[TrollDragon]

The MKIV is an OTL (Output Transformerless) SEPP (Single Ended Push Pull) amplifier with the power tubes configured in a white cathode follower configuration.

Tube CAD's SEPP article:
http://www.tubecad.com/articles_2002/SRPP_Deconstructed/index.html

Valve Electronics cathode follower article:
http://www.valveradio.net/en/home/audio/low-distortion-cathode-follower.html

Lots of good reading there about the theory / pros and cons of the design used in the Little Dot. The bottom line is price, the Little Dot amps were designed the way they were because it is the cheapest way to make these amplifiers and get them to consumers.

Do you have a channel imbalance in your MKIV? There is no way to adjust the tube biasing without changing components on the board. If you are going to go through that trouble it would be better to obtain an amplifier where adjustments can be tuned to your liking, Decware or similar amplifiers would provide this option.

Possibly purchasing matched tubes might solve any perceived imbalance issue in the Little Dot, but that is a solution you would have to try by actually testing out a balanced pair of tubes.

 

[Chris J]

So that infers they are strictly class A. Is that correct? And if that is correct are there any channel balancing inch issues and if so are there any ways to balance the channels?
 
PS I let my own questioning be food for thought to myself. Consequently I have come upon this page "How To Adjust Audio Balance In Windows 7" which will give you a software way of adjusting the balance of an amplifier even if the amplifier is in imbalance because of hardware problems not software interface hardware problems.
 
Perhaps I should amend my above question to do you think by using unmatched tubes and saving money it could be necessary to go through a software balance procedure like the one outlined in the link above due to level in balance caused by using unmatched tubes?
 
I have another question is well. My stock tubes keep improving and improving with increased burning-in. They have now reached the point where on certain files I consider particularly good like the ones of my videos of "John Williams at the BBC proms" which are so good sonically that I have been increasing the volume when listening to them not to give them too much volume overall but to increase the dynamic range. It seems the way my little dot IV amplifier has become with increased burning is that with some very good music video files increasing the volume increases the dynamic range more than what used to happen before my tubes burned in an I would not get increased in dynamic range with increasing volume, but just increase in volume. Have any of you all have experienced the increase in dynamic range with very sonically good files that I am experiencing. If so I will have additional questions.

 


Sounds like you really are a tube lover.
Don't sweat it too much, every now and then you get a bad tube: too noisy, too microphonic, etc. It happens. Just don't sweat it too much.
I suspect your Little Dot would sound even better with a good set of NOS tubes.
My tube amp does (it's not a Little Dot, BTW).

 

[gyzimaki]

I know it probably isn't relevant to the topic, but back in 2010, when I got my first HD800s, I did order and try out a Little Dot MKII, it was back then, I think. Even with the Gain switch turned up, there was this weird channel imbalance between left and right, it wasn't anything shocking, but it was noticeable, and to me, very annoying. I bet I could have gotten used to and adapted to it, but back then I used to be a real perfectionist, so I ditched it and gave it to a friend of mine instead to play around with.
 
Have any of the subsequent models ( MK3/4 etc ) exhibited such an issue with certain sets of headphones for you, guys?

 

[bbmiller]

The MKIV is an OTL (Output Transformerless) SEPP (Single Ended Push Pull) amplifier with the power tubes configured in a white cathode follower configuration.

Tube CAD's SEPP article:
http://www.tubecad.com/articles_2002/SRPP_Deconstructed/index.html

Valve Electronics cathode follower article:
http://www.valveradio.net/en/home/audio/low-distortion-cathode-follower.html

Lots of good reading there about the theory / pros and cons of the design used in the Little Dot. The bottom line is price, the Little Dot amps were designed the way they were because it is the cheapest way to make these amplifiers and get them to consumers.

Do you have a channel imbalance in your MKIV? There is no way to adjust the tube biasing without changing components on the board. If you are going to go through that trouble it would be better to obtain an amplifier where adjustments can be tuned to your liking, Decware or similar amplifiers would provide this option.

