Maverick Audio TubeMagic A1 (Hybrid Amp) - Discussion and Review Thread
Aug 23, 2010 at 7:24 PM Post #61 of 232

_Spanky_

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Quote:
Good point.  No sarcasm received.  I have not auditioned an A1, but I have auditioned a few tube amps while researching which one I was going to purchase.  Many amps did not hum.  It's just my opinion that persistent hums should be remedied during R&D and not passed on to the customers (while blaming the tubes) at any price point.  
 

 


To me, the hum is only noticeable when I'm not playing any audio and I jack the volume up past comfortable listening levels with headphones on. I'm not trying to avoid the fact that there is hum, I'm just trying to put it into perspective so people don't think that they'll get more hum than music. Do you, when auditioning tube amps, rotate the volume knob beyond your comfort zone? Again, I'm not trying to discredit you, I'm just curious.
 
Aug 23, 2010 at 7:30 PM Post #62 of 232

sp70

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Personally, my A1 *is* silent at just about any volume level. I'm in a relatively silent room and I just cranked the volume knob up to 12 o'clock and have to strain to hear even the slightest hum at all. This is likely the quietest amp I think i've ever owned. I can hear a very very minute amount of static at 12, but no hum, and once again, its almost not noticeable its so quiet. Plus, 12 is pretty loud too, if your listening at that level, obviously, you won't be hearing that at all.
 
I believe that a few of these issues are due to other things in the chain, things like using crappy interconnects, unshielded cables of any sort, and being on a busy power rail. I have shielded 14awg volex cords ($15, nothing real special but far better than stock) and good quality interconnects and I think these things really influence the amount of background noise or hum your going to hear - on any amp. Once you fix these things, I think you'll find that the A1 is just about silent. sp70.
 
Quote:
Good point.  No sarcasm received.  I have not auditioned an A1, but I have auditioned a few tube amps while researching which one I was going to purchase.  Many amps did not hum.  It's just my opinion that persistent hums should be remedied during R&D and not passed on to the customers (while blaming the tubes) at any price point.  
 

 



 
Aug 23, 2010 at 7:55 PM Post #63 of 232

hodgjy

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I understand you're not being confrontational at all.  We're just having a civil discussion here.  
beerchug.gif

 
What I did was pause the music, listen for hum, and then turn the volume pot.  It's been my experience that if the amps I auditioned had hum (including certain tube combos in my amp), the hum did not change with volume level.  This is what I considered typical tube behavior.  That's why I'm questioning Ryan's explanation of tube hum.  If changing the volume pot changes the hum volume, I think the problem is more than just noisy tubes.
 
Quote:
Do you, when auditioning tube amps, rotate the volume knob beyond your comfort zone? Again, I'm not trying to discredit you, I'm just curious.



 
Aug 23, 2010 at 8:29 PM Post #64 of 232

_Spanky_

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Quote:
Personally, my A1 *is* silent at just about any volume level. I'm in a relatively silent room and I just cranked the volume knob up to 12 o'clock and have to strain to hear even the slightest hum at all. This is likely the quietest amp I think i've ever owned. I can hear a very very minute amount of static at 12, but no hum, and once again, its almost not noticeable its so quiet. Plus, 12 is pretty loud too, if your listening at that level, obviously, you won't be hearing that at all.
 
I believe that a few of these issues are due to other things in the chain, things like using crappy interconnects, unshielded cables of any sort, and being on a busy power rail. I have shielded 14awg volex cords ($15, nothing real special but far better than stock) and good quality interconnects and I think these things really influence the amount of background noise or hum your going to hear - on any amp. Once you fix these things, I think you'll find that the A1 is just about silent. sp70.
 

 

I agree. It's just such a small amount of hum that is at listening levels beyond that of the average user.


 
Quote:
I understand you're not being confrontational at all.  We're just having a civil discussion here.  
beerchug.gif

 
What I did was pause the music, listen for hum, and then turn the volume pot.  It's been my experience that if the amps I auditioned had hum (including certain tube combos in my amp), the hum did not change with volume level.  This is what I considered typical tube behavior.  That's why I'm questioning Ryan's explanation of tube hum.  If changing the volume pot changes the hum volume, I think the problem is more than just noisy tubes.
 

