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Little Dot Tube Amps: Vacuum Tube Rolling Guide
Aug 29, 2013 at 4:47 PM Post #2,641 of 13,436
TrollDragon-Its got 4 grids[if you count 2+4 as separate] According to my information its a Hexode  a Heptode has 5 grids maybe things are different in the US? -Checked out a -EH90-dual control heptode- its got 5 grids I am taking this from the official Mullard Data book I have several-ECH81 [triode] Heptode -5 grids-not counting the triode.section. Every UK data book on tubes checks out the same as me . Maybe the States add on another element?? If people are happy with them then I am happy I would rather be subjective on this as it is what people hear with their own ears rather than being told not to.by objectives. I am on your side here.  If people cant hear any noise well thats okay  maybe its because  tube radio front ends deal in microvolts of a signal and that is well below what the music signal is on your equipment. But a triode would be clearer as it has a lower noise floor.---Found a European tube book-Radio tube Vade-Mecum lists the Hexode as -6 and the Heptode as-7 so they are adding on the plate and cathode elements but it doesnt change the technical name of the tubes.
 
Aug 29, 2013 at 8:42 PM Post #2,642 of 13,436
Quote:
duncan1 said:
TrollDragon-Its got 4 grids[if you count 2+4 as separate] According to my information its a Hexode  a Heptode has 5 grids maybe things are different in the US? -Checked out a -EH90-dual control heptode- its got 5 grids I am taking this from the official Mullard Data book I have several-ECH81 [triode] Heptode -5 grids-not counting the triode.section. Every UK data book on tubes checks out the same as me . Maybe the States add on another element?? If people are happy with them then I am happy I would rather be subjective on this as it is what people hear with their own ears rather than being told not to.by objectives. I am on your side here.  If people cant hear any noise well thats okay  maybe its because  tube radio front ends deal in microvolts of a signal and that is well below what the music signal is on your equipment. But a triode would be clearer as it has a lower noise floor.---Found a European tube book-Radio tube Vade-Mecum lists the Hexode as -6 and the Heptode as-7 so they are adding on the plate and cathode elements but it doesnt change the technical name of the tubes.
Click to expand...

 
There seems to be a fair amount of confusion about this... But if you look at the pin diagram, the EK90/6BE6 is indeed a heptode (HERE) There are five grids plus the cathode and plate which totals 7 electrodes. It has the same exact pin diagram as the 6BY6/E91H and the 6CS6/EH90, again five grids plus the cathode and plate. However, the fact that grids 2 and 4 are internally connected means that in practice there are only four grids, so it would seem that sometimes these are classified as hexodes.
 
As to noise associated with multiple grids, since we convert heptodes, hexodes and pentodes into triodes for use in the Little Dot, this is not an issue. Depending on the configuration, the extra grids are tied to the plate, the cathode and/or the main control grid so that in the end, there is only one grid. And further, in my experience these tubes are just as quiet as a 6AV6/EBC91, which is a true triode. So if they are in fact measurably noisier, it is below our hearing threshold.
 
Aug 29, 2013 at 9:18 PM Post #2,643 of 13,436
Thanks gibosi for some clarification on this Hep/Hex confusion.

Now my 6BY6 with the square getter I am just warming up to test them out.

Square vs Round, would this have been a different factory, newer design spec, cost thing as to why the different getter shape on the same tube type?

Or don't mean jack, just shutup and go listen to some tunes... :D
 
Aug 29, 2013 at 9:37 PM Post #2,644 of 13,436
EH90 VS 6DT6

I have been rolling tubes like a madman lately, and I figured I'd share my notes on what are in my opinion the best tubes for the Little Dot 1+ we all so love!

Setup

FLAC (PC)> USB ODAC>Little Dot 1+> Grado PS500/sr225i/AD900x

Tubes used

RCA 6DT6A (1/7 strapped everything else is meh)

Valvo EH90

EdiSwan EH90

Mullard EH90

All burnt in a minimum of 10 hours, EH90's EF95 setting  unstrapped, 6/7 and 1/7 strapped (noted in review)

Now the EH90's almost all sound the same, probably because Mullard, as we all know made a lot of tubes for other companies! There are some slight variences in sound between the tubes I have, I'll chalk that up to age and them being in different states of wear.
 
