[baronbeehive]

...................

So..
My tube rolling has come to an end.

Best tubes for this model:
Power tubes = 6F6 / 42 / Russian 6Ф6С / 6F6C Cobra..

Driver tube:
12SL7GT

 
Good work!
 
What is the 42 tube exactly?
 
You used adapters for your tube rolling, but were they also converters, as in voltage converters. I have lots of 6sl7's but no 12sl7's.
 
Could I use the 6F6's as a replacement for the EL84's my amp uses? I just love the way it looks with the big tubes lol!
 
BTW, how did you get your volume knob off?

 

[Maxx134]

...................


So..

My tube rolling has come to an end.


Best tubes for this model:

Power tubes = 6F6 / 42 / Russian 6Ф6С / 6F6C Cobra..


Driver tube:

12SL7GT

Good work!

What is the 42 tube exactly?

You used adapters for your tube rolling, but were they also converters, as in voltage converters. I have lots of 6sl7's but no 12sl7's.

Could I use the 6F6's as a replacement for the EL84's my amp uses? I just love the way it looks with the big tubes lol!

BTW, how did you get your volume knob off?

VOLTAGE ADAPTERS ARE NOT RECOMMENDED!!!
DO NOT USE ADAPTER WHICH DROP 12V TO 6V BECAUSE THEY ARE ALL CHEAPLY MADE IN CHINA USING LOW WATT RESISTOR WICH WILL BURN.
THEY HAVE BEEN KNOWN TO FAIL AND DESTROY YOUR AMP.

I myself tried one (for driver tube on this amp) ,
and although I loved using my 6v tubes, the adapter did get very hot very fast,
So after 4-5min use it was too hot Touch.
BOTTOM LINE IS DON'T USE THEM...

ALSO,
For tube equivalent EL84, check here :
http://www.radiomuseum.org/tubes/tube_el34.html

 

[TheBIGKill1998]

Thank you to everyone who answered my questions on this thread! 
 
 
but i think i should get proper headphones before i get this amp...
also all the tube rolling and the mods would kinda blow my current budget.

 

[benjisun]

   
BTW, how did you get your volume knob off?

 
Also interested, I tried to pull mine off but dont want to break the Knob 

 

 

[baronbeehive]

VOLTAGE ADAPTERS ARE NOT RECOMMENDED!!!
DO NOT USE ADAPTER WHICH DROP 12V TO 6V BECAUSE THEY ARE ALL CHEAPLY MADE IN CHINA USING LOW WATT RESISTOR WICH WILL BURN.
THEY HAVE BEEN KNOWN TO FAIL AND DESTROY YOUR AMP.

I myself tried one (for driver tube on this amp) ,
and although I loved using my 6v tubes, the adapter did get very hot very fast,
So after 4-5min use it was too hot Touch.
BOTTOM LINE IS DON'T USE THEM...

ALSO,
For tube equivalent EL84, check here :
http://www.radiomuseum.org/tubes/tube_el34.html

 
OK, thanks. I have have 6v to 12v adapters made by Glenn but not the other way around! I'll search out some 12SL7's.
 

  Thank you to everyone who answered my questions on this thread! 
 
 
but i think i should get proper headphones before i get this amp...
also all the tube rolling and the mods would kinda blow my current budget.

 
No worries, but just remember, this amp is an absolute bargain in stock form!

 

[TheBIGKill1998]

I will remember, and as soon as i decide to upgrade my headphone amp, this one will be my choice! 

 

[CZ4A]

It's cool to see how far this thread has come since I last posted in here. I like seeing what folks are doing with recaps. I've still yet to install the WIMA coupling caps I ordered months ago!

Anyways, I'm still using the APPJ as my home headphone amp. I have done a little more rolling too - right now I'm burning in a Raytheon 2C52 preamp tube. Power tubes are Mullard EL33s. I also have a FDD20 and adapter on the way.

 

[baronbeehive]

It's cool to see how far this thread has come since I last posted in here. I like seeing what folks are doing with recaps. I've still yet to install the WIMA coupling caps I ordered months ago!

Anyways, I'm still using the APPJ as my home headphone amp. I have done a little more rolling too - right now I'm burning in a Raytheon 2C52 preamp tube. Power tubes are Mullard EL33s. I also have a FDD20 and adapter on the way.

