+1, no, make that +10!!O. M. G. I just performed the "tap test" on my new KR 242's, and I've never heard a tube sing as long as these do. They have a clear tail of resonance for easily over 10 seconds! And it is rather pronounced in level, I'd say. I searched through my Herbies stash, and, alas, I have nothing of suitable diameter to try. [Always a bit shocking to trundle through one's accumulated stash of tweaky things, collected tubes, etc. Makes you feel a bit sheepish at times...] I will have to add some appropriate dampers for these tubes. I have some for my RK 300B's, and they made a clear difference upon installation.
I have the top of my Pacific well controlled with mass/elastomeric dampers (I'm a rubber engineer, so I've got to do it my way, you know). The outer structure of the DAC passes the "tap test" very well with these in place, but not at all with them absent. This need was evident all along with the B7, GG, and Pacific DAC's that I've owned.
What astonishes me is the level of revealing clarity that these 242's already bring relative to all other comers, even with this level of microphonics. It will be very interesting to tame the tubes appropriately, as much as I can with external applications. It is quite clear that the resonance is the plate structures inside the tube, so external applications can only go so far.
Some thoughts of possible interest:
1) I have done extensive A/B/A between the KR 242 and the RK KR 242 on my GG2. I find the RK KR 242 superior in every way. Whether this is due to the thicker glass, higher vacuum or better anode material, or just "system compatibility" I do not know. Nor do I care. Better control and finesse and equally impressive dynamics. Of course, YMMV.
2) If you are using any of these DHTs or an EML 274b recti (as I am) without Herbie's tube rings, you have not heard these tubes at their best, especially if you play at volume. The Lampi's are very susceptible to microphonics due to the high gain of the DHTs as has been previously discussed. Herbie's tube damping rings help reduce this significantly! (as does damping the top and side plates of the GG2).
I strongly recommend their UltraSonic Rx tube dampers (65mm) for the RK-KR 242 output tubes. (Mildly spring-tempered titanium C-ring holds three modified PTFE isolation pads. Each pad holds a specially formulated polymer O-ring against the tube glass).
However, for the EML 274b regulators, which run very hot, the HAL-O III stabilizers (also 65mm) are the way to go, (spring-tempered titanium C-ring and annealed titanium isolation pads).
Tube Dampers
Virtually all vacuum tubes are prone to distortion caused by microphonic vibrations. To overcome audible distortions, a titanium C-ring holds microphonics-absorbing pads against the vacuum tube bulb. The tube's sound is made more clear and precise, less fuzzy and less harsh. Tonal qualities are...herbiesaudiolab.com
By the way, don't hesitate to play with ring position on the tubes. The sound can vary significantly with ring placement (although the middle of the tube is a good place to start and may work best).
Here's what I'm using. You may recognize these as looking an awful lot like HRS Nimbus feet, and they are an awful lot like them. A friend sent me some of his Nimbus to try some years back, and they seemed decent, but being cheap, and a rubber guy, I decided to make a bunch of my own. I traded some rubber fabrication "one offs" to a machinist friend as my favor, and he then machined up a bunch of the 6061 T6 aluminum "middles", as well as a two plate compression mold to make the outers. Analyzing the Nimbus rubber pucks, it is clear that it is a variety of silicone. So I tried out a few types of silicone (regular methyl vinyl, a phenyl type, and fluorosilicone type) and I have a large stock of these. So, that's what I reached for to do the deed on my B7, then my GG, and now my Pacific. Works a charm in this application!
Thanks for sharing your combo's and impressions.I can concur that adding tube dampers to KR 242 tubes is significantly reducing the microphony. I did it following the advice of some members here.
I am trying to make a recap of the different combo ( output + recti) tested.
Based on my reading, seems the KR242 is leading the pack in terms of output tube. In terms of rectifier seems more balanced ( KR 5U4G RK, EML 274B Mesh, Tak 274B etc…)
On my side, in the PACIFIC DAC ( I did not try in any other models)
1) KR 5U4G RK + KR242. The caveat being the very high gain. If no volume control, finding a good matching preamp can be challenging…
2) KR 5U4G RK + KR242 RK. The 242 RK are relatively new. More « gentle » and refined than the non RK one. For the time being , I am finding the Midrange transparency and dynamics better on the non RK one.
Other recti and tubes tried : Acme 274B/ PX25RK and EML 300B XLS. Not in the same league than the first two.
Alex
With all this talk about tube rolling on the Lampi, I have to ask. I am newbie to digital and historically have preferred vinyl. So, is the Lampizator come close to hi-end analog? This is important to me as I listen to a lot of late 20th century and 21st century chamber music, all of which is only available on digital (streaming preferred). I currently have an iFi neo iDSD bluetooth streamer/DAC performing digital duties.
Yes, indeed. The server is just as important as the DAC for sound quality (and some posit that it might even be more so). With a Taiko Extreme feeding my Pacific, I really don't care which medium I'm listening to, they both are very engaging emotionally, if the recording has got it. My Pacific needed the Taiko's sourcing to really achieve tonal density and a fully developed harmonic envelope of sound.Based on my experience…
The quality of digital sound is highly dependent on 2 complements: the DAC and the server/transport. The Lampi plus a high end server should produce sound which will be emotionally engaging.
Conversely, a Lampi connected to a laptop will not be on the same level and any where as pleasing.
Were I the owner of the top of the line Lampi, which I regard in the highest, I think that I might feel a little disheartened to be advised that it will take a 25000 to 30000 Euro server to achieve :
“ My Pacific needed the Taiko's sourcing to really achieve tonal density and a fully developed harmonic envelope of sound.”
Personally I don't see that as much different than needing a really good preamp to get the most out of great amps. I didn't take @dminches comment to mean that is the ONLY way. It might be, I don't know. I've never heard a Taiko. But I do know that I share much the same feeling with my GG2 and Aurender N30SA.Were I the owner of the top of the line Lampi, which I regard in the highest, I think that I might feel a little disheartened to be advised that it will take a 25000 to 30000 Euro server to achieve :
“ My Pacific needed the Taiko's sourcing to really achieve tonal density and a fully developed harmonic envelope of sound.”
But all Taiko owners would say that with their respective dacs. That's why they bought the Taiko. Why else would you buy an expensive server if it did not further develop your sound (assuming sonic rationale)