[uncola]

Hey did more testing to see if I get a hum.. I tried the A1 with my backup headphones, superlux hd681 evo 32ohms and I didn't get any hum at normal listening level but if I turn the volume way up to ear destroying levels with no music playing I do get a high pitched eeeeeee like an angry mosquito.  Maybe you should experiment with your D2, are you sure you're using the right output rca ports?  I vaguely remember some people were double-tubing, if that's a thing and it was bad?  I don't remember

 

[IYAshike]

Hello Uncola, 
 
Thanks for doing that testing l have also been doing some sort of testing and researching. l have researched on HPs amplifiers, noise, hum, and all that's involved. Unsurprisingly, l found that when it comes to noise/hum/hiss, there is one variable that is always involved: sensitivity. So, l went back to look at my HPs, and checked the hum coming from them. This would be the order, from more hum to none (please, pay attention to the sensitivity levels):
 
1- AKG K550 (114db / 32 Ohms)
 
2- Sennheiser HD558 (112db / 50 Ohms)
 
3- Audio-Tehnica PRO700MK2 (106db / 38 Ohms) 
 
4- Philips Fidelio X1 (100db / 30 Ohms)
 
5- Beyerdynamic DT770 (96db / 250 Ohms) 
 
6- Hifiman HE400 (92.5db / 35 Ohms)
 
As you can see, there is a negative correlation: as the sensitivity diminishes so does the hum. Now, more interestingly, l happened to find out just by chance (l felt like a scientist making a casual discovery) the following:
 
l was testing the Audio-Technicas with the normal cable on them (not the coiled one these HPs also provide). Normally, l use the 1/4 adapter that came in the box with the HE400s. Today, given the chaos l had on my desk (all the HPs + cables + adapters around) l reached a different adapter (the one that came with the Audio-Technicas). l couldn't believe my ears (l asked my wife to check it out, too!): the hum was gone. Zero (¡Nada!). Unbelievable! Just because l changed one 1/4 adapter for another! 
 
Thus, following the list above, the Audio-Technicas (using the 1/4 adapter they provide) and the Hifimans do make no noise/hum, at all.
 
No need to say that after the Audio-Technicas 'discovery', l went crazy trying all HPs again with this (supposed to be) 'magic' adapter. l also tried different cables with, unfortunately, same results. The Audio-Technica's 1/4 adapter only makes the difference with the Audio-Technica HPs. Don't ask me why 

   
 
Changing topics and answering to your question:
 
1- l am not sure whether l am using the right RCA outputs or not. Usually, l connect one of the D2's analog out (listed on the device: 'Normal' - 'TubePreOut') to the only A1 analog in. lt appears that by connecting the D2's TubePreOut to the A1's analog in, l would be 'double-tubing' as you mentioned. However, the sound is practically the same (if not absolutely the same) whether connecting the A1 to the D2's 'normal' or 'TubePreOut' analog out. 
 
Moreover, l know that the hum comes from the A1 only. l switched off the D2 (and disconnected the RCA cables from the back of the A1, too). Then, l connected the A1 via 'line in' to my phone/Fiio X3: same results/hum. Besides, l tried different plugs in the house. Same again.
 
Finally, l tried something very simple: l simply switched off the D2, while the A1 was on. The hum continued to be there. 
 
So no, the D2 is not the problem, it is out of the equation 

 lt's seems like the A1 is a 'humy' one (if you allow me to make up a new word for your English dictionary 

)
 
Maybe we get lucky and one of these super knowledgeable Head-fiers happens to read my ignorant posts

, and decide to take my ignorance to an end, once and for all. Maybe even Ryan from Maverick Audio reads these posts, and decide to give us a much appreciated hand... Who knows?
 
Anyway, enjoy the weekend! 

 

[sealykojac]

  Hey did more testing to see if I get a hum.. I tried the A1 with my backup headphones, superlux hd681 evo 32ohms and I didn't get any hum at normal listening level but if I turn the volume way up to ear destroying levels with no music playing I do get a high pitched eeeeeee like an angry mosquito.  Maybe you should experiment with your D2, are you sure you're using the right output rca ports?  I vaguely remember some people were double-tubing, if that's a thing and it was bad?  I don't remember

 
I was running my Maverick with he500's and dont recall hearing any hum but then I never cranked the volume to ear destroying levels. Sadly mine is going up for sale as I've upgraded to a nicer amp. 

 

[IYAshike]

   
I was running my Maverick with he500's and dont recall hearing any hum but then I never cranked the volume to ear destroying levels. Sadly mine is going up for sale as I've upgraded to a nicer amp. 

At "ear destroying levels", l would say you are only likely to 'hear' hiss, not hum or noise. ln my particular case, l hear hum from the A1 only at very low to low volume level (l like to listen to music at night). The moment l turn the volume up to 'moderate level', l don't hear any hum anymore... 

 

[Soundsgoodtome]

Can I ask what headphones you guys are using, on which tubes and where your volume pot is at regular listening levels? I have Mad Dog 3.2s with Telefunken tubes and I'm at 3 O'clock for regular listening levels. Max volume is just a step over being too loud.

