I am using the store F4 boards for a BA output and had a question. What would it do to the input impedance of the BA2 output stage if i grounded the input? Also, would this affect performance of the tL431 regultor? I would like to try as standalone buffer without BA FE, but the impedance as is(about 7500 i thnk), is a little low.
😀
I always appreciate your honesty
I have the F4 boards wired without the input buffer as if it were a PP BA output. I have the BA3 FE setup seperately so that i can remove and add Ba2FE if i want. What i really want is to be able to plug any pre into it, but in order to do so without killing pre, I have to put a pull down resistor(whatever else it may be called) at the input, to ground the input and relieve that caps of their charge. NOt a problem for BA3 FE because of cap, but other pre's may not have this. By adding the resistor, what happens to the input impedance of the Ba2 output? and what affect does it have on TL431 operation.
I always appreciate your honesty
I have the F4 boards wired without the input buffer as if it were a PP BA output. I have the BA3 FE setup seperately so that i can remove and add Ba2FE if i want. What i really want is to be able to plug any pre into it, but in order to do so without killing pre, I have to put a pull down resistor(whatever else it may be called) at the input, to ground the input and relieve that caps of their charge. NOt a problem for BA3 FE because of cap, but other pre's may not have this. By adding the resistor, what happens to the input impedance of the Ba2 output? and what affect does it have on TL431 operation.
just put 100K bleeders directly on input ( either on pcb or on input connector)
they'll bleed , but they'll not burden
voilla !
they'll bleed , but they'll not burden
voilla !
Often in amps, this resitor determines the input impedance of the amp, will it be different in this case and what interaction does this resistor have with the TL431. Does placing it at the input cause it to be in parallel with the TL431 further reducing the input impedance?
you'll find somewhere info from Man with Silver Beard himself , about crippled input impedance ;
that fact wasn't worrying to me , so I didn't remember it ....... and I'm too lazy to calc it now .
100K or 220K or 330K or 470K .......... all of them will bleed enough to prevent any possible zapp! to preceding stage , while being irrelevant to both input impedance of crippled F4 itself and operation of biasing circ .
I hope I'm clear enough now , so don't huh! , please
that fact wasn't worrying to me , so I didn't remember it ....... and I'm too lazy to calc it now .
100K or 220K or 330K or 470K .......... all of them will bleed enough to prevent any possible zapp! to preceding stage , while being irrelevant to both input impedance of crippled F4 itself and operation of biasing circ .
I hope I'm clear enough now , so don't huh! , please
For some readon, I am getting positive voltage on negative rail with both channels hooked up. Using a variac and bringing up slowly, negative rail showing slight positive voltage and also voltage across speaker terminals. Terrible thing is, i have been here before and cant remeber what it was. Checked isolation of fets, changed TL431, input and output isolated from case. zeners check with multimeter, but my guess would be them after the tL431. Man i know how to make something complicated.
I decided to put in some FQA's i got from Generg a while back. Replaced the IRF's, made sure all was OK before power up, hooked up VAriac to bring everything up slowly, and voila, we have a problem. As a roll on the variac, with only a couple of volts on positive rail, when i check negative rail, I get slight positive voltage and also i get positve voltage when checking across speaker output.
I just had a thought. I never raised the voltage beyond a couple of volts. Is it possible that the offset adjustment is throwing things off a t these low levels. I will check later. Wife and Kids just got back and i haven't seen them for a week. No time for audio🙂
it will not burn at ,say , 30% of mains voltage
use bulb thingie if you want - for these first 30%
you certainly need more juice for proper bias circ operating and also conduction of outputs
but I'm still puzzled with your "positive voltage on negative rail" formulation
use bulb thingie if you want - for these first 30%
you certainly need more juice for proper bias circ operating and also conduction of outputs
but I'm still puzzled with your "positive voltage on negative rail" formulation
Its something going on in my second cap bank. I unhooked evrything, checked the umbilical, all is fine. Hook it up to second bank od caps and all of the sudden, nothing. I'll hunt it down hopefully.
Figured it out. Was a bad receptacle on newly installed, unopened Speakon connector. What are the chances of that.
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