Interesting little toob amp

tonyp063

Massdrop has the APPJ mini2013 amp available again. It's a fairly non-crufty little chi-fi tube amp with a whopping 3W per channel. Don't have a schematic for it, so I can't tell for sure if it's running in triode mode.

I got one on a whim a while ago & I'm running it in my office with a pair of full range Fostex kanspeas in near field. It's not too shabby. Does best on jazz & classical chamber music.
Most definitely a conversation starter when people see it for the first time.
The only change I made was to roll in a pair of nos GE Jan5654s.

Worth the little bit of coin IMO/IME*

https://www.massdrop.com/buy/appj-mini2013-6j1-6p1





* with apologies to @mhardy6647

indyhawg

I have one of these driving a small set up. I picked mine up for 85 bucks last year. The amp works great with female vocals and jazz. I changed to tubes out also. I agree it is a very interesting little amp.

motorstereo

Seems like an interesting little amp. I wonder if it's an set amp? Sadly massdrop wants more info than I'm comfortable giving out to them before I can see any info or pricing.

tonyp063

motorstereo wrote: »

Seems like an interesting little amp. I wonder if it's an set amp? Sadly massdrop wants more info than I'm comfortable giving out to them before I can see any info or pricing.

I don't know if it's SET or not. Output tubes are beam tetrodes, which could be run in triode mode.
I understand what you mean about Massdrop wanting info. Price is $100 from them.
Search for "APPJ Mini2013 6J1+6P1 Mini tube Amplifier ( Original miniwatt) "
and various other sites will come up giving you the specs.

mhardy6647

Those get pretty good press (unlike many of the cheap tube/hybrid amplifiers of less honorable pedigree).

3 wpc is plenty -- one just needs big boy loudspeakers as opposed to these cute little designer toys that have proliferated like rabbits in the past couple of decades.

IMO/IME, of course

heiney9

It's sold under many different brand names. It's not an SET, not even close. A simple push/pull tube amp. A neat little amp to mess around with, but nothing to take to seriously, unless you have ultra efficient speakers.

The Chinese or Russian tubes don't have too many Euro or American equivalents so rolling is limited. The 6p1's closest Euro equivalent is the 6bq5 the Euro being EL84. But you'd really have to find out if they were compatible.

Never heard of the 6j1. The 5654 seems to be the closest equivalent. I'm sure there are "close enough" equivalents out there since in general the Chinese and Russian tubes provided are not all that great.

More a novelty than a true hi-fi piece, but I'm sure it would be fun to mess with for the right price and right rig.

motorstereo

Someday I'm in hopes of bringing home a decent yet inexpensive very low wpc set amp to try out on my khorns. Apparently this isn't what I'm looking for.

heiney9

motorstereo wrote: »

Someday I'm in hopes of bringing home a decent yet inexpensive very low wpc set amp to try out on my khorns. Apparently this isn't what I'm looking for.

Probably not. Like I said it's more novelty than pure audio reproduction. SET amps are expensive (I'm not sure what qualifies as inexpensive to you), but worth it in the right set-up.

A good SET lives and dies by the transformer, and very good to excellent transformers aren't cheap.

pitdogg2

heiney9 wrote: »

.

Never heard of the 6j1. The 5654 seems to be the closest equivalent. I'm sure there are "close enough" equivalents out there since in general the Chinese and Russian tubes provided are not all that great..

Brock I think 6ak5 would work as well.

tonyp063

Evidently you can use 6005/6AQ5As in the power section, with an adapter from That Auction Site. Haven't tried it.
The 5654s were drop-in replacements & made a big difference over the chinese tubes supplied with it.

I do agree with Brock, it most assuredly isn't a "Hi-Fi" device. But it's enjoyable in it's own way in the right setting. I do have fairly efficient speakers, which makes a world of difference.

I like it for what it is. Good bang for the buck, as they say.

heiney9

I have one of those Dared/Fatman/HCT tube hybrid integrated amps 12-15 wpc (depending on what literature you read) with the magic eye tube. The front end is a pair of driver tubes (6N1P) and the power output is Mosfet. Rolling various ECC85/6AQ8's in and that thing is amazing. I've had more fun with it and a pair of modded Polk 5B's than anyone should have. It sounds fantastic for what it is. Still amazed it can sound so good.

Does it sound as good as the Dared i30 - 6L6C powered tube integrated with 12AX7 and 12AU7 tubes. Nope, not even close, but they both bring different things to the table and I enjoy both for different reasons.

