[mordy]

On a little dot mkI, II, III, or IV? That's about 4X the max ampere for the bypassed transformer and possibly many other parts in some of them...

I started out with the Little Dot MKIII but like so many others upgraded to different amps over time.
To the best of my knowledge there is no harm to the amp if you bypass the power supply in the amp and use external power for the tubes.
You only apply the higher current to the heater in the tube; the rest of the connections stay as they are.

 

[JazzVinyl]

Heaters are low voltage but draw higher amounts current.
Plate voltages are high but draw super tiny amount of current.

Making available more current amperage for heaters....the tubes will only draw what they need.

Example:
If you had say "up to 8 amps" of heater current available (via an external power supply) but were using two 1.5 amp heater draw tubes, the draw (current usage) would be 3 amps. The other 5 amps are "available" but not being consumed.

Hope that makes sense.

 

[mordy]

Heaters are low voltage but draw higher amounts current.
Plate voltages are high but draw super tiny amount of current.

Making available more current amperage for heaters....the tubes will only draw what they need.

Example:
If you had say "up to 8 amps" of heater current available (via an external power supply) but were using two 1.5 amp heater draw tubes, the draw (current usage) would be 3 amps. The other 5 amps are "available" but not being consumed.

Hope that makes sense.

With all due respect, there is something called in-rush current. When you turn on the amp, the tubes could draw up to three times the amount of current for a moment, and that is why you need the extra margin. If you have an amp meter hooked up you can see this.
Possibly there are heater circuits that avoid this with a slow start.

 

[Cognomen]

I started out with the Little Dot MKIII but like so many others upgraded to different amps over time.
To the best of my knowledge there is no harm to the amp if you bypass the power supply in the amp and use external power for the tubes.
You only apply the higher current to the heater in the tube; the rest of the connections stay as they are.

Will the innards of a little dot mkIII be cool enough with a 4.5 Ampere tube?

 

[Tech collector]

[size=18.0pt]4. POWER TUBES[/size]

4.1 Overview

The power tubes reviewed in this guide only applies to the current production Mk series amps. Unlike their impressive flexibility with signal tubes, most current production Little Dot amps can only accept 6N6/6H6P power tubes with the exception of the MkIV which can accept the 6H30Pi (for clarification refer to this chart). It is important for the longevity and performance of your amp that the power tubes you use are matched pairs, otherwise it is common for power tubes and other components in the amp to fail pre-maturely due to badly matched tubes. I have had several power tubes fail within 100 hours of use due to matching issues.

 

[Tech collector]

[size=18.0pt]4. POWER TUBES[/size]

4.1 Overview

The power tubes reviewed in this guide only applies to the current production Mk series amps. Unlike their impressive flexibility with signal tubes, most current production Little Dot amps can only accept 6N6/6H6P power tubes with the exception of the MkIV which can accept the 6H30Pi (for clarification refer to this chart). It is important for the longevity and performance of your amp that the power tubes you use are matched pairs, otherwise it is common for power tubes and other components in the amp to fail pre-maturely due to badly matched tubes. I have had several power tubes fail within 100 hours of use due to matching issues.

What happened to the rest of this post?

 

[TrollDragon]

What happened to the rest of this post?

Considering the post is 13 years old and Head-Fi went through a major forum software change a few years back. I suspect it was lost in the conversion.

 

[Tech collector]

Considering the post is 13 years old and Head-Fi went through a major forum software change a few years back. I suspect it was lost in the conversion.

Is there any other guide for the little dot power tubes?
What's everyine using on their LD Mk3's?

 

[Cognomen]

What happened to the rest of this post

Is there any other guide for the little dot power tubes?
What's everyine using on their LD Mk3's?

Page 585, post 8766 lists a variety of tubes one can deploy. Some of them require adapters and some require an outside power source because they draw too much current. I have a MKIII. If it take out the tubes and turn it over and look inside with a flashlight, it says v2.0 and regard its transformer as suited for up to 1.00 Amp power tubes without an outside power supply. My transformer is rated 1.25 Ah but I keep it 20% below max in an effort to prevent overheating due to uncertainties about Chinese manufacturing. The prior version(s) were suited for less and came with 6N6 and 6N6P .75Ah power tubes. I have rolled over a dozen different power tubes over the past 10 years and have never paid extra for tube tester electronically matched tubes and have not had a problem or worn out a tube. I believe my experience is typical. I suppose if I rolled a used tube that tested poorly that it might wear out. If one has low z cans, some of the lower Ah power tubes on the list might not drive them well.

 

[triod750]

When it was very hot last summer I didn't want to use external psu and very hot tubes. I found the combination of Ken-Rad 6C5 as input tubes and tall bottle 7N7 with race track bottom mica as power tubes to sound very good. Just an example and I already had the needed adapters. Not much heat produced but a lot of good music.
This was in a LD MKIVSE but would be possible in MKIII too I think.

 

[Derivative]

Is there any other guide for the little dot power tubes?
What's everyine using on their LD Mk3's?

I got the LD MK3 recently as my entry into tube amps and tube rolling, and to pair with Senn HD6XX.
Currently running Novosibirsk 6H6N power tubes and Mullard M8161 (EF92) signal tubes, to enjoyable effect.
I started with the Mullard M8100 (EF95) signal tubes and my assessment is that I get slightly more detail and more neutrality from the M8161.

 

[Cognomen]

As an experiment about 45 minutes ago I powered up my MKIII with 6EM7 output (power) tubes on 6SN7 adapters. 6EM7 have two dissimilar triodes under the same glass, one low mu and the other higher, and it draws .925 Ah. It didn't explode, hasn't overheated and sounds good and has ample power. It tentatively confirms we can successfully run at least some dissimilar triodes as power tubes. There's some push-pull in the circuitry, and I don't know if that eventually could be a problem for the tubes or Little Dot. While I'm not experienced with reading schematics, it looks like the little dot mkIII might use triode #1 and triode #2 in the same order in both channels. It sounds good non-matched with one RCA and one Raytheon. I look forward to listening to a cosmetic pair. The 6EM7's are frontrun by Western Electric 409A driver tubes deployed in EF91/92 mode. I find the Western Electric has a nice midrange and I feel it probably sounds better than a variety of $2-$3 per tube Soviet 6J2P(-ev) tall and short bottle pairs I have auditioned. The 409A, 6J2P, 6AS6, and 5725 are probably all sensible equivalents.

 

[Cognomen]

Formerly a skeptic, I now firmly believe in Cryo treated tubes. I recently got a free junk box of tubes, and some are missing their alphanumeric identity. I put some in the freezer for awhile. When I take them out, I shine a flashlight on the condensation and can sometimes see their identity. Sometimes I only see a portion of it such as 50L... with the last bit of info missing. There seems to be only one 50L... glass octal in datasheet sites. Eventually finding the heater pins with a multitester and seeing if they are the same as the datasheet as well as confirming it is missing the same pin would result in high probability I have identified it. If anyone knows of additional identification tips without a tube tester, let me know.

 

[barbazz]

I guess you're talking about 50L6GT, right? The only other reference beginning with "50L" I could find was an obscure Philips tube: 50L1D.

 

[triod750]

I guess you're talking about 50L6GT, right? The only other reference beginning with "50L" I could find was an obscure Philips tube: 50L1D.

50V versus 1.4V, quite a difference.