* denotes my preference

Songs used
 

Katie Melua - Moonshine

 

 
EH 90
 
EF95 Warm, detailed bassy, amazing mids, above average + very round and well defined sound stage... The Valvo's/Mullard's were and still are my favorite EH90 tube, but the Ediswan's seem to have tighter bass and slightly better clarity in the lower treble regions. On this song these tubes really work well with any of my Grado cans. My AD900x takes on an odd tonality here. Honky, blurred ... The sound stage is smaller then this can is capable of. 
 
1/7 Preferred, less/tighter bass, more focus. AD900x no longer sounds weird. Added sparkle. Gives the illusion of more sound stage.
 
6DT6 *
 
1/7 Huge sound stage very deep, wide and tall (not quite as precise ad the EH90). Slightly warm... good tight bass very detailed, sparkle! These things are amazing on this track! They easily trick you into forgetting about the headphones you are wearing.
 

Jane Monheit Taking A Chance On Love

 

 
EH90 *
 
Unstrapped. Intimate and warm... excellent detail, feels like your front row at the club feeling every word.
 
1/7 No... just no. Thin, boring...
 
6DT6
 
Sound stage seems a little too big. Jane seems like a large part of the center image (not very off, but enough to notice) instead of a single voice. Warm, detailed. The AD900x exaggerates the center image issue. Even with that these are still very musical.

Dave Matthews Band - Warehouse (Folsom Field)


 
EH90
 
Details details DETAILS! all 3 of the EH90's on hand are very detailed! (say detailed enough yet?) Good sound stage, very accurate placement. (Do yourself a favor and get this in loss less)
 
6DT6*
 
See above, add ginarmous sound stage. Enjoy

Loreena Mckennitt - Penelope's Song

 

 
EH90
 
Sweet mids and treble... Loreena's voice is extra enchanting!  Listen for the pianos peddles, the occasional cough... the grain of the stringed instruments. Amazing. 
 
6DT6*
 
all of the above, but presented in a grander fashion. Your feel the sheer size of the venue. Very natural.
 

Opeth - Reverie/Harlequin Forest

 

 
EH90
 
Detailed, fast deep sound stage. Good sense of balance.
 
1/7 lean... almost painful depending on cans (sr225i)
 
6DT6
 
Huge sounding, warm, crunchy.
 
Neither are really better... draw
 

Megadeth - Looking Down The Cross (remaster)

 

 
EH90*
 
There's a lot going on in this song... Gar's drumming is energetic and fun, lots of odd guitar work, an almost funk/thrash groove... These 'todes capture the performance like a boss. Intimate but airy. Fast, aggressive, crunchy.
 
6DT6
 
No detail is lost with the exaggerated sound stage BUT that feeling of intimacy and aggression suffers...
 

Pure Reason Revolution - Apogee

 

 

Pure Reason Revolution - Goshen's Remains

 

 
A double feature!
 
EH90* (Preferred on Apogee)
 
Unstrapped Tight impactful bass, glorious mids!
 
1/7 Fast and detailed, warm, with enough sparkle... bass gets a little lost in the mix... lean...
 
6DT6* (preferred on Goshen's Remains)
 
Similarto the above unstrapped... Instruments seem better separated... This one comes down to personal presentation preferences...
 
Early Conclusions
 
These are easily the 2 best tube families out there for Little Dot amps... so far... I will be keeping at least a pair of both families! More to come this weekend (more 6dt6's incoming)
 
Aug 29, 2013 at 9:49 PM Post #2,645 of 13,436
Quote:
trolldragon said:
Now my 6BY6 with the square getter I am just warming up to test them out.

Square vs Round, would this have been a different factory, newer design spec, cost thing as to why the different getter shape on the same tube type?

Or don't mean jack, just shutup and go listen to some tunes...
biggrin.gif
Click to expand...