 


beerchug.gif
 So hum that doesn't change with the volume pot is tube hum? I'd believe that but I hate forming opinions while knowing extremely little about the actual process going on :)
 
You know what I should do? I currently have the line-out of the D1 connected to the line-in on my computer's onboard audio because I wanted to ghetto-record some stuff. I should take the phone output of the A1 and hook it to the line-in on my computer so people can actually hear the hum and what we're talking about. I have the line-in on my computer calibrated to record about the same level as what the sound actually is so it shouldn't be too far off.
 
Aug 23, 2010 at 8:51 PM Post #65 of 232

JustVisit

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Quote:
IWhat I did was pause the music, listen for hum, and then turn the volume pot.  It's been my experience that if the amps I auditioned had hum (including certain tube combos in my amp), the hum did not change with volume level.  This is what I considered typical tube behavior.  That's why I'm questioning Ryan's explanation of tube hum.  If changing the volume pot changes the hum volume, I think the problem is more than just noisy tubes.
 


Thanks for pointing this out
smile_phones.gif
  I think my previous explanation is not complete.
The hum is very much related to the design of the tube circuit, the power transformer and a lot of other small things in the unit. For example, you can make the tube work in "buffer mode" which it only produces very very low hum. However, we choose to put the tube working in "amplifying mode" which we believe will make the audio quality much better and have more "tube flavor". As a side affect, 6AK5 tube working in this mode WILL have some level of hum. The reason we choose 6AK5 tube is that this particular tube really is very transparent, musical, has terrefic high range and is relatively easy to find. I have spent over 6 months in fine tuning this amplifier, part of my mission is to reduce the hum to the minimum acceptable level.  Due to the size limitation ( everyone who opened the case of the A1 will see how much components in this tiny unit),  we decide to control the hum to not to be heard in "comfortable listening volume".
Yes as hodgjy pointed out, you can make the amplifier silent when you turn the volume in highest and in mute mode. But it requires a lot modification (special shield box for the power transformer and other circuit design trick to archive that) and some scrafices in the sound quality. We decided to scrafice this "feature" in order to get the amp to this particular size and sound quality.
 

 
 
Aug 23, 2010 at 9:47 PM Post #66 of 232

JustVisit

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Quote:
Thanks for the prompt reply Ryan,
I was inclined to believe it was the tube causing the hum.   As mentioned it is hardly noticable through the speakers before 12 o'clock, even past 12 with a program running you will not notice it since the program will mask it.  I was just curious, since the D1, with tube output also, does not have much noise.  I am using the D1 with a p/p el34, and get no noise at all but that amp is so powerful that I can hardly go past 10 o'clock with that setup.
We are early adopters here, I like the Maverick approach to a sound business, we can cooperate to bring a better product for everyone involved, I loved the D1 discussion, tour, etc., threads.  Almost everything can be improved, my comments are on the spirit of constructive elucubration, if someone finds a glitch lets work together and solve it to everyones benefit.
I am happy with this amp.

Yes I completely agree with you. All the comments are extremely helpful for us in order to improve the product. Without help from the community there will be no today's D1 and A1.

 
 
Aug 23, 2010 at 9:52 PM Post #67 of 232

hodgjy

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Well, I think this little debate has been largely settled.  It's partly a transformer hum and partly from the circuit topology.  It's not entirely a hum from humming tubes in the signal pathway, but rather an intentional tradeoff known by the designer.  Now I understand what's going on here, so I apologize if my early comments were inaccurate.
 
Carry on!
 
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Aug 23, 2010 at 11:17 PM Post #68 of 232

DylanHall

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Quote:
 
Hey Dylan, the problem you had before (right channel not working) is obvisouly caused by the tube was moved during transportation.
Don't worry, let me try to sort out the new issue:
 
- You mentioned you use the DAC/A1 combo with your laptop. What kind connection did you use between the DAC and your laptop? Did you have the same hum sound when you use the DAC's headphone output with your laptop? Do you hear the hum sound when you connecting your headphone directly to the laptop's headphone output?
 
- Will you be able to find another wall power socket to connect your laptop? Make sure there is no other electronics using the same power socket. Also, make sure the wall power socket is properly connected to the earth line.
 
- Make sure you use high quality audio cable to connect the A1 to the DAC. Low quality audio cable will cause interference.
 
I don't think your unit is a lemon, I personally tested your unit before the shipment. The minimum requirement for the unit to pass my testing is that I can not hear any noise from two headphones(one PX100 and one HD650) in a very quiet room. It has to be dead silence. Your issue, is probably due to bad power source or audio cable. As you did get it working very well in your office environment.
 
