To retube or not to retube the LDII

[Labtek]

I've heard allsorts about people wanting to retube their LDII due to the microphonics. Now I really don't know why some of the LDII tubes create microphonics and some don't. If they do, do you use "O" rings to dampen the tubes or do you simply ease the tubes out slightly away from the seats so they don't vibrate. Or is it that some tubes are just faulty in some way. If so do you replace with Telefunkels or get more LDII tubes from Zuinqui. Are Telefunkels a better sound (less bright) and what's the cost. Does cusioning the LDII, from the surface it stands on, work for some LDII's or all. Also If you leave the unit on for long periods of time do the microphonics increase or stay the same. Does using the LDII as a pre-amp increase the tube sensitivity (i.e.Bass) and are we all assuming that sensitivity of tubes creates microphonics. If so then someone must know the answer to all with microphonic worries without changing tubes. I'm confused please help.

 

[fran]

AFAIK, microphonics are caused by physical vibrations from outside causing structures within the tube to also vibrate and hence creating a sound signal which those of use with LD2s will recognise as the ringing.

It is really an issue with tubes used in amps for speakers, where acoustic feedback from the speakers cause the tubes to vibrate creating a distortion in the sound. Now in the case of a headphone amp, you have to ask will this affect me? I suspect for the vast majority it won't as you'll be either listening to speakers or phones..... except for those of you using the LD2 as a preamp.

Personally, It doesn't bother me. It really only happens when plugging in or out the phones and when it does it subsides in a few seconds. I bought a few extra sets of tubes from zunqiu and all of them are microphonic, so that route won't really solve this issue.

I wouldn't go changing the tubes to the telefunkens just for microphonics, I'd only do it if there was a marked improvement in sound quality, and you don't read this very much. Bear in mind that the (daf91) TFKs are a replacement for the 1B2's which are not meant to be as good as the 1K2 that the amp now ships with. So sonic improvement may not be much. You need to change the dip switches inside the amp to use these TFKs.

Last time I looked the TFK DAF91 do come up now and again on ebay for small money, <$10 from what I remember.

1. Haven't tried the tube dampers but can't see them making much of a difference.
2. I don't pull out the tubes a little, can't see that making much of a difference.
3. I don't notice any difference in microphonics with the amp left on for extended period.
4. Better support, ie vibration absorbing should help, but the problem is more caused by moving the headphone cable/jack, so a better support won't change this.
5. Its not the "quality" of the tube that makes it microphonic, more the internal structure. AFAIK the tubes used are actually originally designed for radio transmitters or something where the microphonics don't matter. And if you use it as a headphone amp, leaving the cable always plugged in then it shouldn't really be an issue.
6. I've seen others talk about the LD2 being bright. I just cannot see this, mine certainly isn't this way. In fact I had a friend over last night with his original master headphone amp (SS) and the two sounded almost identical, you really wouldn't have been able to tell them apart. Loads of bass (although I'm not a bass freak) maybe the LD2 shaded it over the original master, but by very little. Have you tried yours with a different set of phones, or tried your phones on a different amp?

Fran

 

[Labtek]

Thankyou very much, I now have an understanding behind tubes. The mix and match approach to headphone systems is something I'm going to have to get into as everyones ears are different and I think even though the LDII is a match for the HD600's it is certainly not a match for my HiFi without significant changes. Even then the sound is nowhere near the quality from the phones. It's good really pretty good in fact but theres definitely something about phones that's much more pleasurable even peaceful if that's something you can equate with loud music. It's a whole different experience. The phones sound less fun with an iPOD and a simple amp. The sophistication with the LDII is remarkable though and I'm sometimes really overwhelmed. I would recommend using the LDII with a HiFi just because it makes a lot of difference but phones are a polite addictive obsession that I'm only really just scratching the surface of. I'd be really interested to know what amp to choose for a new venture. I've heard the Darkvoice is good. What have you heard?

 

[fran]

Just a further note on the microphonics issue. I turned on my amp this evening and tapped the side to hear the ringing of the microphonic tubes. I then held the tubes with my (gloved) hands to "dampen" them and had my wife tap again. Absolutely no difference in the ringing.

The upshot of this is that if me holding the tubes, with my hands acting as a damper as an o-ring would, doesn't make even the slightest difference to the microphonics, then I can't see how tube dampers would either.

Just something to note before anyone buys dampers

Fran

 

[Labtek]

Quote:

Originally Posted by fran Just a further note on the microphonics issue. I turned on my amp this evening and tapped the side to hear the ringing of the microphonic tubes. I then held the tubes with my (gloved) hands to "dampen" them and had my wife tap again. Absolutely no difference in the ringing. The upshot of this is that if me holding the tubes, with my hands acting as a damper as an o-ring would, doesn't make even the slightest difference to the microphonics, then I can't see how tube dampers would either. Just something to note before anyone buys dampers Fran

Try tapping the side with the tubes seated then slightly unseat them and tap again. I've found that the more surface area touching directly to the chassis then there is a little more microphonics. But as you say there is no need for dampeners as I think it isn't the glass its the contents. Have you tried leaving the Dot ii on for a few days. It seems to get better every day and no microphonics at all. Any idea why? I know its probably not a good idea. But it takes hours for the sound to get good otherwise.

 

[replytoken]

Quote:

Originally Posted by Labtek Try tapping the side with the tubes seated then slightly unseat them and tap again.

I would not recommend tapping tubes when an amp is turned on. You can damage a tube by tapping on it.

 

[Labtek]

Quote:

Originally Posted by replytoken I would not recommend tapping tubes when an amp is turned on. You can damage a tube by tapping on it.

I've got to agree with James Jamerson. The roughness is a quality all of its own the pure p/f unk of it all. The tubes were cool I was tapping the side of the amp. LDII great amp, drives me wild.

 

[replytoken]

No problem. I just didn't want to see you popping tubes needlessly.

 

[Labtek]

Quote:

Originally Posted by replytoken No problem. I just didn't want to see you popping tubes needlessly.

Thank you I appreciate the concern.