Gemtune APPJ PA1501A Mini Tube Amplifiersearch

Gemtune APPJ PA1501A Mini Tube Amplifier

Gemtune APPJ PA1501A Mini Tube Amplifier

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Hi all I bought the Gemtune APPJ PA1501A Mini Tube Amplifier some time ago. I love the sound it makes and the look it gives. BUT I have a problem it broke and I can not find a part list or drawing of it to by new parts. Is anyone able to help ?
Hi all I bought the Gemtune APPJ PA1501A Mini Tube Amplifier some time ago. I love the sound it makes and the look it gives. BUT I have a problem it broke and I can not find a part list or drawing of it to by new parts. Is anyone able to help ?
https://www.youtube.com/watch?v=p3vXNmGx-h8
I changed the coupling caps from the stock .12uf to some .47uf Solen AGM silver sounds and the bass response is much better now. Linear down to below 16hz. Blue is before, green is after.
FYI, I bought mine in the last drop so I've only had it for a couple of months and this weekend it essentially blew up. Smoke started coming out of the unit and it stopped working completely. I'm waiting to hear from the help center here and don't know if I got a bum unit but thought I'd let people now.
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Orbus
speakers plugged to it.
Orbus
Energy speakers as out and computer as input.
I'd pay a little more for a minimum 8 watts / channel into 8Ohms ... My speakers are 89dB efficiency rated and I know I need that so as not to much the amp into distortion areas I don't want to be in. I missed the Glow Audio Amp Two .... PLEASE bring that drop back. I want to buy one at the price it was offered at previously!!!
I measured mine and can confirm the frequency response has the bass roll off focalpoint reported. People have improved bass response of the APPJ PA1502A headphone amp by changing the coupling and cathode bypass capacitors to larger ones. It looks like this amp uses almost the exact same parts, so I'm going to try the mods and see if they help. Hopefully the bass isn't just limited by the output transformers. In any case it's not a big deal if you're using a sub, you can just turn it up a little.

All of the orders have been shipped and are now on the way to you! Once tracking is available, you will receive a confirmation email with tracking information. Please allow 24-48 hours for this information to update in the courier’s system.

If you have any questions, please visit our Help Center (http://massdrop.com/helpcenter).

We're also on Instagram! We'd love to see photos of the drops you've received. Give us a follow Massdrop and tag your pictures #massdrop. https://instagram.com/massdrop
Bulk shipment received! Our warehouse team confirmed that the group's order arrived earlier and now they're working hard to break everything down into the individual packages for shipment to each of you. We will monitor their progress closely and update the group once all packages are sent out.

Expect another update from us on 9/13 or sooner if something comes up.

If you have any questions, please visit our Help Center (https://massdrop.com/helpcenter).
Thanks again for joining this drop! We have submitted the group's order with the vendor for the Gemtune APPJ PA1501A Mini Tube Amplifier and they are working hard to prepare it for shipment.

As soon as the group's order is ready at the vendor's location, they will send the bulk shipment to our warehouse in New Jersey where our warehouse team will break it up into individual orders and ship them. The current estimated ship date from our warehouse is 9/19.

We will keep the group updated throughout the fulfillment process. You can expect an update from us by the end of the day Pacific Time on 9/6.

If you have any questions, please visit our Help Center (http://massdrop.com/helpcenter).
Sure. I'm not too worried about it but we can close the loop anyway.
I received my amp in the most recent drop a few days ago and just got around to putting it through its paces. For the tests, I used two sets of speakers in addition to advanced measurement equipment. For speakers, I used both Klipsch RB-4 II (small bookshelf with a 4" driver and a horn) and an Ohm Model D (small floor speaker with a 10" woofer and a phenolic ring tweeter). For test equipment, I used a Keithley 2015P THD Multimeter, a Sencore PA81 Stereo Power Amplifier Analyzer, and an Audio Precision System One audio analysis system. My listening impressions, and measurements, were delivered after letting the amp play a tone into an 8 Ohm dummy load for 8 hours over a couple of days several hours at a time, and after having warmed up for 15 minutes.

I'd have to say that I enjoy the sound of the amp well enough. Paired with my efficient speakers I never felt like it was really straining to give me the volume I wanted, without much distortion. Mid-bass through treble was well defined, but the bass was much more reserved than I expected it to be. It's very quiet even with the volume turned up at no signal, surprisingly. Running in Class A certainly helps. The fit and finish was probably a 7/10. Some of the machined edges were a bit rough, and the machined knob manages to actually be *sharp* in one spot. The volume knob doesn't rotate perfectly smoothly through it's travel, it binds slightly in the middle. The transformer covers are a nice touch with the standard-spacing banana plug receptacles on the rear, but it's also obvious they're concealing small output transformers. With an output transformer, the more iron you have the better bass you'll get. Small transformers limit the low-end power available but large, good quality transformers quickly get expensive.

