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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 188

post #2806 of 6823

Well the USAF 6AH6WA's are on their way 6130 61-15 USA7 on both tubes should be from 1961 week 30.

Now the excruciating wait begins!

 

Also the black Neutrik replacement headphone jack is inbound as well. :cool:

post #2807 of 6823

A pair of RCA 6HM5/6HA5/EC900 RF triodes arrived today. These are short, squat little tubes, very much like the standard 6AK5. Interestingly, when I began to inspect them, I noticed "Made in Germany" printed on the glass. Inspecting further, I found Philips tube codes! These RCA tubes were manufactured in 1964 by Siemens!! Finally, I have a pair of real Siemens!! lol :)

 

Anyway, these are plug and play in the EF95 setting, no strapping is required, and I am happy to report that they do in fact light up and play! The bass seems quite strong... Will report back later.....

 


Edited by gibosi - 9/6/13 at 3:14pm
post #2808 of 6823

I'm wondering if 161's in my old LDII++ would sound the same as those tubes in an MKIII... worth the upgrade?


Edited by Advil - 9/6/13 at 10:19pm
post #2809 of 6823

im kind of stumped with this is the Lepai TA2020 a DC coupled amplifier I was planning to pre amp out into this amp but I can't tell whether it is or not?

post #2810 of 6823

Ok, after leaving my Haltron-Toshiba 6CS6 aside for a little while (they're excellent tubes but they have the exact same issues we've mentioned before: too cold), I plugged in and burned-in my -sent to me by mistake- GE Canada 6DT6A, probably made by Marconi in, well, Canada.

 

At first, they sounded detailed, balanced, but the bass was all flabby; that's 2-7 strapped mind you, suppressor grid (grid 3) -considered a secondary control grid here- connected to the cathode; text book example.

 

After 10 or so hours, the bass tightened up and the tubes were still detailed, but something was amiss, music sounded a bit "coarse". So, I pulled them out, and tested them 1-7 strapped, so signal grid (grid 1) connected to the suppressor/secondary control grid (grid 3), meaning no more suppressor grid actually suppressing secondary emissions (may or may not matter in triode-ish mode).

 

Anyway, the tubes sounded much better that way. Slight soundstage improvements, better and more coherent micro-detail, more controlled bass, the usual "dual-controlled" extra treble but without the heptode thinness. So, pretty good, though too early to call these top-tier, which I'm not sure they are; they're just pretty good and balanced right now.

 

Since I intended to plug some good ol' triodes later today, I put the amp back into EF92 jumper mode, and put those 6DT6A back in with no strap. Well, surprisingly enough, this is my favorite setting for those tubes (that's now close to 15 hours of burn-in mind you; I have no idea how the lot of you get tubes burned-in so fast lol, like 25 hours over 24 hour days!).

 

EF92'd, the tubes sound much more controlled. Staging and instrument placement is clearly improved, micro-detail everywhere. Sound may be better balanced than 1-7 strapped, but ultimately still a little coarse, like, a bit of glare in some frequencies. Most likely something that would go away with a longer burn-in; but I don't expect these to become god-tier tubes or anything, just somewhere between good and excellent -and more easygoing than most heptodes!

 

Interestingly, these 6DT6A have a much higher gain than any of the heptodes I tested -even strapped. It also has a much higher gain than the only other dual control pentode I've tested in the past, the 6GX6/6GY6. We're talking about a volume that's about half way between a 6AV6 -mu=100- and a 6CS6 -mu=?? probably less than 40 triode-strapped. I'd say it easily hits a mu of 50 or more, more than regular pentodes like 6AU6 for instance.

 

Most people here don't care much about gain, but I do; and having tubes like the Sylvania 5915 needing 1 o'clock on the volume pot to watch a video or 10 o'clock for music just doesn't sit well with me -especially with low impedance orthos. Not, when 10 and 8 o'clock are enough with high-mu triodes!

 

Speaking of triodes, my goal for today was to give my mystery Pinnacle 6AV6 tubes a listen after weeks of using different tube types or using no tubes at all. So, I plugged them back in earlier and, yeah, I have to admit that these might still be my best tubes, or at least still on my top-tier list. They're realistic, basically; and realistically detailed and staged. I can't say they're the most musical tubes I own -pentodes like the 6485 do this very well, perhaps at the cost of some realism or precision- but they're transparent instead, which to me is just as important.