Let me know your testing result and I will help you further. You can leave your feedback here or reply directly on the support ticket.
 
Cheers,
 
Ryan

 

 
First up, thanks for replying so promptly. I think it's awesome that you take customer service so seriously. This is the reason I chose the A1, that and the beautiful brushed aluminium finish :)
 
Let me try and do a better job of summarising the situation and my setup, then I'll try and answer your questions.
 
Headphones: Sony MDR7506 (63 Ohm)
Speakers: Polk RT-25 bookshelf (8 Ohm)
Sources: Laptop headphone jack, Laptop via AlienDAC, Work Desktop via headphone jack, Work Desktop via AlienDAC, Denon CD Player
 
At home testing with bookshelf speakers: Sounds great! To hear any buzz/hum I need to press my ear to the speaker. No issues here.
 
At work and home, no sources connected to A1: headphones have background buzz, not very loud, but loud enough to hear clearly over background noise in office. Adjusting the volume control has little impact on the buzz.
 
At home, A1 connected to Denon CD player: headphones have background buzz, can be heard during quiet bits in the music or when the music is paused.
 
At home or work, A1 connected to laptop via DAC or headphone jack: Nasty buzz/noise/interference. Sounds a little like a fax machine. Problem is resolved by disconnecting the laptop from the mains. Another curious thing is that selecting the line-in input, then connecting the DAC to the analog-in still causes the extra noise.
 
At work, A1 connected via DAC to work PC: same nasty noise as laptop, but not as loud.
 
At work, A1 connected to headphone jack on work PC: same background noise as when A1 has no source connected.
 
My gut feeling is that there are two separate issues. At all times there is a background noise when using headphones. The second issue is that connecting a PC via a USB DAC there is a far worse noise issue.
 
let me try and answer your questions now :)
 
- You mentioned you use the DAC/A1 combo with your laptop. What kind connection did you use between the DAC and your laptop? Did you have the same hum sound when you use the DAC's headphone output with your laptop? Do you hear the hum sound when you connecting your headphone directly to the laptop's headphone output?
 
The DAC is connected to the laptop with a standard USB cable. The DAC is powered from the USB. The DAC doesn't have a headphone amp, it's not powerful enough to directly drive headphones. I will try connecting it to another amp tonight and see if the hum is still present. There is no hum with the headphones directly connected to the laptop headphone jack.
 
- Will you be able to find another wall power socket to connect your laptop? Make sure there is no other electronics using the same power socket. Also, make sure the wall power socket is properly connected to the earth line.
 
I tried the laptop on one wall socket and the A1 on another, this didn't seem to make any difference. There was other equipment connected to both sockets. I don't have enough sockets in the house so every plug tends to have multiple devices. I have a "circuit tester thing" I'll connect to both sockets tonight and make sure they pass. The device is supposed to be able to find wiring problems. I also tried connected the A1 to a UPS running on batteries which means no actual connection to the house wiring. Connected to the UPS the background buzz/hum was still present. I don't recall if the additional noise from the laptop was present. If it's helpful I can test it again tonight?
 
One final comment, when I crank the volume up a little so the background noise is lost, the unit sounds great :)
 
Thanks again for you help,
 
Dylan
 
 
Aug 24, 2010 at 5:33 AM Post #69 of 232

JustVisit

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Hi Dylan,
 
Thanks for  your detail explanation of the issue. I agree with you, there seems to be two separate issue with your A1, the speaker amplifier part is okay, the issues are just related to the headphone output.
Issue 1: Background hum/noise.
 
A1 should not produce any background noise/hum via headphone in comfortable listening volume . Especially when there is just power cord connect to the unit ( this rules out the possibilities of a bad audio cable or bad audio source).
 
- Could you let me know if the hum exists when the volume is turn to the lowest level?
 
- You mentioned when you crank the volume up a little so the background noise is lost.  Can you let me in which volume level the hum is gone? After the hum is gone, if you turn the volume up, will you hear the hum again?
 
- Will you be able to go to another room (with all electronics stuff shut down), just plug the A1 to the power socket with a new power cord cable ( A1 uses standard power cable, any regular power cord will be able to work with A1), to see if you can hear the hum sound?
 