Possibly purchasing matched tubes might solve any perceived imbalance issue in the Little Dot, but that is a solution you would have to try by actually testing out a balanced pair of tubes.

Thanks for those cathode follower links I did find the reading interesting. I looked up the tubes in my little dot amplifier and it appears that the driving stage is a pentode and the power stage is a double triode. So I could see how if you were using to halves of a double triode the two halves would be in very good balance to each other and balance tubes would not  apply.
 
Can I assume that the pent code driver is actually hooked up as a pentode and is utilizing all the grids?
 
Also without going through the bother of using test equipment I am not hearing any imbalance in my channels, but was just speculating that tube rolling could possibly cause that. And if it did I could use the fact that I am utilizing USB Windows 7 drivers to drive my amplifier and since these drivers have the possibility of rebalancing channels that would be the solution I would use should that occur.
 
I have a question my stock tubes must've taken at least 150 hours to reach their very high level of performance. Do you think if I were to try to do even better by tube rolling at least 150 hours would be what a good try of another combination of tubes would take?

 

[TrollDragon]

Can I assume that the pent code driver is actually hooked up as a pentode and is utilizing all the grids?  
I have a question my stock tubes must've taken at least 150 hours to reach their very high level of performance. Do you think if I were to try to do even better by tube rolling at least 150 hours would be what a good try of another combination of tubes would take?

The driver tubes are run as triodes, on page 77 of the Little Dot Tube Rolling Thread the table shows all the tubes you can use and the mode required to run them.
 
Heptodes like the 6CS6 for example can be run in the default EF95 mode, or pins 1 and 7 strapped together or 2 and 7 strapped together or even in EF92 mode. The 6CS6, 6DT6A, 6HM5 (tall version) are all very popular tubes that have been run in the LD as driver tubes.
 
A lot of the tube rollers swear by Burn In, so if you find your current tubes much more enjoyable after 150 hours of Burn In, then that should apply to any other tubes that you try as well.

 

[bbmiller]

 
run in EF95 mode, EF92 mode. 

Any especially good places to find out about this mode stuff?

 

[TrollDragon]

On the little dot driver board there are jumpers to switch between EF92 and EF95 relating to the pin configuration of the two tube types.
 
In EF92 mode pins 5, 6 and 7 are shorted together. In EF95 mode just pins 5 and 6 are shorted with pin 7 left floating.
 
EF95 tubes have pin 2 and 7 shorted together internally so if you plugged an EF95 tube in with the jumper set to EF92 you would end up shorting the anode to the cathode.  
 
EF92 Tube Info, EF95 Tube Info.

 

[bbmiller]

  On the little dot driver board there are jumpers to switch between EF92 and EF95 relating to the pin configuration of the two tube types.
 
In EF92 mode pins 5, 6 and 7 are shorted together. In EF95 mode just pins 5 and 6 are shorted with pin 7 left floating.
 
EF95 tubes have pin 2 and 7 shorted together internally so if you plugged an EF95 tube in with the jumper set to EF92 you would end up shorting the anode to the cathode.  
 
EF92 Tube Info, EF95 Tube Info.

Thanks
so I suppose we are talking about the driving tube now.
Does the power to have strapping options too? And do you have any similar information on its modes or whatever?
 
Which tube has more impact on the sound?

 

[TrollDragon]

  Thanks
so I suppose we are talking about the driving tube now.
Does the power to have strapping options too? And do you have any similar information on its modes or whatever?
 
Which tube has more impact on the sound?

Yes that is the information for the driver tubes.
 
There are no strapping options or different modes for the power tubes. The stock 6H30Pi's are very good, you can try to seek out the Soviet "Super Tube" 6Н30П ДР, this is supposed to be the best tube you can put in an unmodified LD. On eBay they were demanding at one point upwards of $200 for real ones, beware though as there are plenty of fakes for sale as well. I have never head these tubes so I can't comment on the sound.
 
I could not tell you which would have more impact as I have never changed the power tubes on my amplifier, that is a question you should ask in the Rolling Thread.

