Douk Audio H7 Amplifier Review

[pma]

to my mind this is overly *fiddly* for what is a 40w amp

at this point i guess its supposed to be a power amp w/ trim knobs... also what is the point of a 3 position input switch when one is "OFF"... its like a mute button then? no remote also lends to this case

also all those charts make it seem like there's a huge degree of slackness in the tolerances of this unit

so what does this do every the perrenial favorite, the Aiyima A07? not friggin' much

they spent their money on silly stuff like a VU meter and case and i'd be ok with that if it performed better than an amp costing half as much

i also think these things are largely disposable outside of warranty so all these frills mean for naught when it ups and dies even during warranty

Exactly. And we are seeing no THD+N vs. power plots at frequencies higher than 1kHz, because they are not “nice”. Seems to be a new trend. And this toy with poor parameters gets “recommended” verdict.

 

[respice finem]

...I've never understand the fascination with VU meters. I don't think they look good nor are they much useful. Log LED meters are better to me if you have a use for that.

In the "consumer HiFi" world, they are a gimmick, yes. For some, maybe some nostalgia in play? But to each their own, and I think if at all, there should be one for each channel.

 

[solderdude]

The load dependency is not ok imho ( among some other issues ) , so therefore I voted poor

And this is with an 8ohm resistive load. What will that be with an inductive impedance above 8ohm ?

+1dB at 14kHz (8ohm) may well be audible (depending on the speaker impedance) perhaps it could even be beneficial for older cheap-skate 'audiophiles'.
Maybe some better tuned inductor + Boucherot filter could improve performance a little in this particular aspect.

When a class-AB would do that it would be shot down for peaking due to being on the verge of oscillation, fortunately the reason for the peaking differs.

 

[PeteL]

I don't know what it is measuring. I set it to 0 dB but forgot to check to see if it accurately displays other levels.

"Beyond bling, VU meters are also useful to know if the amp is doing anything. I use the spectrum analyzer on my RME DAC all the time for this purpose. You get no sound but if the display is moving, then you know everything upstream is OK."

I am a bit confused, what does "I set it to 0 dB" means? 0dB compared to what? Unity gain? You "Set" what to zero dB ? is the sensitivity change the calibration value of the reference level, or does it change the number of dBs per 1 VU movement? Does increasing the volume make the needle go higher?
If the needle is moving but no sound, you say it means "everything upstream is OK" So that would show the input and not the amplification? Then how does it tells "If the amp is doing anything" Isn't the definition of an amp doing nothing? but the VU showing movement? does going past zero on the needle tells us the amp is clipping or at least is there a way to calibrate to do so?

 

[JktHifi]

SINAD below 80 but has XLR input. So, cast vote #2.

 

[TonyJZX]

btw. that advertising diagram

stackable to satisfy both warm-hearted and cold-blooded audiophiles..

Douk Audio H8 HiFi Tube Bluetooth Preamp Receiver Balanced XLR/RCA Pre-Amplifier Headphone Amp

Features Multiple audio inputs and outputs: Support Bluetooth/Balanced XLR/RCA input, compatible with most audio sources such as mobile phones, tablets, TV, CD players, etc. With balanced XLR/RCA/3.5mm headphone jack output, you can connect amplifiers/active speakers/headphones, maintain...

doukaudio.com

Douk Audio H6 HiFi S/PDIF USB DAC Preamp Bluetooth Receiver D/A Audio Converter Headphone Amp

Features With multiple audio inputs and outputs: support Bluetooth / PC-USB / coaxial / optical inputs, compatible with most digital audio sources such as phone, tablet, computer, TV, digital player etc. With stereo RCA / XLR and 6.35mm / 4.4mm headphone jack outputs, greatly improve the sound...

doukaudio.com

Douk Audio DAC-T2 HiFi Bluetooth 5.0 Tube Preamp USB DAC S/PDIF D/A Converter Headphone Amp DSD512

