Hi,
What you have now is a resistively loaded anode follower, cap coupled.
If the anode resistor is replaced by a choke you'll have to lower B+ to maintain the same operating points and you'll still have cap couple the output.
With an SE OPT you'll have the choke load, no more cap and the possibility to lower the output impedance. Moreover you'll also benefit from the ground isolation the xformer offers.
Cheers,
What you have now is a resistively loaded anode follower, cap coupled.
If the anode resistor is replaced by a choke you'll have to lower B+ to maintain the same operating points and you'll still have cap couple the output.
With an SE OPT you'll have the choke load, no more cap and the possibility to lower the output impedance. Moreover you'll also benefit from the ground isolation the xformer offers.
Cheers,
One word: money.
It was just a suggestion. I guess Hammonds cost something like 1/10 of the prize for a pair of Baccoluchi (sp?).
If money isn´t a problem there´s absolutely no reason to use Hammonds instead of "proper" platechokes, but I guess I´m not the only one that thinks twice about paying ~300 bucks for a pair of chokes.
We can always take a deeper look into our goals here. Is it to build the best linestage in the world or is it about having some fun with our hobby and build something cool and maybe learn something during the time?
I don´t know and honestly I don´t care either, I just wanted to make a suggestion about chokes that might be used.
And, as some might have noticed, I can´t stay away when chokes are being discussed
BTW: I don´t mean to sound aggresive here.
My preamp is from MCcaps i just took from http://www.diyparadise.com/12B4pre.html
It's sound good... but heard that people modified this amp in to choke load. since i don't have knowledge about choke load... then i ask you guys for help....
and i knew that there's someone who can help me....
well.....thanks guys... i'll try using 100H choke... and lowering B+ based on DCR of choke itself....
Thanks all.....
It's sound good... but heard that people modified this amp in to choke load. since i don't have knowledge about choke load... then i ask you guys for help....
and i knew that there's someone who can help me....
well.....thanks guys... i'll try using 100H choke... and lowering B+ based on DCR of choke itself....
Thanks all.....
Hi Ferry
If you use the 100H choke ( insted of 12k res) , you can safely avoid the cathode capacitor with little loss of gain (.7 db
if the load is 50k).
So you avoid a problematic component
(360u cap are not transparent as 1u polyprop caps.)
gain (db) with 50k load ( paralleled with 470k):
.......................with cap.................without cap
res ............... 6.2(15.9)...................4.5(13.1)
choke............. 6.7(16.5)..................6.17(15.8)
bye
Federico
If you use the 100H choke ( insted of 12k res) , you can safely avoid the cathode capacitor with little loss of gain (.7 db
if the load is 50k).
So you avoid a problematic component
(360u cap are not transparent as 1u polyprop caps.)
gain (db) with 50k load ( paralleled with 470k):
.......................with cap.................without cap
res ............... 6.2(15.9)...................4.5(13.1)
choke............. 6.7(16.5)..................6.17(15.8)
bye
Federico
And these are the plate characteristics for 12B4A
I use , fitted from Frank's electron tube pages.
http://www.mif.pg.gda.pl/homepages/frank/sheets/093/1/12B4A.pdf
Maybe, some differences?
bye
Federico
I use , fitted from Frank's electron tube pages.
http://www.mif.pg.gda.pl/homepages/frank/sheets/093/1/12B4A.pdf
Maybe, some differences?
bye
Federico
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