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Any opinions / reviews on Gemtune APPJ PA1502A - Page 20

post #286 of 296
Quote:
Originally Posted by Maxx134 View Post

OK here are some pics of my internal/external mod:

...

...

...

...

...

...


I can safely say I can place this baby next to any amp and it will hold it's own in quality sound.
All areas of sound are now top notch.(detailing/depth/dimensionality/realism/micro¯o dynamics)

The only weakness was in blasting.
Like my 20ohm HEKV2, it did so, but did run out of gas at a earbleed levels of end game power.
I was still able to shake them good and with other cans it did have authoritive power.
I atribute this to the 1000uf cathode caps as suggested by member "Kryl0071".
smily_headphones1.gif


Edit2:
As I am nit-picking here , I would say channel separation is not at endgame level,
I believe due to using one tube a driver for both channels..

This applies to every amp like this in my opinion.
Still very good but probably 95℅ of what it can be.

It is not fair for me to compare it to a "balanced" OTL & OCL tube amp,
But it still is quite impressive considering this amp is less than $200,
and the upgrade was $134 in parts ..

So for about $330 total plus some soldering you get near top level sound!

Hi Max,

Can you show us the soldering points you did on the other side of the board please?

I am trying to do the same mod as you

Below is the pictures of my board. Looks like i have version 1 board

 


Edited by jekjek - 3/20/17 at 4:53pm
post #287 of 296
Yes they are the same exact points posted in thread by others,
but I will post again:

smily_headphones1.gif

I am trying to find the top​side pics..
post #288 of 296
Here is a close up of the Electrolytics and the film caps soldered on the leads.

For the square coupling cap replacement,
I used silver wire in the holes to bring wires to that area for big coupling caps..

Edit:
Go here for clear pics on the solder points on the topside / surface mount side of board:

https://www.aradiogurl.net/hhjournal/2016/06/01/gemtune-pa1502a-appj-headphone-tube-amp-mod/

smily_headphones1.gif
Edited by Maxx134 - 3/20/17 at 7:03pm
post #289 of 296

Below us my modified appj 1502

 

I would like to say thank you to @Maxx134 for his support

 

My modification is:

- wima 0.47 uf 400v

- panasonic fr 1500uf

- solen 0.1 uf

 

I have completed the modification but there is no sound on the right channel

I will need to resolder it again tonight

post #290 of 296
Wow that is excellent work!
Now onto your "no sound" issue.

The board is double sided.
It is also easy to rip the trace :pads: were the leads go into hole.

Although you should check the right side coupling cap first,
My guess is the right side electrolytic cap not have ground connection.

That is where my trace broke when I pulled out old one,
and then it was essentially an open circuit.


So, on those holes that I pulled up the trace, I had to scrape the board to expose the copper trace.
post #291 of 296
Quote:
Originally Posted by Maxx134 View Post

Wow that is excellent work!
Now onto your "no sound" issue.

The board is double sided.
It is also easy to rip the trace :pads: were the leads go into hole.

Although you should check the right side coupling cap first,
My guess is the right side electrolytic cap not have ground connection.

That is where my trace broke when I pulled out old one,
and then it was essentially an open circuit.


So, on those holes that I pulled up the trace, I had to scrape the board to expose the copper trace.

Thanks Max
Its working now


I'm using EL33 with old Philips ECC83
Sounds awesome. Very smooth

EL33 is basically octal version of EL3N.
post #292 of 296
I never tried that ...
EL33 Hugh?
Ok now I wanna try!
Also caps need burn in..
Edit**
I just checked and EL33 is not as optimal as it will give lower output performance over 6v6 in this amp.

EL33 may still sound very good as those tube number are usually designated from Europe.
Edited by Maxx134 - 3/23/17 at 10:22pm
post #293 of 296
Quote:
Originally Posted by Maxx134 View Post

I never tried that ...
EL33 Hugh?
Ok now I wanna try!
Also caps need burn in..
Edit**
I just checked and EL33 is not as optimal as it will give lower output performance over 6v6 in this amp.

EL33 may still sound very good as those tube number are usually designated from Europe.

Agree about the lower output however people from the felix audio elise gang loves it

Let me try and compare the EL33 vs rca 6v6 this weekend
post #294 of 296
Quote:
Originally Posted by Maxx134 View Post

.........
That is where my trace broke when I pulled out old one,
and then it was essentially an open circuit.


So, on those holes that I pulled up the trace, I had to scrape the board to expose the copper trace.

 

He, he...... I've been there, tell me about it!

 

I just wondered if you guys would be interested in the other .....!!! APPJ ...... the Miniwatt, or APPJ PA0901A speaker amp. This amp is just so good I don't want anything else, but having already modded my LD I'm interested in pushing it to see how far it will go. I'm from the Little Dot Supermods thread along with Maxx134. I'm planning on doing the coupling and cathode caps mod to this amp also.

 

I've had the little Miniwatt for 5 years or so and am pretty awestruck with it, I can say. I'm using it with only 87db speakers yet it sure rocks. I'm planning on adding the highly rated Jupiter copper foil, paper and wax caps, and the Audio Note Kaisei's that Maxx134 has used. My alternative plan if the Jupiters produce too much bass for my set up is to use Audyn True Copper caps with a lower capacitance than Maxx134 used because the amp as it is produces plenty of bass for me and the 0.47uF Jupiters might just be too much of a good thing! While increasing capacitance for headphone amps is the thing to do to get better bass I'm not sure about doing that for a speaker amp.

 

Anyway if you are interested I will report back when I've done the mods.

 

I didn't know about this sister amp until recently, great thread guys :p.

 

Edit:

Thanks to Maxx134 for the info on the mods.


Edited by baronbeehive - 3/24/17 at 2:48pm
post #295 of 296
Quote:
Originally Posted by baronbeehive View Post

He, he...... I've been there, tell me about it!

I just wondered if you guys would be interested in the other .....!!! APPJ ...... the Miniwatt, or APPJ PA0901A speaker amp. This amp is just so good I don't want anything else, but having already modded my LD I'm interested in pushing it to see how far it will go. I'm from the Little Dot Supermods thread along with Maxx134. I'm planning on doing the coupling and cathode caps mod to this amp also.

I've had the little Miniwatt for 5 years or so and am pretty awestruck with it, I can say. I'm using it with only 87db speakers yet it sure rocks. I'm planning on adding the highly rated Jupiter copper foil, paper and wax caps, and the Audio Note Kaisei's that Maxx134 has used. My alternative plan if the Jupiters produce too much bass for my set up is to use Audyn True Copper caps with a lower capacitance than Maxx134 used because the amp as it is produces plenty of bass for me and the 0.47uF Jupiters might just be too much of a good thing! While increasing capacitance for headphone amps is the thing to do to get better bass I'm not sure about doing that for a speaker amp.

Anyway if you are interested I will report back when I've done the mods.

I didn't know about this sister amp until recently, great thread guys tongue.gif .

Edit:
Thanks to Maxx134 for the info on the mods.

Dig it. Show us what you have done
post #296 of 296

OK, thanks. I'll let you know how the mods went when I've done them, I've got to order the parts first, the fun comes later!!

 

Forgot to say my APPJ has EL84's for power tubes instead of your 6V6's, I have Amperex Bugle Boy type power tubes and Tungsol 5751 for the 12AX7.

 

Edit:

Parts on order.


Edited by baronbeehive - Yesterday at 6:30 am
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