# A970 Isoundyou Line5 Mobile Headphone Amplifier review



## viperxp

Greetings All,
  
 It is one of my first threads here, so please be easy on me with the comments 
  
 Well, this review will be dedicated to a portable headphone amplifier, Line5 A970. There are many different names on the package, I think that Line5 is the actual brand.
 I got the item free for review from www.gearbest.com website. As I yet don't know all the rules of the forum, I will try to post as little links as possible, If you have any questions please pm me. English is not my mother tongue, but I will try to be as clear as possible.
  
 So ... Let's start.
  
  
*Part 1 - Physical*
  

  
 The amplifier has arrived in a nice colorful box. It has tech.specs specified and possible amplifier applications.
  
 Please note that the store has different specs for the amplifier, I don't know which one is correct ..
  

*Specifications:*
Power source: DC 5V, 600mA
Frequency response: 10-100KHz
S/N ratio: >98dB
Crosstalk: 60dB
Gain: >12dB(high): 6dB(low)
Total harmonic distortion: <0.009%(10mW)
Max output power:
Voltage = high 300mW(16Ω); 200mW(32Ω); 35mW(200Ω)
Voltage = low 120mW(16Ω); 88mW(32Ω); 13mW(200Ω)
Battery charge time: 200 minutes(PC USB)
Battery play time: More than 10 hours
Recommended headphone impedance: 16-200Ω
Input impedance: >15KΩ
Product weight: 104 g
Package weight: 210 g
Product size (L x W x H): 10.0 x 5.3 x 2.2 cm
Package size (L x W x H): 17.0 x 16.5 x 4.0 cm
  
  
  
  
  
  


  
 Well, the package does not contain much. The package contains the amplifier, 3.5-3.5 mini cable, standard usb charging cable and silicone band for connecting the amplifier to a mobile device. No manual of any kind.
  

  

  

  
 Well, I did not know what do expect really. The amplifier is pretty cheap, so I did not expect much. I was really surprised by the quality. The amplifier itself is not light, feels pretty good in hand. The build is solid, It does not bend in any point, even under a heavy pressure. I would even suggest it's made of magnesium alloy. The only moving part - the volume/power knob moves quite nicely, with some resistance - it does not feel cheap in any way. When volume is adjusted no hisses or any cracking sounds get to the headphones. When the device is being turned on, there is a not loud low frequency "spike" delivered to the headphones. It's not really disturbing, even nice in some way. The volume knob is made of aluminum.
 The amplifier has build in rechargeable battery, and can also be operated when USB connected. When no signal connected and the volume is moderate/high - some clicks can be heard (I experienced it when connected to my pretty old desktop PC). When there is music - I could not hear any of the sounds, even in the quiet parts. When USB is connected, a green LED lights at the rear of the amplifier.
  

  

  
  
  

 We can see some size comparisons between the amplifier and Sansa Clip Plus, and Nexus 5 phone. I think that the amplifier is just barely portable, but am sure that some of the members will not agree with me.
  

  
 This is my budget friendly setup  . Clip+,the amp and Koss TBSE1.
  
*Part2 - Sound*
  
 Well, I think the amplifier does it's job pretty well. I found no real problems with it's operation, nothing that will make me not want to use it when I can. No hissing sounds, no clicks/cracks when touching the connected jacks.
 If I get my hands on some more equipment I will be happy to share the results. I thing the next headphones will be HD580, and maybe Fiio E6 amplifier.
  
*Clip+ A970 + Koss TBSE1*
  
 The soundstage seems a little bit wider, the mids smoother and not as "in your face" as directly from Clip. The sound overall became a little bit "smother" and less fatiguing. Maybe in some complicated parts the instruments separation is better.
  
*Clip+ A970 + Sennheiser HD202*
  
 Those power-hungry headphones sound a little better for me with the amplifier, providing a little more detail.
  
*Clip+ A970 + Koss KSC75*
  
 A little more punchy bass, and less bright highs
  
*Nexus5 + A970 + Koss TBSE1*
  
 The amplifier just gave a lot's more volume. I find the sound straight from Nexus 5 almost acceptable, but too warm and lacking volume. The amplifier makes Nexus a really usable music device.
  
