[raoultrifan]

If it does the job well, then "mission accomplished".
Hope that small AC/DC switching supply is not inducing any noise; I see it's positioned nearby input traces and plugs.

 

[canthearyou]

If it does the job well, then "mission accomplished".
Hope that small AC/DC switching supply is not inducing any noise; I see it's positioned nearby input traces and plugs.

No noise that I can hear. That's why the power wire was long in the pic. I was testing areas to see if it introduces noise. The power supply is actually an old usb phone charger I had lying around. I gutted it and soldered some power and output leads on. Then I used thick heat shrink tubing to cover it.

It's been running continuously since around noon. Hottest spot I can find on the case is 83.9*F. That's right where the heatsinks are bolted to the cover.

 

[migasson]

The HPA-3U sounds brilliant!
 
I'm using HD600's, standard cable, stock amp, and DSD64, Brubeck, "Time Out" There's nothing wrong with this amp as it stands. Maybe I'm less picky, but this images great, soundstage is just spot on, bass delivery is just right for me. 
 
I don't think I need anything else. It's a great natural sounding system. I won't hang around here.. starts giving me ideas. 
 
Signing off HeadFi again.

 

[canthearyou]

I'll be trying the Sparkos Labs op-amps here shortly.

Placed the order today. Hope they sound great!

***Received the op-amps today. Very first things noticed are the soundstage and instrument separation. Improved upon compared to the stock op-amps.

Will add more after more listening.

 

[canthearyou]

Ok. After a few hours listening I have a few more things to add. The Sparkoslabs op-amps are crystal clear! I am hearing new things in songs I've heard a hundred times before. I can't even really describe it. Pitch black background, extreme instrument separation and positioning.
Compared to the stock op-amps it's not a night and day difference. More like a black hole and a supernova.

I wish I didn't just sell my Gustard H10 because I would've liked to hear a full set of Sparkos in it.

 

[canthearyou]

DT880/600 sounds great on HPA-3B. With this new balanced cable soundstage increased and details seem more focused. I really think that moving from single-end to balanced is a real upgrade for anyone, especially if DAC is really-balanced as well.

BTW, I'm already thinking in doing few "mods":
- upgrading volume knob with a black anodized aluminium knob as burdie suggested (headamp will look much better)
- adding an EMI/RFI AC noise filter (should take care of any possible AC line hum/noise)
- shielding toroidal transformer with G.O.S.S. (Grain Oriented Silicon Steel)
- replacing WIMA MKS 4 (Metallized Polyster) with JB JFX Premium Film Cap (Polypropylene Film)
- replacing 2SC3421/2SA1358 1A/10W transistors with 2SC5171/2SA1930 2A/20W transistors used in Burson HA-160 (I don't think sound will change, but the heatsinks temp should decrease with at least 5C)
- increasing heatsinks on the voltage-gain transistors (these 4 small heatsinks inside the headamp are incredible hot!)

I don't really believe I will have the time to do all of these mods, but at least some of them will probably do sometimes.

Thanks,
Raul.

Raul, do you have a direct link to the JB JFX poly caps?

 

[raoultrifan]

Hello,
 
I bought my capacitors from TME (http://www.tme.eu/ro/details/jfx-4.7u_250/condensatoare-cu-polipropilena-audio/jb-capacitors/), but more details could be also found herel: http://www.jbcapacitors.com/Plastic-Film-Capacitors/JFX-Premium-Metallized-Polypropylene-Film-Capacitors-Axial.html.
 
MKP caps made by WIMA, MIFLEX etc. should be a fine choice too, per their price/quality ratio.
 
Regards, 
Raul.

 

[canthearyou]

Thanks!

 

[canthearyou]

Any U.S. source for the JFX caps?

 

[canthearyou]

Here we go! Just finished modding my HPA-3B.
 
My main reason for this mod was to lower the voltage to allow me to swap other op-amps. I went with Sparkos Labs discrete regulators in 15V.
 
I started by removing all necessary components. 

 
Here is the new discrete regulator mounted to the heatsink. The reg is not insulated so I used an adhesive thermal pad, some thermal paste and a nylon shoulder washer to make sure it was well insulated.

 
I had to make room for the new regs and that meant moving the caps closest to it.

 
 
As you can see in the above photo, the new reg interferes with the capacitor directly in front of it. To remedy this I ordered a pair of ELNA Silmic II caps. I angled the wire leads to offset the position of the cap.

 
Here is the completed board.

 
And here it is ready to test. I am running Sparkos Labs discrete op-amps.

 
Here it is in its fan cooled case I did a few weeks ago.

 
I want to thank Mr. Andrew Sparks of Sparkos Labs for his patience in answering all my questions.
 
I will get some listening impressions in a little bit.

 

[canthearyou]

I've given the new amp a decent listening. It is powerful, clear, and revealing. It allows me to hear things I've never heard before. I can hear the artist breathing between passages, guitar picks plucking the strings, the grain/grit of a bow on a violin. It sounds like cymbals and tambourines are live. Vocals have a new life to them.

One thing I noticed is that each sound is pronounced on its own. I can't really explain it. I guess it would be separation. And there is zero "fuzz" around each sound. The cleanest sound I've heard yet.

 

[raoultrifan]

Nice clean work, I totally love it!
 
BTW, after lowering the voltage I believe you don't really need that fan anymore, what do you think?
 
P.S.: In case you'll find out a scope around sometimes it would be great to measure AC ripple after Sparkos power regulators.

 

[canthearyou]

Nice clean work, I totally love it!

BTW, after lowering the voltage I believe you don't really need that fan anymore, what do you think?

P.S.: In case you'll find out a scope around sometimes it would be great to measure AC ripple after Sparkos power regulators.

Thank you! Like you said I probably don't need the fan anymore. But since I already drilled holes and all that, I'll keep it. I did lower the fan speed quite a lot. It is completely silent.

I don't have a scope of my own, but the specs on the Sparkos are great.

 

[allinhead]

hi guys, look awesome !
 
i want this amp but ther is a big but 
 
this "heatsink" amp is so hot ? i mean can you let your hand on the top of it or it s burning you ?
can you fell the warm at 1m away ?
 
i live in very hot country with out air condition so it s important for me 
(i am not DIY guy by the way)
Thanks

 

[raoultrifan]

Hi, it is hot indeed, but that should be expected from a Class-A amplifier. All Class-A amps are getting hot after 1 hour or more of operation, so if amp heat is so important for you, then maybe you could get something "cooler" working in AB-class.
 
Note: Theoretically a Class-A amplifier may sound better than Class-AB-or Class-D amplifiers, so this is why most audiophiles are trying to buy Class-A.