[haywireman]

A reasonable explanation. 'Replace the red tip tube with a red tip tube'. But they would need to know which tube that was faulty...

I read that in the days of computers that ran thousands of tubes the most economical method of maintenance was not to wait for a failure to occur, but using statistical charts of a group (like 100) of tubes' operating life. Thus a group of tubes would be installed on the start date, and identified with, say, red paint. At intervals, say two weeks, the next group of tubes in the system would be replaced with, say, yellow paint. At the next interval a group would be replaced marked with, say, green paint. This allowed for a rolling tube replacement program that could be scheduled, and not require troubleshooting of the whole system. After the last group was replaced they went back to the beginning. Of course the system would be confined to the organization that was responsible for maintaining the system. It maximizes reliability while keeping the total cost low. It reminds me of painting the Golden Gate Bridge. As soon as the bridge is finished being painted at one end. they went back to the other end and started over.

 

[barbazz]

Does anyone have experience with the Little Dot 1+ and the Little Dot MKII?
Do they sound identical?

I have an MKII and it's fantastic. I do a bit of tube rolling and listen a lot with an HD800 and a Grado GH2.
Does it make sense to buy an LD 1+ as well? I've read that Burson offers opamp rolling options for the LD 1+.
This isn't available for the MKII.

No experience with MKII, but LD 1+ is a fun amp for rolling both tubes and opamps, and definitely the Burson V6 Vivid is a top-notch option.

 

[Moak]

Front and back ones. Here's my LD 1+ open:

Thanks a lot for the photo.
I changed the impedances with the jumpers of the MKII but there is no difference between them if I hear with my HD800 and Grado GH2. The max. volume if I turn the poti are 1-2cm. Not more. Otherwise it is too loud.
What’s wrong?
My source is a cd-player but I can’t change the volume.

 

[Cognomen]

I've been rotating various brands of dissimilar double triode co-listed 6EA7/6EM7/6GL7 vs 6SN7's in my MKIII. The various brands I have auditioned of the dissimilar triodes seem to sound about the same while the 6SN7 have had more variation. The 6EA7 etc, in my opinion, YMMV, tend to beat the average old lower to mid cost used 6SN7 even though there are some 6SN7 I currently prefer over them, subject to change (or not). I have not listened to expensive "antique" VT-231 6SN7 etc or other very esteemed expensive 6SN7 but to those of lower cost and some probably intermediate in cost. In terms of price to performance ratio, I regard the 6EA7 etc as a better deal. I am running Siemens C3G as drivers while comparing them. I mostly listen to tubes new to me these days I find in "junk boxes." A couple of weeks ago, I bought an estimated 1,000 tubes for $40 from a retired electric engineer that worked on the Univac, a tube computer. While 6SN7's can be elevated in price as singles or in pairs, they are a fairly common tube. I have good luck finding them, including occasional cosmetic pairs, in junk boxes along with a few single 12BH7(A) etc. I'm shopping for relatively "affordable" cosmetic used matches for the latter.

 

[grailnewt]

Maybe someone can help me im very new to tube rolling and know next to nothing about it. I'm looking at the littledot mk6+ and I'm wondering what i can substitute for the 6080wc power tubes will 6550s work or 6l6s? i honestly have no clue. im looking for a suitable replacement as 6080wc are very difficult to find in a matched quad or pair or period.... Any assistance or guidance would be appreciated..

 

[triod750]

Have you bought this amp already or are just thinking about it? These tubes have become expensive and rolling will cost a lot if you get bitten of the bug.

A pair of these single triodes in an adapter from for example @Deyan on this forum will sound better than most 6080 types and are available at a good price from this seller:
https://www.ebay.co.uk/itm/26534868...7QZV6T&hash=item3dc8039307:g:A-EAAOSwBnZbD5AW
They come from old German Bundeswehr supply. This would mean that you use eight single triodes instead of four double triodes. You would have to make sure there is room for them on the amp. I have used these, four of them in two adapters in a Little Dot MKIVSE with excellent result.

 

[grailnewt]

Have you bought this amp already or are just thinking about it? These tubes have become expensive and rolling will cost a lot if you get bitten of the bug.

A pair of these single triodes in an adapter from for example @Deyan on this forum will sound better than most 6080 types and are available at a good price from this seller:
https://www.ebay.co.uk/itm/26534868...7QZV6T&hash=item3dc8039307:g:A-EAAOSwBnZbD5AW
They come from old German Bundeswehr supply. This would mean that you use eight single triodes instead of four double triodes. You would have to make sure there is room for them on the amp. I have used these, four of them in two adapters in a Little Dot MKIVSE with excellent result.

I'm seriously contemplating getting the mk6+ just trying to understand what I'm in for. I don't know anything about adapters either and have very little to no experience with diy and no skills to do so. I'm okay with spending more money if they work I'm just trying to understand if a 6550 or 6l6 or other tubes would work instead of 6080wc. I can easily find the driver tubes and use alternatives it's much easier to find.

 

[triod750]

6550 or 6L6 won't work without output transformers and Little Dot are OTL design; Output TransformerLess.

These are my adapters to use CV4079 in Little Dot MKIVSE:

You don't see in this photo the bottom that has the 'male' pins that you put into the sockets in the amp. You can also use 6BX7GT or 6BL7GT but they can be difficult to find too. They have the same pinout as 6080 and 6AS7G.

 

[grailnewt]

6550 or 6L6 won't work without output transformers and Little Dot are OTL design; Output TransformerLess.

