possible DC through secondaries is a main thing , when rails are not symmetrically loaded
Very interesting AndrewT and Audiosan...in the next build it would be easy (and inexpensive) to try some regular rectifiers, I could always "upgrade" later if it proves necessary.
Andrew, is there a formula or rule concerning the values of the cap/resistor
snubbers you speak of? What values for this in F-5?
Thanks in advance,
Russellc
Andrew, is there a formula or rule concerning the values of the cap/resistor
snubbers you speak of? What values for this in F-5?
Thanks in advance,
Russellc
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yes, is it Hagerman?
There is a lot more discussion on R+C snubbing going on in recent postings than there has been over the past few years. Worth digging into these Threads.
The important point is that the R does the damping.
The C stops the low value of the R blowing up due to excess dissipation.
I was using a couple general purpose GBPC-3510 for my F5 build. Recently, I decided to change them out and use 8 pcs of MUR3060 to make up the rectifier. This change brought some noticeable improvements over the GBPC-3510. The most apparent are the detail levels improvement and the image solidity. For the $30 I paid for the MUR3060, this is a very worthwhile upgrade for any F5 builds.
I also used the MUR 3060 and had great results, I didnt have any "glare" that a few have complained of, and have often felt that these rectifiers, and the use of the IRF devices and their known second harmonic distortion were partly responsible for my very sweet sounding F-5.
Hearing Andrew and others bring up snubbers, (which I have seen used to great effect on the output transformers of tube amps) I thought I would inquire. Sorry if anyone is that sensitive, I'll continue using my MUR 3060s. As to A.Wayne's comment,
Trust me, if I want to get smart with anyone, there will be no doubt. Just trying to learn, sorry to those put off by the inquiry!
The only thing I didnt like about the MUR devices is the multiple solder points involved, and positioning the pads under all 16 of them!
Russellc
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Nothing , i left of the smiley
Sorry then, maybe I'm the sensitive one! I'm needing to go back to the Hagerman site and study up on the snubbers, I will try them in place of the MURs, they were not cheap! Snubbers worked well in the output transformers
I was talking about, I've no idea how the values are calculated, I'll sort it out. I'm trying to make this next F-5 a little more modular, so various things, like rectifiers can be experimented with...I've only built one pass power amp so far, so nothing to really contrast it with.
I am also building a turbo, whose heatsinks will allow me to also try BA 2 and BA 3 boards, and I would like it to be easily switchable as well. Once that is done, I am planning on (and have a parts pile beginning) for an Aleph 2, but it will require two for the mono obviously. The Aleph will be built to stay as they are, but the others can be more like platforms to try different things.
Russellc
I didnt match mine either...they were from the same batch, in a tube like thing, everything measures well so I guess I was lucky?
Russellc
yes & no.
The snubbers are part of the PSU to damp the PSU response such that transients don't promote instability in the PSU. This is all based on the transformer and the rectifier diodes. It has virtually nothing to do with the F5 or any amplifier hung on the output end of the PSU.
Design the snubbers for the PSU. Do not design the snubbers for the F5.
Hi guys, like the other diy-er, I also have a problem adjusting F5 BIAS on one of the channels. Only turning P1 makes voltage rise on R11 and R12 while turning P2 makes almost no difference. I power on with 2 turns on P1 and P2, then turning P1 and P2 by 1 turn at the time, makes voltage rise on R11 and R12 but not equally. I noticed that turning P2 makes both voltages stays the same. If I have say 0.35V on R11 I get about 0.53V on R12. P ch MOSFET IRFP9240 gets hot really fast at about 0.5V and R11 starts getting hot, also R12 but not quite as hot. The voltage on R12 is almost twice that on R11 but the N ch MOSFET stays almost cool. Has anyone seen these symptoms before. Could it be that the P ch JFET (P1086), or the N ch MOSFET (IRFP240) maybe bad? Any advise would be appreciated.