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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 403

post #6031 of 10506
Quote:
Originally Posted by gibosi View Post

 

You sure can! I was thinking about doing this, but I just don't have enough room on my desk. With a couple of loctal breadboard sockets, you can connect G3 to the Cathode and G2 to the Plate using the compression terminal blocks and then you will have two nice pentode-strapped triodes. :)

 

Purchase two 8-pin breadboard loctal sockets for the C3g's. In each socket, tie pins 2 and 5 together, which straps Grid 3 to the Cathode. Tie pins 3 and 4 together, which straps Grid 2 to the Plate. Route pins 3 (Plate), 5 (Cathode) and 6 (Grid) in each of the two sockets to the corresponding pins in the two Vectors. And finally, hook up your heaters, either through the Vectors or an external heater PS.  This done, the C3g's are very properly strapped, per the textbook. as triodes, and "plugged" into the LD.

 

8-pin loctal                                    Vector

 

1 Heater                                         3 (or external PS) 
2 Grid #3 to pin 5 in socket
3 Plate                                           5       
4 Grid #2 to pin 3 in socket
5 Cathode                                       2
6 Grid #1                                        1
7 Cathode 
8 Heater                                         4  (or external PS) 

 

(It is not necessary to tie pins 5 and 7 together, as they are already tied together inside the tube) 

post #6032 of 10506
Quote:
Originally Posted by i luvmusic 2 View Post
 

I tried running one side  6AS7 as a power tube and the other side is 6SN7 and driver is 6SN7 and the sound is lacking in power on 6AS7 side but it's smooth sounding. As for the amp did not get warm at all i run it for 15 mins.So far i can't try running two 6AS7 power tubes because my regulator can't handle the current(i just screwed up my 12A)

 

Hi ilm2.

 

Just back from my hols and I notice you've beaten me to it re. 6AS7 as power tube...WELL DONE! With low amplification factor, we will certainly need to be using 2 of same.

 

I'm glad your amp has not gone up in flames...gives me more confidence to continue with the experiment. However, even though you say the amp did not get warm, I have a horrible feeling things could go drastically wrong at almost any time...I would have thought a resistor could reach critical point with little warning as regards obvious external overheating (perhaps I'm being my usual over-anxious self!). Therefore, just to be extra sure I will be removing the front panel of my MKIV SE and be using a temperature probe - VERY CAREFULLY! - to keep an eye on things. Hopefully this may give a somewhat higher level of reassurance...(when I've managed to get everything sorted back in the house and garden, that is - holidays make a lot of work!!).

 

Quote:
Originally Posted by superdux View Post
 

good, i have some money spare.If it were always as easy and relatively cheap to get to audio heaven:) Do you think they´ll make a good matching with my HD650s?

 

Hi superdux.

 

In a word - or rather 2 - YOU BET! I never thought I would get such a sound from my 650s...truly a match made in heaven...

I do hope you managed to get those C3Gs...as gibosi said, it is not worth paying a great deal more for the 'S's, but I have to admit my pair did have the edge over the standard tubes...so if they can be found for not too much more, they are certainly worth the extra.

 

Good luck.

post #6033 of 10506

thats great hypnos1, i´m already eager as how the C3g will sound from my setup! But the delivery of the adapters will take a few weeks from China if they don´t also get stuck in customs too, as stuff usually does that i order from China.

 

Also i'm happy to say that i was highest bidder on the 4 used c3g's and it was a reasonable price.Someone from this board is also inclined to make joint effort and i will forward 2 tubes to him.

 

Thats what i like about this board, as i have met members that trusted me and sent items before me being able to pay as i'm usually broke.

Tubes and adapters have cost me approx. ~250Euros so far and i plan to put an end to spending after i have the c3g's.My brother always laughs at me when i tell him i want to put my bank account back to black numbers.

post #6034 of 10506
Quote:
Originally Posted by hypnos1 View Post
 

 

Hi ilm2.

 

Just back from my hols and I notice you've beaten me to it re. 6AS7 as power tube...WELL DONE! With low amplification factor, we will certainly need to be using 2 of same.

 

I'm glad your amp has not gone up in flames...gives me more confidence to continue with the experiment. However, even though you say the amp did not get warm, I have a horrible feeling things could go drastically wrong at almost any time...I would have thought a resistor could reach critical point with little warning as regards obvious external overheating (perhaps I'm being my usual over-anxious self!). Therefore, just to be extra sure I will be removing the front panel of my MKIV SE and be using a temperature probe - VERY CAREFULLY! - to keep an eye on things. Hopefully this may give a somewhat higher level of reassurance...(when I've managed to get everything sorted back in the house and garden, that is - holidays make a lot of work!!).

