[lupoal]

ok, it's time to put hands inside the LD...
following the original project and some suggestions from people here inside but also from other italian formuns and one of my friends (he is a appreciated hi-fi manufacturer) I left the two output tubes floating, that means no connection between the 0Vdc supplying them and the 0Vdc inside the LD electronic, and I grounded the two inputs tube connection the 0Vdc supply not were is in the original project (that is elevated of few volts) but at the 0Vdc of the electronic... the first picture is about this connection, the others are about cutted and identified cables from original transformer and DIY cable gland output (the holes inside the LD2 backplate are only 10mm diameters.. I've not been able to find any industrial PG with out 10mm and inside 4,5mm) so I had to realize one by myself

about the cables, those are 4x0,34mmq which more then enough to drive the tubes... I named "high" that one dedicated to the two output tubes... as both are M12 male + M12 female just cut them in two parts and you will have a perfect prewired cables that will allow you to disconnect PSU from LD if/when necessary and reconect with reliability

then comes the time to connect them togheter, without any powering on the LD and without tubes, just for check there are no shorts or missing connections and to measure the voltages at the valves sockets

ok... no smoke... good ... the voltage with no load at sockets is 0,1Vdc below the value on the display

 

[lupoal]

ok... my expectation was to have maybe something slight better in the sound and much more reliability about tubes now with proper power supply...

I installed four tubes I can sacrifice n case of troubles ... two 6N6P dated 1984 and two 5654 JAN brand Penta, made in USA probably by GE... to be honest nothing really special... I also plugged in my old, but in MINT conditions, HD530 that I tried with LD2 without any fun, not enough bass response, not enough details and dynamic, not deep stage, nothing I would lie to use to listen music, something to leave in his cardboard box (that HD530 was amazing with cd player Marantz CD63 KIS)... the dac is my IFi nano BL iDSD, that I use with mobile and for tubes burn in, a nice dac but not really special.. I mean it is not a Mojo, source my mobile with Qobuz... mobile with USB Audio PLayer Pro

now... I'm simply surprised by the differences... it sound quite better ….
I should have done it before... it is really, to my hears, a quite big jump forward... almost speechless...

few additional notes:
- I've read in an old post about MK3 mods about problems of hisss coming from use of LT317... that's wrong, no hiss at all... in that case there were probably something wrong somewere else
- if you don't want to add cooling fan then you have to choose different way and build the electronic by yourself,just follow one of the many scheme you can find in the web (for example --> here ) and use much bigger heat sink... if you build the circuit by yourself consider to do something with higher output current capability, you can do that even with the LM317 adding a transistor like in the scheme you can find at the link I posted

please note: if you want to use with loudspeakers then is a MUST to go for passive cooling with bigger heat sink, or maybe you can try with a larger fan like a Noctua 100mm diameter, as the 40x40mm fan even underpowered do emit a noise clearly audible without headphone...in some moments I think I can hear them even trough the headphone, ummm, I have to change the place where it is now

June 21st 2021... see update here

 

[lior777]

hey all !

I purchased a Little Dot 2 + maverick d2 dac with headphones hifiaman Sundra

I would like a recommendation for which tubes to upgrade and from where to buy? Hear mostly ethnic instruments, male voice, like this:





thanks

 

[TrollDragon]

hey all !

I purchased a Little Dot 2 + maverick d2 dac with headphones hifiaman Sundra

I would like a recommendation for which tubes to upgrade and from where to buy? Hear mostly ethnic instruments, male voice, like this:





thanks

The Sundara is a 37Ω/ 94dB planar headphone that really comes to life with a little bit of power behind it. The Little Dot MK 2 is an OTL tube amp designed for high impedance headphones of 150Ω or higher and it can't really provide the current required to properly drive low impedance planar headphones like the Sundara. You will also find that the output resistance of OTL amplifiers is higher than those headphones and will mess with the sound. You might find that the MK 2 will power the Sundaras, but IMHO you are doing yourself a disservice by not pairing those headphones with an amp that has better synergy.

What you need is an OTC (Output Transformer Coupled) tube amp or a Hybrid (tube input/solid state output). The OTC amps are quite expensive and generally start around $1000 where the Hybrids can be found for much cheaper.

 

[triod750]

not so much space left inside...

How about right inside?

 

[lupoal]

How about right inside?

nice joke...

but only that? nothing to say about all the other things?
ummm... maybe a should use more audiophile-maniac sentencies... I would like to avoid but... ok, more black between instruments, improved high register with better reproduction of piano, better low frequencies with more articulated infos and more details, slightly improved sense of space (that could also be because of HD530).... bla bla bla...

now... I've done and verified that power supply really matter for both better silent background (my LD had no hummm or hissss at all) and better heaters temperature (that meand better electrons emission)... there is the list of items to be used and a quasi-step-by-step instruction... it is your time to move fingers not only on keyboard

 

[triod750]

nice joke...

but only that? nothing to say about all the other things?
ummm... maybe a should use more audiophile-maniac sentencies... I would like to avoid but... ok, more black between instruments, improved high register with better reproduction of piano, better low frequencies with more articulated infos and more details, slightly improved sense of space (that could also be because of HD530).... bla bla bla...

now... I've done and verified that power supply really matter for both better silent background (my LD had no hummm or hissss at all) and better heaters temperature (that meand better electrons emission)... there is the list of items to be used and a quasi-step-by-step instruction... it is your time to move fingers not only on keyboard

I saw your posts in the middle of the night when I was going to shut down for bed. A lot of information not yet read. Will have to get back on this but thank you for the full report. Great contribution.

