[carlo]

most owners with the DT are probably drooling over the new ASL products and plan to dump theirs, so this is more than likely a waste of time

but whatever, i've got time.

I did the non-negative feedback thing, dig it quite a bit for it's better clarity and seperation and all that's been said here before. however, as a caution to those who are considering trying it, i was using unshielded interconnects and got a huge hum after the mod. switching to shielded ics solved that problem.

for isolation and damping i started by placing the Head on a cement slab spray painted with dynashield spray, didn't hear a difference. tried BDR #3 cones between the two for about a week, removed them and thought i heard less extension, but it's too subtle to call. same with vibrapods. i also experimented with diy rollerblocks but the Head slipped around way too much to warrant the tweak.

i'm cutting and pasting from another post of mine with power cords: in regards to the mg head dt, i've used four aftermarket cords, the tek-line pc12w (silver, $450), pc5w ($250), empirical audio magnum 22 ($400), and a diy cord using wattagate 330 termination. while i heard a major improvement in dynamics with the above cords compared to stock, the differences between the four are non-existent to my ears.

interconnect swaps so far have been between kimber's pbj w/ wbt0147, tara labs air 3 and reference generation 2, synergistic sterling alpha (silver over copper), jps ultraconductor 2, and empirical audio. both the tara labs and jps are my favorites for their improved clarity and harmonic richness without emphasis on any part of the signal chain. i prefer the jps for it's price/performance ratio (you can buy these everywhere used as well) and because the air 3, while subtly but audibly superior in terms of high frequency extension and sweetness, resides in the main system.

the tubes i had on hand and their affect in my system are listed below:

el84s
Ei Yugo: frequency extension to both extremes, slightly recessed midrange, excellent seperation. i prefer this tube mated with the amprex or mullard listed below.

JJ Tesla: a little more upfront in the midrange, a touch of sweetness, slightly slow bass. i think the tube rolls off the top a bit, but with the no-neg fb mod (which does make the head sound brighter to my ears) it's a nice match. i think this tube has a tendency to blend instruments together, fine for some music but annoying on others.

Sovtek (stock): i blew one out so can't really compare, but i can say that i prefer either tube above by a large margin.

input
amprex 12ax7a orange globe, holland: rolls off the top and bottom, upfront and groovy midrange, smears on complicated passages. with a simple guitar and vocal or a nice sax solo it's magic.

mullard 12au7a, great brittan: my reference tube. excellent tone with good dynamics and instrument seperation, not as up front as other tubes but with a touch of sweetness. great decay and attack for a tube of this family.

jan phillips 5814a: lots of perceived top end, but sounds super harsh to my ears. midrange sounds a touch sloppy, bass is tight, don't really use it.

national 12ax7a, chinese: as above with a slightly more linear balance.

jan phillips 5751: wanted to dip into the family due to nick's recommendations... good tube, maybe the quietest of the bunch, good seperation. overall maybe my second favorite tube, but gives up tone and decay to the mullard. it's stong bass and upfront upper midrange does a lot for the hd580s to my ears.

rca 12au7: pretty good bass is about all i remember. turned microphonic on me in a hurry.

anyway, all tweaks in my system are usually done for a week then removed, compared, and notes taken. headphones used were sennheiser hd580s and the njoe tjoeb 4000 was the primary source, rega planar 3 (phillips vintage receiver as phono stage, sumiko oyster) and arcam alpha 9 the rest of the time.

best,
carlo.

 

[timoteus]

Great post Carlo-

You have been very busy and methodical in your tube rolling. I'm not quite that disciplined or scientific. I agree with your opinion of the Mullard 12AU7. I pop it in every so often and think it offers great separation and air. More so than any of the 5751's I've tried. A keeper.

 

[carlo]

timoteus,
thanks for the kind words, i realised after hitting "submit" that i should have just added this to the mghead rolling thread. i'll need to further explore the 5751 family as well as try some vintage el84s soon. maybe take a shot at the amprexes you're using

best,
carlo

 

[timoteus]

I'm glad you started a new thread. After so many pages a thread becomes a little unwieldy.

It has been posted numerous times that rolling the 12AX7/5751 makes more of a change than rolling the output tubes, and I agree. But using the Amperex EL84 sure added an extra dimension and refinement. NOS Amperex, Mullard, and Telefunken are often considered the best of these tubes and can be very expensive. I lucked into mine, otherwise I would never have sprung for them. I hope they last a good long while.

I have seen little posted about rolling the outputs or EL84 other than the Ei Yugoslavia, JJ, or the 6P14 that Joe Lau sometimes substitutes. I think it would be very interesting to hear how some of the less costly NOS EL84 or even 7189 RCA or Sylvania stack up against the current production tubes.

 

[carlo]

Quote:

I think it would be very interesting to hear how some of the less costly NOS EL84 or even 7189 RCA or Sylvania stack up against the current production tubes.

i agree, just the difference between the ei and jj are enough to pique my intrest into nos. i know that nos rca or russians aren't that pricey (approx. $30/pr) so the price is right, however the tricky thing is that i don't have any other components that use tubes from the family, so stockpiling tubes for experimentation isn't the wisest investment. i'll need to call some tube stores one of these days and ask for a half dozen pairs of pulls and see what comes out of it.

have you gotten around to trying any other old production el84s yet?

best,
carlo

 

[CaptBubba]

I have three RCA EL84s that I may be able to let you try. I really have four, but one has a melted plate, which isn't exactly good.

I have never heard them, nor do i know how good of shape they are in (or even if they work).

 

[carlo]

bubba,
wow, that's very generous of you. let's work it out next time we're both on #headfi.

best,
carlo

 

[timoteus]

Quote:

Originally posted by carlo have you gotten around to trying any other old production el84s yet?

The only output tubes I have tried are the Chinese 6P14 which Joe Lau has said sounds better than the Sovtek but costs more. I think he substitutes these when he runs out of the Sovtek. Also the Ei Yugoslavia and the Amperex.

When I compared the Ei to the Amperex I noticed the internal structure excluding the getter were the same for these tubes. I searched the archives at audioasylum and found that Ei bought the machinery and tooling for these tubes from Philips (Amperex is/was? a subsidiary of Philips). The Amperex still sounds much better than the Ei so I guess there are differences in metallurgy, tolerances, vacuum, or fairy dust at play here.

I'm hoping someone that has rolled some NOS EL84 will post.