[randytsuch]

A couple of weeks ago I finished building a pair of Little Giant Killer (LGK’s) designed by Danny at GR Research.  So I connected my Audiobah TPA3116 amp up to drive them.

The amp is powered by an Astron RS-12A power supply.  The supply is adjusted to 12VDC.  I did this when I was using the Astron to power my PC, and I didn’t readjust it back to 13.8VDC.

I have already made several mods to the amp.  I swapped out the two input power caps.  I have a pair Nichicon 1000uf caps.  They are mounted on the bottom.  I also have a pair of Oscon 330uf caps mounted on top. 

I implemented the bootstrap snubber mod using surface mount parts.  I used a 470pF cap and a 11 ohm resistor because that’s what I had available.  470 is easier to find than 330 pf, but I have no idea if it makes a difference or not.  Using surface mount parts wasn’t too hard, but I have built stuff with SM before so it isn’t new to me.  You need the right tools, a good pair of tweezers, find solder and a good iron with a small tip. 



As shown in the picture, I soldered one end of the 470 pf caps to existing caps on the board.  The existing caps go grom the bootstrap pin to output.  I soldered the 470 pf caps to the output end of the caps.  I put kapton tape under my additional parts to make sure there would be no shorts, even though there is already solder mask.  I soldered my 11hom resistors to the other end of the 470 pf caps, and then scrapped off some solder mask at the board ground so I could solder the other end of the 11 ohm resistor to ground.  For a couple of the resistors, I used some copper tape to get from the resistor to the ground point.

At the input end, I removed the 4 input caps, and feed the amp a differential input signal.  My dac has Lundahl LL1684 output transformers.  I used fine wire to connect the input signals to the right (3116) side of the input cap pads.  This is not as hard as it sounds, as long as you have the tools I described above.

Here is a picture of the input.  I run a fine wire from the cap pads to the RCA jacks.




Finally I replaced the output inductors.


I used copper tape to connect the inductors, and needed to scrap off some solder mask so I could connect.

The rest of my system is fully balanced from my ES9018 DAC, which is connected directly to the amp.  The DAC handles volume control, so no preamp is used.  I hear almost no noise from my amp when I put my ear right against the driver, and system is very transparent.  Input to DAC is USB through a highly modded PC.  PC is powered by linear PS’s among other tweaks.

So I’m pretty sure my amp sounds better than the most TPA3116 amps because I already had Lundahl transformers in my system, so I was able to remove the amp input caps and run the input signal differentially directly into the amp.

But given this, it sounds really good.  I’m impressed by the sound I’m getting out of the combination of my amp and my LGK speakers.


Longer term, I’m going to build the Dug 3116 boards which are designed for dual mono operation.

[Markvdv]

If your not considering PBTL with ac1308...the bootstraps have each a solderpad for snubber

[dboy]

Randytsuch, great to see a fellow traveller with the ES9018 - transformer - tpa3116 balanced inputs approach. Makes a fine dedicated digital setup indeed. I liked the YBDZ board more than Audiobah. I suspect your dual mono Dug boards will be even better! Happy listening. 

[randytsuch]

Hey Mark
I guess I should have looked at the other side
The board was already mounted, and I was too lazy to unmount it to look at the backside.  And it really wasn't too hard to do it the way I did it.

Dboy
What ES9018 do you use?
I have the first generation of this one
http://www.audiodesignguide.com/DAC32/
I like it because it has all the voltage regs built in, and it came with a display and a microcontroller that handles the volume.

I have lundahl 1684 trannys on the dac output.

Randy

[rhing]

Nice work Randy. You must be a neurosurgeon to be able to modify the Audiobah board like that. Indeed, having high quality transformers like the Lundahl's on your DAC output and feeding the signal directly to the differential inputs of the TPA3116 amp IC is an ideal setup.

I just received my DUG TPA3116 PBTL amp PCB's with the TPA3116 IC's mounted on them. I purchased these PBTL boards through the diyAudio.com Group Buy thread:

http://www.diyaudio.com/forums/group-buys/257996-gb-tpa3116-8-pbtl-bare-pcb.html

I can work with the other SMD's, but I didn't want to risk wasting my money or boards trying to mount the TPA3116 IC's myself. DUG will test them too for an additional charge.



In the meantime, I've been assisting Roger Modjeski of Music Reference and RAM Tubeworks in setting up his audio engineering school and laboratory near Berkeley, CA. The other day I was at his lab, he lent me a prototype of a single 12AT7 dual triode line stage preamp. I've been listening to this preamp in my system, and I am really amazed with how well this works with my modified Yuan Jing TPA3116 blue amp. It is giving my Audio Research LS7 some serious competition. I am trying to talk Roger into making this preamp a DIY project to offer through the school.

Roger is willing to test my modified TPA3116 amp in his lab and get measurements. Should be interesting what we measure.

[dboy]

Dboy
What ES9018 do you use?
I have the first generation of this one
http://www.audiodesignguide.com/DAC32/
I like it because it has all the voltage regs built in, and it came with a display and a microcontroller that handles the volume.

I have lundahl 1684 trannys on the dac output.

Randy

It is a Twisted Pair Buffalo II kitted out with a full set of Paul Hynes regs and the 'Volumite' volume control. Goes into Sowter 3575 (OCC wire version) then to YBDZ board with upgraded caps and inductors (Bourns) and gain set for 60k input impedance. At the moment I'm still on RBCD via a Stello transport (not the really pricey ones) but I recently bought a Windows 8 tablet partly thinking to try that for some ones and zeros. Haven't got around to it yet, still pondering on the USB converter. The huge improvements I've heard with my current setup have directed my imagination more toward making new speakers (hope that makes sense), but funds are a bit tight at the moment so not rushing into it, just enjoying the current system hugely. 