*Samsung Galaxy SII + A970 + HD202/TBSE1*
  
 I think the boost that the amplifier makes here is the most obvious. It adds a lot's of volume and even some stereo separation. Personally I thing SGS II is an awful audio device, but the amplifier makes it useful in an emergency situations 
  
*Conclusion*
  
 I am really happy with the amplifier. It improves long-term comfort for me, while still being portable.
  
  
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 I would like to hear your comments and questions


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## viperxp

I ran RMAA with the amplifier. Seems like I am limited by my integrated soundcard. Overall - very happy with the results.
  
Summary (with the amp) 
*Frequency response (from 40 Hz to 15 kHz), dB:*+0.01, -0.03Excellent*Noise level, dB (A):*-94.3Very good*Dynamic range, dB (A):*93.7Very good*THD, %:*0.0032Very good*IMD + Noise, %:*0.0084Very good*Stereo crosstalk, dB:*-83.7Very good*IMD at 10 kHz, %:*0.0071Excellent


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## rafaelroxalot

Noise floor on sensitive iems? I have topping nx1 and has a lot of noise more in high gain, but has some on low gain too


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## viperxp

rafaelroxalot said:


> Noise floor on sensitive iems? I have topping nx1 and has a lot of noise more in high gain, but has some on low gain too


 

 There is a slight high frequency hiss - that I cannot hear on any headphones on any volume, it gets louder on high gain. I managed to hear it when connected amplified speakers to the output of the amplifier.
  
 b.t.w. - If someone is interested at buying the amplifier - there is a coupon for it - GBA970  . The price after applying the coupon is only 22.49$ .


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## viperxp

If someone is interested at buying the headphones, there is a coupon code for them - GBHeadset . The price should be 25.49$ after applying the coupon.


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## H20Fidelity

I have one of these. Can you please explain to me how charging works?

 When I plug mine into a USB charger there is a green light, is yours green?

 Does it go out once charged?


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## viperxp

h20fidelity said:


> I have one of these. Can you please explain to me how charging works?
> 
> When I plug mine into a USB charger there is a green light, is yours green?
> 
> Does it go out once charged?


 

 It's always green - regardless of the battery status as long as USB is connected.
 I disassembled mine - the battery BTW is 14500 1200maH UltraFire so it explains why it has such long battery life.


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## H20Fidelity

viperxp said:


> It's always green - regardless of the battery status as long as USB is connected.
> I disassembled mine - the battery BTW is 14500 1200maH UltraFire so it explains why it has such long battery life.


 


 But how do we know when it's charged?

 For example :

 Green when plugged into USB

 Charged when???

 I have never seen the green light go out.

 I've had mine open too trying to work it out.


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## viperxp

h20fidelity said:


> But how do we know when it's charged?
> 
> For example :
> 
> ...


 

 I don't know, just charge it once in a while. The battery is a non-protected one, and I don't really know how far it will be discharged, so I'll just keep it charged.
 By the way - I see that you are much more experienced head-fier than me, how can the amplifier be compared to others, more or less expensive?


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## H20Fidelity

viperxp said:


> I don't know, just charge it one in a while. The battery is a non-protected one, and I don't really know how far it will be discharged, so I'll just keep it charged.
> By the way - I see that you are much more experienced head-fier than me, how can the amplifier be compared to others, more or less expensive?


 


 The problem I had with this amp was it arrived charged and I used it on the first night, then thought I better charge it. I plugged it into my USB charger the green light came on but never went out for over 4 hours, as a safety precaution I took it off charge.

 Where things become confusing is the next day I plugged it in again and there was no light, nothing, the LED stayed blank. I tried different cables, ports, chargers but no LED came on. Considering it still had charge I tried running it flat where it continued to run for about 35-40 hours none stop in the laundry driving a pair of Takstar HI2050.

 (so it goes for a long time)

 When it finally did go flat I plugged it into USB again (no LED) left it for a few hours , nothing, didn't charge at all. I figured the charging circuit on mine was dead so went ahead purchasing an external charger removing the battery and charging it manually. But to make matters more confusing since doing that manual charge the green LED comes on again when plugged into USB. As you can see its got me quite confused.

 To be honest, I was A/Bing earlier with FiiO E06 and find the E06 better by a decent margin. The Line5 sounds clean enough though, for the price and appearance it's quite nice. I think I could hear some unwanted distortion with low impedance IEM's at a certain frequency, at least with this unit. I just want to sell mine atm, I have other amps here (too many).


