party (swapping the inductors on the stock board) and these were handy. I remember the folks at Diyparadise liking the aircores with TA2020 so thought it worth a try.

Not got the amp on my good speakers yet, but with some fairly average ones it sounds very impressive so far - certainly better than stock. The caps have not been used for ages though so will not be at their best for a while.

[rhing]

dboy,

You are probably better off taking that shielding ground wire off since it doesn't appear to be connected to ground anyway. As for hiss, air core inductors are notorious for radiating RFI and they are generally not recommended for audio applications. However, they can provide pleasing sonic results as long as the RFI isn't an issue. If the hiss isn't an issue and the sound quality meets your satisfaction, then stick with the air core inductors.

[fredgarvin]

I've been following this interesting  thread for some time. I'm wondering what you guys think about the cheap $50 tube pre's that some guys are pairing with these amps. To me it seems the pre has to be very limited in it's sonic qualities, in a way that the tiny amps are not. I enjoy my T amps and I don't find them very limiting even in my main system. I sincerely doubt those little pre amps would fare so well. It seems a bit dubious when on another forum guys rave about these little Chinese pairings 'blowing everything else out of the water'. I just can't imagine that to be accurate. The amps alone, possibly so. The Pre just seems to be a limiting factor for the amp. What are your thoughts or findings?

[dboy]

Thanks rhing - the wire is connected to ground but the photo does not show this (inductor in the way). I took the wire off the side of the board and to the bottom of the screw terminal where gnd/0v enters the board. I figured this would give it the best chance of not polluting the circuit - especially if I connect 0v to mains earth at my power supply.

It does actually sound very good and hiss is not a problem now. I can just hear some if I put my ear up to the speaker, but not like before when it really intruded on the music. I'll try disconnecting the wire for comparison when it seems the caps have settled in a bit. I'm expecting the sound to change anyway over the next few days so would be hard to compare.

I should have changed the caps and the inductors on separate occasions to properly monitor the effect. But anyway, before the mods I could definitely hear the 'harsh highs' I read about. Now everything sounds pretty sweet. I've not had chance to listen much but I'm hearing a very delicate touch with acoustic instruments and extremely natural voices.

I've got a Buffalo Dac I made a few years ago with digital volume control, Paul Hynes Regs and just an isolation transformer as the output stage. Sounds bloody marvellous. A member on Diyaudio wrote about replacing the caps on the input of the 3116 with an isolation transformer. I don't think the impedance match is ideal, but I'm tempted to try taking the caps off the front of the 3116 and connecting to the Buffalo output transformers directly. Haven't quite worked up the courage to try this yet, but it is simmering at the back of my mind.

[dboy]

Like Fred, I'm also tube-pre-curious. The approach to DIY that I picked up over the last few years says don't stick anything in the signal path if you don't need it. But those tube-preamps look so pretty and everyone loves 'em!

Surely they can't add clarity to an existing signal... just degrade it in a way that sounds kinda nice?

[rhing]

Thanks rhing - the wire is connected to ground but the photo does not show this (inductor in the way). I took the wire off the side of the board and to the bottom of the screw terminal where gnd/0v enters the board. I figured this would give it the best chance of not polluting the circuit - especially if I connect 0v to mains earth at my power supply.

It does actually sound very good and hiss is not a problem now. I can just hear some if I put my ear up to the speaker, but not like before when it really intruded on the music. I'll try disconnecting the wire for comparison when it seems the caps have settled in a bit. I'm expecting the sound to change anyway over the next few days so would be hard to compare.

I should have changed the caps and the inductors on separate occasions to properly monitor the effect. But anyway, before the mods I could definitely hear the 'harsh highs' I read about. Now everything sounds pretty sweet. I've not had chance to listen much but I'm hearing a very delicate touch with acoustic instruments and extremely natural voices.

