[Cognomen]

Some also had this issue way back when .Like some had issues (hum)when using 6DJ8 with adapter Thanks for sharing .

I have rarely had noise with my LDIII. Sometimes I have gotten rid of it by rotating it 90 degrees or moving my smartphone away. Also, when I plugged all my audio into 1 outlet, it reduced noise that was probably caused by a ground loop.

 

[warp2600]

I also re-auditioned the M8100 (EF91 setting). While it has a nice warm midrange, I felt it was lacking elsewhere so I continue to rank it good. Thereafter I re-auditioned the Siemens C3g (adapter needed) and Yugo 6HM5 (plug and play EF95 and excellent price to sound quality ratio) and felt they qualify as some of the best driver tubes in my collection for the LDIII. While the 6AR5 is not a best tube, I still find it better than run of the mill EF95 and EF91/92 and euphonic, in a word, fun.

M8100 in EF91 setting? Hmm.

 

[Cognomen]

M8100 in EF91 setting? Hmm.

 

[Cognomen]

Oops M8161!

M8100 in EF91 setting? Hmm.

Oops, typographical error - I listened to the M8161, edited/fixed the original post. Thank You!

 

[barbazz]

I have continued auditioning plug and play car radio tubes. The Philips SQ E90F Miniwatt (EF91/92 setting) is better than typical EF95 and EF91/92 LDIII tubes, with perhaps a skosh higher treble and more detail, perhaps why it was merciless on a poor recording but very good on other recordings. It's a high gain tube. As a pentode: 4.6 transconductance and 1.4 M ohms plate resistance. The E90F is a longer life mesh tube promoted as a higher quality and longer life than the abundant functionally equivalent 6BH6, perhaps worth exploring. While the 6BH6 is a car audio tube, Marantz deployed it in its highly collectible 8B tube amp but as far as I can tell, not as a triode. Also auditioned a IEC/Mullard 6ES6 (EF91/92 setting) whose stats were questionable before I rolled it: less than 1 transconductance and 200k ohms plate resistance and variable mu. I had to pull out all the stops: flicked the gain switches on the LDIII to max and turned up the input gain on my cap-coupled power amp for speakers. While the midrange was good, sometimes the rest of the spectrum seemed somewhat muddy and not euphonic. I suppose it was an adventure. With the LDIII volume set at over 12:00, the headphone volume on somewhat low volume music was medium on my 250 ohm corded Beyer Amirons. Initially one tube was producing fuzz sound and then nothing but looked ok. I flicked it with my finger and it caught on and worked. I tend to rate my tubes good, better and best in terms of the LDIII sound they produce. The 6ES6 is not good! While the car RCA 6AR5 smooth shield sacrifices a bit of detail and is also lo amplification (too low probably for low ohm headphones and/or people who like high volume), I continue to feel the 6AR5 may be the most euphonic tube species I have heard in the LDIII. I also re-auditioned the M8161 (EF91 setting). While it has a nice warm midrange, I felt it was lacking elsewhere so I continue to rank it good. Thereafter I re-auditioned the Siemens C3g (adapter needed) and Yugo 6HM5 (plug and play EF95 and excellent price to sound quality ratio) and felt they qualify as some of the best driver tubes in my collection for the LDIII. While the 6AR5 is not a best tube, I still find it better than run of the mill EF95 and EF91/92 and euphonic, in a word, fun.

Thanks for sharing your experiences.

Now that you talk about radio car tubes, I wonder if you have already tried EF98/6ET6. According to Radiomuseum it's a B7G Pentode that can be used with either 6.3V or 12.6V. With 300mA at 6.3V and the same pinout as 6DT6/6DT6A/6GY6/6ES6 seems suitable for the Little Dot with EF91 settings, right?

 

[barbazz]

I just got to 30 rollings (well, 31 if we count the original configuration), and it seems like a good occasion to share my findings.

I know this is a Little Dot tube rolling thread but, since I own an LD 1+, I quickly came to the conclusion that the opamps in the amplification stage play an important part in the overall sound. So, my rolling has these two sides: opamps and tubes.

Having said that, here are my current top 5 combos.

#5 Muses MUSES8820 + RCA 6ES8
This double triode is a good surprise (yes, it needs a 6DJ8 adaptor). Great bass extension and detailed sound. Wonderful with an acoustic guitar. It only needs a little more sparkle.

#4 Muses MUSES8820 + Voskhod 6Zh1P-ЕV
The definition of attack! Amazing with the metals of Albeniz's Spanish Suite. Quite analytical, but sometimes dry in the percussion.

#3 National Semiconductor LME49720NA + Elektronska Industrija 6HM5
The Yugos are very well regarded in this thread, and for good reason. Another analytical one, superb with female voices. It has the best treble of the bunch, but it lacks some bass.

#2 National Semiconductor LME49720NA + Mazda 6CB6
Probably the biggest surprise so far, since it seems that the 6CB6's went a little unnoticed in this thread. This one is the bass master. It goes down under but can still provide a very detailed soundstage. If there's something to point out, maybe it could have a bit more treble extension.

