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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 354

post #5296 of 7541

Got two new production tung sol 6SN7GTB's running as power tubes with a 6SU7GTY as the driver, AMAZING!

 

Bass is well defined, mids are very forward and real (I kept thinking my speakers were on), highs are super extended and sweet. and everything is crystal clear!

 

I love this combination!

post #5297 of 7541
Quote:
Originally Posted by mab1376 View Post
 

Got two new production tung sol 6SN7GTB's running as power tubes with a 6SU7GTY as the driver, AMAZING!

 

Great news!!

 

I have been waiting for someone to try running 6SN7s as power tubes in their LD. I was pretty sure that electrically, they would work fine, but I wondered how they might sound....

 

And I think 6SN7s might have less gain than the standard tubes.... So do you find that you are setting the volume a bit higher than before?

 

Oh.. and by "new production", do you have the Tung Sols made in Russia?

post #5298 of 7541

I am using a pair of Raytheon N.O.S. 6AK5 in the Mk II- absolutely stunning in the amp both as a headphone amp driving DT880 600ohm cans as well as a preamp feeding a Virtue Two.2 amp for my power loving Role Sampans.

post #5299 of 7541

900x900px-LL-d43b538a_Test.jpeg

1st Reading=5.09V    and     2nd Reading=5.09V

                                                                                                                                                                     

                                                                      

                                                                      IRF 630N

Thank You TD!


Edited by i luvmusic 2 - 3/9/14 at 5:17am
post #5300 of 7541
Quote:
Originally Posted by gibosi View Post
 

 

Great news!!

 

I have been waiting for someone to try running 6SN7s as power tubes in their LD. I was pretty sure that electrically, they would work fine, but I wondered how they might sound....

 

And I think 6SN7s might have less gain than the standard tubes.... So do you find that you are setting the volume a bit higher than before?

 

Oh.. and by "new production", do you have the Tung Sols made in Russia?

 

I normally play at 12 o'clock, with these i use 1 o'clock, so minimal difference.

 

and yes they're from russia.

post #5301 of 7541
Quote:
Originally Posted by mab1376 View Post
 

Got two new production tung sol 6SN7GTB's running as power tubes with a 6SU7GTY as the driver, AMAZING!

 

Bass is well defined, mids are very forward and real (I kept thinking my speakers were on), highs are super extended and sweet. and everything is crystal clear!

 

I love this combination!


Well done mab...indirectly you have me sleeping a little better at night as finally, at last, I have incontrovertible proof of my insanity - against all gibosi's sensible advice to try some cheaper 6SN7s first (sorry g!), I have bitten the bullet and gone for some Psvane CV181-T MKIIs (supposedly a step up from the Shuguang CV181-Z). If they come near (or even surpass?) your findings, I shall be a happy chappie...at least I will have achieved the look I seek...But , of course, it's very much down to how things partner each other, so I live in hope (not to mention patience...ie that darned slow boat!).

And I now realise it's not you I should blame for leading me astray - 'tis thou MORDY shouldst take the blame, viz your post saying things had gone quiet, and inciting to 'wake things up'!!.(Well, I can't blame myself now can I?!).

 

Perhaps you will be trying some of gibosi's musings on different 6SN7s as power tubes -  or are you now happy enough as things are?...

We wait with baited breath!...

post #5302 of 7541
Great to read good comments about 6sn7 as power tube!
My parts finally arrived and i am going to build my clean adapter in the next days.
Would you wish to see a picture by picture tutorial on how to assemble?
I think it could serve newbies (actually i am a tube wiring etc newbie, too XD) very well if they decide to build one...
And also i will give something back to the community!
Hopefully all works like i imagined! XD
Edited by CollectoR13 - 3/9/14 at 10:46am
post #5303 of 7541

Hi Dr4Bob,

 

Is it safe to smoke in the underground bunker? LOL....

 

Anyhow, way back then I tried several different 6AK5 Raytheon tubes. I found that the the only type I liked was from the 50's and had a large mica plate as the top one, and a much smaller mica plate underneath. The smaller plate did  not reach the glass envelope and was supported by the wires and pins underneath.

 

Is this the Raytheon tube you refer to?

post #5304 of 7541

Hi hypnos1,

 

Thank you for your kind comments. Truth is, I am perfectly happy to listen to the offspring of a 6SN7 and a 6DJ8. This baby is called 8FQ7 and made for Raytheon in Japan, probably by Hitachi. This tube has amazing clarity and musicality, and great treble and amazing bass detail and punch.

 

But I am not adverse to try 6SN7 as power tubes; I am just wondering if I am capable of building the adapters needed. Gibosi's solderless breadboard solution suits me fine,

 

 

Hi CollectoR13,

Please share with us how you build the adapters for the 6SN7 tubes as power tubes.

post #5305 of 7541
Quote:
Originally Posted by CollectoR13 View Post

My parts finally arrived and i am going to build my clean adapter in the next days.
Would you wish to see a picture by picture tutorial on how to assemble?
I think it could serve newbies (actually i am a tube wiring etc newbie, too XD) very well if they decide to build one...
And also i will give something back to the community!
 

 

Please do!

 

Currently, I am very happy with my ugly and easy, "wires-flying-everywhere" adapters. But I am sure that eventually I might want to put together some clean and "pretty" adapters, and I would much rather copy than invent! lol :)

post #5306 of 7541
Quote:
Originally Posted by mordy View Post
 

Please share with us how you build the adapters for the 6SN7 tubes as power tubes.

