Little Dot Tube Amps: Vacuum Tube Rolling Guide
Aug 14, 2021 at 10:47 AM Post #12,721 of 12,769

TrollDragon

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I’m following a DIY forum to try to improve my knowledge about how to build a tube amplifier in “ classical” mode, without pcb
Good luck and have fun, there are thousands of amps designs out there to build on.


Building a PTP wired amp would be a great project, nothing looks nicer than PTP IMHO.
La Figaro 339.jpg
 
Aug 20, 2021 at 5:24 PM Post #12,722 of 12,769

Deleeh

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Little Dot 1+

Hello,
My repair on the Little Dot 1+ was slow at first with a few difficulties after the rebuild/repair.
Thanks to 2 guys who helped me Diy Threath to find the causes, he runs again.Here again a big thank you.

As a reminder, an electrolytic capacitor from the power supply was defective on one of the poles and the left tube socket was also defective.

I replaced the 2200uf/ 25 v electrolytic capacitors with the Audio Note standard ones. (Hificollektiv)
The 2 tube sockets were replaced by ones with gold pins and set a little higher for more stability.(Hificollektiv)
The Elna electrolytic capacitors were replaced with 470 uf/16 v Nichicon Fg.(Hificollektiv)
Replaced the film capacitors with 2 new ones from Mex.(conrad electronik germany)
Some of them were bent to 90 degrees, one was pressing on the PCB and the other on the tube socket.
Replaced the Rca sockets with Audio note ones and re-soldered the wiring with silver instead of copper.(Hificollektiv and supermarket)

I kept the standard values for the capacitors, but replaced them with higher quality ones.

I kept running the little one to give burn in in a few hours.
I used the Brimar Ef92 tubes.
I left the Opa original for now.
(more about that later)
Headphones are currently the Aeon R/T.

I was glad that it was running again.
During the burn in I noticed that the bass had increased a bit and that the treble range had gained a bit more shine (probably due to the Nichicon Fg).
This remained the same afterwards, and it was remarkable that the overall temperature of the device was reduced by quite a bit and remained stable throughout, even after 4 hours and more.
I suspect that the Audio Note standard electrolytic capacitors contribute a lot to this.

With time I noticed that I was missing a bit of the final touch that it had before.
I spontaneously remembered that I still have a Burson V5i Opa.
I used it and gave it some time.
I didn't like the Burson as much as the original Opa before the rebuild and found it more than a step backwards compared to the original.
I thought it coloured the sound a bit too much and the bass was a bit off.
After rebuilding and replacing the Elna's with the Nichicon Fg, I think the Burson suits it better.
I think it brightened up the stage a bit more, and the breaks and separations are more coherent and fit better together in terms of tuning.
And brings a bit more stage freedom and closer to the vocals.
The bass has also become crisper and more to the point with a bit of pressure and in the right place.

What I was still missing after the rebuild was the light syrupy and fluid flow of the music.
That came back with the Burson.
I am blown away even though I personally did not know much about capacitors etc.
The result was positively surprising and not even expected.

Finally, it is worth making the small investment.
The capacitors are not too expensive.
In fact, you would probably only have to replace the Elna with the Nichicon Fg to get right down to the cost with the Burson V5i.
I can't say whether the Audio Note standard really has an additional influence.
Possibly they do.
The most expensive will probably be the Burson, which costs around 50€ at the time.

It's a pity that Little Dot saved money because of two or four capacitors in order to do without a better result.
This would have been a good added value and would have reduced the failure rate.

You are welcome to use this excursion as inspiration from me or as help for a repair or tuning possibility.
If the results were not so good, I would have left it uncommented.Have fun,✌️.
 
Aug 23, 2021 at 7:12 PM Post #12,725 of 12,769

mordy

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Aug 23, 2021 at 7:43 PM Post #12,727 of 12,769

jonathan c

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Excellent, thanks. Looks like this will work excellently for the larger (preamp?) tubes, though the driver tubes are 7 pin.
The adapters should work for the seven-pin tubes if the tube pins are similar in thickness to those of the adapters. One question does come to mind. Do the tube sockets for the driver tubes have nine outer “holes”?
 
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Aug 24, 2021 at 3:04 PM Post #12,732 of 12,769

triod750

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Seven pin socket saver are just about impossible to find these days.
I don't know about other Little Dot models but the sockets in my MKIVSE seem like they can take a lot of abuse. I have changed tubes a lot and the grip is as snug as when I received the amp. Socket savers can be of help in the output position to isolate the chassis from heat though, depending on tubes used. 6SN7 and 6H12C run a lot cooler than 6N6P but since you use these with adapters you have extra isolation anyway.
 
Aug 24, 2021 at 4:21 PM Post #12,733 of 12,769

mordy

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Seven pin socket saver are just about impossible to find these days.
You can still find them, but some prices are crazy. The one to look for is this one - $49 at this site:
(TUA) TVS-7
Pomona 7 pin miniature tube socket saver test adapter. Eyelets for hook clip leads for each pin.
1629836012148.png

https://www.surplussales.com/Tube-Sockets/TubeSkts-1.html
There are some offers on eBay for better prices. As always, PP - Patience Pays, and if you take your time you will be able to find them at more reasonable prices.
Here is another listing for $23:
https://picclick.com/Vintage-Vector®-Model-7-Pin-Miniature-Extended-Tube-Socket-324705644406.html?refresh=1
One search tool, in addition to eBay, that I found useful is to bring up the item on Google Images and then click on individual items to see what is for sale:
https://www.google.com/search?q=7+pin+vacuum+tube+socket+tester+adapter&sxsrf=ALeKk03_-LWbQaPgHL13-svpmyXRt-V76Q:1629835752066&tbm=isch&source=iu&ictx=1&fir=O8Gd1L684PT5XM%2C7YGaq6-wA2Ta_M%2C_&vet=1&usg=AI4_-kRJC9KmaNy2abK4G1KJPi4jOX2tBw&sa=X&ved=2ahUKEwjJy6you8ryAhUuElkFHctLCVYQ9QF6BAgLEAE#imgrc=odefUf5trNhtMM

You can also try Leeds Radio:
https://www.etsy.com/shop/LeedsRadio?ref=shop_sugg


Good luck!
 
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Aug 25, 2021 at 11:04 AM Post #12,735 of 12,769

TrollDragon

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I don't know about other Little Dot models but the sockets in my MKIVSE seem like they can take a lot of abuse. I have changed tubes a lot and the grip is as snug as when I received the amp. Socket savers can be of help in the output position to isolate the chassis from heat though, depending on tubes used. 6SN7 and 6H12C run a lot cooler than 6N6P but since you use these with adapters you have extra isolation anyway.
Yes they are quite durable, I've have jumpers in mine as well as tubes with crooked pins etc. If they do get sloppy it would be easy enough to resolder a new pair of ceramic machined pin sockets onto the board.

Ceramic Sockets.jpg
 

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