[lupoal]

@MIKELAP @mab1376

thanks a lot!
very useful tools to not get lost inside this really huge thread

one question... I’ve read many of the pages, not all 800 but for sure a lot of them, and didn’t find a word about changing the output capacitors... now I understand that here is about tube rolling and for modding there’s another thread but... that possible mod it is not mentioned here (to be honest I don’t even know if it is mentioned there) because of... not applicable in MK3 or MK4 that are the most common LD here? ... or... because it does not improve the sound so much, it doesn’t worth? ... it is more difficult / dangerous then rolling tubes? (well, I’ve seen here some quite complicate DIY adapters... so I don’t think it a matter of difficulty)

 

[triod750]

Could it be this? I have saved it as a document.

Posted by Acapella 2014, I think.
___________________________________________________________________________

Hi, Just for Christmas I have put together a table as a reminder for everyone in the thread and to help new arrivals. The table is now pretty much complete.

Please, let me know if you find any additions or anything that requires correction.

Little Dot I" / II/ III / IV Endgame Tube Table

Power Tube
Name	Adapter	Heater Current (A) / 6.3 V	Notes
5687/7044/7119(E182CC)	5687 Powersocket Adapter	0.9	easily usable substitutes, sound great
6AS7G/6080	Adapter + External Power Supply, see 1 and 2 and 3	2.5	this is probably the icing of the power tube cake
12AU7/12AT7/12AX7/7025/5751/ECC83/6057	Powersocket Adapter	0.35
6BL7/6BX7/6BQ7	Adapter + External Power Supply, see 1 and 2 and 3	1.5
6DJ8	not needed	0.365
6GU7/6CG7/6FQ7	not needed	0.6	not compatible with 12AX7 driver tubes
6N23P	not needed	0.31
6SL7*	6SN7 Powersocket Adapter	0.3	lower gain than 6SN7, not compatible with low impedance cans
6SN7*	6SN7 Powersocket Adapter	0.6	classic high end tube, not compatible with low impedance cans
6N6P-IR	not needed	0.9	high quality, long lasting version of the 6N6P-I and considered best sounding 6N6P before the very expensive 6N6P-DR
Maximum recommended heater current for power tubes is 1.0 A. Tubes exceeding this are highlighted in red.
Driver Tube
Name	Adapter	Heater Current (A) / 6.3 V	Notes
5687/7044/7119(E182CC)	External driver socket ^, external power supply	0.9	6.3 V / 12.6 V **
6350/6463/ECC813	External driver socket ^, external power supply	0.9	6.3 V / 12.6 V**
2C51 / 396A / 5670	External driver socket ^ + driver socket adapter	0.35
7AU7	External driver socket ^	0.6	3. 5 V / 7 V**
12AU7	External driver socket ^	0.3	6.3 V / 12.6 V**
12AU7/12AT7/12AX7/7025/5751/ECC83/6057*	External driver socket ^	0.3	One triode can be used besides a non-powered one, 6.3 or 12.6 V**
6BQ7A	Adapter	0.4
6DJ8	External driver socket ^	0.365	probably noisiest double triode, both triodes must be powered
6HM5	none	0.19	probably best standard AK5-type option
6N23P	none	0.31
6SL7*	6SL7 driver adapter	0.3
6SN7*	External driver socket ^, external power supply	0.6
C3G(S)* ^^	C3G AK5 Adapter	0.37	C3G(S) tubes sound great but they are produced with a fragile glass base. Widen the socket holes before inserting the tube to avoid breaking.
ECC81	External driver socket ^	0.3
ECC40	External driver socket ^, external power supply	0.6
E80CC/6085	External driver socket ^, external power supply	0.6	6.3 V / 12.6 V **
Maximum recommended heater current for driver tubes is 0.4 A. Tubes exceeding this are highlighted in red.
*: Requires socket extenders for LD MKIII	": For Little Dot I only driver tubes.
9 Pin power socket extender
7 Pin driver socket vector extender
**: Generally, when doubling the voltage, the apparent current is halved.
^: The external driver socket adaper uses a breadboard and allows the use of a single double triode to drive both channels.
^^ Hypnos1 (post 5670): How to remove the C3Gs metal shielding, this requires care to not break the fragile tubes.
Power Tube Requirements (Gibosi post #7937)
1) Double triode
2) Separate cathodes (there are some double triodes such as the E90CC where the triodes "share" a cathode. These will not work.)
3) Heater current 1.0A or less
4) 6.3 Volts
List of compatible tubes and 6DJ8, 6SL7, 6SN7, 12AX7 wiring instructions

For old school driver tubes operable without adapter, see page 77.

