This isn't about cheap Asian-sourced amps/preamps -- but it IS about economics and value :)

paulbottlehead

Active Member
Yeah -- I thought 10% was the hifi cutoff ;)
(actually I am not being entirely facetious -- the old tube manual data for audio power output tubes often, perhaps generally, list power output at 10% THD)
It kind of depends for me on where all that distortion is. If it's a lot of 2nd harmonic, then I'll stretch to 10%. If it's a lot of 3rd, I'm less willing. (With this amp it's a lot of 3rd)
As to the contour -- have you looked at any square wave reproduction yet? I am guessing that might not be pretty.
I don't tend to do a lot of square wave testing unless I'm doing feedback compensation or looking for something extremely specific. Lots of nice sounding amps don't make pretty 10kHz square waves, that's more a function of using as much feedback as possible to obtain that specific desired result.
 

mhardy6647

Señor Member
It kind of depends for me on where all that distortion is. If it's a lot of 2nd harmonic, then I'll stretch to 10%. If it's a lot of 3rd, I'm less willing. (With this amp it's a lot of 3rd)
It's a push-pull amp,right?
I don't tend to do a lot of square wave testing unless I'm doing feedback compensation or looking for something extremely specific. Lots of nice sounding amps don't make pretty 10kHz square waves, that's more a function of using as much feedback as possible to obtain that specific desired result.
Absolutely true, but given the output impedance, doesn't it seem like there is something funny goin' on with that amp? Is there no NFB at all? Are the outputs triode-wired?
(Just curious)
 

mhardy6647

Señor Member
Power bandwidth isn't all that bad. The amp will do:
10.5W at 40Hz/10% THD and 9.2W at 30Hz/10% THD, but then down to 5W at 20Hz 10% THD.
That's not really bothersome for what this amp is and it would be totally fine as a desktop amp.
...
I would concur (FWIW, not that I am anything close to expert!) that's perfectly reasonable (and better bandwidth, e.g., than the SE 2A3 amp I listen to, I reckon!).
 

paulbottlehead

Active Member
So I don't see any hilariously obvious fake parts on the inside, that's a good sign. Yes, there absolutely is some GNFB. The amp operates the EL84s in ultra-linear mode, which explains why it's a bit down on power compared to a traditional EL84 pentode amp, but it's still making more than the 4-5 watts that a triode wired EL84 push-pull amp would make.

This definitely isn't presenting the problems of the Nobsound type amps, but it's also $1100, so there's that. The guy who owns this amp uses it with open baffle 15" full range drivers that are definitely benefiting from the low damping factor and the tipped up treble, so it's a tool that has some practical applications.
 

adaug

Senior Member
I think that comment is broadly applicable to vacuum tube audio hardware (and I don't mean that snarkily; I am a vacuum tube audio kind of fellow, as y'all know).

DSC_8376 (2) by Mark Hardy, on Flickr
(speaking of Bottleheads... :))
Hmm... $1100 is real money (at least from my perspective) for a ppEL84 amplifier!
nice bottleheads! ive got a BH preamp in similar size and case. (its at my studio so no photo here).

concur that for $1,100 one could get a great (used at least) tube amp. 2A3 etc. for sure an EL34 and have money left over.
 

mhardy6647

Señor Member
I sure would be thinking about the SCA-35 for a lot less money.
Plus there is (or at least, there has been) a whole cottage industry of aftermarket/retrofit/upgrade PC boards/hardware for the SCA-35.
I took advantage of one of them (power supply, from a now-defunct vendor, unfortunately) for mine. The SCA-35 was my daily driver for a while both in MA and when we first had the NH house "on line".

DSC_6212 by Mark Hardy, on Flickr
(heh... with a Seduction phono preamp, too!)

... but I digress...

:rolleyes:
 

Richard Austen

Junior Member
Power bandwidth isn't all that bad. The amp will do:
10.5W at 40Hz/10% THD and 9.2W at 30Hz/10% THD, but then down to 5W at 20Hz 10% THD.
That's not really bothersome for what this amp is and it would be totally fine as a desktop amp.

