[gibosi]

  Found the information for the current draw of the EF91 and EF92 families of tubes. These tubes are recommended for use in the Little Dot MKIII. Here are the values:
 
The EF91 draws significantly more current (300mA) compared to the EF92 (200mA) and EF95 (175mA) families. (The source is post #2 on this blog!)
 
Am I correct that with a design parameter of 300mA  current draw the LD should be able to handle 6AS7 tubes?

 
There are essentially two circuits. One to supply current to the heaters and the other to supply current to actually run the amp. The values quoted above refer to the heater circuit. For the 6AS7, you are using an external heater power supply to provide 2.5 amps to heat the heaters. What is burning up resisters and perhaps killing transformers involves the other circuit. And again, the LD is designed for a maximum current of 100ma to actually run the amp, the driver and the output tubes. The 6AS7's want 80ma each, or 160ma for two. This excessive current may well damage the amp.

 

[lemonjelly]

Hi because it's interesting and it helps me to learn this stuff as well.. I drew some load lines on the valve curves to try and show what's happening:
 
6AS7:
 

6n6p:
 

 
I've only really learnt all of this stuff in the last month, but I *think* this is right.  So basically the load line is for the plate resistance we're using (I was using 120ohm for the power tubes) and then I've plotted the cathode voltages that I have.  So if you change the cathode bias voltage (via changing the resistance or whichever method) then you move up and down the line.  If you change the plate resistance then the line becomes steeper if you decrease, and less steep if you increase.
 
So you can see with the 6n6ps you move up and down from ~25ma, while with the 6AS7s you're moving down from over a 100ma.  The measurements aren't that exact... I just scribbled them down while modding so I wouldn't say the load line is that accurate, but it does to show what's happening.
 
So if you wanted to get the current on the 6AS7s down to 40ma then you would increase the cathode resistance to:
V = IR, ~65v = 0.04A * R, R = ~1600ohms.  And for that resistor you would need a rating of:
P= VI, P = 65v *.04A = 2.6W so you'd need probably at least a 3W resistor.

 

[hypnos1]

   
There are essentially two circuits. One to supply current to the heaters and the other to supply current to actually run the amp. The values quoted above refer to the heater circuit. For the 6AS7, you are using an external heater power supply to provide 2.5 amps to heat the heaters. What is burning up resisters and perhaps killing transformers involves the other circuit. And again, the LD is designed for a maximum current of 100ma to actually run the amp, the driver and the output tubes. The 6AS7's want 80ma each, or 160ma for two. This excessive current may well damage the amp.

 
Hi gibosi....It's certainly looking more like the resistors all the time, lol! - those in the Little Bear P8 to come look MUCH more up to the job...lovely fins on 'em, and TWO for the one 6AS7 (equiv)...pics below...

 

  Hi because it's interesting and it helps me to learn this stuff as well.. I drew some load lines on the valve curves to try and show what's happening:
 
6AS7:
 

6n6p:
 

 
I've only really learnt all of this stuff in the last month, but I *think* this is right.  So basically the load line is for the plate resistance we're using (I was using 120ohm for the power tubes) and then I've plotted the cathode voltages that I have.  So if you change the cathode bias voltage (via changing the resistance or whichever method) then you move up and down the line.  If you change the plate resistance then the line becomes steeper if you decrease, and less steep if you increase.
 
So you can see with the 6n6ps you move up and down from ~25ma, while with the 6AS7s you're moving down from over a 100ma.  The measurements aren't that exact... I just scribbled them down while modding so I wouldn't say the load line is that accurate, but it does to show what's happening.
 
So if you wanted to get the current on the 6AS7s down to 40ma then you would increase the cathode resistance to:
V = IR, ~65v = 0.04A * R, R = ~1600ohms.  And for that resistor you would need a rating of:
P= VI, P = 65v *.04A = 2.6W so you'd need probably at least a 3W resistor.

 
Nice work, lj...I think the LD's is 1W...so the poor thing certainly has been working hard lol!...

 
Anyway, just thought you guys might like to see the cheap chappie on its way...
 

 
But mine will have the toroidal transformer...
 
This metal-cased version should have innards like so....
 
 

 
And...
 
Are American "Dale" resistors good ones, as they are being made out to be?
 
I DO like the look of those 2 finned ones, though!
 
So, it's going to be VERY interesting to see what this baby can do, with my GEC 6AS7G driven by either my C3GSs - if possible - or a pair of 5687s in place of the 6N3Ps (whichever, I've got a bit of work on my hands! But looking forward to it, nonetheless...).