Driver Tube 7-Pin Vector Socket Adapter

Power Tube 9-Pin Socket Adapter


Revisions 1 & 2, 24/12/2014: Thanks for the input Gibosi and Mordy, thanks for sending the socket extender pictures Mordy, which are now included. Added a reference to Hypnos1 on how to remove the C3G(S) metal shielding.
Added ECC40 and E80CC/6085 as suggested by Gibosi, thanks.
Merry Christmas.
Revision 3, 09/01/2015: Added links to the implementation of 6AS7G/6080 power tubes, thanks Gibosi for finding the posts and suggesting the implementation and Mordy making it work. Added link to page 77 and 6N6P-IR.
Revision 4, 10/02/2015: Updated power tube links for 6080/6AS7G by Mordy's post 9059 on page 604 (3)

To this list from Acapella I would like to add Melz 6H12C/6N12S that is close to 5687 in electric parameters but more resolving soundwise. 5687, while sounding good, to me are more 'distant' and closed in as 'power tubes'. I have not yet tried them as 'drivers'. They have the same pinout as 6SN7 so the same adapters can be used and they don't need external heater PSU.

 

[johanchandy]

Shanghai 6J1. They're an improvement over the stock Beijing 6J1 in every way while still keeping the soft treble that seems to be a characteristic of NOS Chinese tubes. You can tell them apart from the Beijing and Shuguang 6J1 by the atomic whirl logo.

The one problem you might have is finding them. There's very little information about the different Chinese tube factories available on the English speaking internet and Chinese sellers don't usually distinguish tubes by the factory that made them.

Thank you! I'll try to find a pair!

Edit: found a nos matched pair an ebay, can't wait to get them!

 

[lupoal]

... any opinion about GE 6SN7 GTA?

 

[TrollDragon]

Images of the 6SJ7 in the I+ and the MK IV SE. The weather was much brighter this morning so I was able to take some pictures with my ancient digital camera.



I also tried solving the issue about reaching into the MK IV to get to the jumpers. I had the idea of attaching jumper wires to the internal pins which would then allow the jumpers to be changed externally. However the access holes on the bottom of the amp don't leave enough room for me to be able to fit the female end of the jumper wires to the internal pins with tweezers. I'll have to rethink that one.
Link if anyone is unsure what I mean by jumper wires

I did this with my MK IV.
The red DPST switches toggled EF92/95. The black DPDT (Center Off) switched did the strapping. Unfortunately there was a hum with certain tubes and was most likely due to the way I routed the strapping wires from the switches to the sockets. The only problem with the MK IV is once you remove the face or backplate you get hum. In order to test the layout you have to put the amp back together again. The board is a PiTA to remove so I spent a fair bit of time trying to solve the hum issue and eventually abandoned the switches.

If you only put switches in for EF92/95 I don't think that would generate any hum. I believe that it was once I tied into the grids, the problem surfaced. Probably better shielding and routing on those wires would have fixed it.

 

[TrollDragon]

Majestic version...

Voskhod 6Н2П-ЕБ driver.

 

[TrollDragon]

@MIKELAP @mab1376

thanks a lot!
very useful tools to not get lost inside this really huge thread

one question... I’ve read many of the pages, not all 800 but for sure a lot of them, and didn’t find a word about changing the output capacitors... now I understand that here is about tube rolling and for modding there’s another thread but... that possible mod it is not mentioned here (to be honest I don’t even know if it is mentioned there) because of... not applicable in MK3 or MK4 that are the most common LD here? ... or... because it does not improve the sound so much, it doesn’t worth? ... it is more difficult / dangerous then rolling tubes? (well, I’ve seen here some quite complicate DIY adapters... so I don’t think it a matter of difficulty)

If you have a look at this post here, this user did quite a bit of circuit modification to his LD MK III, there might be something in that you can apply to your amp.
https://www.head-fi.org/threads/little-dot-mk-iii-mods.439449/page-10#post-10697619

The big problem with modifying a LD MK III/IV is getting the board out of the case as you have to unsolder the transformer connections to slide it out and work on it. You can't run the amp with the board removed from the chassis due to the transformer wires not being long enough. It should be much easier to mod the MK II since the whole bottom comes off of the amp.