P.S. Had a look at the link for your dac, looks fantastic. Hadn't come across that one before.

[randytsuch]

It is a Twisted Pair Buffalo II kitted out with a full set of Paul Hynes regs and the 'Volumite' volume control. Goes into Sowter 3575 (OCC wire version) then to YBDZ board with upgraded caps and inductors (Bourns) and gain set for 60k input impedance. At the moment I'm still on RBCD via a Stello transport (not the really pricey ones) but I recently bought a Windows 8 tablet partly thinking to try that for some ones and zeros. Haven't got around to it yet, still pondering on the USB converter. The huge improvements I've heard with my current setup have directed my imagination more toward making new speakers (hope that makes sense), but funds are a bit tight at the moment so not rushing into it, just enjoying the current system hugely. 

P.S. Had a look at the link for your dac, looks fantastic. Hadn't come across that one before.

A Buff II with PH regs and Sowter TX outputs must be a nice sounding DAC.

Off topic, but the Amanero USB to I2S converter is probably the best low cost way to get USB audio into you Buff II.
http://amanero.com/

He had a bunch of group buys at diyaudio for around $60 a card, but I don't think he is doing that anymore.

For more money, the Sonore looks nice.

And I was able to built an audio PC pretty cheaply, I have a thread in the diy section here about my build, but I already had some of the parts which saved some money.

It is a pain to rip all your CD's to a PC, but once you do it, and get used to it, you can't go back to handling disks.

Randy

[dboy]

Randy, thanks very much for the recommendation of the Amanero. That looks a very strong contender.

I am currently a little out of my depth with the full complexities of computer audio, but will get there. I have to admit to being one of those guys who actually like handling discs and having a physical music collection. But then it is hard to argue with better sound. I'll look up your PC build thread for info. I built my current PC to be very quiet - only one fan including in PSU - but that was more because I valued the silence for writing. I don't really want a PC in the living room though, and am hoping the tablet will do an acceptable job (no fans and running on battery sounded a good start to me, but I could be wrong).

[randytsuch]

My PC has a linear PS, no fans.  It actually has 3 linear power supplies, and I'm still going to tweak it some more.

I have one fan, for the processor heatsink, and it's really quiet.  You basically have to be right next to the PC to hear it.

I'm convinced that a dedicated audio PC is the way to go, but that's my opinion. 

Randy

[dboy]

Indeed, I just spent a while reading your thread and with the attention to detail you have paid I don't doubt that that is a phenomenal solution.

[ClefChef]

I followed dboy's lead and installed a pair of CineMag CMLI-15/15B input transformers on my modified Yuan Jing blue amp. This has to be the ultimate mod for these amps. The soundstage is huge and the tonality is so natural. I wouldn't recommend this for a desktop computer system, but if you use these TI Class D amps in your main system, this should be a serious consideration.

I put two amplifiers together using modified Audiobah boards - one with CMLI-15 inputs, and one without.  I burned both for at least 75 hours before listening. Transformers gave the amp what I felt was harsh and somewhat accentuated top end that gave me listening fatigue. Capacitor coupled amp sounded significantly smoother on the top end.  After listening for a while I took out the Cinemags and replaced them with Wima 3.3uf caps (just as in the other amp) - now it sounds excellent.

both amps R-input = 30k

Good experiment, but in my case it did not lead to superior results.

[ClefChef]

I suppose I should have loaded the transformer output with 30k resistor to get 15k resistance (given 30k amp input resistance), but I don't think results would have been too much different 

[Markvdv]

I put two amplifiers together using modified Audiobah boards - one with CMLI-15 inputs, and one without.  I burned both for at least 75 hours before listening. Transformers gave the amp what I felt was harsh and somewhat accentuated top end that gave me listening fatigue. Capacitor coupled amp sounded significantly smoother on the top end.  After listening for a while I took out the Cinemags and replaced them with Wima 3.3uf caps (just as in the other amp) - now it sounds excellent.

both amps R-input = 30k

Good experiment, but in my case it did not lead to superior results.

I am curious if you noticed a difference in bass output too.

[Markvdv]

I suppose I should have loaded the transformer output with 30k resistor to get 15k resistance (given 30k amp input resistance), but I don't think results would have been too much different 

Did you use a preamp or a passive potmeter? If a pot, was the pot befor or after transformer?

[ClefChef]

I used LDR preamp (~20k constant z), fed by a DAC (600R). Transformers were after the LDR, directly into TPA chip.

[randytsuch]

I used LDR preamp (~20k), fed by a DAC (600R). Transformers were after the LDR, directly into TPA chip.

So it could have been a synergy thing with the LDR.  The output impedance of a LDR may not be a good match for driving a transformer.

Randy

[ClefChef]

So it could have been a synergy thing with the LDR.  The output impedance of a LDR may not be a good match for driving a transformer.

Randy

Could be or it could just be the transformer sonic "signature". Transformer primary impedance is high enough not to affect the sound, higher impedance output loading should not negatively affect the sound either. Oh well...

[ClefChef]

[randytsuch]

Could be or it could just be the transformer sonic "signature". Transformer primary impedance is high enough not to affect the sound, higher impedance output loading should not negatively affect the sound either. Oh well...

LDR's are known to be finicky about the system they are used in because of their impedance.

And Cinemag transformers have a good rep, so I would be surprised if this is an issue of the transformer sonic signature.

So I'm inclined to believe the cinemags and LDR's are not a good match, or for that matter any tx with the LDR.

Randy

[Folsom]

20k is simply high. These amps would do well with a buffer. As is 20db gain with a 10k volume is about as good as you'll get for analog/attenuator control.