• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Review and Measurements of Monoprice Liquid Spark Headphone Amp

restorer-john

Major Contributor
Joined
Mar 1, 2018
Messages
2,051
Likes
3,044
Location
Gold Coast, Queensland, Australia
#21
...What's stopping amps from much heftier power outputs at clean levels?...
Lawsuits.

Consider headphones are >[email protected], yes ONE thousandth of a watt. You simply don't need power of any significance for headphones, just an ability to swing a suitable voltage over the impedance of the cans to give levels that aren't in firmly in permanent hearing damage territory SPLs.
 

derp1n

Senior Member
Joined
May 28, 2018
Messages
481
Likes
575
#22
Headphone tests are rough on the headphones and our dogs. :)
Testing high SPL headphones on dogs seems a little unethical... I hope PETA don't find out. :oops:
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
19,478
Likes
20,556
Location
Seattle Area
#23
Testing high SPL headphones on dogs seems a little unethical... I hope PETA don't find out. :oops:
I keep a large stock of rib bones to keep them quiet or else, I would be in trouble already! :D
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
19,478
Likes
20,556
Location
Seattle Area
#24
I don't think so. I think its volume changes with the volume knob. I actually tried RCA output. The sound *seems* different too.
You are right. The output goes above 8 volts! Seems to be connected to the headphone output. Here is 2 volt in, 2 volt out:

1542086500780.png


Having a heck of a time nulling ground loops. The above is the best I can do without spending forever on it. :)

It seems to be similar to headphone out.
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
19,478
Likes
20,556
Location
Seattle Area
#25
@amirm
How is the snr test done? Is it done at max power at 300 ohms?
It is maximum power at 600 ohm. I am not too happy about this since there is no way to even the playing ground this way.
 

mi-fu

Senior Member
Patreon Donor
Joined
Jun 7, 2018
Messages
336
Likes
278
Location
New York
#26
You are right. The output goes above 8 volts! Seems to be connected to the headphone output. Here is 2 volt in, 2 volt out:

View attachment 17567

Having a heck of a time nulling ground loops. The above is the best I can do without spending forever on it. :)

It seems to be similar to headphone out.
Thanks Amir! :D
 

Jimster480

Major Contributor
Patreon Donor
Joined
Jan 26, 2018
Messages
1,037
Likes
548
Location
Miami
#28
You also forgot to mention that you can get a custom O2 without all this nonsense for around the same price.
My O2 has custom gain and RCA jacks for input on the rear of the unit.
 
Joined
Apr 8, 2018
Messages
222
Likes
261
#29
Thank you for the review Amir! It's a real shame it has that 30hz hum.... it would have measured quite well otherwise it seems. I've not observed any audible hum while listening to mine so that is good. Do you think it's purely an issue with the power supply they provide? If so is there perhaps a good replacement for it that would eliminate the issue?
 

folzag

Member
Patreon Donor
Joined
Jul 24, 2018
Messages
53
Likes
56
#30
Here's a couple (newbish/naive) questions I've always had:

Component pre-amps always seemed lamentably expensive to me, but if one only needs to support a single digital source is there any problem with using a headphone amp as pre-amp? (I think the risk is that they can drive much higher voltages than the 2V RMS line level, but I'm not sure if that's it, or even the whole story.)

Along the same lines, since almost all DACs have a volume control, if one only had need to support a single digital source, could you connect the DAC directly to any old classic amp and be in business? Again, any downside to that as a solution? Seems like there's still a good number of classic amps kicking around that owners are moth-balling (or heirs are blowing out on Craigslist/eBay) because HDMI, MCH, etc.

Thx!
 

garbulky

Addicted to Fun and Learning
Joined
Feb 14, 2018
Messages
828
Likes
227
#31
Lawsuits.

Consider headphones are >[email protected], yes ONE thousandth of a watt. You simply don't need power of any significance for headphones, just an ability to swing a suitable voltage over the impedance of the cans to give levels that aren't in firmly in permanent hearing damage territory SPLs.
I get ya and that makes sense. But I've heard units that put out a meager 5-12 milliwatts and they never sounded good to me coming off as strained. Perhaps its the ability to swing it over the range of impedance that's the tough bit for amps, not the wattage - but I can't see why.
 

graz_lag

Addicted to Fun and Learning
Joined
Oct 13, 2018
Messages
845
Likes
648
Location
Le Mans, France
#32
The fact that the O2 remains a competitive design after 7 or 8 years is quite an achievement for an open source design from a guy that basically wanted to prove good audio equipment didn't need to be expensive and demonstrate the value of measurement.
Are you referring to the NwAvGuy ? Does any one know what is he doing right now ?
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
19,478
Likes
20,556
Location
Seattle Area
#33
Thank you for the review Amir! It's a real shame it has that 30hz hum.... it would have measured quite well otherwise it seems. I've not observed any audible hum while listening to mine so that is good. Do you think it's purely an issue with the power supply they provide? If so is there perhaps a good replacement for it that would eliminate the issue?
The only way to know is to use a different supply and see if it goes away. Let me see if I can do that.