Not sure if the amp is outputting correctly or there's something wrong. I understand that each tube will output a little different but there can't be that wide of a swing. I bought the AMP used and have new Telefunken tubes as well as Mullard. The mullards output even less than the Telefunken.


Source is Laptop > ODAC > A1 via rear line-in > Mad Dogs HP Out

 

[uncola]

Damn 3 o'clock seems high.. I use them with zmf modded fostex t50rp with a thick canare cable made by zmf and never go above like 10 o'clock.. hifimediy sabre 9023 dac and raytheon factory matched tubes.. I leave my pc volume at 100%

 

[IYAshike]

Can I ask what headphones you guys are using, on which tubes and where your volume pot is at regular listening levels? I have Mad Dog 3.2s with Telefunken tubes and I'm at 3 O'clock for regular listening levels. Max volume is just a step over being too loud.

Not sure if the amp is outputting correctly or there's something wrong. I understand that each tube will output a little different but there can't be that wide of a swing. I bought the AMP used and have new Telefunken tubes as well as Mullard. The mullards output even less than the Telefunken.


Source is Laptop > ODAC > A1 via rear line-in > Mad Dogs HP Out

Hello there,
 
If you look at the previous posts, you'll see the HPs other people are using. In my case (copied from a previous post):
 
1- AKG K550 (114db / 32 Ohms)
 
2- Sennheiser HD558 (112db / 50 Ohms)
 
3- Audio-Tehnica PRO700MK2 (106db / 38 Ohms) 
 
4- Philips Fidelio X1 (100db / 30 Ohms)
 
5- Beyerdynamic DT770 (96db / 250 Ohms) 
 
6- Hifiman HE400 (92.5db / 35 Ohms)
 
 
l have the Raytheon 6AK5 tube in my A1. 
 
About the position on the volume knob, put it this way: the Hifiman HE400 are the HPs that my A1 struggles the most to drive (in that, having the volume knob at the same position (e.g. 20%) l get less volume in the music, compared to all the other HPs of the list above). Now, l never reach 50% on the volume control. l have the feeling a listen to music at levels below the average but, in any case, if l turn the volume knob to 75%... man that's loud as hell! There is no way l have any HPs on my head with the volume knob beyond 40%. My normal listening position, l would say is 25 to 30%...
 
With all the other HPs, l truly believe the A1 has the capability to simply blow their drivers away... 
 
As it appears, orthodynamic HPs require a lot more current than their dynamic counterpart. ln my case, it is well clear (the HE400 requiring significantly more volume than any of the others HPs l have). That may be the case on your Mad Dogs, too. However, given my experience with the A1, it's hard for me to believe you can turn the volume all the way up. ln my case, doing so is 'counter intuitive': you have the feeling you're going to blow up your HPs...
 
Hope l could help    

 

[IYAshike]

  Hello Uncola, 
 
Thanks for doing that testing l have also been doing some sort of testing and researching. l have researched on HPs amplifiers, noise, hum, and all that's involved. Unsurprisingly, l found that when it comes to noise/hum/hiss, there is one variable that is always involved: sensitivity. So, l went back to look at my HPs, and checked the hum coming from them. This would be the order, from more hum to none (please, pay attention to the sensitivity levels):
 
1- AKG K550 (114db / 32 Ohms)
 
2- Sennheiser HD558 (112db / 50 Ohms)
 
3- Audio-Tehnica PRO700MK2 (106db / 38 Ohms) 
 
4- Philips Fidelio X1 (100db / 30 Ohms)
 
5- Beyerdynamic DT770 (96db / 250 Ohms) 
 
6- Hifiman HE400 (92.5db / 35 Ohms)
 
As you can see, there is a negative correlation: as the sensitivity diminishes so does the hum. Now, more interestingly, l happened to find out just by chance (l felt like a scientist making a casual discovery) the following:
 
l was testing the Audio-Technicas with the normal cable on them (not the coiled one these HPs also provide). Normally, l use the 1/4 adapter that came in the box with the HE400s. Today, given the chaos l had on my desk (all the HPs + cables + adapters around) l reached a different adapter (the one that came with the Audio-Technicas). l couldn't believe my ears (l asked my wife to check it out, too!): the hum was gone. Zero (¡Nada!). Unbelievable! Just because l changed one 1/4 adapter for another! 
 
Thus, following the list above, the Audio-Technicas (using the 1/4 adapter they provide) and the Hifimans do make no noise/hum, at all.
 
No need to say that after the Audio-Technicas 'discovery', l went crazy trying all HPs again with this (supposed to be) 'magic' adapter. l also tried different cables with, unfortunately, same results. The Audio-Technica's 1/4 adapter only makes the difference with the Audio-Technica HPs. Don't ask me why 

   
 
Changing topics and answering to your question:
 
1- l am not sure whether l am using the right RCA outputs or not. Usually, l connect one of the D2's analog out (listed on the device: 'Normal' - 'TubePreOut') to the only A1 analog in. lt appears that by connecting the D2's TubePreOut to the A1's analog in, l would be 'double-tubing' as you mentioned. However, the sound is practically the same (if not absolutely the same) whether connecting the A1 to the D2's 'normal' or 'TubePreOut' analog out. 
 
