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HeadAmp Gilmore Lite Mk2 Review (headphone amp)

amirm

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#1
This is a review and detailed measurements of the HeadAmp Gilmore Lite mk2 headphone amplifier. It is on kind loan from a member and costs US $499 from the company direct.

In a sea of same looking black boxes, the Gilmore Lite manages to look distinct:

HeadAmp Gilmore Lite mk2 review.jpg


The volume control color doesn't match the matt finish of the rest of the unit but feels very good. Note that there is no gain selection. The switch on the right allows selection of one of two inputs in the back instead:

HeadAmp Gilmore Lite mk2 review back panel power supply.jpg


A massive and beefy AC transformer provides +-15 volts AC but at just 1/4 of an amp. This means low impedance loads may provide some limitation.

HeadAmp Gilmore Lite mk2 Measurements
As usual, we feed headphone amps 2 volts in and set the volume control to get the same voltage out (for balanced units I use 4 volts):

Gilmore Lite mk2 measurements.png


The Gimore Lite uses class A amplification which makes people think it has lower distortion but such is not the case here. We have distortion products reaching up to -88 dB which is decades worse than best in class products we test (at much lower prices):

best headphone amp review 2021.png


Signal to noise ration is good enough at 2 volts out but not at 50mv:

Gilmore Lite mk2 measurements SNR.png


most quiet headphone amplifier review.png


Lack of gain control hurts the design when producing very low outputs so you may experience some noise with very sensitive IEMs.

Power is everything in headphone amps so let's measure that starting with high impedance of 300 ohms:

Gilmore Lite mk2 measurements power into 300 ohm.png


My threshold here is 100 milliwatts and the Gilmore struggles to get there even for allowing for much rise in distortion.

Switching to 32 ohm we get:

Gilmore Lite mk2 measurements power into 32 ohm.png


Fortunately in both cases noise is kept under control before distortion sets in which occurs very early.

I have a new test which shows the output voltage at a number of impedances. You can convert them to watts using the formula power = Voltage * Voltage/Load resistance:

Gilmore Lite mk2 measurements THD+N vs Power vs Headphone Impedance.png


Nice to see that it can handle even 12 ohm load but distortion rise as the load impedance reduces is quite significant.

Frequency response while not as flat as some competitors, is certainly more than good enough:

Gilmore Lite mk2 measurements frequency response.png


Finally, I was impressed with how accurate channel matching was as I was rotating the volume control:

Gilmore Lite mk2 measurements channel balance.png


If they are all like this, this could be a rather unique asset of the Glimore Lite.

Headphone Amp Listening Tests
As usual I start with my tough to drive, low impedance Ether CX headphone. The Gilmore Lite managed to drive it well, distorting toward the last 25% of the volume range. By then though it was too loud to listen to it. Same happened with the Sennheiser HD650. I detected no magic related to Class A implementation or any other. It sounded very good until it got distorted at extreme volumes.

Conclusions
The developments in the last 18 months in headphone amplifiers has turned the market upside down. We can now get units that have more power than you can use with distortion levels so far below hearing threshold that I call them "instrument grade." Classic designs like Gilmore Lite mk2 are simply not a player there. Objectively this unit is a loss. Fortunately the ears are not as critical as they eye looking at measurements so subjectively the performance is there if you don't ask it to get crazy loud.

Given the many wonderful choices in the market, I cannot recommend the HeadAmp Gilmore Lite mk2. If you own it though, it is a fine choice and I would not run out and get something else.

------------
As always, questions, comments, recommendations, etc. are welcome.

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

MZKM

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#2
You can convert them to watts using the formula power = Voltage * Voltage/Load resistance:
For those forgetting PEMDAS (aka GEMDAS or BEDMAS or BODMAS or BIDMAS):
(Voltage^2) ÷ Impedance
As a teacher of remedial math to seniors, I have to drill this into them.
_______________
But back to the amp: yeah, nothing bad (expect noise for IEMs), but nothing broken.

Regardless of speaker amp vs headphone amp, does there even exist a pure Class A amplifier that actually has better distortion than its AB counterparts, with decent output power?
 
