Green, G9 and slowblow mic pre.

[sismofyt]

what Dave said. we don't have a lot of space here in europe so we have to compound everything.

you must float tubes if the heater to cathode potential becomes to big, like above 100VDC which often happens in srpp designs. the max value is noted in the datasheet of most tubes.

 

[Samuel Groner]

I love how the Europeans make compound words out of everything.

Probably mostly germanspeaking people, no? :razz:

Samuel

 

[Michael Krusch]

[quote author="Samuel Groner"]

I love how the Europeans make compound words out of everything.

.. germanspeaking...

Samuel[/quote]

german speaking :grin:

 

[clintrubber]

[quote author="NewYorkDave"]... I love how the Europeans make compound words out of everything :wink.
[/quote]
As you know, over here in Europe there are strong forces at work to unite & combine everything....
into one big uncontrollable entity - with its point of gravity in Brussels... (ehh, or Straatsburg ? :roll: )

...but rest assured, the French & the Dutch will stand strong :twisted: :wink:

 

[clintrubber]

[quote author="kubi"][quote author="clintrubber"]...but rest assured, the French & the Dutch will stand strong :twisted: :wink:[/quote]

Resistance is futile! :twisted:[/quote]

Dream on ! :wink:
Our government has recently approved buying Tomahawks ! :sad:

 

[sismofyt]

my country is the size of a NY subway station, sowearetight. if i lived in W_Y _O_M_I_N_G I W_O_U_L_D P_R_O_B_A_B_L_Y W_R_I_T_E L_I_K_E T_H_I_S

how are you all doing anyway?

 

[sismofyt]

eu rocks

 

[clintrubber]

[quote author="sismofyt"]eu rocks[/quote]
Sure, for so far. But about the stuff that's still up to us to decide about we'd like to think for ourselves :wink:

 

[FotisGR]

Sismofyt, i was thinking design a pcb for this mic pre ( i am really good on this).
:sad: I wish you don't shoot me if i do it...

Cheers
fotis

 

[sismofyt]

bang. pcp suck for tubes. P2P better, more fun and easier to fix

are you thinking about making a PCB for my new designs? don't bother, with only seven components and people probably using all kinds of different caps and trannies, it would be pointless

 

[FotisGR]

Today i received the LL transformers , new ceramic tube sockets and 4 nice HV 10uH/100mA (each for tube). So this weekend i will try to build again with better construction the 2 ch Slowblow's orgasm machine :grin:

Planning to use one 78S12 for each tube's heater , what about the heater biasing of each tube?
What is the better way to do it?
The voltage will be 50-60V for both 12AU7 and 5687?

Cheers
fotis

 

[rafafredd]

Have a look at my four channel tube mic pre box for a nice circuit for balanced tube heater biasing using 7812 regulator...

http://hps.infolink.com.br/rafafredd/bd1_bd11.gif

 

[Emperor-TK]

Fred, I have a quick noobie question about your bias circuit. How do you get a voltage drop across the two 100K resistors comming off B+? You would need 1.15 mA of current through the resistors to drop down to the 115V bias point. What is the driving force for this current, since there is no ground referenced in the 12V section?

Thanks,
Chris

 

[rafafredd]

The two 100k resistors works as a 200k resistor that forms a voltage divider with the other 100k (with the 270nF cap in parallel) resistor that goes to ground. So, you should have 1/3 of the B+ voltage, that equals 115v as a reference for the heaters.

I guess this is it.

For a lower reference voltage, like 50-60v, I would drop the 100k resistor value that goes to ground or raise the 200k value. Both methods should work fine, I guess. Pretty noob also. :?

 

[Emperor-TK]

Ahhh, I somehow missed that ground. I guess I saw that capacitor and thought only of noise filtering and didn't see what that section was really doing. It makes complete sense now, thanks Fred. :thumb:

I am much happier when I completely understand a small detail in a circuit, than when I loosely grasp the general concept of the whole circuit.

 

[FotisGR]

:shock: I didn't seen ever something like this . Thank you very much.
Cheeers
fotis

 

[sismofyt]

i mostly use a 50Kohm/5W pot for biasing, which also helps loading and bleeding the PSU. if you use 4x 7812 you should lift the (single) voltage going into the four Vregs, not lift each seperate output.

 

[ioaudio]

i know this question was already stated: whats the european sub for the 5687?

 

[sismofyt]

there is no sub

 

[sismofyt]

you can check for subs, datasheets etc here:

http://tdsl.duncanamps.com/tubesearch.php