 

 

Hi superdux.

 

In a word - or rather 2 - YOU BET! I never thought I would get such a sound from my 650s...truly a match made in heaven...

I do hope you managed to get those C3Gs...as gibosi said, it is not worth paying a great deal more for the 'S's, but I have to admit my pair did have the edge over the standard tubes...so if they can be found for not too much more, they are certainly worth the extra.

 

Good luck.

I tried mine with 1 6AS7(Driver Tube) so your expirement would different from what i did take extra caution.I would love to try 2 6AS7 power tube but that would take sometime i'am still waiting for my 12A regulator.I'am tempted to get those C3Gs but in few months i will be backhome then i will get the Bottlehead Crack and i know that the 6SN7 will work with Crack so i'm OK with that but for C3Gs i'm not sure if it's compatible with crack.

post #6035 of 10506
Quote:
Originally Posted by i luvmusic 2 View Post
 

......I'am tempted to get those C3Gs but in few months i will be backhome then i will get the Bottlehead Crack and i know that the 6SN7 will work with Crack so i'm OK with that but for C3Gs i'm not sure if it's compatible with crack.

 

We don't know... The Crack's default driver is a 12AU7 configured in 6-volt mode. C3g's are pentodes, so you would need to build an adapter to convert them to triodes and connect them to the 12AU7 socket. But this is just "sockets and wires" and we know how to do that. What we don't know is if triode-strapped C3g's have too much gain.

 

I have read that 12AT7's with a gain of around 70 and 12AX7's with a gain of around 100 will not work in the Crack. Too much gain. The gain of the 12AU7 is about 20, about the same as the 6SN7. I have read that folks have had good success running 6DJ8's, with a gain of 33, in the Crack. So I think we know that tubes with a gain between 20 and 33 are compatible with the Crack.

 

I believe a triode-strapped C3g has a gain of around 40. This is twice as high as the tube the Crack was designed around, the 12AU7. So the C3g might have too much gain for the Crack.... or it might just be fine.....

 

When you get your Crack, I hope you will give them a try and tell us how the sound. :)

post #6036 of 10506

I'm not sure if already mentioned, but there are 3 versions of C3g:

 

the C3g with 8 pins (those must be the ones we can use for our LD's)

 

http://www.radiomuseum.org/tubes/tube_c3g.html

 

the C3g new with pin 5 missing

 

http://www.radiomuseum.org/tubes/tube_c3g_newi.html

 

and the C3g old with 9 pins and no serial fabrication.

 

http://www.radiomuseum.org/tubes/tube_c3g_old.html

 

sorry, the links are all in German, but you can see the mapping of the pins.

 

I guess there could be problems if you plugin the C3g new into a adapter?

 

Quote:
 Pentode for wide-band amplifiers (PTT)from SN 10001 onwards with a different base diagramme in respect to C3g_new.

Important Note:
Already in WWII a pentode named C3g was developed. We call it C3g_old.
After the war, a pentode with different spec's was produced also named C3g. SN 501 to 10000. For clarification we call those C3g_new.
This document shows the final version of the C3g, which was produced in large numbers.
In case the final factory-tests of a C3g revealed a transconductance equal or higher than 105% of the nominal value ( 14000 µmhos), these tubes were marked with the suffix /s. C3g/s

Edited by superdux - 5/5/14 at 6:48pm
post #6037 of 10506

I did not know about these other versions! And yes, if one was to obtain these other versions, it would be necessary to rewire the socket, and for the C3g_old, the heater voltage is 18 volts, instead of 6.3. However, I would guess that these earlier versions are very rare and probably don't turn up very often. I know that I have never seen them.... But for sure, it is good to know that they exist.

 

Thanks! :)

post #6038 of 10506

you´re right gibosi, the other versions had either a serial number from 501 to 10000 and the second one didn´t go into mass production.

btw. i contacted the seller of those adapters and he has added 2 extra fotos to his auction where you can see a different socket from the one initially presented and he can only deliver them atm.

 

see ebay auction nr.:301131714830

post #6039 of 10506
post #6040 of 10506
Here is a great tip for posting eBay links, I'll use mordy's link as an example.

If you chop off everything from the "?" back it gets rid of all the eBay tracking / referral stuff.

www.ebay.de/itm/R208-Siemens-C3m-Hochfrequenz-Verstarker-Pentode-ca-1941/160715042053

Much cleaner link and no nosey foolishness attached. smily_headphones1.gif
post #6041 of 10506
Quote:
Originally Posted by superdux View Post
 

thats great hypnos1, i´m already eager as how the C3g will sound from my setup! But the delivery of the adapters will take a few weeks from China if they don´t also get stuck in customs too, as stuff usually does that i order from China.

