[BigTony]

I might just pop the hood on the amp this weekend and have a butchers inside; i'll use a blunt pencil to poke about.

 

[Mullet]

Quote:

Originally Posted by BigTony /img/forum/go_quote.gif What I think he meant to say was 'Have the signal tubes had 100 hours of burn in' after 100 hours there should be no hum. My 332S hummed right out of the box, now after about 40 hours of use the hum is only in the lefthand side and is much quieter than when I first turned the amp on. I had planned to run the amp for a week (or about 100 hours) to bed everything in, so don't be too alarmed at noises right out of the box.

I'm hearing two different things... if I'm using my HD650s I hear a crackly microphonic type noise. I don't hear it when listening to music because it's so low. It's on the right side. If I touch the small right tube with a lintless rag it's even less noticeable. I think it's the tube in this situation.

The second thing I'm hearing only when I'm using IEMs (which by the way sound pretty damn good) is this low level hum. I think I hear it in both channels. It's more of hum than a crackle.

 

[Audict123]

Mullet: if I understand correctly you don't hear any hum with the HD650? I have the same headphones but I do get som clearly noticeable hum with my 332s. To me it makes no sense then it would be inherent to the design (proximity of signal to power wires), like Ogyga suggested. Or are there other factors in play that may be exacerbated by this design feature?

 

[BigTony]

After a further night of use, there is now no audible hum in the right hand chanel - which is good. Left hand chanel is still huming - its still too loud for me to enjoy listening to music with quiet passages, but while the amp is still changing i'm hoping this hum settles and disappears.

 

[yuking09]

6 * 1是70年前的苏联管，比我年龄还要大。本身发热量小，所以很难烧出来。一个星期每天烧18个小时，我只烧 了两三只出来。耐心烧管哈，烧不出来我发两只烧透澈的给你。

 

[BigTony]

Quote:

Originally Posted by yuking09 /img/forum/go_quote.gif 6 * 1是70年前的苏联管，比我年龄还要大。本身发热量小，所以很难烧出来。一个星期每天烧18个小时，我只烧 了两三只出来。耐心烧管哈，烧不出来我发两只烧透澈的给你。

Google Translate ' 1 was 70 years ago the Soviet Union pipes, bigger than my age. Itself, heat is small, it is difficult to burn out. Burn for a week to 18 hours a day, I just burned out of 23. Patience and burning tube, ha, do not burn out of me 2 burn Rosen's for you.'

Ok, so more time required, which I kinda guessed, I just don't like to leave the amp on while I'm a) out of b) asleep.. so it takes a long time to build the hours up.

Any hints on how to reduce the gain to a more managable level?

 

[Audict123]

>> Any hints on how to reduce the gain to a more managable level?
I got my -14db rca attenuators in. Now I usually play in the 9-10 o'clock region, which is good.

More elegant would be to convert the linear pots to log pots by adding a resistor. Liuyi explained they are 100kohm. All it takes is a 15kohm resistor placed between out and ground of the pot, see ESP - A Better Volume Control
I may try this trick later, no time this weekend and have to order them.

Still no 403B tubes in...

 

[BigTony]

ok - i'll look out for sensibly priced attenuators, £39 for a pair is steep!

 

[Mullet]

Quote:

Originally Posted by arie123 /img/forum/go_quote.gif Mullet: if I understand correctly you don't hear any hum with the HD650? I have the same headphones but I do get som clearly noticeable hum with my 332s. To me it makes no sense then it would be inherent to the design (proximity of signal to power wires), like Ogyga suggested. Or are there other factors in play that may be exacerbated by this design feature?

I don't hear any low level hum with the HD650 on a 332c. However, with my SE530s I do hear it when there is low volume levels or no audio at all. This even occurs when the volume is completely turned down. I haven't tested this with my Triple.Fis yet. How high is this hum? Is it really noticeable?

On another note, I don't hear the microphonics coming out of my right channel when I have the tube covers on the tubes. The microphonics sound more like a hiss type sound, where as the hum is more of a buzz.

