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Old 16th August 2010, 05:12 PM   #8661
Blues is offline Blues  United States
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Nope, not at all...and these have been verified as similar to his by sangram. All I'm trying to point out is the interpretation of what you are reading from the F5 output...at first glance it will tell us the readings come from the 2 feedback loops and the Source Rs but from the measurement values you called out other paralleled loops are also involved.

Btw, have you powered up your creation and listened?
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Old 16th August 2010, 09:03 PM   #8662
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Oh fine. I might be able to borrow a scope as I would like to make sure everything is OK. The amp sounds good, apart from a slight hum.

Thanks for asking the questions
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Old 17th August 2010, 05:08 AM   #8663
sangram is offline sangram  India
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Hum would be due to a ground loop problem, how have you connected the input, output and power grounds? My amp is dead silent, probably the quietest I've ever built.
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Old 17th August 2010, 01:34 PM   #8664
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Quote:
Originally Posted by sangram View Post
Hum would be due to a ground loop problem, how have you connected the input, output and power grounds? My amp is dead silent, probably the quietest I've ever built.
Hi Richard. I know it's a pain, but it's well worth trying to eliminate the possibility of an earth loop before you delve deep into F5 component failure analysis. They are some right bloody gremlins to track down sometimes, because they sometimes occur due to cables that you can't practically remove from the setup, like your pre to power RCAs for example. That's why I sent you that link to the page that discusses directionality of earthing, and how the flow direction must be forced back away from the pre-amps and sources by way of cable size differences. The biggest mistake with earthing is, noting that all of the earth points link up to the same destination/source, deciding to not to send separate cables for each earth point and instead making a string that catches each one. I made that mistake, and I'm sure it's quite common to do so, but it causes hum, so check that you haven't done that anywhere.
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Old 17th August 2010, 03:34 PM   #8665
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To paraphrase LucasA;
Star ground > parallel > series grounding techniques.
Ron
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Old 17th August 2010, 10:36 PM   #8666
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Quote:
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To paraphrase LucasA;
Star ground > parallel > series grounding techniques.
Ron
Yeah, sorry to have used such descriptive, non technical terms, like I'm talking to a dumbass, rather than someone who has actually built a Class A amp (unlike me).

But yeah, Star grounding with tiny cables for signal earth to a signal sub-star linking with larger cables to the master star on the case body with power earths and huge cable to link the master star to the power inlet earth, keeps the flow in the right direction. Make sure that the signal earths are not directly attached to the case body.
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Old 18th August 2010, 06:00 AM   #8667
shaan is offline shaan  India
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Hello everyone here and hello papa! This is my first post in this thread, however I've been a reader of this thread for quite some months and have started to think of f5 as my next project. I have a question about the power mosfets.

Can Laterals be used in place of those IRF devices without problem? Has anyone here tried something alike?

I actually have some spare hitachi devices resting, so I thought I'd better put them to work. so...

Thanks in advance.
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Old 18th August 2010, 09:41 AM   #8668
AndrewT is offline AndrewT  Scotland
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Laterals swapped for the F5's Verticals are discussed a few times in this thread.
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Old 18th August 2010, 10:18 AM   #8669
shaan is offline shaan  India
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I see... I must have missed some pages... my bad

Thanks... I'll try to find the posts.
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Old 18th August 2010, 01:03 PM   #8670
tinitus is offline tinitus  Europe
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Laterals

yeah, I was daft enough to actually buy a bunch of selected Renesas

no good low conducting, they say

so I decided to use for other amp(AB)

But now I have decided to try them as double pairs in F5

I dont care if it wont be the best ever

I think part of the trick is to beat them hard with aggressive bias and that means huge heatsinks, which I happen to have
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