[1800yolk]

Hi!
I got one. This is really good amplifier. I was skeptical, but decided to try it. You must take several steps to improve the sound. First - replace the two coupling capacitors to wima mkp4 0.47 µf pitch of 15 mm. Secondly, to replace two electrolytic capacitors in the cathode of the tubes at Slimic ELNA 220uF 25V. The third is to replace all the tubes in accordance with your choice.

 
for the First item, what should the nominal voltage of the coupling capacitors be? Thanks!

 

[Kryl0071]

60v in this point so use wima mkp 0,47uF 250V

 

[eluslve]

could you use muse caps instead of elnas??

 

[Kryl0071]

Yes, of course! It is better to take 470uF 25V Nichicon KZ 470uF or Elna Slimic.

 

[eluslve]

if 470 muse caps are used, what voltage coupling caps should I consider?

 

[Kryl0071]

Coupling caps WIMA MKP 0,45uF 250v only. Do not use electrolytic caps!!!!!

 

[stolikat]

Static. Do any of you get a fair amount?

 

[sealykojac]

I recently bought one of these off Amazon and really liked the sound but it's going back. I've been experiencing issues with the left channel dropping out after an extended period of use. Everything would work great for two hours then the left channel would just go silent. I switched tubes and still would lose the left side. Turn it off, let it sit for 10 minutes, turn it back on and once again good for a few hours then it would drop again. Might try a Project amp instead of gambling on another one of these.

 

[Maxx134]

Sad to see that this thread has gone dead even though massdrop keeps selling this amp. I just grabbed some JJ Tesla 6V6's and this sweet Sylvania 12ax7. Cant wait!

I was looking into maybe a Vali2 for a low cost second amp, to use as a "burn-in" amp for headphones and maybe tubes...
Then was looking at project ember hybrid, which I already knew..
I have the "O2" amp which I already rolled opamps but wanted better.

In stumbled upon this unit and it is perfect suited to my needs while giving maximum tube rolling for a small amp..












The stock WIMA coupling caps are very nice , soft , neutral .
The stock sound is also very good.
The Tung-sol reissue newn stock KT88 in picture is alsl a cryset pair..
It is better but not as good as NOS National Union 6L6 ..

The sockets are hard to swap so I would get socket savers.

For driver tube a Valvo e180cc pinch waist preferred over all.

The sonic level is more juicy and almost surpassing level of a "project ember" in some traits, notably the liveliness.

I know very well the sonic traits of the WIMA coupling caps from my past amp mods, so I full expect that doing the Cap upgrade suggested by "Kryl0071" should send this unit into seriously good sound territory.

This tiny amp once upgraded will put to shame many mid grade tube amps...

 

[Kryl0071]

+100%

 

[Maxx134]

I very curious as to why they used surface mount parts on socket side of board,
And what are those solid state devices doing by the output tubes,
And what are the heater current limits for driver tube...

I will eventually open to install some nice coupling caps first...

 

[Kryl0071]

Coupling caps and cathode caps in same time.

 

[Maxx134]

Coupling caps and cathode caps in same time.

Agree..
But I will do a bit more and post pics...


Round two with stock amp( w/nos tubes) versus Project Ember( w/nos tube)...

This time ember wins in soundstage "distance" and elevated treble presence...
Edit:
Change to the New Production Tung-sol KT-66 would make very similar as it also had more distance and treble, but was not burned in.
The point is tube rolling will make one or the other seem nicer.


Soundstage size still deeper on this amp.
Also more linear tonality whereas Ember have a bit pronounced bass & a slight distant mids.

I am fairly certain the stock configuration is holding this baby back..

 

[Kryl0071]

Very interesting. Let us know what you done.

 

[Keeter]

Hello,
I'm a newb to Head-Fi. I'm wondering if anyone has any experiences using Sennheiser HD600s with the APPJ PM1502A. I'm intrigued by this amp and encouraged by what I've read in the few reviews that I could find. Right now I'm using a Bravo Ocean with a NOS GE 12AU7 and it sounds quite nice but the sound stage is pretty flat. I had a Schiit Magni 2 Uber for a while and really didn't like it with my HD600s. It sounded too clinical and thin. I find that the Ocean provides a bigger, more organic sound but the sonic landscape seems kind of one dimensional. What I'm looking for out of the APPJ PM1502A is maybe a deeper, more three dimensional soundstage with some additional clarity in the mids. Of course, let's face it, part of what I'm looking for is also the fun of rolling different tubes through the amp. I guess I should also mention that I'm not interested in doing any surgery or replacing any of the innards - my experimentation will end at tubes swaps.
 
I realize this is a fairly inexpensive amp and might not have the refinement of something higher on the food chain but it would be great to be able to fire it up and add a little more space to Steely Dan, Steven Wilson, or Miles Davis.
 
Thanks!