What are your source components etc? Could it be something in your signal path?

~Mullet

 

[Mullet]

Quote:

Originally Posted by BigTony /img/forum/go_quote.gif ok - i'll look out for sensibly priced attenuators, £39 for a pair is steep!

So you actually need attenuators for the 332s? I'm at about 9 - 10 o'clock with my 332c. I have an iPhone with SendStation mini USB LOD > Belkin mini to RCA > 332c > HD650s. With my Shure SE530s I can get it to 7 o'clock before its too loud.

~Mullet

 

[BigTony]

Quote:

Originally Posted by Mullet /img/forum/go_quote.gif So you actually need attenuators for the 332s? I'm at about 9 - 10 o'clock with my 332c. I have an iPhone with SendStation mini USB LOD > Belkin mini to RCA > 332c > HD650s. With my Shure SE530s I can get it to 7 o'clock before its too loud. ~Mullet

Yeah, the lowest balanced level is much to loud for me, you can hear the music clearly with my hd650s sat next to the amp - 6 feet away from my ears! To compare, on my Jade amp i need to switch to high gain and turn the amp to 3-6pm.. its that loud!

 

[Audict123]

Quote:

Originally Posted by Mullet /img/forum/go_quote.gif How high is this hum? Is it really noticeable? ...... What are your source components etc? Could it be something in your signal path? ~Mullet

Yes, it's really noticeable and disturbing in silent passages or when music stops. When I pull the plug from the amp, real silence sets in. If I disconnect it from my source (a valab dac) by pulling the rca plugs out, the hum stays exactly the same. I also tried different power chords and another room (away from PC). No improvement. It has about 50 hours max on it now, so I keep hoping it will reduce further. Also, I could be lucky that the 403B that are on the way don't show the problem.

 

[Mullet]

Quote:

Originally Posted by BigTony /img/forum/go_quote.gif Yeah, the lowest balanced level is much to loud for me, you can hear the music clearly with my hd650s sat next to the amp - 6 feet away from my ears! To compare, on my Jade amp i need to switch to high gain and turn the amp to 3-6pm.. its that loud!

Yeah no doubt. I can hear the music perfectly fine out of the HD650s at 9 o'clock and a few feet away. I can hear it clearly at 6'. So these amps are pretty powerful then.

Excuse my ignorance... So how do you know when you're at a balanced level? I'm assuming that having balanced levels at a lower volume level is what you're trying to achieve.

~Mullet

 

[Mullet]

So I can confirm no buzz or next to none with large cans. IEMs -- slightly audible but only when nothing is pumping out of the amp. I'd say I'm a pretty happy camper and this is with the stock tubes. I'm letting them burn in for maybe 100 hours and then going to move on to bigger and better things.

My general impressions are that the MS2s work fairly well with this amp. The sound is a little more fuller than my Penguin Caffeine Ultra amp. The highs are more sibilant though. At times when there are a ton of symbols they seem to be a little congested and over saturate the rest of the sound. They still sound good though.

The HD650s are definitely perfect with this amp. I really can't complain. They seem to have a pretty nice soundstage that is semi-wide. Separation is good too. I'm sure the different tube combos will accentuate the different qualities of these phones.

I've also tried the amp with both Shure SE530s and Triple.Fis and they both seem to do pretty well with the amp. I've listened the least to these so I can't really comment other than the highs on the SE530s seem to be slightly lifted.

These are just general impressions being that I'm no expert and don't purport to have golden ears.

~Mullet

 

[ogygia]

For the hum.............I think of one way to test it!
you all can try to switch off the power of 332s and keep the music playing! Since those caps is discharging and the tube is still hot, you all can hear the music for a few sec. But at this moment, the noise of the rippling current from rectifier shouldn't exist, since there is no power supply. You can try to listen whether the hum still come out from the amp at normal volume level and the lowest. Try them both! If no hum I think the hum problem is 80% affected by the stupid design...If the hum is still here, the design is not a problem.

Caution: Power switching may produce loud sound, so please take your lovely cans off from your head before doing the test.