The output impedance at 1kHz is a whopping 5 ohms, which is totally unacceptable and telling some of the story about why the frequency response looks a little weird.
I own this amplifier which sounds terrific - The amplifier is rated as 6 ohm - not 8 ohm or 4 ohm - it sounded poor with the KEF LS-50 - it simply can't drive them - on HE speakers it's a dream.

FWIW: The rectifier tube in the picture you posted is not stock - it is supposed to be a 5AR4. King's recommended tube is the NOS RCA 5U4G.

Lastly, remember the Kingko amp is made mostly for the Hong Kong market - where apartments are tiny and there is not a lot of space for big systems - this amplifier is a tube headphone amp, integrated amp, power amp, uses cheap EL85 tubes - it's auto-bias and it's going to drive speakers in a small room. There are not a ton of amplifiers that are the jack of all trades this one is and small and tube rectified. El34 and KT88 for this money don't sound as good - though they offer considerably more power. I am not too concerned by the measurements because if that was really a deal breaker - why the hell are any of you buying tube amplifiers. A Marantz receiver at $400 mops the floor with tube amplifiers at $10,000! And the closer a tube amp measures to a SS amp - the worse the tube amp sounds - umm because it then sounds like a Marantz receiver.
 
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Richard Austen

Junior Member
First and foremost, I am probably the problem here! ;)

I am perversely fascinated by the long threads on various hifi fora (y'all know the one/ones) that gush over 31 dollar preamps, 129 dollar hybrid integrated amps, and 299 dollar all tube integrated amplifiers. These products are offered under a plethora (nay, a surfeit) of brand names and sometimes feature the use of unusual (from a Western perspective) vacuum tubes (some without exact "Western" substitutes).

Now, here's the thing... one comment I read a lot in these threads strikes my cheap/frugal Yankee sensibility as distressing.
Here is an exact quote from one post to one such thread.



I find myself horrified:mad: by such an attitude! Now -- yeah, I know, it's their money and they're grown-ups and all... but the notion of just urinating away a couple of hundred dollars (or even 31 dollars) just because something is cheap seems very, very wrong to me.

Believe it or not, my dudgeon isn't directed at individuals -- it's directed at the culture that puts so little value in its own spending power.

Finally -- as you've likely guessed, I am on the cusp of buying one of those damned 31 dollar preamps! :(
Somebody. Stop. Me.

:)

Thanks for "listening"!
My dad used to say that a lot of people know the price of everything but the value of nothing.

X speaker is on sale for half price - so out they go to buy it. Umm yes but do you like the speaker or do you like the "deal" you're getting?

Most of us are susceptible to this in some form - oh it's 50% off wow - what a bargoon - and we end up with a lot of rubbish we would not normally buy. And, generally speaking, high end gear never goes on sale.

I've been watching a few car review channels - and even some of the best ones like Alex on Autos still doesn't really talk about reliability or resale value when discussing price and cost of ownership. Yes the American Car may very well be $25,000 and the Japanese car may be $26,000 so woohoo - you save $1000. But 7 years later if that Japanese car gets you $4,000 more when you go to sell it - then what looks like a $1,000 saving winds up losing you $3,000. And rarely do these reviewers discuss some "example parts" that may be replaced and what the manufacturer charges.

In audio I get why people want a deal. Hey I can get a Topping amplifier for $25. And then try and convince themselves it's the best. On another forum there are still people who have convonced themselves that they can use the volume on their CD player to replace a high quality preamp - arguing no preamp is the best preamp - umm the volume pot on the CD player is still a preamp.
 

paulbottlehead

Active Member
I own this amplifier which sounds terrific - The amplifier is rated as 6 ohm - not 8 ohm or 4 ohm - it sounded poor with the KEF LS-50 - it simply can't drive them - on HE speakers it's a dream.
A 6 ohm rated tap with 5 ohms output impedance is even worse.

FWIW: The rectifier tube in the picture you posted is not stock - it is supposed to be a 5AR4. King's recommended tube is the NOS RCA 5U4G.
The tube in there is a 5U4 with fancy packaging. The amp may perform a bit better with a 5AR4 than it does with a 5U4, especially if that's what it's designed for.

I am not too concerned by the measurements because if that was really a deal breaker - why the hell are any of you buying tube amplifiers.
The tilted treble would be very concerning if I had horn speakers.