 
Keeping in mind that most of these tubes were in continuous production from at least the 1940s through the 1970s and in some cases, even into the 1980s, some thirty, forty or more years, it is not surprising that over such a long time period, internal construction would change, as feedback from the field and new advances in materials and technology made their way back to the factory floor. Square getters were the norm through the 1950s, but slowly gave way to round getters in the 1960s. Of course, there were likely lots of other changes as well, but most are undetectable to the untrained naked eye. In general, the consensus thinking is that newer is better. However, in practice, it is very rare that I am able to hear any difference between the older tubes and newer ones. So I would expect that if you can discern any differences, they will be quite subtle.
 
Aug 29, 2013 at 9:49 PM Post #2,646 of 13,436
I have finished ~40 hours with mil-spec Soviet 6BE6 tubes. Most of my listening has been to 1950's jazz and vocals over FM using a Carver TX11a tuner.
 
This tube seems to really find its voice with this source material. Sibilance is not unpleasant,  high hat brushwork is crisp and I can hear detail when the musician is fingering clarinets or saxophones. The sound stage does not seem to be as wide as with 6J1P Voskhods. Shall try some DG Sibelius and Lucinda Williams CDs later this week for variety. In any case, the 6BE6 is an improvement over the tubes supplied with the LD III. This is using Alessandro Music Series One headphones. Given how little these tubes cost (at least now) you might want to consider picking up a set or two.
 
Aug 29, 2013 at 10:59 PM Post #2,648 of 13,436
Quote:
kvtaco17 said:
EH90 VS 6DT6

I have been rolling tubes like a madman lately, and I figured I'd share my notes on what are in my opinion the best tubes for the Little Dot 1+ we all so love!

Setup

FLAC (PC)> USB ODAC>Little Dot 1+> Grado PS500/sr225i/AD900x

Tubes used

RCA 6DT6A (1/7 strapped everything else is meh)

Valvo EH90

EdiSwan EH90

Mullard EH90
Click to expand...

 
It's great to have another voice in the forum , the more the merrier, with different equipment, different ears and a different musical perspective.
 
A great review!
 
And especially, thanks for introducing me to some great music I had never heard before! :)
 
Aug 29, 2013 at 11:01 PM Post #2,649 of 13,436
No problem... I pretty much listen to everything! (yeah I'm that guy)
 
Aug 30, 2013 at 12:01 AM Post #2,651 of 13,436
I'll find out soon!
 
Aug 30, 2013 at 4:34 AM Post #2,653 of 13,436
Wow, 13 posts again since last night. I have to get used to that time lag again lol; I had gotten used to posting in the same time frame as North Americans for a few days. Now, I'm back to the "one-way radio effect" where a couple of lost Europeans and Asians post a few posts, I post once or twice, then go to sleep, and when I wake up, bam! 20-some Americans have suddenly posted and won't again until the next day. Strange sensation, come to think of it.
 
Great work, kvtaco! I guess that's also one more point for the Mullard-ish EH90, huh? I find it interesting that one of the key words that always comes to mind when using the 1-7 strap is "thin" along with "detailed", as it's consistently been my impression on most heptodes. It always sounds great in the beginning, like better than unstrapped, and the next time I switch the amp on with the 1-7 strap, I find it unbearably thin and lifeless... Odd... And probably why I keep going back to the unstrapped setting most of the time. I still think we need to find a way to adapt those heptodes, especially the EH90/6CS6, to tie grid 1 to the cathode and use grid 3 as the exclusive signal/control grid. Now, that, would be interesting.
 
Back from the last page, we had people wondering about the similarity between "Siemens" EH90 and "Japan" EH90. The main reason why I was curious about it is because when Oskari pointed it out -I had thought about it previously when I saw the ebay ad weeks ago but dismissed the idea as being silly- I kinda panicked and bought those tubes, since they were so cheap anyway.
 
But that's not the interesting part, we've got Mikelap testing those tubes, so he's got us covered. What's interesting is the other tubes I bought along with these from the same seller.
 
http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=200950779149&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
 
"Please take a good comparative look at these."
 
Don't these tubes kind of remind you of something? They remind me of something. Anyway, these were made in Japan and have the same rib plates and holes as the Foreign Siemens tubes, so I'm hoping I bumped in to Siemens-ish 6DT6 tubes. If not, that's fine too, they were dirt cheap and I needed some 6DT6 tubes to test.
 
Aug 30, 2013 at 5:40 AM Post #2,655 of 13,436
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