Moreover, l know that the hum comes from the A1 only. l switched off the D2 (and disconnected the RCA cables from the back of the A1, too). Then, l connected the A1 via 'line in' to my phone/Fiio X3: same results/hum. Besides, l tried different plugs in the house. Same again.
 
Finally, l tried something very simple: l simply switched off the D2, while the A1 was on. The hum continued to be there. 
 
So no, the D2 is not the problem, it is out of the equation 

 lt's seems like the A1 is a 'humy' one (if you allow me to make up a new word for your English dictionary 

)
 
Maybe we get lucky and one of these super knowledgeable Head-fiers happens to read my ignorant posts

, and decide to take my ignorance to an end, once and for all. Maybe even Ryan from Maverick Audio reads these posts, and decide to give us a much appreciated hand... Who knows?
 
Anyway, enjoy the weekend! 

EDIT: Sorry, l made a noob mistake. Forget all l say about the 'magic' 1/4 adapter. What happens is this adapter only fits properly in the coiled cable the Audio-Technicas bring (you screw the adapter to the cable). The adapter does not fit properly in the 'normal' cable. Therefore, there was no hum, at all... but also no sound! l didn't realise the adapter was not properly plugged... Sorry.

 

[Soundsgoodtome]

Can I ask what headphones you guys are using, on which tubes and where your volume pot is at regular listening levels? I have Mad Dog 3.2s with Telefunken tubes and I'm at 3 O'clock for regular listening levels. Max volume is just a step over being too loud.

Not sure if the amp is outputting correctly or there's something wrong. I understand that each tube will output a little different but there can't be that wide of a swing. I bought the AMP used and have new Telefunken tubes as well as Mullard. The mullards output even less than the Telefunken.


Source is Laptop > ODAC > A1 via rear line-in > Mad Dogs HP Out

Put on a new pair of stock Raytheon tubes and volume went up considerably. What was 3 o'clock before can be achieved at 1 o'clock. Max volume is substantially louder and probably above safe listening levels.

 

[genclaymore]

Do the Tube magic A1 a good match for the Beyerdynamic T90? I asked as I been thinking about getting it or the little dot mK2 but I can't make up my mind.

 

[IYAshike]

l can't tell you as l don't have the T-90s. Now, in case it could help you (in any way), let me tell you that when it comes to the DT-770 pro (250 Ohms), the impact the A1 (in my case, combined with the D2, both full-upgrades) has on them is simply amazing. l have read many times how an amplifier can bring a HP to life... l was pretty skeptical about it but, in the case of the A1 and DT-770... man there is a huge improvement. Put it this way, before (via Xonar Phoebus) l didn't like the Beyers so much... now... they are one of my favourites HPs.
 
Be very aware of the hum the A1 will very likely produce (specifically, if you like to listen to music at low levels, especially using highly sensitive/low impedance HPs). Chances are the same applies for many tube amps. 
 
Good luck!   

 

[IYAshike]

Hello there!
 
lt's just to say that l sent another email to Ryan (from Maverick Audio) about my problem with the A1 and, for the second time, l got no reply. l sent my first email back then in November 2013, and the second one like 2 weeks ago or so. l mean, he had plenty of time to answer. 
 
Unfortunately, this time Ryan was not helpful (other people claim he really is). He was nice and friendly until l placed the order. The moment l emailed him asking for help about my problem with the A1 producing hum, he never answered.
 
On the contrary, l wrote to Kingwa (Audio GD) to enquire about one of his DAC/amps. l made the point about my problem with the A1 (in order to make sure it does not happen again) but, to my surprise, he tried all he could to help me sort out the problem instead of simply try to sell me a new device. He gave me advice, a troubleshot steps to follow, and what's amazing the most (quoting his on words): 
 

 "I wish can help you fixed the hum noise at first, then you consider if want to buy the gear from us. If you can fixed the noise, you may don't need buy the device now."

 
This is beyond customer service, IMHO.
 
Sometimes, it's not only about what you buy or the warranty, but the post-buy service the company offers.
 
Regards to all!

 

[Soundsgoodtome]

Audio-GD ftw

 

[uncola]

I strongly considered audio-gd but their ordering process was weird and I ended up deciding I wanted the speaker amp feature of the a1.. my a1 sounds great but there are minor build quality issues(enclosure too tight, tube sockets sideways kind of hard tow ork with) and the rca out seems not to work right preventing me from recommending maverick

 

[BeatsWork]

Line-In Problem
 
Anyone using the line-in on A1?  I have tried several different adapters and all have the same issue - I have to back the plug out about 1/8" to get the right and left channels to balance.  Using wrong type of plug?  Bad socket?