 

[Arro]

I did this with my MK IV.
The red DPST switches toggled EF92/95. The black DPDT (Center Off) switched did the strapping. Unfortunately there was a hum with certain tubes and was most likely due to the way I routed the strapping wires from the switches to the sockets. The only problem with the MK IV is once you remove the face or backplate you get hum. In order to test the layout you have to put the amp back together again. The board is a PiTA to remove so I spent a fair bit of time trying to solve the hum issue and eventually abandoned the switches.

If you only put switches in for EF92/95 I don't think that would generate any hum. I believe that it was once I tied into the grids, the problem surfaced. Probably better shielding and routing on those wires would have fixed it.

I remember reading about your mod earlier in the thread. It would have been a great mod if not for the hum. My solution is much less impressive. The jumper wire would just act as an extension to the jumper pins on the circuit board. Instead of needing to reach inside the amp with either pliers or tweezers it would be possible to just flip it over and change the jumpers on the male end of the jumper wire.

 

[lupoal]

@TrollDragon
thank you

 

[TrollDragon]

I remember reading about your mod earlier in the thread. It would have been a great mod if not for the hum. My solution is much less impressive. The jumper wire would just act as an extension to the jumper pins on the circuit board. Instead of needing to reach inside the amp with either pliers or tweezers it would be possible to just flip it over and change the jumpers on the male end of the jumper wire.

I think the jumper wires will work perfectly.

 

[triod750]

I have received my adapters and psu from @Deyan. I previously posted a photo of them. First one put to use is one made after MIKELAP:s design; 6AK5 to whatever - in my case ECC88, 6CG7, 6N6P etc.

Using this adapter I have been trying a NOS Mazda ECC804 as per previous recommendations from Gibosi and JazzVinyl. Until now C3g have been my endgame tubes as drivers with Melz 6H8C/6N8S and Melz 6H12C/6N12S. Although my ECC804 has few hours so far I have to say it has my preference with the music I have tried; an acoustical jazz quintet and Joe Bonamassa. It gives a better balance to the frequency range, a more natural tone to instruments and better texture to especially the upright bass. And the piano. And the trumpet. And the saxophone. And I can listen to Bonamassa at a much higher volume.
Most impressive.

Mind you- this is early impressions. I bet they won't change.

Thank you, Deyan, Gibosi, JazzVinyl.

I have plenty more combinations to explore. I'm happily retired.

 

[triod750]

Right now listening to Sylvania 6SN7W as driver and a pair of GE 6BX7GT as power. All adapters working well and dead silent background. All heaters fed from Deyan made PSU. Input is a tower of power - three stacked adapters. First ; bottom dual 6AK5 to single ECC88, next; bottom ECC88 with heater input to top ECC88 or, with the use of a switch, ECC81,82 or 83, next; ECC88 to 6SN7. On its way also; bottom ECC88 to 6N7. Forgot to mention the secret weapon; adapters with bottom 6SN7 to top dual GEC A2293. Thank you @Deyan

 

[triod750]

Today I have tried Tung-Sol Chatham 6080 with Mazda 804. First strong impression is that they in my amp are far behind Melz, both 6H8C and 6H12C, in presenting my jazz quintet in a natural way. Red Mitchell tuned his up-right bass like a cello. That was his trade mark. The sound is very special and T-S Chatham makes a blur of it. Even if these tubes could develop with use they are so far behind in this amp that it's highly unlikely they ever will be on par. Maybe for some other music but I doubt it.
(I'm well aware of that this circuit wasn't designed for this tube. 6H12C is much closer to what it was designed for).

I also tried a pair of 6H13C Winged C from 1963 that I have had waiting 'forever'. They are much closer to Melz and could very well become an interesting alternative, especially for other kinds of music. The right (for them) driver might make them deliver. Since they are NOS they might become even better. Right now they are 'leaner' than Melz. I have a few 6SN7 that might change this.

 

[triod750]

Today I have tried the pair of 6H13C first with Ken-Rad 6SN7GTA with a less favoured outcome and now with a Brimar 6SN7GT (marked with a P over a 4 to the left and 1 over a 4 to the right of the 'BRIMAR' on the socket. @gibosi will probably tell you what that means). This combination has a lot going for it. So much so that I don't want to make any changes for a while. I can't say that it is better than 804 with 6N12S but somewhat different. More agile maybe. More bite, but not overly so, at least not with this jazz quintet. (Yes, I will listen to something else too). But if you want to, you can find 'West of the moon' with Bosse Broberg, Gosta Rundqvist, Joakim Milder, Thomas Lofgren and, not least, Red Mitchell on Spotify. My version is better than that. I listen to CD. Semi-old school.

 

[MIKELAP]