APPJ-PA0901A Mini Watt Tube Amplifier owners what do you think of it?

Yeah I read that review and it's too bad he didn't use better speakers.

The APPJ S1 was reviewed on 6moons with Zu Druids.
 
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I was looking at the 1501A but decided I wanted more options for tube rolling. This is such a neat little amp and a good alternative to a budget receiver as long as your expectations are in line with what this can and cannot do. The FM interference is the only negative I have about this little amp. For a first time tube experience I think it is a nice way to get to acquainted with tube audio and if you like it then you can start thinking about the next tube amp with say 12 watts per channel. It sounds like everyone is enjoying these in the various incarnations they come in and that is a good thing indeed.
 
Increased wattage doesn't mean improved SQ.

The APPJ S1 makes 2.5 watts and my upgrade path lead me to the 2a3 which makes about 3 watts.

If I buy another SET amp it might be a "45" which makes 1.5 watts.

With HE speakers ( my Lowthers are 98 dbs ) it's hard to tell a difference between 3 watts and 20 watts.
 
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The APPJ PA0901A was my first tube stereo amp (have many tube guitar amps.).

I use a Hegel HD2 DAC (.wav rips from CD) as a source and B&W CM8 series I speakers.

I had a Marantz 6004? SS amp and quickly sold it and had the APPJ for 2.5-3? years...

Now I have a Dennis Had Inspire SE EL84 amp at 5wpc SEP, the APPJ was UL I think. The new amp is much better in many ways- but the APPJ for $200 ish is a deal.

My favorite tubes for the APPJ were 1950s Long Plate Tung Sol D getter 12AX7, Long Plate GE 12AX7, Telefunken ribbed plate 12AX7, and even sometimes GE short plates. Have tons of Mullard 1970s short plates and they always sounded a little too soft. ALWAYS used and still use JJ EL84 tubes.

Also make sure the triode halves match as there isn't a balance control!
 
For new tubes the Sovtek LPS for $12? Is a deal and a half.

From my experience ANY long plate will sound much BIGGER compared to any short plate and I've tried most vintage tubes from almost all makes- (have lots of 12AX7 from guitar use.)
 
DSCI0276.JPG UPDATE The Tung Sol 12ax7 started to crackle on the left channel so back to Amazon it goes. They did a crappy packaging job so the tube got thrown around a bit and I bet this is why it bit the dust. Just ordered a Sovtek 12ax7lps from Tube Depot with balanced triodes for just a bit more than the Tong Sol. So back to the stock tube until it arrives and here is a picture of the packing job from Amazon when I opened the box.
 
I would also advise you to invest in some NOS preamp tubes if you intended on keeping the amp. The NOS Tung Sol 12AX7 long plate D getter in that amp was amazing- usually you can get one for $70-110
 
I will be living with it for the next couple years so may do a little experimenting but the next upgrade will be the output tubes either Sovteks or Telefunkens.
 
I ordered up a new production Mullard 12AX7 for the TubeCube|7 and after a couple of hours I already hear an improvement. This is just a desktop/computer amp, so the speakers are nearfield. Some of the stuffiness seems to be gone from the amp (it is more detailed), and the sound seems to come from just outside the speakers or solidly between them, hovering in air. (Diana Krall is whispering in my ear as I speak; Elvis is gonna be pissed. :D ) The problem now is that I'm under a deadline and supposed to be working, and the music is distracting me. :D Nice little tube for the money. No complaints, and, seeing this is non-critical, I'm not dumping money into expensive NOS tubes here. (I'll save those for the "big" audio rig.) Plenty good enough with this tube, and I've just ordered a matched pair of new production Mullard EL84s to match.
 
I just put two 6094 nos in my PA0901A and get pulsing in both or just one tube after a few min... ideas? Pulse is audible and flashing, but not an arc. Adapters used are from tubedepot.
 
No idea why it would do that especially with the adapters you might want to stick with the EL84/6BQ5 tubes. I'm using a JJ EL84 output and a Sovtek 12AX7LPS and the combo sounds great.
 
So I've replaced the stock 0.1uf coupling caps in the PA1502A with WIMA 0.47uf MKP4 caps, and I'm kicking myself for not doing it sooner! This was already a pretty good amp (esp. with NOS tubes) but WOW, it's superb now! Some folks on the Head-Fi thread have gone further with 1000uf cathode caps in place of the 220uf caps and audiophile coupling caps instead of WIMA. The PA0901A uses almost the same circuit, but with allowances for EL84s instead of 6V6s, so replacing the coupling caps will yield the same results. This post shows the 0901's PCB: https://www.head-fi.org/f/threads/a...une-appj-pa1502a.780178/page-20#post-13392987

Too bad my amp doesn't use a 6DJ8 or equivalent--I used to use one of those Musical Fidelity tube buffers, and I have three spare pairs of tubes from it, plus a single Amperex 7308 gold pin (which sells for north of $75). I likely will sell these off, along with the buffer, since my preamp uses M8080s and I wasn't all that excited about the buffer anyway.

