Spencerleehorton
Well-known member
its definetly a step down transformer right? 6:1 should be the right ratio i thought!!
as in mic side pri should be 6 and to socket should be 1.
as in mic side pri should be 6 and to socket should be 1.
U47 multi pattern build
- Thread starter Spencerleehorton
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Help Support GroupDIY Audio Forum:
rock soderstrom
Tour de France
right. Original BV08 is 6.5 to 1. EF80(0) will work with 7:1 or more, too.
Spencerleehorton
Well-known member
well the helarious mistake this time was i'd put in a 47mH inductor in place of a 1G resistor! looked pretty much the same!!!
all works perfectly now!! doh!!
all works perfectly now!! doh!!
rock soderstrom
Tour de France
Very good, you are always very creative with your mistakes!
I would solder another resistor into the position of the 20R so that you have some pre-filtering. How much voltage do you have at the input of the LM317 now?
Spencerleehorton
Well-known member
10v at input so as there is no noise i think im good?
rock soderstrom
Tour de France
Basically yes, but a small resistor at this point would still form a nice RC filter with the following large capacitor. With a 1R resistor, approx. 0.3V would be converted into heat, the LM317 would still have sufficient voltage to regulate and would become less warm. Win - win.
0.3A x 0.3V = 0.09W ---> 0.6W or 1W type resistor would be sufficient
Spencerleehorton
Well-known member
i'll see if i have a low 1watt resistor and put it in, thanks again for all your help bud
Accelerator
Active member
Yes, the BV.08 is definitely a microphone output step down transformer with 6.5:1 ratio.
The primary side of the 6,5 should be connected to the 1μF/250V coupling output capacitor - ground, the secondary side of 1 should be connected to the socket…
The BV.08 it is not the “perfect match” for the EF80(0) tube with 100KΩ plate load, but you came pretty close…
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Spencerleehorton
Well-known member
I’ve got a couple of 7:1 transformers on order so will check them out
Spencerleehorton
Well-known member
I put in 3 x 5R in paralell to get 1.6R in replacement of the 20R, all sounds good, it was pretty quiet anyways but probably even quiter now.
well worth building this version if youve got some fibreboard and some turrets, modding the psu was much less of a pain than building one from scratch, having all the diffferent polarities really helps as well and buying the bodies saved me so much hastle and looks so much better than my versions.
well worth building this version if youve got some fibreboard and some turrets, modding the psu was much less of a pain than building one from scratch, having all the diffferent polarities really helps as well and buying the bodies saved me so much hastle and looks so much better than my versions.
rock soderstrom
Tour de France
Perfect! Do you hear a difference in noise when you change the heater voltage? (6.3V vs. 5V). I would be interested to know how you see this.