I've got a Buffalo Dac I made a few years ago with digital volume control, Paul Hynes Regs and just an isolation transformer as the output stage. Sounds bloody marvellous. A member on Diyaudio wrote about replacing the caps on the input of the 3116 with an isolation transformer. I don't think the impedance match is ideal, but I'm tempted to try taking the caps off the front of the 3116 and connecting to the Buffalo output transformers directly. Haven't quite worked up the courage to try this yet, but it is simmering at the back of my mind.

You should read the Texas Instruments datasheet for the TPA31xx Class D amplifiers.

http://www.ti.com/lit/ds/symlink/tpa3116d2.pdf

You'll read on pages 15 and 16 that the differential inputs are biased at 3VDC, which could spell disaster for your speakers if you remove the input capacitors that also block DC. You can try using your Buffalo DAC outputs, but you must have amp input caps for DC blocking.

Like Fred, I'm also tube-pre-curious. The approach to DIY that I picked up over the last few years says don't stick anything in the signal path if you don't need it. But those tube-preamps look so pretty and everyone loves 'em!

Surely they can't add clarity to an existing signal... just degrade it in a way that sounds kinda nice?

Not sure where you picked up that misinformation. Bad circuits and poor implementation of circuits, good or bad, are what can degrade sound quality. I don't have one of those tube preamps, but many have reported improvements, especially when rolling in better tubes.

[wushuliu]

I've been following this interesting  thread for some time. I'm wondering what you guys think about the cheap $50 tube pre's that some guys are pairing with these amps. To me it seems the pre has to be very limited in it's sonic qualities, in a way that the tiny amps are not. I enjoy my T amps and I don't find them very limiting even in my main system. I sincerely doubt those little pre amps would fare so well. It seems a bit dubious when on another forum guys rave about these little Chinese pairings 'blowing everything else out of the water'. I just can't imagine that to be accurate. The amps alone, possibly so. The Pre just seems to be a limiting factor for the amp. What are your thoughts or findings?

I consider the high gain a limiting factor.

[Markvdv]

I consider the high gain a limiting factor.

+1
ebayseller hiamplifier has an informative schematic for connecting the 3 tube ~23dB gain preamp (find the D-amp)

buffer or low gain might help, a drv134 unbalanced to balanced with 6dB gain might be interesting, any experiences here?

[dboy]

You'll read on pages 15 and 16 that the differential inputs are biased at 3VDC, which could spell disaster for your speakers if you remove the input capacitors that also block DC. You can try using your Buffalo DAC outputs, but you must have amp input caps for DC blocking.

You are correct of course. It perhaps cannot be done easily with this board. Diyaudio member Sharpi did it with the balanced inputs on an Audiobah board (which I have on order). The idea is that because both balanced inputs are biased at 3v the transformer sees no potential difference between them.

The balanced outputs of the ES9018 on my Buffalo dac are also biased at a certain voltage, but because the bias is equally present on both they can be connected directly to the transformer without incident. Gnd is not connected.

Not sure where you picked up that misinformation. Bad circuits and poor implementation of circuits, good or bad, are what can degrade sound quality. I don't have one of those tube preamps, but many have reported improvements, especially when rolling in better tubes.

Well, it was a question rather than a statement so does not really count as misinformation. I was simply explaining the doubt in my own mind about the effect the tube pre-amp could have, while also acknowledging my curiosity and openness to information.

I am no expert at electronics. My PhD. is in a branch of philosophy. To me the question was vaguely philosophical - can adding a whole new circuit (with input and output capacitors, etc.) add new information (clarity) to the signal without actually retrieving new information from the audio recording? Obviously there is impedance matching that can be improved, but other than this I am not clear what can be added to the audio signal that is not a distortion of that signal.

I mean no disrespect. I was and am curious and open-minded. 

[Markvdv]

....It perhaps cannot be done easily with this board. Diyaudio member Sharpi did it with the balanced inputs on an Audiobah board (which I have on order)....

For green Audiobah board you have SMD ceramics going to ground, for blue/black you have through hole film caps going to ground. You need to break that, so desoldering SMD parts a bit or cutting groundplane contact around them, or desoldering filmcap to free 1 leg (to wire directly), both not very hard but I think most would say blue/black was more appealing to them.