(Watching European Championships consumes a lot of hours).

 

[lior777]

The Sundara is a 37Ω/ 94dB planar headphone that really comes to life with a little bit of power behind it. The Little Dot MK 2 is an OTL tube amp designed for high impedance headphones of 150Ω or higher and it can't really provide the current required to properly drive low impedance planar headphones like the Sundara. You will also find that the output resistance of OTL amplifiers is higher than those headphones and will mess with the sound. You might find that the MK 2 will power the Sundaras, but IMHO you are doing yourself a disservice by not pairing those headphones with an amp that has better synergy.

What you need is an OTC (Output Transformer Coupled) tube amp or a Hybrid (tube input/solid state output). The OTC amps are quite expensive and generally start around $1000 where the Hybrids can be found for much cheaper.

thanks. i also buy it

so i pull down the volume of dac and its good sound.

where i can buy new small and big tubes?

 

[TrollDragon]

thanks. i also buy it

so i pull down the volume of dac and its good sound.

where i can buy new small and big tubes?

eBay is your best source for replacement tubes.

 

[lior777]

i find the big tubes..how i search for the 2 small tubes?

 

[TrollDragon]

i find the big tubes..how i search for the 2 small tubes?

What do you mean by big tubes? Which ones did you find?

The input tubes (2 in front) have a lot of compatible choices, it all depends on what you want to try and which ones you like the sound of. This thread is full of different tubes members have used in their amplifier.

This post has the table of compatible tube you can choose from.
https://www.head-fi.org/threads/lit...ube-rolling-guide.563884/page-77#post-9392055

 

[triod750]

nice joke...

but only that? nothing to say about all the other things?
ummm... maybe a should use more audiophile-maniac sentencies... I would like to avoid but... ok, more black between instruments, improved high register with better reproduction of piano, better low frequencies with more articulated infos and more details, slightly improved sense of space (that could also be because of HD530).... bla bla bla...

now... I've done and verified that power supply really matter for both better silent background (my LD had no hummm or hissss at all) and better heaters temperature (that meand better electrons emission)... there is the list of items to be used and a quasi-step-by-step instruction... it is your time to move fingers not only on keyboard

I enjoy reading about other people's projects but I am not up to copying them due to lack of knowledge and skills. I have followed another path than you have to arrive at where I am right now. I can't be proud of my own doings as you can and should be but I can be satisfied with the result I have achieved, so far. I'm convinced that you will not stop here and am looking forward to further reports. Congratulations!

Regarding the more important European Championships, I expect the Italian team to be more successful this year since they are playing so well. I don't expect my team to beat your team this time, if they meet each other .

 

[lior777]

What do you mean by big tubes? Which ones did you find?

The input tubes (2 in front) have a lot of compatible choices, it all depends on what you want to try and which ones you like the sound of. This thread is full of different tubes members have used in their amplifier.

This post has the table of compatible tube you can choose from.
https://www.head-fi.org/threads/lit...ube-rolling-guide.563884/page-77#post-9392055

hey, the little dot mk2 have 2 big tube and 2 small tube...

i find this:
https://www.ebay.com/itm/224482318506

 

[lupoal]

update to this post

the problem with noisy fan has been solved replacing the two 50x50x20 with a single 80 x 80 from Noiseblocker... this fan has nominal voltage of 12Vdc but start running at 6Vdc, the speed is slower but more then enough to not go in overheating

two little problems are still open... supplying DC to all tubes via pcb, and cutting the wire from the transormer, put the status led into dc circuit.. that could also be fine but... the circuit in LD is done in a way that the led has roughly the same voltage at both sides, so it doesn't work... now
- I could connect on side of led to Ground, leaving it connected on the other side to heater +Vdc... that would probably work but showing only the PSU status or
- I could connect the led directly to the 6Vac free in the trafo... putting in between a diode + a resistor... in this case the led show the ampli status, but I have to place two additional wires inside the ampli (easy) but should disassemble the ampli again to reach the trafo... boring

in any case I wanted to push a single button and start everything .... or start first the PSU for pre-heating and then the ampli... to reach the first possibility I've added a solid state relay (was in one of my drawer doing nothing) driven by one of the heaters power units... if I leave the switch back the ampli ON and use the switch of the PSU all go OFF or ON as required

 

[Shane D]

Just got some tubes in today. Not sure what to expect. They were pretty affordable and bought off Amazon. I will try them out tomorrow morning.