For now, our threshold of hearing at 30 Hz is many, many decibels higher than that so it is not an audible concern and hence the reason you don't hear it.
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
19,478
Likes
20,556
Location
Seattle Area
#34
Are you referring to the NwAvGuy ? Does any one know what is he doing right now ?
No one knows. Sadly while his website is up, you can't send him any messages (I tried).
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
19,478
Likes
20,556
Location
Seattle Area
#35
Along the same lines, since almost all DACs have a volume control, if one only had need to support a single digital source, could you connect the DAC directly to any old classic amp and be in business? Again, any downside to that as a solution? Seems like there's still a good number of classic amps kicking around that owners are moth-balling (or heirs are blowing out on Craigslist/eBay) because HDMI, MCH, etc.
If you want to drive speakers, sure, you can do that. If you want to use their headphone output, then there are issues:

1. Many use a resistor inline with the jack to lower the output power. This increases the output impedance of the amp and can affect the frequency response of the headphone.

2. They can be noisy. With speakers and sitting far from them, you may not hear the same noise. But hook up headphones, especially sensitive ones and noise can become a problem.

The general approach is correct though: you don't need a pre-amp if your DAC has volume control and you only need that one source to play.
 

graz_lag

Addicted to Fun and Learning
Joined
Oct 13, 2018
Messages
845
Likes
648
Location
Le Mans, France
#36
... but if one only needs to support a single digital source is there any problem with using a headphone amp as pre-amp? ...
I think you are fine if the headphone amp has passive ground
 

graz_lag

Addicted to Fun and Learning
Joined
Oct 13, 2018
Messages
845
Likes
648
Location
Le Mans, France
#37
No one knows. Sadly while his website is up, you can't send him any messages (I tried).
Amir :
Here in the Old Europe, this "headnhifi" has got some sort of very good reputation.
This gentleman (Walter, which in German it can be either the family or the given name ...) builds in Zurich, Switzerland, DAC, amplifiers & combos strictly following the O2 specs.
Would you mind dropping an eye of the specs of his most mobbed combo ?
http://www.headnhifi.com/dac/O2-ODAC-fully-modded
I may buy it for my son for Xmas.
Thank you !
 

amirm

Founder/Admin
Staff Member
CFO (Chief Fun Officer)
Joined
Feb 13, 2016
Messages
19,478
Likes
20,556
Location
Seattle Area
#38
Amir :
Here in the Old Europe, this "headnhifi" has got some sort of very good reputation.
This gentleman (Walter, which in German it can be either the family or the given name ...) builds in Zurich, Switzerland, DAC, amplifiers & combos strictly following the O2 specs.
Would you mind dropping an eye of the specs of his most mobbed combo ?
http://www.headnhifi.com/dac/O2-ODAC-fully-modded
I may buy it for my son for Xmas.
Thank you !
Since he is not allowed to change the design, I am not seeing what is costing so much to want 299.99€. For that kind of money, I would get the massdrop THX AAA amplifier instead.
 
Joined
Aug 6, 2018
Messages
33
Likes
16
Location
Sweden
#39
Since he is not allowed to change the design, I am not seeing what is costing so much to want 299.99€. For that kind of money, I would get the massdrop THX AAA amplifier instead.
Note that it's with an ODAC included + 50€ in tax. Still feels a bit expensive though and something like a modi 3 would be better than an ODAC anyways right?
 

JJB70

Major Contributor
Joined
Aug 17, 2018
Messages
1,109
Likes
1,843
Location
Milton Keynes, England
#40
For a customer in Europe that isn't a bad option, as you have to factor in international shipping from Massdrop plus VAT (in the UK that is 20% but it varies around Europe) and probably a customs handling charge (in the UK that is about £13 from Royal Mail, other carriers differ). Taking all that into account the price equation can change with respect to buying from the US. However, I'd agree that the THX AAA amp is a more impressive product so worth paying more for.
 
Top Bottom