There are two 12V 6DJ8 equivalents out there. The 12DJ8 I think was only made by Sylvania and is extremely rare. The Amperex 8416 is a 12V version of the 7308 made for Tektronix oscilloscopes. It's only "merely" rare. I have an 8416 for my APPJ and it sounds excellent, very similar to the 7308. They go for cheaper than the 7308 (~$35-40 each) on the 'bay.

The 0901 and 1502 supply 12V instead of 6V to the preamp tube. So if you want to roll the preamp tube you'll either need a dual-voltage tube like the 12AX7 or a 12V-only tube with the 6DJ8 pinout, like the 8416, 12DT8, or 12SN7 with the appropriate adapter.
 
So I've replaced the stock 0.1uf coupling caps in the PA1502A with WIMA 0.47uf MKP4 caps, and I'm kicking myself for not doing it sooner! This was already a pretty good amp (esp. with NOS tubes) but WOW, it's superb now! Some folks on the Head-Fi thread have gone further with 1000uf cathode caps in place of the 220uf caps and audiophile coupling caps instead of WIMA. The PA0901A uses almost the same circuit, but with allowances for EL84s instead of 6V6s, so replacing the coupling caps will yield the same results.
Interesting. I can't say I really like this amp (I have the TubeCube|7 branded version of one of these APPJs), but if this opens up the top end and flattens out response to where it should be, I may be willing to dig in and try it. It is OK in my desktop system (due to nearfield listening), but it sounds dull in any other system. They are known to have a high-frequency rolloff. (I didn't find this review until I had purchased mine...and it explains the dull sound.) The tube upgrade did help--I'm running all new-production Mullards in it. Still, not ideal.
 
Interesting. I can't say I really like this amp (I have the TubeCube|7 branded version of one of these APPJs), but if this opens up the top end and flattens out response to where it should be, I may be willing to dig in and try it. It is OK in my desktop system (due to nearfield listening), but it sounds dull in any other system. They are known to have a high-frequency rolloff. (I didn't find this review until I had purchased mine...and it explains the dull sound.) The tube upgrade did help--I'm running all new-production Mullards in it. Still, not ideal.

The APPJ is pretty easy to disassemble, so it took me all of 15 minutes to do the cap upgrade. I think the capacitance increase has a greater impact on the sound than the brand of cap. So if you have any nonpolar, 250+V, 0.3uf-0.5uf caps lying around I think it's worth replacing the coupling caps. If you like what you hear than you can replace those with your favorite brand later and also upgrade the cathode caps to 1000uf.
 
No idea why it would do that especially with the adapters you might want to stick with the EL84/6BQ5 tubes. I'm using a JJ EL84 output and a Sovtek 12AX7LPS and the combo sounds great.

It was after seeing this: http://glowinthedarkaudio.com/RH-EL84.html , and reading the spec sheet on the 6094 is what intrigued me to get a set, even if they don't "show" well in the APPJ, at least I own a set, before they are gone, to try on a better SET amp later.

For the last 39 years I have been involved in making equipment used to make solid state devices, PVD sputtering and evaporation systems. The only tubes I used were for RF 1-5Kw generators, that have also been almost 100% replaced by solid state. Well,,, I got the tube bug, and am intensely intrigued by the nuances, old tribal knowledge vs new, in tube manufacturing. These 6094's look to be the epitome of an EL84 design, and you can shoot them off in a rocket if you so desired...

The HK fellow I got the 6094's from is sending me the "proper" adapters, with internal resistors, not just the pin out changes, that he forgot to send with the tubes. The adapters I got from tubedepot.com do not say if they have resistors for gain internally, waiting for a response from them.

Currently running all nos Baldwin Raytheon black plates, do sound great.

Any other input would be great; go with a 12AT7 vs the 12AX7? different coupling caps?
 
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APPJ has made five different models which include my S1 ( 4 tube ) , the N3 ( 3 tube ) , the 2 tube ( power supply on bottom ), the 4 tube ( power supply on bottom with same tube compliment as the S1 ) and the latest which is the PA1501A shown below. From all accounts the 1501A is the best of the bunch.

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This Is kind of cool. I saw a build thread using those and thought it would be a fun build. But at that price I might just order one. I just read another one where a dual triode was used that was made for a tv as well. Only two tubes and 1.5 wpc.
 
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