[lupoal]

thank you! very interesting
I've seen somewhere a mod with different caps, they barely fit in but seems was ok.... here
I've read somewhere else that the most useful mod was about power supply capacitors instead of output caps, I tried some tuning adding mass to LDII to lower resonance frequencies or dumping feets... but it never liked those care with, as result, dryer sound and, mainly, poorer bass
so because of that I'm a little scared in removing the transformer ... in the meantime talking with and audio engineer, in the field with success since decades, he explained me how important can be transformers in audio application and how big are differencies between transformers for common use and dedicated one (in terms of material, geometry, etc.) ... as this kind of transformers can cost easily more then the entire LD2 I'm thinking that all our games/efforts could are probably limited in results by poor quality transformer installed

in the meantime, to keep everything as fun and simple as possible I've done one of this ... is in burn-in now, under the fridge in the kitchen

 

[TrollDragon]

I installed switches in my MK IV to facilitate easy tube rolling, unfortunately they induced hum and microphonics. Too bad as it was very convenient.

Red up EF92, Black switches disabled.
Red down EF95, Black toggle strapping 1-7, NS or 2-7.

If the MK IV was easy to work on like the MK II, I would have tried to correct the problem. With the MK IV you have to unsolder the transformer to remove the board, then put it all back together for testing each time.

 

[Datun Walnut]

I installed switches in my MK IV to facilitate easy tube rolling, unfortunately they induced hum and microphonics. Too bad as it was very convenient.

Red up EF92, Black switches disabled.
Red down EF95, Black toggle strapping 1-7, NS or 2-7.

If the MK IV was easy to work on like the MK II, I would have tried to correct the problem. With the MK IV you have to unsolder the transformer to remove the board, then put it all back together for testing each time.

Shame. It's a nice looking mod.

 

[TrollDragon]

thank you! very interesting
I've seen somewhere a mod with different caps, they barely fit in but seems was ok.... here
I've read somewhere else that the most useful mod was about power supply capacitors instead of output caps, I tried some tuning adding mass to LDII to lower resonance frequencies or dumping feets... but it never liked those care with, as result, dryer sound and, mainly, poorer bass
so because of that I'm a little scared in removing the transformer ... in the meantime talking with and audio engineer, in the field with success since decades, he explained me how important can be transformers in audio application and how big are differencies between transformers for common use and dedicated one (in terms of material, geometry, etc.) ... as this kind of transformers can cost easily more then the entire LD2 I'm thinking that all our games/efforts could are probably limited in results by poor quality transformer installed

in the meantime, to keep everything as fun and simple as possible I've done one of this ... is in burn-in now, under the fridge in the kitchen

Output transformers in OTC tube amps are very important and usually make up the majority of the cost of those amps. The Little Dot MK 2/3/4 only uses a power transformer since it is OTL and should only affect the sound if it is not providing enough power, changing it would probably do nothing for you except possibly provide higher filament current to run 6AS7G or 6080 output tubes.

The power transformer in the Little Dot is a custom wound transformer with no off the shelf replacements available, so one needs to be careful rolling tubes that you don't draw too much current from the filament windings. Trying to incorporate a different transformer would require modifications to the power supply circuit of the amp.

If you are looking to turn your amp into something similar to the Woo WA6SE you might be better served actually picking up a WA6SE.

 

[TrollDragon]

Shame. It's a nice looking mod.

Yes I was quite stoked to incorporate it and if the MK IV didn't him when out of the case it would have been an easy fix.

 

[lupoal]

Telefunken EK90 + Sylvania 6SN7GTB --> amazing !

 

[Datun Walnut]

Telefunken EK90 + Sylvania 6SN7GTB --> amazing !

I've not heard an EK90. I suppose I'll have to buy more valves now.

 

[gibosi]

I've not heard an EK90. I suppose I'll have to buy more valves now.

Have fun!

https://www.head-fi.org/threads/lit...ube-rolling-guide.563884/page-77#post-9392055

 

[lupoal]

ok, the TNT TTS cable burn-in is over and I tested it and... do yourself a big favour, try it... the change in performance are simply unbelievable, at least for me that I'm cable skeptic... but... wow

here are very few words about it in an italian forum (google translator will help you easily)
--> click

 

[Datun Walnut]

ok, the TNT TTS cable burn-in is over and I tested it and... do yourself a big favour, try it... the change in performance are simply unbelievable, at least for me that I'm cable skeptic... but... wow

here are very few words about it in an italian forum (google translator will help you easily)
--> click

I'm afraid it won't sound good on mine - it went 'phut!' last night. LED flickers slightly on power up and there's a massive hum.

 

[lupoal]

really?

that cable? there must be something wrong somewhere... did you checked it for short circuit?
if "electrically" is fine it should give you in the worst case... nothing... not that bad result

 

[Datun Walnut]

really?

that cable? there must be something wrong somewhere... did you checked it for short circuit?
if "electrically" is fine it should give you in the worst case... nothing... not that bad result

I'm thinking the power supply side of things as the LED is off. I've ordered a capacitor tester. The smoothing caps are rated at 250v max yet the schematic shows the transformer has 175v output. After smoothing that dangerously close to the max of the cap.
I'm gutted, I love my liitle dot.

 

[Arro]

Great thread. I've using it as a reference to get the most out of my I+ and my MKIVSE.

Recently I've been looking at other Russian double triodes that might work as output tubes and I came across the 6N26P (6Н26П) among a few others. It can currently be found on eBay for around $30 a pair and is being sold as a 6H30P-DR alternative. It draws less heater current than a 6N6P but it has a plate voltage of 150, compared to the 6N6P's plate voltage of 120. It's pin out appears to be the same as the 5670. Would the 6N26P be safe to use in the Little Dot amps?
This is the closest I've come to finding a data sheet - http://www.russiantubes.com/prop.php?t=12&p=230

 

[gibosi]

Great thread. I've using it as a reference to get the most out of my I+ and my MKIVSE.

Recently I've been looking at other Russian double triodes that might work as output tubes and I came across the 6N26P (6Н26П) among a few others. It can currently be found on eBay for around $30 a pair and is being sold as a 6H30P-DR alternative. It draws less heater current than a 6N6P but it has a plate voltage of 150, compared to the 6N6P's plate voltage of 120. It's pin out appears to be the same as the 5670. Would the 6N26P be safe to use in the Little Dot amps?
This is the closest I've come to finding a data sheet - http://www.russiantubes.com/prop.php?t=12&p=230

While it is certainly safe, with the heater drawing only 0.6amps, I suspect that it will be somewhat under-powered as an output tube, similar to a 6SN7GT.

 

[TrollDragon]

I'm thinking the power supply side of things as the LED is off. I've ordered a capacitor tester. The smoothing caps are rated at 250v max yet the schematic shows the transformer has 175v output. After smoothing that dangerously close to the max of the cap.
I'm gutted, I love my liitle dot.

Check to see if you have AC off of the transformer and what is coming out of the DC side, possibly fried the bridge rectifier... Should be easy enough to hunt down.