I think there are two possibilities for this issue. 1) the power source is not clean in your home or office.  2) It's either the unit's volume controller or the tube has issues, after all the shocks during transportation. If you can perform the above testing, we can conclude the issue. If it is indeed the issue with A1, I can just send you a replacement.
 
Issue 2: Problem with the DAC.
 
It is obviously your DAC has some strange interferences to affect A1 to produce the "nasty" noise. I will suggest we work on the issue 1 first, then focus on the issue 2.
 
Cheers,
 
Ryan
 
Aug 24, 2010 at 5:36 AM Post #70 of 232

DylanHall

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Quote:
<snip>
 
My gut feeling is that there are two separate issues. At all times there is a background noise when using headphones. The second issue is that connecting a PC via a USB DAC there is a far worse noise issue.  
let me try and answer your questions now :)
 
- You mentioned you use the DAC/A1 combo with your laptop. What kind connection did you use between the DAC and your laptop? Did you have the same hum sound when you use the DAC's headphone output with your laptop? Do you hear the hum sound when you connecting your headphone directly to the laptop's headphone output?
 
The DAC is connected to the laptop with a standard USB cable. The DAC is powered from the USB. The DAC doesn't have a headphone amp, it's not powerful enough to directly drive headphones. I will try connecting it to another amp tonight and see if the hum is still present. There is no hum with the headphones directly connected to the laptop headphone jack.
 

 
Something of a breakthrough here. I've hooked the laptop/DAC up to my main amp (Sony DA1200ES) and the nasty noise/interference is clearly audible here also, so that rules out the A1. Looks like my DAC is mis-behaving. Rather annoying. I've built two and the other one is working perfectly. Will have to figure out what I've screwed up now... Sorry for not testing the obvious in the first place. Maybe this is the excuse I need to buy a D1 also
wink_face.gif
.
 
That just leaves one issue, the buzz in the background when no sources are connected or a source is connected but quiet/paused.
 
 
Quote:
 
 
- Will you be able to find another wall power socket to connect your laptop? Make sure there is no other electronics using the same power socket. Also, make sure the wall power socket is properly connected to the earth line.
 
I tried the laptop on one wall socket and the A1 on another, this didn't seem to make any difference. There was other equipment connected to both sockets. I don't have enough sockets in the house so every plug tends to have multiple devices. I have a "circuit tester thing" I'll connect to both sockets tonight and make sure they pass.  <snip>

 
All the sockets tested ok, so it looks like the wiring is ok.
 
Dylan
 
Aug 24, 2010 at 6:08 AM Post #71 of 232

DylanHall

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Looks like you posted your reply while I was still writing mine :)
 
- Could you let me know if the hum exists when the volume is turn to the lowest level?
 
Yes.
 
- You mentioned when you crank the volume up a little so the background noise is lost.  Can you let me in which volume level the hum is gone? After the hum is gone, if you turn the volume up, will you hear the hum again?
 
Sorry, I think I explained myself poorly there. With the volume at it's lowest the hum (which thinking about it might better be described as a buzz) can be heard. As I increase the volume to around 12 o'clock there isn't any noticeable change. After 12 o'clock the buzz is still present but a second source of noise, this one more a hiss becomes apparent. I believe the hiss at that volume is normal. Were I to try and listen to music at that level I suspect I'd damage my hearing!
 
- Will you be able to go to another room (with all electronics stuff shut down), just plug the A1 to the power socket with a new power cord cable ( A1 uses standard power cable, any regular power cord will be able to work with A1), to see if you can hear the hum sound?
 
Plugged the A1 into a socket in the bedroom. Disconnected all the electronics that are nearby. The hum/buzz is still present. I've been using a cable I supplied for all the testing so far (the supplied cable has a US plug, we use an NZ/AU plug here). I've replaced my cable with another (slightly heavier duty). No change with the new cord, the hum/buzz is still present.
 
This is the first time I've had the A1 in a truly quiet environment. The unit itself is also making a buzzing noise. It's hard to tell with the case on, but I think it's coming from the transformer end of the unit.
 
For good measure I tried another pair of headphones, this time some AKG in-ear ones. The buzz/hum is still present.
 
Issue 2: Problem with the DAC.
 
It is obviously your DAC has some strange interferences to affect A1 to produce the "nasty" noise. I will suggest we work on the issue 1 first, then focus on the issue 2.
 
Agree. As stated in my previous post (shortly after your reply), it looks like the DAC isn't working right.
 
