CCS plate follower 12bh7 schematic needed pls

[milen007]

hi guys

anyone got the schematic of CCS anode follower of 12bh7 to share?

i got pair of 12bh7 and would like to try out. i got zero knowledge in design. but have build a PTP preamp base on working schematic.

thanks in advance

erwin

 

[SGregory]

I fyou want to keep it simple for learning and decent performance use a 10M45S. One to220 and two resistors and you have a load. Easy P2P.

 

[milen007]

hi SGregory

thanks for the reply, however my electronic knowledge is very limited though i learn as i go. but i still not sure bout your suggestion.

would you kindly elaborate?

thanks,
Erwin

 

[cjkpkg]

SimpleSE Schematic

An externally hosted image should be here but it was not working when we last tested it.

Check the Tubelab link to the SimpleSE schematic for HOW to implement for plate loading a 10M45. The above chart guides you to what value resistor you need for the amount of current you desire. ~300 gives you 10mA. ~500 gives you 6mA ect...

 

[DF96]

If your electronic knowledge is very limited why do you think you need a CCS and anode follower? Is the CCS used to bias it (at the cathode) or load it (at the anode)?

What is the application? What gain and input impedance do you need?

 

[euro21]

12BH7a PF

12BH7 preamp, 15mA CCS.

 

[DF96]

12BH7, but not an anode follower, just a normal grounded-cathode stage.

 

[euro21]

True.

 

[euro21]

Is this correct?

 

[milen007]

If your electronic knowledge is very limited why do you think you need a CCS and anode follower? Is the CCS used to bias it (at the cathode) or load it (at the anode)?

What is the application? What gain and input impedance do you need?

Because my 1st srpp ptp that has gain of 6 is to high for my system

Someone told me that i need a simple stage. He also told me that ccs anode follower will sound better than the simple stage

Checking from web. from John Broskie's Guide to Tube Circuit Analysis & Design, Anode follower ia just adding another stage

http://www.tubecad.com/2007/05/blog0105.htm

I need gain around 2-3. Input impedance is not very important as the cap grom mu dac is big enough. Can handle any reasonable or normal input impedance

Thanks very much

 

[milen007]

Is this correct?

thanks euro for the schematic. yeah i can handle this. wondering why the c2 is that high? 22uf? is this proven schematic or from simulator? as i need to know so when i counter any problem i know where is the fault.

sorry bout my ignorant. i assume the input is V2 right?

thanks again for the time and effort

 

[DF96]

Is this correct? (post #9)

Yes, that is an anode follower. It will have a voltage gain a bit below 10, and an input impedance a bit above 1K which is rather low for a line stage.

A simple anode follower with a gain of 2-3 is difficult to design, unless you are not too bothered about noise. This is because the feedback resistor and the input series resistor are in the ratio 1:2-3. This means that either the input resistor has a high value (which creates thermal noise) or both resistors are low which both loads the input and the valve. Having a low value feedback resistor negates the whole point of having a CCS load. I suppose a reasonable compromise is input 10K and feedback 22K.

I suppose the real question is: what is a good circuit for a low gain line stage?

 

[milen007]

hi DF96

yes. thats the question. its no point building a line stage that sounds bad

 

[euro21]

I suppose the real question is: what is a good circuit for a low gain line stage?

For me it's the 12B4a CF preamp (cascode CCS 25mA, gain=6.5).

 

[milen007]

hi euro21

how could a CF gain is 6.5? isnt it suppose to be gain of 1?

mind share the schematic? thanks in adv

erwin

 

[euro21]

Correcture: grounded cathode. :-(

Same as post 6.

Rk=470R, Ck=100u, RsetCCS=50R, B+=160V.

 

[milen007]

ah.. gain of 6.5 is too high in my systems. help guys

 

[DF96]

Possibly cathode-coupled amp, with some feedback to the second grid? This seems to be popular with some people, even when it is misnamed as a grounded-grid preamp. It is difficult to get down to a gain of 2-3 without using either attenuation or feedback.

 

[milen007]

hi DF96

so my best bet is using cathode follower?

as i am using an SS amp with gain of 2 give me a good range of volume control. however my tube pre though its gain is 6 floored this SS pre. hence that prompt me to build a tube pre.

i did some research that tube 26 give gain of 2-3. whats your opinion?

thanks,
erwin

 

[DF96]

CF gives a gain of 1, and may be unnecessary unless you have long cables - just use a volume pot. Do you actually need a preamp?

I don't know anything about 26, but I'm sure others on here can comment.