F5Turbo Illustrated Build Guide

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alexkosha

alexkosha

Member
Joined 2013
Main when both monoblocks on power is 117VAC. Transformer mains receive 116.5VAC probably due to thermistor. Transformer output is 23.6 VAC. PSU out is 28.9VDC.

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A

AndrewT

R.I.P.
Joined 2004
alexkosha said:
BTW, I mistaken with my transformer. I have Antek AN-8412 - 800VA 12V: AN-8412 - 800VA 12V Transformer - AnTek Products Corp
Click to expand...
Alex,
looking at the datasheet, I see it is a 115/230Vac 800VA transformer
They give test results using 120Vac to primary.
At 12Vac out, the regulation is up at 9.17%. That is exceptionally high for a 800VA transformer.
I suspect it would overheat pulling that 75.8Aac when driven @ 120Vac since it is outputing 910VA instead of 800VA.

If you reduce the input to 115Vac, then the 13.1Vac open circuit output becomes 12.55Vac. Now the apparent regulation when the output is loaded to 12Vac would be 4.55%. That is a more reasonable regulation value for a big toroid., maybe very slightly high, but OK.
But they don't show any data for 115:12Vac by 4off.
I can't tell what the real rating of this transformer is.
Shame Antek can't, or won't, adopt the standard transformer rating method.
It is 800 VA, 4x12V, 16A.
Click to expand...
That is spot on for a 4A bias and should run cool.
 
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alexkosha

alexkosha

Member
Joined 2013
I see. Thank you for that detailed explanation. Would you recommend to try mentioned Schottky rectifiers with low Vf in order to try to get higher output (about 32V with 4A bias)? Or or it is waste of time and money? They cost about $6 each and I need 16 pieces....


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alexkosha

alexkosha

Member
Joined 2013
Hi Andrew,

Second monoblocks is on (fully assembled) and my tube preamp is on. Tested first monoblocks is on, but PSU is disconnected from F5T front-end ...

1. Main in - 117.6VAC
2. Transformer 1st secondary - 24.33VAC
Transformer 2nd secondary - 24.35VAC
3. PSU output - +32.22VDC and -32.41VDC.


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A

AndrewT

R.I.P.
Joined 2004
working back from those numbers.
I'll assume the regulation is 5%
Vout = Vin/Vrated*Vsec*(1+regulation)
Therefore Vsec = Vout/Vin*Vrated/(1+regulation)
Vsec = (24.33+24.35)/117.6*115/1.05 = 45.34Vac
If the regulation is 5% then you have a 115:0-22.67, 0-22.77Vac transformer.
If the regulation is 8.2% you have a 115:22+22Vac transformer.
Simple measurements and a bit of arithmetic tells you a lot.
 
alexkosha

alexkosha

Member
Joined 2013
Since all settled in my head about max PSU Voutput under load, I need your opinion about Vripple and PSU output impedance.
Based on your point of view, does it make sense to try to use DC chokes on F5T PSU instead of let's say one or even all resistor in Pi? I know that Spencer uses crossover aircoils in his builds and he claims that ripple is x20 lower then in CRC.

About impedance sensitivity of F5T, I just curious if someone uses film caps to bypass Ele. Any improvement in sound? Do you bypass every Ele? What values/brands used?
Thank you.
 
A

AndrewT

R.I.P.
Joined 2004
rCRC is lower mains ripple than using rC
replacing the R with an R+L will slightly lower the mains ripple, but I guarantee that for all sensible values of L that you will not get anywhere near x20 lower (5%).

What will be lower for the rCRC and for the rC{R+L}C is the HF content of the output ripple.
 
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