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amirm

amirm

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Thread Starter #5

YSC

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#6
beside the SINAD the channel balance seems worse than what I would expect, not the volume pot balance but the output level in the dashboard and the FR plot.
 

milosz

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#7
Back in the day this was considered a decent amp. It still is "decent" but not a value proposition, considering all the stuff coming out these days.

"Back in the day" there were very few actual decent headphone amplifiers. Headphone amps were a boutique item.

Head Amp started making this amp- along with others- in small quantities for aficionados, and I think that Head Amp is a small operation and there may be just one person soldering these products together so the cost is going to be higher than something coming out of an automated factory in China.

You had other makers - Ray Samuels, etc - making stuff, and then when the headphone market took off - headphone sales are about the only bright spot in high-end audio these days from a business point of view - some big players came along with headphone amps that were also fairly high-priced. But now we have some really good designs being mass-produced like paperclips so these earlier products have lost their relevance in the market. But like Amirm said, if you have one of these there's nothing really to be gained in terms of sound quality by replacing it with a newer product that measures better, unless you are trying to drive difficult low-impedance 'phones.
 

wwenze

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#9
I detected no magic related to Class A implementation or any other.
Soft increase in THD vs power (or rather, current)

I can spin it as "Class A implementation that recreates tube sound into sensitive loads"
 
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amirm

amirm

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Thread Starter #10
Amirm- What is the output source impedance of this amp? You usually measure that.
Spec says less than 1 ohm so probably right. Didn't notice that until I was writing the review. :)
 
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amirm

amirm

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I can spin it as "Class A implementation that recreates tube sound into sensitive loads"
At those power levels though it just gets badly distorted. There is nothing euphonic, nor would most people listen at those levels.
 

milosz

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#12
It's easier to design a linear class A amplifier than it is to create a class AB amp that is just as linear, and when you are talking about such a low power level, there's really not that much penalty to a class A design. A little extra heat, a little extra power consumption.
 

sssn

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#15
I wonder if a power supply capable of delivering higher current might make a positive difference.
 

pma

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#16
Could you please explain what was the load impedance in this measurement

Gilmore Lite mk2.png


Was it 100 kohm? Does it make any sense to measure a headphone amplifier into 100k?? Would not it be better to measure and show the spectrum into 32, 50, 100, 300 and 600 ohm?

Because the mesurement shown is good. There is only H2 and H3 in inaudible level. No high order harmonics that are much worse and much more audible. I bet that measurement into 100 ohm would show very different spectrum.

So again, this is a headphone amplifier and measurements into 100 kohm are thus pointless.
 

solderdude

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#17
see:
1609851913392.png


Otherwise Amir would have to post 7x the spectrum plots and these would only say something about the 2V in output level.
Given the small difference between 300 and 600 Ohm load I would suspect 100k to be the same as the 600 Ohm load ?
 

pma

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#18
see:


Otherwise Amir would have to post 7x the spectrum plots and these would only say something about the 2V in output level.
Given the small difference between 300 and 600 Ohm load I would suspect 100k to be the same as the 600 Ohm load ?
I know and I can/could read this plot, however it does not show the distortion spectrum profile. There would be a big difference if -60dB THD+N was constituted only of H2 and H3 or of a tail of harmonics spread to infinity. Again that's why I do not like using THD+N/SINAD.

I agree that the result into 300 and 600 ohm would be very similar to the 100k measurement. Most probably. Or, in case of the poor design, higher harmonics start to emerge, though small in level they may not affect the THD+N number.

I agree that these THD vs. frequency plots are useful - IF they also display H2 - H5, H6+ and not only the rooted squared sum (aka THD+N) + noise. If you see higher harmonics, you may guess on audibility. If you see the sum only, you can't.
 

solderdude

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#20
To fully evaluate an amp I agree but Amir only does his standard suite for easy comparison.
One could of course make many plots at many frequencies and both on or near max level and at much lower levels but it would become a complete booklet. I guess these are the choices Amir makes in order to churn out 1 or 2 reviews a day.
It would be nice to see very elaborate measurements of each device but fear those that sent in stuff to be measured would have to wait years for it to be returned.
 
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