[dboy]

Thanks Markvdv - you are right. I had not properly done my homework when I wrote that, just noted that specific instructions had been given for doing it on the Audiobah board.

I have now had chance to connect my modified blue/black board to the output transformers of the Buffalo Dac with no potentiometer but with the caps still in the circuit. Unfortunately there is an annoying background hum coming through. Time for more homework I guess. 

[Markvdv]

You mean Audiobah board comes with instructions? Does it come with schematic indicating what SMD's are used? That could be reason not to replace all parts I mean, although..chinese fake many parts, so faking a BOM is probably too tempting.

[dboy]

Ha ha! No, i meant that Sharpi provided instructions on Diyaudio for using an isolating transformer instead of the input caps.  He specified what to solder and where on that board. Idiot-proof instructions are what I like, and even then it takes me a while to build up to an audacious plot like this.

[Markvdv]

Oh ok. So you removed the inputcaps completely

[dboy]

No - sorry if I was unclear. I have not done that yet. I removed the potentiometer and connected the Blue/Black's L in, R in and Gnd to the Buffalo's output transformers. The Buffalo has a firmware volume control so I can get the pot out of the signal path. I have kept the caps in so far as I like to work up to big changes gradually and to feel like I know what I am doing. So far I don't feel very confident or knowledgable with these boards.

Anyway, there was a hum coming through the speakers even with the caps in, so I have not proceeded to remove them.

I had a hum problem before once with the Buffalo. I used to use a biascap modded TA2020 board (i.e. no input caps!) with the Buffalo. At first I had a Paul Hynes Regulator on the power supply of this. It sounded marvellous with other sources, but with the Buffalo/output transformers there was a hum. I never really got to the bottom of why, but when I changed the power supply of the TA2020 to one based on a Bybee Music Rail the hum vanished. And the sound was (& is) pretty sublime with that setup. I'm intrigued now by the possibility that the TPA3116 might offer me a step-up in performance from this setup.

I don't know whether anyone here has tried a Bybee Music Rail with the TPA3116? They are pricey but made a truly fantastic power supply for my TA2020. I don't want to take mine out of that amp, so am waiting for a new one to arrive from Parts Connexion to try with TPA3116. Just add them on to a linear supply made with transformer, diode bridge and smoothing cap. They reduce noise on your power lines apparently, but also have very low output impedance, which is possibly the key factor. Might be worth a try as an alternative to the regulated supplies that seem popular here? I'll let you know when I get mine.

Sorry for waffling on! 

[lacro]

I've been following this interesting  thread for some time. I'm wondering what you guys think about the cheap $50 tube pre's that some guys are pairing with these amps. To me it seems the pre has to be very limited in it's sonic qualities, in a way that the tiny amps are not. I enjoy my T amps and I don't find them very limiting even in my main system. I sincerely doubt those little pre amps would fare so well. It seems a bit dubious when on another forum guys rave about these little Chinese pairings 'blowing everything else out of the water'. I just can't imagine that to be accurate. The amps alone, possibly so. The Pre just seems to be a limiting factor for the amp. What are your thoughts or findings?

 As I sit here listening to my YJ 3 tube pre, and my stock TPA3116 blue board, I am truly mesmerized by this pair. The TPA amps are way better than any T-Amp I have heard, especially with simple mods. The 3 tube pre just makes everything so much better!
 I can't say this pair blows everything out of the water as I don't have anything better to compare it to, but I will say I agree with what others have said that the SQ from the 3 tube pre paired with the TPA3116 brings tears to my eyes. The 3 tube pre-amp is definitely not a limiting factor for the amp, it's an improvement for sure.
 These things are cheap enough, why not take the plunge and try the combo yourself?

[Folsom]

dboy, I can give you information to try a better linear PSU, with or without Bybee Music Rail. The cost isn't free though, but less than $200. PM if you like.