These are my adapters to use CV4079 in Little Dot MKIVSE:

You don't see in this photo the bottom that has the 'male' pins that you put into the sockets in the amp. You can also use 6BX7GT or 6BL7GT but they can be difficult to find too. They have the same pinout as 6080 and 6AS7G.

I see the mk6+ is sepp design with ocl but anyway appreciate the other two you mentioned I'll see what I can find... I know sepp is transformer less.

 

[triod750]

I see the mk6+ is sepp design with ocl but anyway appreciate the other two you mentioned I'll see what I can find...

I don't know much about that amp but I don't think you can use pentodes in it. OCL means output capacitorless?
I bought my LDMKIV almost new from a person who bought MK6 since he wanted a balanced amp just because
He then told me that he would not afford to get other tubes for it. But he didn't regret his move from start.

I should also say that I had to get an external power supply for the heaters to use 6080/6BX7/CV4079 with special adapters in LDMKIV. You won't need that in MK6.

I got these from @Deyan too. And plenty more adapters that aren't shown here. The external PSU is in the grey box and the adapters with cables to use it to the left of it.

 

[grailnewt]

I don't know much about that amp but I don't think you can use pentodes in it. OCL means output capacitorless?
I bought my LDMKIV almost new from a person who bought MK6 since he wanted a balanced amp just because
He then told me that he would not afford to get other tubes for it. But he didn't regret his move from start.

I should also say that I had to get an external power supply for the heaters to use 6080/6BX7/CV4079 with special adapters in LDMKIV. You won't need that in MK6.

I got these from @Deyan too. And plenty more adapters that aren't shown here. The external PSU is in the grey box and the adapters with cables to use it to the left of it.

Thank you for the help. I really appreciate the insight. I did find some nice nos RCA/tung sol 6AS7G for reasonable price so I'll probably get those if I get the amp. Price for tubes isn't a huge concern at the end of the day it will still be cheaper than buying a 6-7k OTC amp

 

[Cognomen]

6550 or 6L6 won't work without output transformers and Little Dot are OTL design; Output TransformerLess.

These are my adapters to use CV4079 in Little Dot MKIVSE:

You don't see in this photo the bottom that has the 'male' pins that you put into the sockets in the amp. You can also use 6BX7GT or 6BL7GT but they can be difficult to find too. They have the same pinout as 6080 and 6AS7G.

6550 or 6L6 won't work without output transformers and Little Dot are OTL design; Output TransformerLess.

These are my adapters to use CV4079 in Little Dot MKIVSE:

You don't see in this photo the bottom that has the 'male' pins that you put into the sockets in the amp. You can also use 6BX7GT or 6BL7GT but they can be difficult to find too. They have the same pinout as 6080 and 6AS7G.

I'm curious to know why they wouldn't work without an output transformer and how one figures that out. Is it a comment specifically about those two tubes specifically or about many tubes in general? Or is it a comment based on the idea they would need a better output transformer than stock in the mkVI? My understanding of such things has its limits. As far as I understand the MKIII and similar MKIV, the output path has a capacitor (instead of a transformer) to block dc direct current output while allowing the music to pass through. The MKVI is output capacitor less. Doesn't that mean it has an output transformer in it to block dc? It seems to me tubes require high voltage dc to function even though it has to be removed from the output either by a capacitor or output transformer to avoid killing the user and speakers. I understand it's possible my limited understanding might require a reading a book rather than short posts one puts up here.

 

[Cognomen]

Thank you for the help. I really appreciate the insight. I did find some nice nos RCA/tung sol 6AS7G for reasonable price so I'll probably get those if I get the amp. Price for tubes isn't a huge concern at the end of the day it will still be cheaper than buying a 6-7k OTC amp

In case you don't know, there is a Little Dot MKVI forum on headfi.

 

[triod750]

I'm curious to know why they wouldn't work without an output transformer and how one figures that out. My understanding of such things has its limits. As far as I understand the MKIII and similar MKIV, the output path has a capacitor (instead of a transformer) to block dc direct current output while allowing the music to pass through.

So has my understanding. I expected someone to tell me I'm wrong. I just wrote what I have been told. I have asked previously if it is possible to use the pentodes EL41 and EL42 triodestrapped in pairs as output tubes and the answer was no.

 

[Cognomen]

So has my understanding. I expected someone to tell me I'm wrong. I just wrote what I have been told. I have asked previously if it is possible to use the pentodes EL41 and EL42 triodestrapped in pairs as output tubes and the answer was no.

While it may take quite awhile, because this is a hobby, I'm planning to do some reading from the library, hopefully in a book that has some practice problems, hoping to cultivate better understanding of electricity in general and tubes. Then I plan to get back in touch with a friend of my brother's who earned a Masters or Doctorate in Physics in the early to mid 70's which he applied as an electrical solid state engineer at IBM. He was intrigued and amused by my Little Dot MKIII, as a modern example of never dying tube audio, and reverse engineered it based on what he could understand and produced schematics. I think he was curious to learn about modern tube audio compared to HeathKit he built before college. His reaction to my tube rolling was...paraphrasing.... "Of course various tubes sound different due to being used outside of their design specifications; the Little Dots have fixed parameters that mean they will sound different." Nonetheless, I enjoy rolling and listening to tubes and music. He kept listening to his tube audio during the 70's transistor revolution, I believe because he not necessarily liked tubes better toward the end of the decade but because he was satisfied by their sound and saw no need to buy something else. He's very into Ham radio and has tube equipment he explained to me. It requires turning on many components and turning many dials compared to transistors. He hopes to Ham simplify some day.