Well, what are you waiting for lol!
This amp is that good it's a keeper for me now. It's proven by the fact that it's on a par with my headphone amp which has been heavily modded, and if a speaker amp can do that then I know it must be good. Frankly I haven't heard anything better.
Re: the tubes, I've decided to stick with my Amperex bugle boy EL84's and TS 5751. The EL84's are all small tubes, not the larger coke bottle type which I would have tried, and the TS's sound similar to the TS12SN7's that I had a while back so I see no reason to change now.
I shouldn't really be posting on this thread but I feel it's an APPJ so why not, the Miniwatt threads are dead now but this one is still going.....

 

[wendyKL]

Hi what is the recommended load impedance on this? I have 18 Ohm headphones (IEM) would they be okay?

 

[CZ4A]

Well, what are you waiting for lol!

I wish I hadn't waited! I installed the WIMA coupling caps over the weekend - yowza, what an improvement all around!

Hi what is the recommended load impedance on this? I have 18 Ohm headphones (IEM) would they be okay?

- Output Impedance: 8 to 600 Ohms

 

[wendyKL]

I wish I hadn't waited! I installed the WIMA coupling caps over the weekend - yowza, what an improvement all around!



- Output Impedance: 8 to 600 Ohms

Thank you, I'll be purchasing one. Black or Silver? hmmm.

 

[baronbeehive]

I wish I hadn't waited! I installed the WIMA coupling caps over the weekend - yowza, what an improvement all around!

.............

Ha, ha, goodwork!

What capacitance wima's did you use? They should be excellent.

I know the Jupiter caps I put In are expensive but the level of realism you get with them is incredible. I only used them because I had one left over from my previous mods so I only had to get one more. Because of them I now have a band playing in my own living room..... btw how do you get rid of them.... they can get a bit rowdy lol .

 

[jekjek]

Hi Guys,

I tried RCA 1633 also known as 25SN7 on the Gemtune amp with 12SN7 adapter and I can tell you that the amp still works properly with a pair of EL33 power tubes!

Imagine the possibility of tube rolling with this cute amp

 

[Maxx134]

Hi Guys,

I tried RCA 1633 also known as 25SN7 on the Gemtune amp with 12SN7 adapter and I can tell you that the amp still works properly with a pair of EL33 power tubes!

Imagine the possibility of tube rolling with this cute amp

Wow, that tube still work when it rated to need double the heater voltage at 25v.!
That 1633 tube is supposed to be a 6sn7 type with just a higher voltage heater:
http://www.radiomuseum.org/tubes/tube_1633.html

Sometimes tube numbers just don't make sense.
It should have been labeled a "25sn7" of the was such a thing..
Probably already used number at the time lol

 

[CZ4A]

Ha, ha, goodwork!

What capacitance wima's did you use? They should be excellent.

I know the Jupiter caps I put In are expensive but the level of realism you get with them is incredible. I only used them because I had one left over from my previous mods so I only had to get one more. Because of them I now have a band playing in my own living room..... btw how do you get rid of them.... they can get a bit rowdy lol .

I used 0.47uf WIMA MKP4 caps per Kryl0071's suggestion. I have some Jantzen Z-Superior 0.1uf caps on hand for my Eico HF81 project. I may try some cap rolling to see if its the caps or the capacitance that have the largest effect on the SQ.

On a side note, I'm glad the designers used actual Rubycon and Nichicon caps in this amp, although they aren't audio-rated.

Wow, that tube still work when it rated to need double the heater voltage at 25v.!
That 1633 tube is supposed to be a 6sn7 type with just a higher voltage heater:
http://www.radiomuseum.org/tubes/tube_1633.html

Sometimes tube numbers just don't make sense.
It should have been labeled a "25sn7" of the was such a thing..
Probably already used number at the time lol

Those four-number tube codes (1633, 7308, 8416, etc.) often mean the tube is industrial-rated. Not always though - like you said the tube designations don't make sense sometimes! However, just because the 1633 works in the APPJ doesn't mean it's working properly. When you run a tube's filaments (heaters) below their rated voltage, it reduces the tube's life by causing cathode poisoning.

https://www.w8ji.com/vacuum_tubes_and_vaccum_tube_failures.htm
We must NEVER operate the 3CX1500A7/ 8877, 3CX800A7, or other oxide-cathode tubes at reduced heater voltage! This would allow the cathode's protective electron cloud to be depleted, and nothing would prevent positive ions from striking and poisoning the cathode.

Tube heaters have a operational tolerance of ±7%-±10% (depending on manufacturer suggestions). The APPJ's preamp section supplies 12.6V for the heater, so you're running the 1633 at 50% lower than what is is rated for. It probably won't last too long.