Thanks,
 
Dylan
 
Aug 24, 2010 at 6:23 AM Post #72 of 232

JustVisit

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Hi Dylan,
 
Can you go to my web site to submit a support ticket, and I will arrange a replacement unit for you. Based on what you've described,  I suspect it is either the tube or something else get damaged during the transportation and certainly I would love to exchange another unit for you:)
 
Cheers,

Ryan
 
 
Aug 24, 2010 at 8:28 AM Post #73 of 232

patkhan

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An interesting fact: I received by mistake a pair of 6AK7, I did not notice this until after I put them on the A1.  With this tubes in the hum was intolerable, I pulled them out immediatly.
Tubes in amplification mode, with this incident I tend to believe there is some noise from the tx, or the circuit, that is being amplified by the tube.  I have read before about compromises in tube curcuitry design, it is true that you have to walk a very fine line to get everything working to the best possible result.  And it is also true that, many times, you have to accept certain tradeoffs.  The magic of tubes, for me, is something that goes way back to childhood, and to be able to have this magic at this stage of my life at a reasonable price and with customer care that resambles a good friend's help is something that really doesn't have a price tag.  Hum as faint as the one encountered on my A1 is not an issue for me, I grew up listening to very old tube radios that had no spares in the country I was living in, perhaps for me imperfection is part of the magic, but let me be clear the A1 is not an old tube radio, it is a very nice mix of old and new technology and as everything else it has good and not so good features.  No one can please everyone all the time, Maverick audio is offering, IMO, a fair product and a TERRIFIC customer experience.  Kudos to Ryan!
 
Aug 24, 2010 at 11:47 AM Post #74 of 232

JustVisit

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Quote:
An interesting fact: I received by mistake a pair of 6AK7, I did not notice this until after I put them on the A1.  With this tubes in the hum was intolerable, I pulled them out immediatly.
Tubes in amplification mode, with this incident I tend to believe there is some noise from the tx, or the circuit, that is being amplified by the tube.  I have read before about compromises in tube curcuitry design, it is true that you have to walk a very fine line to get everything working to the best possible result.  And it is also true that, many times, you have to accept certain tradeoffs.  The magic of tubes, for me, is something that goes way back to childhood, and to be able to have this magic at this stage of my life at a reasonable price and with customer care that resambles a good friend's help is something that really doesn't have a price tag.  Hum as faint as the one encountered on my A1 is not an issue for me, I grew up listening to very old tube radios that had no spares in the country I was living in, perhaps for me imperfection is part of the magic, but let me be clear the A1 is not an old tube radio, it is a very nice mix of old and new technology and as everything else it has good and not so good features.  No one can please everyone all the time, Maverick audio is offering, IMO, a fair product and a TERRIFIC customer experience.  Kudos to Ryan!


Unlike digital circuit design, analog circuit design sometimes is very unpredictable.  You have to perform a lot different testings in order to archive the best result. For example, the voltage of the tube, the value of certain resistors and capacitors, tube working mode and etc. A tiny change in the analog circuit might result dramatic change in the audio quality. Yes you have to accept certain tradeoffs. Like I have said before, if I make the tube works in the "buffer mode", it will produce very small amount of noise and it is relatively easy to kill the hum. However, 6AK5 tube working in the buffer mode can not offer the same level of the sound quality as when they are running in the amplification mode, it can be described as day and night difference. So we decide to use the 6AK5 tube in the amplification mode, the tradeoff is that the it will amplify the noise from the circuit. After a lot of adjustments, we have controlled the noise level to the minimum that you'll not notice any in comfortable listening volume even when using a low impendance headphone, as we know a lot of people will use it as a headphone amplifier and noise level is the key factor to a good headphone amplifier. To design a class a/b hybrid amp in such a small case is really a challenge, and there is a lot fun in analog circuit design :)
 
 
Sep 1, 2010 at 10:11 AM Post #75 of 232

uelover

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Hi. I have gotten this amp with the upgraded tube from Ryan a few days ago. The bass sounded awesome from the box.
 
However, I find the sound too warm and the mid a little too recessed. I find myself enjoying HD600 out from my D1 because at least I would not need to strain my ears to listen to what the singers are singing in the songs.
 
Anyone experienced what I experience?
 
Spanky, I saw you looking for WE403 tube on head-fi. Managed to find one?
 
I would either need to get a super bright headphone to pair with this A1 or I would need to get a very forward sounding tube...
 
 
 
 

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