D3a Russian equivalent recommendation

[artosalo]

want to skip source follower due to need 2 sections to get + and - 100V

The you have to skip the use of 811A too...

 

[supernut]

http://eestaff.kku.ac.th/~mongkol/E...c/Lecture36 MOSFET Common Drain Amplifier.pdf

Khonkhan U has stydy a bit

 

[supernut]

The you have to skip the use of 811A too...

Yes sorry for my humble knowlege. Source follower need to feed positive volatage to 811a.thank you for notify me. I am just want to build low budget amp with very little knowledge.

 

[supernut]

To save budget, does chinese 6p3p works? It just provide 20v 18ma to 811a. Does quality of tube effect?

6p3p in china is very cheap can save a lot of budget.

Then i use my old 5814a + RMB 30 of 6p3p to drive 811a

Thx

 

[supernut]

Connect (triode connected) pentode halve in parallel with the triode halve of 6F12P. Then you get almost D3A equivalent combination.

Any drawing picture possible?

 

[jcalvarez]

Thete are schematics showing EL509 G2 driven, in a similar, i.e. "control" grid current with poritive biad, but not the same situation.
https://www.diyaudio.com/community/threads/el509-jj-or-pl519.178773/

 

[supernut]

Thank you so much mr jcalvarez,

I just google for awhile and found 6SN7 drive 811A.

I still have 6SN7 left from my Cary AE1 and 45SE

I am thinking about this schematic too to save cost.

But it use low voltage compare to 600VDC of 12AU7 EL34 811a

And 10k 10watts resistor to drop 400V to 200v is too much. I might insert HV REG to drop it instead with big heat sink.

 

[jcalvarez]

I'm not sure I understand the purpose of the 10K 10W resistor:

It is connected to both the centre tap of the doubler and the final B+. If the designer needed 200V, why not get it from the centre tap of the doubler, which will be at a bit more than 200V?

 

[supernut]

Then designer has a flaw. I just contact a guy from China.

He will clone source follower for me. He had learn in his University. Then cost of 6L6GC OMIT

 

[supernut]

He also implement ROD COLEMAN R8
But i think AC FILAMENT is fine as my 45 no buzz no hum

 

[waltube]

Thank you so much mr jcalvarez,

I just google for awhile and found 6SN7 drive 811A.

I still have 6SN7 left from my Cary AE1 and 45SE

I am thinking about this schematic too to save cost.

But it use low voltage compare to 600VDC of 12AU7 EL34 811a

And 10k 10watts resistor to drop 400V to 200v is too much. I might insert HV REG to drop it instead with big heat sink.

First of all the 6SN7 is not good for this use
Then if the Ibias of driver is 15 mA x 100kohm = 1500 volts. !!!

Do you think that something is wrong?

 

[jcalvarez]

First of all the 6SN7 is not good for this use
Then if the Ibias of driver is 15 mA x 100kohm = 1500 volts. !!!

The 15mA are going through the 811 grid, not the 100K resistor.

 

[waltube]

Ops!
my error
But this tube is not fine for the job
The EL84 triode has lower Z and more current to deliver, for example

 

[Depanatoru]

https://geeseang.wordpress.com/811a-single-end-class-a2-audio-amplifier/

I'm not convinced at all that this is a good working schematic or just the guy's dreams ...
That 19mA , or what it is , the grid current , should be driving signal AC not a static DC current from driver , besides this the driver has non linear cathode resistor aka grid-cathode impedance of the power tube

 

[waltube]

In fact the grid current is not linear and this type of driver will suffer with great swing of signal

 

[Palustris]

This is from Jim Doyle's Flickr page. It seems rather clever to run the driver plate current off of the 811's grid current:
Class A2 811A amp amended to use
MQ Parafeed transformers. The original
Hammond OPT was converted into a plate load choke for the 811A. FYI - with Parafeed the performance is amazing, especially with bass!

​

 

[jcalvarez]

Ops!
my error
But this tube is not fine for the job
The EL84 triode has lower Z and more current to deliver, for example

I'd actually use something from the *CL series, like a PCL86, high mu triode plus triode-strapped beam tetrode section.

 

[supernut]

Dear mr Palutris, thank you so much for schematic need to calculate CHOKE value based on plate resistance of 811a

From datasheet there are so many values of plate resistance which value do I use to calculate L

 

[supernut]

For 6v6gt can I modify using russian 6p15 which i have unused from abolish 6p15 PP 10 watts i make 4p1l pp 8 w instead.

If can use 6p15 instead of 6v6gt will save cost

 

[supernut]

For someone whom concern about cost of OPT choke and power Transformer from previous post, i try to limit budget by order from local Bangkok and sometimes China.

Even efficient is not good as major company but suffice to me. These shops sell OPT for many years and have quite good experience. My 45 SE can push deep bass of " better be home soon' of andrea zonn quite well. Hence I am not concern much and quite confident in quality of these shops which do business more than 20 years