So you can have a lot of fun with some of these smaller type tube integrated amps.

Dared MP-5



Dared i30

heiney9

While we're at it I have this one as well. 6V6 powered and 6SL7 drivers and it also has it's own sound. This one is rated at 16wpc and the 1950's RCA gray glass, black plate 6V6's power tubes are sublime! What a tone! Leo Fender built his guitar amps around the 6V6 tube. Favorite combo is the 1950's Sylvania JAN CHS 6SL7WGT tubes w/the 1950's RCA 6V6's. No other 6V6 compares. Still trying to find a good deal on a quad of Bendix 5992's. Not paying $500 or more for an amp like this for the Bendix's.

The blue light is sort of hokey, but it really doesn't bother me.

Dared VP-16

mhardy6647

heiney9 wrote: »

It's sold under many different brand names. It's not an SET, not even close. A simple push/pull tube amp. A neat little amp to mess around with, but nothing to take to seriously, unless you have ultra efficient speakers.

The Chinese or Russian tubes don't have too many Euro or American equivalents so rolling is limited. The 6p1's closest Euro equivalent is the 6bq5 the Euro being EL84. But you'd really have to find out if they were compatible.

Never heard of the 6j1. The 5654 seems to be the closest equivalent. I'm sure there are "close enough" equivalents out there since in general the Chinese and Russian tubes provided are not all that great.

More a novelty than a true hi-fi piece, but I'm sure it would be fun to mess with for the right price and right rig.

Pretty darned sure it is a single-ended amplifier; not sure it operates in triode mode, though. With two small signal tubes and two power amplifier tubes, as a stereo amp (which I believe and understand it to be) there's pretty much no way to for it to operate push-pull.

http://audiokarma.org/forums/index.php?threads/return-of-the-original-miniwatt-set-appj.647921/

https://frank.pocnet.net/sheets/095/6/6P1.pdf

The 6p1 is similar to a 6AQ5 (not 6BQ5), which is itself essentially a 6V6 in a 7 pin miniature format. The 6AQ5 doesn't get a lot of audiophile cred but they're not bad tubes at all (tho' I have minimal experience with the 9 pin, Chinese 6p1 morph).

I don't know squat about the 6J1 either; Brent Jesse sez:

US: 6AK5 = European EF95 = Chinese 6J1 = Russian 6J1B = Premium/industrial 5591

http://www.audiotubes.com/chinese.htm

This thing is a rung or more further up the "novelty" ladder than that Monoprice thing that was recently a topic elsewhere on these fora

mhardy6647

heiney9 wrote: »

motorstereo wrote: »

Someday I'm in hopes of bringing home a decent yet inexpensive very low wpc set amp to try out on my khorns. Apparently this isn't what I'm looking for.

Probably not. Like I said it's more novelty than pure audio reproduction. SET amps are expensive (I'm not sure what qualifies as inexpensive to you), but worth it in the right set-up.

A good SET lives and dies by the transformer, and very good to excellent transformers aren't cheap.

[Emphasis added]

I don't disagree per se but -- in fairness -- there have been some very clever workarounds that deliver very good sound with (very) unimpressive iron. The original Bottlehead Paramour is a sterling example, using ridiculously cheap 70V line matching transformers backwards as the OPTs, eliminating the need for large, air-gapped iron by using an old, old SE radio amp trick -- a parallel feed capacitor -- to deal with the plate voltage so that the OPT doesn't have to.

Now, the Paramours (and the current, single chassis morph, the Stereomour) are in a different ballpark than this titular APPJ amplifier... but they're great examples of "value engineering" a hifi product to maximize enjoyment at a low/reasonable cost.

mhardy6647

speaking of almost toy tube amplifiers -- these are silly, goofy and dangerous but they ain't half bad.

http://www.s5electronics.com/thome.html

Sadly, they're not as cheap as they used to be but they are a fun little project and they can be "domesticated" and they can be tweaked and modified to a fare-thee-well if one were so inclined.

I built one of the 11BM8 push-pull amp on a board kits* many years ago (the all in cost for the kit then was about $125) and ultimately bought the enclosure kit for it (another $75). The amplifier sounds good, is darned quiet (i.e., good S/N) and has withstood the test of time. Both of our kids had it with them at college over the span of several years and it is still alive and well (although living back at our house).

Not single ended and not triode mode, but not junk either. Trivially easy to build, being PC board based.