Features Multiple audio inputs and outputs: With Bluetooth 5.0 / Coaxial / Optical / PC-USB digital inputs, compatible with most home audio device such as phones, tablets, computers, digital players etc. With stereo RCA, 6.35mm and 4.4 mm headphone jack outputs, greatly improve the sound quality...

doukaudio.com

btw. there's two or three matching companion pieces which have tube stages or dac stages but even looking at them i can tell there's going to be a variety of operational issues with this 'stack' but i would expect as much

 

[Robbo99999]

I don't really follow this type of product much, as it's not in my use case or particular interest, but the following graph looks a bit worrying to me, quite a lot of uncertainty as to what this amp would give you in the treble, I'm not sure if this is normally seen in these types of products or in the best of these types of products, but it's not ideal:

EDIT: ok, I've looked at the y-axis, we're talking about a max of 1.5dB range of difference at 20kHz, 0.5dB difference at 10kHz, and about 1.25dB of difference at 15kHz - ok they're small differences, but I suppose not ideal.

 

[Sokel]

(Heavily) load depended and channel mismatch are enough to see.
Nope!

Thanks Amir!

 

[DavidMcRoy]

This reminds me. Under extreme pressure, i.e. at or near clipping, there is a high pitch squeal from this amp as well. But otherwise it is quiet.

My A07s (and A04s) are all super quiet. These particular 48 VDC power supplies cause the A07s to squeal with no signal present.

I use these amplifiers to power individual drivers in a tri-amped DIY speaker with active crossovers via DSP, and they're great in that application. I'm sticking to 32 VDC supplies for now.

 

[SMen]

What's the thought process behind the dual volume controls? Who asked for this feature?

Dual volume controls can be really useful. I have an 'L' shaped room that requires a bit of a tweak left, and then some old (vinyl) recordings where you wonder what on earth happened in the recording change to have such an unbalanced result!

This is a crowded market, so it makes sense to differenciate with a product like this. Using a pre-amp for volume, and with these controls on full, or almost on full, gives a bit of room adjustment in many scenarios.

It's just a pity about the bit of harshness / brightness commented on top - and the channel variation regarding noise etc - puts me off.

 

[ctrl]

EDIT: ok, I've looked at the y-axis, we're talking about a max of 1.5dB range of difference at 20kHz, 0.5dB difference at 10kHz, and about 1.25dB of difference at 15kHz - ok they're small differences, but I suppose not ideal.

Honestly, I am also not understood how this amplifier could get a recommendation. Know about LS, but can not assess the impact of the amplifier.

When looking at the impedance response of randomly selected inexpensive bookshelf speakers on spinorama.org (measured by Amir or Erin), each of these speakers will probably cause ripples in the frequency response.

Up to 65 ohms impedance due to the BR Helmholtz resonance and 30 ohms at the crossover frequency. But there are also LS that reach up to 80 ohms at the crossover frequency.

Amplifiers are not my specialty, is the correlation linear? So if at 4 ohm load difference at 2kHz the FR is changed by 0.2dB, will it be changed by 2dB at 40 ohm difference (or must the phase also be considered)?
Or asked another way, based on the 4 and 8 ohm load impedance measurements of the amplifier, can one simulate the effects of an arbitrary speaker impedance on the frequency response?

If the impact on the frequency response from 20-20000 Hz would remain below 0.5 dB (actually, one would have to consider the Q of the deviation as well, but it makes the consideration even more complicated), the amplifier is almost transparent, otherwise it additionally acts as an EQ and should not be recommended.

For me as an amplifier layman, these analyses by Amir were much easier to understand:

 

[TNT]

"It caused some kind of interference that would keep it from switching loads"

Switching loads - whats does it mean?

//

 

[Sokel]

"It caused some kind of interference that would keep it from switching loads"

Switching loads - whats does it mean?

//

I think power cube automatically changes loads from 8 to 1 Ohm (?) (and all between) as proceeding the measurement.

