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Old 18th August 2010, 05:14 PM   #8671
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Default Current limiting or no?

OK, so I have most of my F5 parts now, and I'm wondering, in light of what some have said about audible gains, whether or not to remove the current limiting part of the circuit.

I know it has been done several times with success, and apart from some reports that there is a marked improvement in the sound, (post 2814) all I know is that there will be a longer bias adjusting procedure and that I must make doubly sure that my heat sinks are adequate and that I don't short my outputs for so much as a split second.

Should I built the full circuit first and then cut the traces later, build the full circuit and be happy, or go straight for the purer/simpler circuit from the off?

So far, I have this: F5 without Current limiting/Thermistors

Unsubstantiated opinions welcome!
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Old 18th August 2010, 05:18 PM   #8672
tinitus is offline tinitus  Europe
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ehh, I thought all the bias issues only related to that thermistor thing, and that the thermistor it could still be used and work well, without the transistor limitor

anyway, Nelson's own F5 beats them all, with thermitor and limitor, as pr manual
but probably a balance act with special care to adjustments and parts

I suspect its also a matter how its put in use, with regards to speaker load, SPL, etc
Nelson suggest easy going speaker, and it is probably also tested that way, when winning the prices

others here may use totally different and tougher speakers, and that may change everything

you may have to look a summed amplification gain through your whole setup
sometimes we know very little, and sometimes we know too much
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Old 18th August 2010, 05:22 PM   #8673
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I'm sure you're right. I got this schematic from somewhere in this thread some time ago, where someone had clearly removed both.

Perhaps the thermistors should stay. I don't know really, so I ask...

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Old 18th August 2010, 05:29 PM   #8674
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You can do quite a few variations on this sort of circuit,
and each will bring something different to the table. No
reason you can't try as many as you like (easy enough!)
and take a listen, I do it all the time.

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Old 18th August 2010, 05:40 PM   #8675
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Well, I think I will do the circuit as you settled on it Nelson. I can then evaluate it for myself instead of taking other's word for it.....if they knew so much, I guess they would have designed it in the first place and not you.

Thanks Admiral! My mind is made up. You the man!

OT: I've been meaning to ask you your thoughts on the DCB1. Have you tried it yet?
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Old 18th August 2010, 05:55 PM   #8676
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Hi Lucas

Its much easier to snip the legs of some of the parts after you have assembled the amp, rather than carefully disassembling the amp at a later date...I guess that will happen regardless!

That's the most sensible thing I have said all day...

Last edited by Tripmaster; 18th August 2010 at 06:06 PM.
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Old 18th August 2010, 06:37 PM   #8677
AndrewT is online now AndrewT  Scotland
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post2819 offers an explanation and a solution to the current limiter being audible.
regards Andrew T.
Sent from my desktop computer using a keyboard
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Old 18th August 2010, 06:52 PM   #8678
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i have a question. what condition will make R11 and R22 on fire? I try to adjust the pot again and again, but it still on fire
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Old 18th August 2010, 07:56 PM   #8679
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Originally Posted by AndrewT View Post
post2819 offers an explanation and a solution to the current limiter being audible.
Shame it's all above my head Andrew. You might as well be talking Saturday night Glaswegian
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Old 18th August 2010, 08:33 PM   #8680
Join Date: Nov 2006
Build one channel with current limiter and one channel without current limiter.
Have a listen to both. If the circuit without current limiter sounds better, then remove the current limiter from the other channel.
If you can't tell the difference, then you may as well add it to the other channel.
Don't be afraid to experiment.
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