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## viperxp

h20fidelity said:


> The problem I had with this amp was it arrived charged and I used it on the first night, then thought I better charge it. I plugged it into my USB charger and the green light came on, but it never went out not for over 4 hours, as a safety precaution I took it off charge. Where things become confusing is the next day I plugged it in again and there was no light, nothing, the LED stayed blank. I tried different cables, ports, chargers but no LED came on. Considering it still had charge I tried running it flat to see if it was accepting a charge, where it continued to run for about 35-40 hours none stop in the laundry driving a pair of Takstar HI2050. (so it goes for a long time)
> 
> When it finally did go flat I plugged it into USB again (no LED) left it for a few hours and nothing, it didn't charge at all. I figured the charging circuit on mine was dead so went ahead and purchased an external charger removing the battery and charging it manually. But, to make matters even more confusing since doing that manual charge the green LED comes on again when plugged into USB. As you can see its got me quite confused.
> 
> To be honest, I was A/Bing earlier with  FiiO E06 and find the E06 better by a decent margin. The Line5 sounds clean enough though and for the price and appearance it's quite nice. I think I could here some unwanted distortion with low impedance IEM's too at a certain frequency. , at least with this unit. I just want to sell mine atm, I have other amps here (too many)


 

 Thanks for sharing.
 From what I understood, and my knowledge of charging I think you discharged the battery at your unit below the limit that the built-in charger could charge, that's why it didn't charge.


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## H20Fidelity

viperxp said:


> Thanks for sharing.
> From what I understood, and my knowledge of charging I think you discharged the battery at your unit below the limit that the built-in charger could charge, that's why it didn't charge.


 


 I don't think so because it had just been charged the night before for about 4 hours, yet the very next day - no light at all. (this was just before it ran for 40 hours in the laundry)

 It has me quite bewildered indeed. If you can work it out please let us know.


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## viperxp

Well, I got to an insteresting situation with mine.
 I haven't used mine for a while. When I tried - I heard a lot of distortions even on low volume levels, and the operating red led got dimmer and dimmer. I understood that the battery is dead, and tried to charge it. The green light at the rear of the unit started blinking. I left the unit in this mode, but battery never got charged - I also confirmed it with USB tested - there was no current when the unit was "charging". So I removed the battery and guess what ... It's dead. Not only discharged but useless - I tried to revive it using Opus 3100 charger - the battery simply can't hold any charger. So I replaced it with another one, this time protected battery. Now when I plug the USB the light lights solid green.
 I will try to use the amp and see if it charges the battery or not.


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## tenchujin

Thanks for giving time making this review. I was quite happy with this amp and every description you made is spot-on.
 Yes, sadly the battery is unprotected. I never seen the LED in mine go green, I just know that the battery is low when distortions come in. I just monitor the charging time in mine.


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## slaurro

Hey there! I realise this is an old topic but maybe you guys can help. I was planning on getting the A970 to use it in my car. It would stay connected to the ligher power socket. I want to use it to amplify the signal from my bluetooth receiver to the AUX port. But given that it has an unprotected battery i'm kind of reluctant to leave it unsupervised in the car everyday. I was thinking... Is there anyway i could remove the battery and bypass it? The amplifier would be permanently connected to the lighter socket which turns on with ignition. So it would power on only when i start the car. 
Or do you guys know of another cheap amp that doesn't have a battery and would work like that?


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## Tomasinodio

viperxp said:


> Well, I got to an insteresting situation with mine.
> I haven't used mine for a while. When I tried - I heard a lot of distortions even on low volume levels, and the operating red led got dimmer and dimmer. I understood that the battery is dead, and tried to charge it. The green light at the rear of the unit started blinking. I left the unit in this mode, but battery never got charged - I also confirmed it with USB tested - there was no current when the unit was "charging". So I removed the battery and guess what ... It's dead. Not only discharged but useless - I tried to revive it using Opus 3100 charger - the battery simply can't hold any charger. So I replaced it with another one, this time protected battery. Now when I plug the USB the light lights solid green.
> I will try to use the amp and see if it charges the battery or not.




Is it easy to change the batteries? Since it uses a 14500 1200maH UltraFire battery did you just simply replaced it? No soldering? If you don't mind, can i see the internals of the amp? 
Thanks!


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