 

[i luvmusic 2]

What i'am interested in is this DarkVoice 336SE.

 

[TrollDragon]

What i'am interested in is this [COLOR=333333]DarkVoice 336SE.[/COLOR]

I would go with the La Figaro 336C, looks much nicer and was my first choice before the MK IV.

http://www.yuking09.com/336c.asp

 

[i luvmusic 2]

 

What i'am interested in is this DarkVoice 336SE.

I would go with the La Figaro 336C, looks much nicer and was my first choice before the MK IV.

http://www.yuking09.com/336c.asp

Are they the same amp in defferent  chassis?

 

[TrollDragon]

I don't know the history behind them both but they are the same design. I just liked the 336C's layout and looks better.

 

[i luvmusic 2]

 What i don't like about the crack is by using 6SN7 it sucks not to my liking lack of power and details.I invested in 6AS7G/6080 and 6SN7 tubes for the crack but unfortunately 6SN7 and crack are no no for me that is why if i will get another amp i need something that is good for 6SN7 and 6AS7/6080 so my tubes are not going to be dust collector.I don't want to spend more $ on tubes i would like to use what i have,so far i have no choice but to get more 12AU7's i only have 4 and 2 of them i don't really like they sound flat/weak in bass.MK III with 6SN7 is wonderful that is why i have no plan on getting rid of this amp. 

 

[i luvmusic 2]

I don't know the history behind them both but they are the same design. I just liked the 336C's layout and looks better.

I like the P2P wiring they are easy to work with than PCB's IMO that is. 

 

[superdux]

 
Anyway, just thought you guys might like to see the cheap chappie on its way...
 

 

 
Hi Hypnos,
 
whats the name of the amp? I'm old, so i can hardly read the writing on the frontplate

 

[genclaymore]

Its Little dot

 

[TrollDragon]

That amp is the Little Bear P8.

 

[gibosi]

   What i don't like about the crack is by using 6SN7 it sucks not to my liking lack of power and details.I invested in 6AS7G/6080 and 6SN7 tubes for the crack but unfortunately 6SN7 and crack are no no for me that is why if i will get another amp i need something that is good for 6SN7 and 6AS7/6080 so my tubes are not going to be dust collector.I don't want to spend more $ on tubes i would like to use what i have,so far i have no choice but to get more 12AU7's i only have 4 and 2 of them i don't really like they sound flat/weak in bass.MK III with 6SN7 is wonderful that is why i have no plan on getting rid of this amp. 

 
You have tried 6SN7's in the Crack and they don't sound as good as they do in your MK III??? I am very surprised! The MK III uses two output tubes, whereas the Crack uses only one.... And I assume you are using two 6AS7's in the MK III? And if so, I wonder if that could be the difference......

 

[kvtaco17]

   What i don't like about the crack is by using 6SN7 it sucks not to my liking lack of power and details.I invested in 6AS7G/6080 and 6SN7 tubes for the crack but unfortunately 6SN7 and crack are no no for me that is why if i will get another amp i need something that is good for 6SN7 and 6AS7/6080 so my tubes are not going to be dust collector.I don't want to spend more $ on tubes i would like to use what i have,so far i have no choice but to get more 12AU7's i only have 4 and 2 of them i don't really like they sound flat/weak in bass.MK III with 6SN7 is wonderful that is why i have no plan on getting rid of this amp. 

Get a Glenn OTL amp...

 

[hypnos1]

   
Hi Hypnos,
 
whats the name of the amp? I'm old, so i can hardly read the writing on the frontplate

 
Hi superdux...yep, TD's right - Little Bear P8. They come in different flavours...acrylic "open" jobs, or metal-cased (silver or black) with the option of toroidal transformer for just another $10.
 
Wish there was more info out there from users...at least I shall be able to assess without any preconceptions, lol! (But I will be VERY harsh in my comparison to the ill-fated experiment with the MKIV SE + C3GSs + GEC 6AS7Gs!!...this poor little thing might be doomed before it's even arrived

...).
 
 
Despite fear of repetition, the more I read other peoples' feedback on different amps and tube combos, the more I am convinced that the partnership of C3G and 6AS7G (especially the Chatham, and even more so, the GEC family versions) is a truly wondrous one...so long as you have an amp you can put them in lol!).
 

  Get a Glenn OTL amp...

 
Hey, kvt, you payin'?...If so, put me down for one

.