The tube this amp uses, 6AD10 has a pentode voltage amplifier and a 4.2W beam power tetrode section, so it can serve as both input and output tubes in one. These tubes were originally designed to be the integrated audio sections of entry-level televisions towards the end of the tube era, among other things. I couldn't get the bottom cover off due to the corner screws using something I don't have in my toolbox but I could see Nichicon electrolytic capacitors and possibly WIMA film capacitors inside, and the board looked well made. It seems to use a switching power supply.

While some individual variation is possible due to manufacturing differences in tubes and component quality, I did find the manufacturer's specifications to be somewhat...optimistic. Most surprisingly were the sensitivity and frequency response measurements.

The manufacturer proposes 3.5W into 8 Ohms with 500 mV sensitivity, in other words, with the volume control turned to maximum applying a 500 mV signal to the input jacks will cause the amplifier to deliver 3.5W into an 8 Ohm load. However, as shown on the "Sensitivity Into 8 Ohms" my example of the amplifier only delivered 2W; it took about 1.5V at the input terminals for 3.5W output. Into 4 Ohms, the amp fared even worse making about 1.7W with 500 mV, rising to 3W at 2V. At those power levels, I'd be worried about damaging something if operated that way long-term. The kink in the sensitivity charts occurs about 700 mV and gives about 3W into 8 ohms or 2.7W into 4 Ohms, and that's as hard as I'd really like to push it.

The frequency response was somewhat lacking as well. Gemtune specified 30 Hz - 40 kHz +/- 1 dB. (Generally, the level at 1 kHz is defined as 0 dB) The amp's upper -1 dB point is very close to 40 kHz so I'll give them that one (Freq Response 10-100K) but the low-end frequency response was disappointing. Makes sense why I felt the bass was lacking. The channels diverged by about 0.5 dB on the low end (less than the specified frequency response flatness by comparison, so that's good) and the -1 dB point was 46-55 Hz; at 30 Hz it's down to -2.3/-2.65 dB and at 20 HZ it's down to -4/-4.55 dB.

That's not to say I think the amp is a bad performer. I think it's a good, starter tube amp. It's not trying to be anything more than what it is, which is a slightly novel desktop tube amplifier with a sleek and minimalist design that will fit in nearly anywhere. The 6AD10 tube is an interesting touch, and they're available pretty inexpensively. You'll probably want a DAC to drive it, as testing with a cell phone and a small desktop computer showed that those devices just didn't have enough oomph to get more than 1-1.5W of output even at maximum hardware, OS and application volumes. If you have a nice PC with a good sound card, you could probably drive this directly. It only has one input, so keep that in mind.

Overall, this is a 3/5. It's value matches the price paid for it, and this type of performance is what you get for that price. A great splurge for a person just getting into audio in high school or college, someone who wants a small tube amp for their desk and wouldn't mind having someone ask about it, someone who likes oddball tube amps, or who just wants something a little different.







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Seems like Massdrop's loss then. ROI on a quality honest review like that one is usually very good (especially if it is a positive one)
It's actually for that reason I've started shopping more on here since there doesn't seem to be as much "I got this product for free by promising a good review" I seem to see so much on other popular sites... Looking at you *cough* Largest South American Rainforest/Webs Vendor *cough*
That's a bummer. Mind if I email you some time to figure that out? I want to make sure you get whatever is owed.
All of the orders have been shipped and are now on the way to you! Once tracking is available, you will receive a confirmation email with tracking information. Please allow 24-48 hours for this information to update in the courier’s system.

If you have any questions, please visit our Help Center (http://massdrop.com/helpcenter).

We're also on Instagram! We'd love to see photos of the drops you've received. Give us a follow Massdrop and tag your pictures #massdrop. https://instagram.com/massdrop
Just about there! We've been in touch with the vendor regarding the group's order and they've let us know that they are still working to gather and pack the group's order for shipment to our warehouse in New Jersey. We will continue to check in with them throughout the fulfillment process and update the group again as soon as everything is en route to us!

Expect another update from us on 8/8 or sooner if something comes up.

If you have any questions, please visit our Help Center (https://massdrop.com/helpcenter).
Awaiting confirmation! We are still in contact with the vendor and just awaiting updated shipment estimates from them. We have a call scheduled first thing tomorrow morning and should get a bit more visibility in regards to when we can expect these in our warehouse.

Expect another update from us on 8/1 or sooner if something comes up.

If you have any questions, please visit our Help Center (https://massdrop.com/helpcenter).
Thanks again for joining this drop! We have submitted the group's order with the vendor for the Gemtune APPJ PA1501A Mini Tube Amplifier and they are working hard to prepare it for shipment.

As soon as the group's order is ready at the vendor's location, they will send the bulk shipment to our warehouse in New Jersey where our warehouse team will break it up into individual orders and ship them. The current estimated ship date from our warehouse is 8/5.

We will keep the group updated throughout the fulfillment process. You can expect an update from us by the end of the day Pacific Time on 7/25.

If you have any questions, please visit our Help Center (http://massdrop.com/helpcenter).