#1 National Semiconductor LME49720NA + Voskhod 6Zh1P-ЕV
And the Soviets again. This combo was love at first sight. The feeling is that with this tube, there is no frequency that cannot be reached; everything is in the right place at the right time and has the right extension. Well, to be fair, it's not only the tube. The dryness and the almost too analytical sound of the Muses completely dissipated with the LME49720.

It's been a good trip, but there's still a lot to see. I'll keep you posted.

 

[Cognomen]

Thanks for sharing your experiences.

Now that you talk about radio car tubes, I wonder if you have already tried EF98/6ET6. According to Radiomuseum it's a B7G Pentode that can be used with either 6.3V or 12.6V. With 300mA at 6.3V and the same pinout as 6DT6/6DT6A/6GY6/6ES6 seems suitable for the Little Dot with EF91 settings, right?

The 6ES6, 6ET6 and 6DT6(G) 7 pin miniatures all have a cathode and internal shield on pin 2, and pin 7 is a grid like EF91/92. I figured, hopefully correctly, it was safe to run 6ES6 in EF91/92 mode. Looking at the back pages, one poster opined there were 4 ways to run the 6DT6(G). One way was EF95 unstrapped. Is it advisable to not connect the grid on pin 7 (in the LDIII)? There were 3 additional modes: EF95 with pins 1 and 7 strapped, EF95 with pins 2 and 7 strapped and EF 91/92. All 4 or some of the modes may have been because the 6DT6(G) is a tetrode or like one. Is it likely one can safely electrify the 6ES6 and 6ET6 in all those permutations?

These wiring experiments were popular quite awhile ago. What did people conclude about how all these wiring possibilities? Were some wiring configurations better or not or were there some better than the simplicity of EF95 or EF91/92 without wire strapping? Perhaps it's unclear. Or was it likely that if a tube was not great in one mode that it would not be great in the other 3?

While I don't know for sure it's possible that no one ultimately nominated any of the tubes run in various strapped configurations as among the best. I regard the sound impressions as subjective and influenced by specific equipment and a limited sample size so one should not conclude anything but one can have some hunches/hypotheses about it.

 

[TrollDragon]

It's been a good trip, but there's still a lot to see. I'll keep you posted.

Awesome job!

 

[dpump]

do you use the 6676 & 6CB6A on the EF91or EF92 tube setting with no modification needed?

 

[barbazz]

do you use the 6676 & 6CB6A on the EF91or EF92 tube setting with no modification needed?

I do, although, according to the table on page 77, you can also use the 2/7-Socket Wire Mod.

 

[barbazz]

Was checking the compatible 12.6V double triodes on page 326 (thanks to @MIKELAP and @Artsi for the effort) when I realized there are plenty of tubes with currents equal to or above 300mA (6N4P, 12AU7, E180CC, etc.). I do remember that, as a rule of thumb, when halving the voltage, the current would double. That means currents in the 600-800mA range for those tubes, something LD's could not cope with.

Am I missing something? That rule shouldn't apply to all 12.6V double triodes?

 

[Cognomen]

Was checking the compatible 12.6V double triodes on page 326 (thanks to @MIKELAP and @Artsi for the effort) when I realized there are plenty of tubes with currents equal to or above 300mA (6N4P, 12AU7, E180CC, etc.). I do remember that, as a rule of thumb, when halving the voltage, the current would double. That means currents in the 600-800mA range for those tubes, something LD's could not cope with.

Am I missing something? That rule shouldn't apply to all 12.6V double triodes?

 

[gibosi]

Was checking the compatible 12.6V double triodes on page 326 (thanks to @MIKELAP and @Artsi for the effort) when I realized there are plenty of tubes with currents equal to or above 300mA (6N4P, 12AU7, E180CC, etc.). I do remember that, as a rule of thumb, when halving the voltage, the current would double. That means currents in the 600-800mA range for those tubes, something LD's could not cope with.

Am I missing something? That rule shouldn't apply to all 12.6V double triodes?

The 12AU7, configured to run on 6.3V, draws 300mA. When configured to run on 12.6V, it draws 150mA. And as far as I know, this pattern holds for all 12volt tubes that can be configured to run on 6volts.

 

[barbazz]

The 12AU7, configured to run on 6.3V, draws 300mA. When configured to run on 12.6V, it draws 150mA. And as far as I know, this pattern holds for all 12volt tubes that can be configured to run on 6volts.

I stand corrected. Misread the data in Radio Museum. Since it begins with a 12, automatically read 12.6V/300mA . The same goes for the others. Thanks.

 

[Cognomen]

What would happen if I put tubes rated 4.9 volts, .45mA in the Little Dot MK III driver sockets? Could it damage the Little Dot? Or would it probably just wear out the tubes faster than at their specified lower voltage? Also, when one doubles volts does current decrease by 1/2 in a straightline relationship? Or is that variable and specific to each type of tube?