 

[Chris J]

Yes that is the information for the driver tubes.

There are no strapping options or different modes for the power tubes. The stock 6H30Pi's are very good, you can try to seek out the Soviet "Super Tube" 6Н30П ДР, this is supposed to be the best tube you can put in an unmodified LD. On eBay they were demanding at one point upwards of $200 for real ones, beware though as there are plenty of fakes for sale as well. I have never head these tubes so I can't comment on the sound.

I could not tell you which would have more impact as I have never changed the power tubes on my amplifier, that is a question you should ask in the Rolling Thread.

In any amp I've rolled tubes in the driver or input tubes have more effect than the power tubes.

 

[HeatFan12]

Waz up TD!!!!!  Long time.........I took like a year off of head-fi...Great to see you are still enjoying your MKIV...
 
Mine is still kickin' after 5+ years.
 
Went old skool today with the drivers and threw in some RCA Command 5654s.  iPod 5.5G--> Apple Lossless--> LDMKIV SE--> Ultrasone PRO650s--> Good times!!!!!
 
 

 

[TrollDragon]

Waz up TD!!!!!  Long time.........I took like a year off of head-fi...Great to see you are still enjoying your MKIV...

Mine is still kickin' after 5+ years.

Went old skool today with the drivers and threw in some RCA Command 5654s.  iPod 5.5G--> Apple Lossless--> LDMKIV SE--> Ultrasone PRO650s--> Good times!!!!!

Hey HF!
Wow bro I was wondering where you snuck off to... Hasn't been much love in the Ultrasone thread in a while... Yes the MKIV is a great amp with the 6SL7 as a driver these days, the bigger plates seem to give it a fuller, richer sound. LOL

Braided me a nice portable cable for the 780's and picked up a sweet pair of German Maestro 8.300 D Pro's. There are two of us on Head-Fi that own those GMP's.



Good to have you back bro and time to kick up the Ultrasone Love, unless you went all Stax Mafia on us....

 

[HeatFan12]

Hey HF!
Wow bro I was wondering where you snuck off to... Hasn't been much love in the Ultrasone thread in a while... Yes the MKIV is a great amp with the 6SL7 as a driver these days, the bigger plates seem to give it a fuller, richer sound. LOL

Braided me a nice portable cable for the 780's and picked up a sweet pair of German Maestro 8.300 D Pro's. There are two of us on Head-Fi that own those GMP's.

Good to have you back bro and time to kick up the Ultrasone Love, unless you went all Stax Mafia on us....

 
Thanks bro!!!!!
 
Looks awesome TD.  Great job!!!!
 
Stax?!?!?  Stax can't fulfill the bass craving we need.!!!!!  lol
 

 

[koc]

Hi guys, i want to buy Little Dot MK IV for my D7100, but i need a dac to connect it to my computer,
Can you please reccomend a good dac that match the Little Dot MK IV SE ?
What about Little Dot DAC_II ? or maybe Little Dot DAC3 ?

Thank you.

 

[Brooko]

Hi guys, i want to buy Little Dot MK IV for my D7100, but i need a dac to connect it to my computer,
Can you please reccomend a good dac that match the Little Dot MK IV SE ?
What about Little Dot DAC_II ? or maybe Little Dot DAC3 ?

Thank you.

 
I haven't heard the D7100 - but I'm actually wondering if the LD MKIV is actually a good match for them.  The D7100 has an impedance of 25 ohms, whilst I think the LD output impedance is more in the 40-50 ohm bracket (from memory).  it's an OTL anyway - so the high output impedance is going to better suit headphones with a higher impedance.  What I'm suggesting is that due to an incorrect damping factor, you may find that the LD MKIV (or any OTL tube amp) could end up playing havoc with the D7100's frequency response due to poor damping.
 
You may be far better trying a hybrid tube amp with a lower output impedance.
 
If you wanted to go Little Dot - you could get the DAC_II (which would give you DAC + solid state amp), and then add a hybrid like the LD MK1+.
 
Just a thought ......