 

For a while, I thought that some of those heptodes would turn out to be my favorite tubes, but going back to other tube types, I can tell that something is lacking in these tubes; detail without realism, or something like that? I need to do some more comparative listening to validate my impressions...

post #2811 of 6823
Quote:
Originally Posted by siles1991 View Post
 

im kind of stumped with this is the Lepai TA2020 a DC coupled amplifier I was planning to pre amp out into this amp but I can't tell whether it is or not?

 

It seems that littledot mk3 and dc coupled amps is a major NO NO you could potentialy blow your speakers if a tube goes out could send a surge of DC and potentialy blow your speakers i contacted David Zhezhe of littledot regarding this and a vintage pioneer amp SX750  i have ,I wanted to use littledot mk3 as preamp and he said not to do it and heres what a fellow headfier told me regarding this please  download to enlarge sorry.Its better to be shure or dont risk it. Hope this help but looks like you already know regarding this just in case you dont.

 

 

 

 

                                              

post #2812 of 6823
Quote:

Well the USAF 6AH6WA's are on their way 6130 61-15 USA7 on both tubes should be from 1961 week 30

I just got mine in the mail , 61...same year. They look nice

well protected in a hard cardboard tube wrapped in bubble wrap

Just have to find some thin copper wire to make a jumper. Just have never saved any bits of wire that fine in my parts bins

post #2813 of 6823
Quote:

 I put the amp back into EF92 jumper mode, and put those 6DT6A back in with no strap

I thought from the chart on page 77 that the 6DT6A were supposed to be in the EF95 setting ?

no, yes , maybe ?

post #2814 of 6823
Quote:
Originally Posted by Advil View Post
 

I'm wondering if 161's in my old LDII++ would sound the same as those tubes in an MKIII... worth the upgrade?

 

Can you use the same power tubes in the MKIII? If so, then I think you should expect your 161s to sound the same. If the MKIII uses different power tubes, then there will likely be a difference.... 

 

Can you use EF95 tubes in your LDII++? If not, then I believe the MKIII is a very worthwhile upgrade.

post #2815 of 6823
Quote:
Originally Posted by KR500 View Post
 

I thought from the chart on page 77 that the 6DT6A were supposed to be in the EF95 setting ?

no, yes , maybe ?

 

The 6DT6 and 6HZ6 are very similar to heptodes, and therefore, can be used similary. That is, there are four possible configurations: EF95 unstrapped, EF95 1-7 strapped, EF95 2-7 strapped and EF92. I suggest you try them all to see which works best for your ears and your equipment.

post #2816 of 6823
Quote:
Originally Posted by KR500 View Post
 

I just got mine in the mail , 61...same year. They look nice

well protected in a hard cardboard tube wrapped in bubble wrap

Just have to find some thin copper wire to make a jumper. Just have never saved any bits of wire that fine in my parts bins

 

Excellent!

Since the 2-7 strap is the only way to use the 6AH6 as per page 77, I'll probably solder the wire in place on the tube permanently. Some 30 awg wire wrap wire should attach nicely to a well cleaned pin, two wraps around the pin then solder.

 

On a side note, I removed the 2-7 strap from the 6BY6's as the Bass was increased in that mode but it was way too boomy for me, they are back in EF95 mode.


Edited by TrollDragon - 9/7/13 at 7:25am
post #2817 of 6823

I'll have to inquire with the guru's over on DIY Audio and see if there is not some economical way to make a little box to go between the LD's pre-amp out's and a power amplifier, either with some blocking caps or a 1:1 transformer that does not cost $100 to implement. 

 

The quest is a foot for a solution!

post #2818 of 6823
Quote:
Originally Posted by TrollDragon View Post
 

 

Excellent!

Since the 2-7 strap is the only way to use the 6AH6 as per page 77, I'll probably solder the wire in place on the tube permanently. Some 30 awg wire wrap wire should attach nicely to a well cleaned pin, two wraps around the pin then solder.

 

On a side note, I removed the 2-7 strap from the 6BY6's as the Bass was increased in that mode but it was way too boomy for me, they are back in EF95 mode.

 

Yes indeed, 30 awg wrapping wire works great. :)

 

post #2819 of 6823
Quote:
Originally Posted by gibosi View Post
 

 

Yes indeed, 30 awg wrapping wire works great. :)

 

That is why I just love this thread and the people in it, if it's been done you'll have a pic or solution within minutes!

Thanks gibosi! Looks perfect. :)

post #2820 of 6823

Does copper only stranded wire have to be used ?

I have some 25 guage stranded wire but it's not copper

Cut apart an old cheapy RCA interconnect but it's too round and fat to use

never mind , just located a short Cat5e cable in the boneyard and cut it apart to make a jumper


Edited by KR500 - 9/7/13 at 9:18am
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