The gist of this thread is to test the claims of certain import amps that appear to be a little dubious. This particular manufacturer doesn't really make any claims, so there wasn't a lot to say in this regard, but I still figured I would measure it and see how it did.
 

Richard Austen

Junior Member
A 6 ohm rated tap with 5 ohms output impedance is even worse.


The tube in there is a 5U4 with fancy packaging. The amp may perform a bit better with a 5AR4 than it does with a 5U4, especially if that's what it's designed for.


The tilted treble would be very concerning if I had horn speakers.

The gist of this thread is to test the claims of certain import amps that appear to be a little dubious. This particular manufacturer doesn't really make any claims, so there wasn't a lot to say in this regard, but I still figured I would measure it and see how it did.
The tilted treble is interesting and it shows me, and all of us really, that when purchasing amplifiers in isolation, or sources, or speakers that we probably should know what the designer has in mind (actually used) when voicing the product.

I know King's speaker's for example are not horns - and indeed when he was the head repair tech for Rogue Audio, Line magnetic, Melody Valve at Hit Audio in Hong Kong the store's number one speaker was, curiously, the ATC SCM 100. A low efficiency professional monitor designed largely for the nearfield. As space is small in Hong Kong - large horns is not really the order of the day here.

They also have some ZU Audio speakers which were hit and miss with all the brands I just mentioned - though like a horn they offer High Sensitivity. Still his speakers are ATC and my speakers are not horns and have a shelving down in the treble. Thus the match is strong - but I could see that if someone has a brighter leaning speaker - this could be a poor match indeed.

I noted in my review that the Kingko was brighter but that tube changes did combat this quite a bit - interestingly I find the rectifier tube to have made substantial improvement and personally I think he should sell the amp with the NOS RCA but small manufacturer and being able to get enough of those rectifiers is difficult. I think the tube alone is around $70. And you can't put the cover on it as the tube is too big.

The new Pro version of the amp is substantially quieter from the headphone output.

Still I think it is somewhat important to recognize that tube amplifier makers actually listen to the stuff they're designing more than they are designing to do great on Stereophile's test bench. They are willing to make a choice that sounds better knowing that it will measure crap.

Take Audio Note's no times oversampling, no jitter correction, no error correction, no digital AND no analog filter DAC. The owner of the company acknowledges that it "measures a bag of nails" and it does - Stereophile called it "broken" but yet the resulting sound is often deemed closer to sounding like real music than anything else. So they have said - yes we have the best measuring equipment available and yes it measures "weakly" and yes we can design the best measuring CD player in the history of the world but this sounds better so in spite of taking it on the chin in measurements discussions we're going with this. And usually - it is people who own bomb proof measuring CD players that trade those Krells and Brystons in for the AN and not the other way around.

But then I say this about SS and SET - People don't sell their 2a3 for a Bryston - it is almost always people trading their SS in for a SET. So it goes back to the old saying - If it sounds good it is good and if measures bad and sounds good, you're measuring the wrong thing.

This is interesting discussion on the Audio Note DAC and why they chose to build it even though, arguably, it is the worst measuring digital source.


I think though anyone designing a SET amplifier or even a PP tube amplifier is making choices in spite of measured performance. We all know going in that they're not going to measure well.

Now SS is different - for SS I think people expect big boxes with big power and impeccable measured performance.
 
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paulbottlehead

Active Member
Yes, I think this amp would be a good pairing for open baffle full range drivers. I would not pair it with any bass reflex speaker. The high output impedance will through off the QES and rather dramatically change the tuning.
 

paulbottlehead

Active Member
The Audio Renaissance 845 amp is back!
IMG_20200224_102700.jpg
When it was first here, I noticed all those 6A rectifier diodes mounted way off the board and let the owner know that I could make new proper filament rectifier bridges on separate PC boards, or he could just not run the amp for more than a couple of hours at a time. Well, he fell asleep with the amp on, and now one of the 10V DC supplies that heats the left channel 845 has a shorted diode. The datasheet for these diodes specifies resistive/inductive loads for that high current rating, not capacitive loads!

I'll be making a new pair of custom PCBs to hold a quad of 40A/45V Schottky diodes mounted to heatsinks to prevent this from happening again. I keep telling him to sell this amp before it shows up here and something is broken that I can't fix!
 
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