 

Or you can purchase a couple of pre-made adapters:

 

http://www.ebay.com/itm/1pc-6SN7-TO-6CG7-6FQ7-tube-adapter-for-you-amp-/191082280257?pt=US_Home_Audio_Amplifiers_Preamps&hash=item2c7d643541

post #5307 of 7541
Quote:
Originally Posted by hypnos1 View Post
 


Well done mab...indirectly you have me sleeping a little better at night as finally, at last, I have incontrovertible proof of my insanity - against all gibosi's sensible advice to try some cheaper 6SN7s first (sorry g!), I have bitten the bullet and gone for some Psvane CV181-T MKIIs (supposedly a step up from the Shuguang CV181-Z). If they come near (or even surpass?) your findings, I shall be a happy chappie...at least I will have achieved the look I seek...But , of course, it's very much down to how things partner each other, so I live in hope (not to mention patience...ie that darned slow boat!).

And I now realise it's not you I should blame for leading me astray - 'tis thou MORDY shouldst take the blame, viz your post saying things had gone quiet, and inciting to 'wake things up'!!.(Well, I can't blame myself now can I?!).

 

Perhaps you will be trying some of gibosi's musings on different 6SN7s as power tubes -  or are you now happy enough as things are?...

We wait with baited breath!...

 

Definitely give it a try with a 6SN7/6SL7/6SU7 driver tube if it doesn't seem all that impressive with the c3g's! I'm loving my 6SU7GTY.

post #5308 of 7541
Quote:
Originally Posted by i luvmusic 2 View Post
 

                                                                                                                                                                     

                                                                      

                                                                      IRF 630N

Thank You TD!

 

Sorry been out all day long and wasn't able to make this post for you.

 

The 12AU7 is run in 6V mode.

 

Are you sure that those two are IRF 630N's? They are the output mosfets and should be on the other side?

Ok then what are the numbers of the two on the other side? ;)

 

The LM317 max's out at 1.5A, it provides the current for the mosfets and the 12AU7 filament.

 

So you can test it by running wires out to a socket matching both sides of the 12AU7  Anode / Gate / Cathode with the 6SN7 pins.

You will use pin 5 and 9 from the bravo socket for your octal filaments, it does not matter which way you hook them up to the octal socket, 5 to 7 and 9 to 8 or vice versa.

 

The LM317's will probably get a LOT hotter from the doubled current draw, you will have to watch for this and if it gets TOO hot, I'd just forget about the octal in the bravo amp.

 

Thinking about this further, the two LM317's (to be confirmed by ILM2) are providing 6V to each side of the 12AU7's filaments with the center tap to ground. This also provides a load for the LM317 and for the IRF 630N mosfets. So no you will not be able to run a 6SN7 tube easily. I can't tell you to jumper pin 4 and 5 to 9 with a resistor and use an external power supply on the tube as I do not know what size and wattage resistor you would need to make this work.

Sorry.:(

 

You can feel free to experiment, but you do it at your own risk to the amp.

:beerchug:


Edited by TrollDragon - 3/9/14 at 5:53pm
post #5309 of 7541
Quote:
Originally Posted by TrollDragon View Post
 

Sorry been out all day long and wasn't able to make this post for you.

 

Thinking about this further, the two LM317's (to be confirmed by ILM2) are providing 6V to each side of the 12AU7's filaments with the center tap to ground. This also provides a load for the LM317 and for the IRF 630N mosfets. So no you will not be able to run a 6SN7 tube easily. I can't tell you to jumper pin 4 and 5 to 9 with a resistor and use an external power supply on the tube as I do not know what size and wattage resistor you would need to make this work.

Sorry.:(

 

You can feel free to experiment, but you do it at your own risk to the amp.

:beerchug:

 

Suppose we tie pins 4 and 5 together and then measure the resistance across pins 5 and 9 of a 12AU7, held in our hand, and not plugged in! Wouldn't this give us the value of the internal resistance of the tube's internal 6V heater circuit? Or is it just not that simple (as usual)?

 

Edit: Oops!! should be pins 4 and 5!


Edited by gibosi - 3/9/14 at 10:21pm
post #5310 of 7541
Quote:
Originally Posted by gibosi View Post
 

 

Suppose we tie pins 4 and 6 together and then measure the resistance across pins 5 and 9 of a 12AU7, held in our hand, and not plugged in! Wouldn't this give us the value of the internal resistance of the tube's internal 6V heater circuit? Or is it just not that simple (as usual)?


Tube filaments change resistance (goes up) when they heat up, it might be 4 ohms cold and 90 when hot.

 

The circuit uses the LM317's not in the same way your regulator does, such as put 12V in and adjust to 6V out. These are tied into the output of the mosfets through the tube filaments to ground like a constant current or voltage source.

 

The pictures do not show if pins 4 & 5 on the board are tied together, there might be a trace joining them under the socket. This could be measured with the amp shut off for a while to let the capacitors drain, then measure the resistance across pins 4 & 5 with the tube out and see if it is 0 ohms. If that is the case then 4 & 5 are most likely bridged and it might possibly just work with a 6SN7 using pins socket 5 & 9 to the octals 7 & 8.

 

ILM2 will have to decide if he wants to experiment with this and see. :D

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