DSC_0631 by Mark Hardy, on Flickr

______________
* The current morph uses 10GV8 tubes.
http://www.s5electronics.com/gtube.html

tonyp063

Curse you Doc!
You're pushing me down that glass rabbit-hole, ya know.

heiney9

When I speak of SET, I'm thinking along the lines of a 2A3, but yes, the amp in the first post is single ended not push/pull. I had an EL34 tube amp that used a single EL34 for each channel. It was single ended, but not an SET.

mhardy6647

heiney9 wrote: »

When I speak of SET, I'm thinking along the lines of a 2A3, but yes, the amp in the first post is single ended not push/pull. I had an EL34 tube amp that used a single EL34 for each channel. It was single ended, but not an SET.

Right -- 'twas a SEP unless, of course, the EL34 was wired as a triode.
FWIW, I call an amp using an output pentode wired as a triode a "SE-pseudo-T" (or "pseudo-SET") but it could be argued to be a matter of semantics. An EL34 wired as a triode makes a decent enough power output triode.

The "T" stands for "triode". Power triodes are relatively uncommon as they were replaced fairly quickly in vacuum tube evolution by tetrodes, pentodes, and beam power tubes (a special case of pentode). The latter offered more power at reasonable plate voltages at the expense of the tremendous linearity of true power triodes. In full disclosure, there have been, over the years, plenty of different DHT power tubes -- many of them, though, were developed for use as transmitter output tubes ("finals") and not for hifi per se.

For the benefit of those who are just being sucked in, the 45, 50, 2A3, 300B and some other power output triodes are "DHT" tubes -- direct heated triodes. These tubes use the filament element inside the tube (typically tungsten or tungsten-containing wire) that is also the cathode. There is (or there may be, depending upon one's perspective) a certain magic to the DHT.

There were a few indirectly heated power output triodes -- the 6A5 was an indirectly heated variant of the 2A3 in an octal base.

I'm a SE DHT believer -- but all y'all knew that already.

MrBuhl

Of course - no one's subjective listening is of value . . . but I did find this interesting - seems to be a similar unit?

http://www.6moons.com/audioreviews/miniwatt/miniwatt_3.html

mhardy6647

Yeah, the same Chinese amplifier (design?) has been sold under many names over the years.

heiney9

It most certainly is a Mini-Watt knock off.

tonyp063

heiney9 wrote: »

A good SET lives and dies by the transformer, and very good to excellent transformers aren't cheap.

From the "Getting my learn on" dept.
I've read a lot about this & other SET tidbits as it's something that has really piqued my interest lately. (thanks Mark)

Doing some sleuthing I *think* it may have these transformers, or something very close.


https://www.aliexpress.com/item/Tube-Amplifier-Output-Transformer-Z11-Single-ended-Silicon-Steel-EI-Transformers-Power-3W-Audio-HIFI-DIY/32309794406.html


Looks like it's time for a tear apart & guts shot of mine.

mhardy6647

Those are pretty generic looking.

Now: These are not (!!!) the same OPTs, but to illustrate the averageness of the appearance of the above, note the little line matching transformers used as OPTs on the Paramours (in the foreground in this photo).

DSC_8376 (2) by Mark Hardy, on Flickr

The transformers used as OPTs on the Paramours are probably very similar to these PE buyouts -- and probably cost about the same ($4.00 a pop)!

https://www.parts-express.com/dukane-710-3092-09-4-watt-25v---70v-speaker-line-matching-transformer--249-410

ThomasD

Interesting. I just found this thread after I ordered one of the APPJ mini2013 amps not long ago. Due for shipping around May 25th from Massdrop. Thought this amp might be an inexpensive way to 'test the water' and see what this 'tube' thing is all about. What speakers are you all using for these 'flea' watt amps. Is that the proper term or is 3 watts under a different category? I know it requires a pretty efficient speaker. And where are you sourcing your tubes for rolling? Last time I bought a tube it was with my dad at the grocery store when they still had those tube test stations and the tube selection was underneath the tester.

mhardy6647

Let's start with fleapower
I think that the true fleapower devotees would balk at calling 3 watts truly fleapower.
"Fleapower" is probably in the realm of a single-ended 45 amplifier (about 2 watts) and below... but I'd say that's splitting hairs!

Loudspeakers: well, there are two things to consider - sensitivity and impedance curve. They're both important, not mutually exclusive, but a priori a speaker probably shouldn't be excluded on one count depending on the other one. Bottom line, one cannot beat empiricism!