 

Also i'm happy to say that i was highest bidder on the 4 used c3g's and it was a reasonable price.Someone from this board is also inclined to make joint effort and i will forward 2 tubes to him.

 

Thats what i like about this board, as i have met members that trusted me and sent items before me being able to pay as i'm usually broke.

Tubes and adapters have cost me approx. ~250Euros so far and i plan to put an end to spending after i have the c3g's.My brother always laughs at me when i tell him i want to put my bank account back to black numbers.

 

Hi again superdux.

 

I think I am fairly safe in saying that once you hear what the C3gs can deliver, you will feel quite happy "putting an end to spending"...BUT - what about the power tubes?! I am currently listening to some of my favourite music - Clannad's 'Past Present' (Irish progressive acoustic/electronic folk) - and after just 2 weeks' absence I had almost forgotten how mind-blowing is the combination of MKIV SE/C3gSs/Psvane CV181 TII & Tung Sol 7N7/HD650s...I simply cannot imagine anything bettering what is entering my ears and brain...AWESOME!! (Why am I even contemplating the 6AS7s as power tube experiment? - I haven't a clue!!...yes I have : it's called tube-rolling mania/addiction! Heaven help us, lol:confused_face(1):

 

I look forward to your impressions when those adapters finally arrive...you have my sympathies re the long wait! Patience mon ami/mein freund/amico mio...

Quote:
Originally Posted by superdux View Post
 

I'm not sure if already mentioned, but there are 3 versions of C3g:

 

the C3g with 8 pins (those must be the ones we can use for our LD's)

 

http://www.radiomuseum.org/tubes/tube_c3g.html

 

the C3g new with pin 5 missing

 

http://www.radiomuseum.org/tubes/tube_c3g_newi.html

 

and the C3g old with 9 pins and no serial fabrication.

 

http://www.radiomuseum.org/tubes/tube_c3g_old.html

 

sorry, the links are all in German, but you can see the mapping of the pins.

 

I guess there could be problems if you plugin the C3g new into a adapter?

 

 

Wow! I never knew that...well found, superdux.

 

Yo, it's the 8-pin version we certainly need...

 

As for the 'S' version being merely one with higher transconductance, I am wondering why the top of the S's tube is slightly flatter than the standard tube? Ah well, the wonderful vagaries of tube land!


Edited by hypnos1 - 5/6/14 at 11:26am
post #6042 of 10506
Quote:
Originally Posted by gibosi View Post
 

 

We don't know... The Crack's default driver is a 12AU7 configured in 6-volt mode. C3g's are pentodes, so you would need to build an adapter to convert them to triodes and connect them to the 12AU7 socket. But this is just "sockets and wires" and we know how to do that. What we don't know is if triode-strapped C3g's have too much gain.

 

I have read that 12AT7's with a gain of around 70 and 12AX7's with a gain of around 100 will not work in the Crack. Too much gain. The gain of the 12AU7 is about 20, about the same as the 6SN7. I have read that folks have had good success running 6DJ8's, with a gain of 33, in the Crack. So I think we know that tubes with a gain between 20 and 33 are compatible with the Crack.

 

I believe a triode-strapped C3g has a gain of around 40. This is twice as high as the tube the Crack was designed around, the 12AU7. So the C3g might have too much gain for the Crack.... or it might just be fine.....

 

When you get your Crack, I hope you will give them a try and tell us how the sound. :)

In that case i'm not jumping into C3g wagon i will wait until i get my crack then get some nice 6AS7/6080 tubes because i know i can used these tubes with my LD amps.

post #6043 of 10506

Thanks for the info G!

post #6044 of 10506

I can barely keep up with all your different tube configurations!

 

On another note, can anyone share experience of the Little Dot I+ paired with an LCD-XC? or perhaps another LD model which is more suitable to drive the planars? Many thanks!

post #6045 of 10506
Quote:
Originally Posted by Rossliew View Post

I can barely keep up with all your different tube configurations!

On another note, can anyone share experience of the Little Dot I+ paired with an LCD-XC? or perhaps another LD model which is more suitable to drive the planars? Many thanks!
I ran the LCD-3's with the MK IV for a few weeks on the Burson Loaner program and really enjoyed the sound from the Audeze's with the tubes, my only comparison was the DT880's and the LCD-3's do everything in spades compared to the beyers.

The MK IV had plenty of power compared to the Conductor SL's 2 watts of output, I didn't find it lacking in drive power by any means. I even ran the LCD-3's from my FiiO E09K with good results.

I miss the Audeze's, incredible sound and plush earpads. smily_headphones1.gif
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