 

[milosz]

For this kind of money, I could see driving it from a DAC where volume is set someplace else - like in JRIver running on a PC. Then use the level controls on this amp to balance the channels as needed. Be great for a desktop, office, bedroom or other small room setup.

The price is very good, especially considering it exhibits almost luxurious cosmetics - solid metal, nice control feel, attractive meter. Double plus good.

 

[respice finem]

Dual volume controls can be really useful. I have an 'L' shaped room that requires a bit of a tweak left, and then some old (vinyl) recordings where you wonder what on earth happened in the recording change to have such an unbalanced result!

Fair point. On the other hand, I would then prefer a "balance" knob to set once, instead of having to "tweak" each time I change the volume.

 

[restorer-john]

"Beyond bling, VU meters are also useful to know if the amp is doing anything. I use the spectrum analyzer on my RME DAC all the time for this purpose. You get no sound but if the display is moving, then you know everything upstream is OK."

I am a bit confused, what does "I set it to 0 dB" means? 0dB compared to what? Unity gain? You "Set" what to zero dB ? is the sensitivity change the calibration value of the reference level, or does it change the number of dBs per 1 VU movement? Does increasing the volume make the needle go higher?
If the needle is moving but no sound, you say it means "everything upstream is OK" So that would show the input and not the amplification? Then how does it tells "If the amp is doing anything" Isn't the definition of an amp doing nothing? but the VU showing movement? does going past zero on the needle tells us the amp is clipping or at least is there a way to calibrate to do so?

It's just a cheap Chinese moving coil meter strapped on the front panel just for fun. Don't take it seriously. After all, the 'amplifier' is just a teenage kid's toy in the first place.

Those actual meters (I have some here- they are made by the millions in China) are incapable of any accuracy or repeatability regardless of how you drive them. Their DCR coil resistance varies from 600R to 650R. They require between 250uA to 290uA to indicate 0dB and are not remotely linear or even return with reliability to the last position you mechanically zeroed them to. Compared to even the battery level meter on a Japanese 1960s cassette player, they are total and absolute junk. They are too small for anything useful.

Definitely very cute looking, with the internal warm white LED lighting and visually reminiscent of the proper (VU ballistics) meters on Sony/Marantz etc 'pressman' cassette recorders used in the 1980s:

On my desk:

Backlight LEDs powered at around 5mA:

 

[bboris77]

This type of product annoys me because it’s trying to capitalize on the whole nostalgia factor omnipresent in the audio world by using a cheap VU meter as its selling point. This marketing angle is confirmed by its sister product that is using tubes for the same effect.

I’m also confused by the review because I thought that the general sentiment on these forums is not to fall for this kind of sentimentalism and focus on the objective performance and engineering. Plus, I find it shocking that it is implied that the fact that the longevity of a product is irrelevant at a cheaper point price. Accepting this kind of disposable product and giving it a pass/recommendation despite its many annoying design issues is not ok.

 

[Mathijs Kok]

Hmm, needs to be level matched every time its used. That would be a showstopper for me
Great review Amir

I found many amps with a single volume control (and no balance knob) that were also not balanced. Did you level match your current amp? And if so, how did you do that?

It seems many readers did not see the price of this product, $144

 

[Sokel]

It seems many readers did not see the price of this product, $144

Price is (or should be) irrelevant in technical reviews.
Only the performance and hints of good engineering,maybe durability,safety,etc matters.

 

[escape2]

SOT: Speaking of VU meters https://doukaudio.com/products/dual...r-speaker-audio-switcher-box-db-panel-display

Yes, Amir tested it a while back:

Douk VU3 Review (VU Meters)

This is a review and detailed measurements of the Douk / Little Bear VU3 dual analog VU meter and 2-way amplifier/speaker switcher. It is kindly sent to me by testing by a special member. VU3 costs US $140 from Amazon including Prime shipping. The VU meter are the "paper back" ones which I...

www.audiosciencereview.com