As a broad generalization (and remember, all generalizations are false, including this one!) with 3 watts per channel, you'd probably like to find something with a sensitivity of at least the mid to high 90s (95 dB-up) dB SPL range measured at 1 meter for a signal input of 2.83 AC volts (1 watt into 8 ohms). The "heritage" Klipsch loudspeakers are popular, fairly inexpensive, and appropriate (if something of an acquired taste), as are many classic drivers & loudspeakers from JBL, Altec, and Electrovoice. Generally, we're talkin' large and expensive -- which may not be ideal

There are modern, small(er) and inexpensive options -- especially if one can build enclosures. There are also kits. Fostex has a few reasonably priced but decent performing kits using their "full range" (extended range) drivers. If you're in North America, look at them at www.madisound.com

Another whacky but easy to try option is a full-range driver (e.g., an Electrovoice "Wolverine" LS-12 twincone driver from the 1960s) mounted on an "open baffle" (just a board with a hole cut in it to accommodate the speaker driver!). Not all drivers are suited for "OB", but there are many - particularly vintage ones - that can be used thus to good effect.

Tonnes of information on the internet about all of the above

If you happen to live in northern New England -- send me a PM and I can probably loan you something appropriate to try


DSC_6727a by Mark Hardy, on Flickr

tonyp063

@ThomasD
I basically did the same thing when I bought mine last year. Got it on a whim.
I hadn't done anything with tubes since my ham radio days in my youth.
And really never anything with tube audio.

I did read up enough to know that good efficiency in speaker was mandatory to get the most out of the thing, so I got a pair of full-range, single driver kits from Madisound.
I'll be building pair of Frugel-Horn Mk3s over the summer & see how it plays on them.

A friend of mine has a pair of vintage Infinity Qa speakers & this little thing sounds better than it has any right to on them.
They're about 90dB efficient, IIRC

This whole exercise is for my edification & amusement at this point.

ThomasD

Thank you both @mhardy6647 & @tonyp063. I appreciate the quick education. I'm not near Northern England but my wife and I have that area on our 'to visit' list for someday. I realize this is an 'entry' level tube amp but the reviews for it were surprisingly positive. As is the case with much of this audio equipment, I'm trying to not jump blindly down the 'rabbit hole'. Have a pair of SDA 2A's & M7c's that are in the process of being upgraded. Thought the TL'd Monitor 7's @90db sensitivity might be a candidate for this 'almost' flea powered endeavor. Looks like I better keep looking. I am partial to the 'heritage' Klipsch's, the Heresy's have the right numbers but used ones are hard to come by up here in Alaska. I'll check out Madisound . Don't know if I've got anymore project time available to build more speakers but I do need something to give this little amp a try. Thanks again.

mhardy6647

Mrs. H will be birding (again) in AK this June, but I reckon she'd balk at my sendin' a pair of Heresys up with her

Were I you, I would absolutely try your Polks with the amp. Depending on your taste in music, the space you intend to use and your expectations, you might find it satisfactory, or even very good! The playing field, e.g., can be very different for a nearfield application (e.g., computer sound on a desktop) in terms of acceptable quality loudspeaker/amp combinations.

These are small and they're also not bad (within, of course, their limitations).

https://www.madisoundspeakerstore.com/2-way-speaker-kits/fostex-p1000e-diy-kanspea-4-full-range-speaker-kit-pair/

049 by Mark Hardy, on Flickr

(in the interest of full disclosure -- the photo above shows my little pair of "Kanspeaks" being driven by a Paleolithic soiled state, push-pull, quasi-complementary HH Scott stereo integrated amplifier... but they work well with, e.g, single-ended 2A3 amplification, too)

ThomasD

mhardy6647 wrote: »

Mrs. H will be birding (again) in AK this June, but I reckon she'd balk at my sendin' a pair of Heresys up with her

Are you sure she would balk? Lol.
They’ve just cleared ‘Creamers Field’ in Fairbanks for the annual arrival of the cranes, swans and several other migratory species. Always a wonderful sight.

verb

Why professor @mhardy6647 is that a Bottlehead amp I see?

mhardy6647

verb wrote: »

Why professor @mhardy6647 is that a Bottlehead amp I see?

The one you see is -- ahem, umm.... cough-cough... @mrbiron's Reduction phono preamp It's kind of being held hostage here (although benignly) -- IOW, he lent it to me to try, and it hasn't quite made its way back home. I think it was probably pushin' three years ago now

There are some bought-n-paid for (and built by us) Bottlehead components here, too. You didn't know that?

Coupla Paramours (good sounding inexpensive SE 2A3 amps, they were) and a Seduction (the Reduction's forebear).