I used some 30mH and came down from 100mV ripple to 10mV...measured in CLC. Actuall Hammond produces nice chokes which do not cost a fortune, I will try this once I got new xformers...I spent a lot of time trying different setups in the PSU with tube amps amd the PSU is what yOu hear, it is all a modulation of what comes out of the powerplug....and my favorite is a FW rectification with two diodes and LCLC wit a very small C im front, just big enough that it will not raise voltage compared to pure LC...you got the fine details of Lc and the nice airy, vibrant presentation of CLC.
What do you mean you must go off of CIP ? This is the whole fun, no ?
What do you mean you must go off of CIP ? This is the whole fun, no ?
. You are right about "the whole fun". I have other several DIYAudio CIPs on the fly now, so can't deal currently with any additional one. Can you please link me to your specific Hammond made choke? Is it potted one? If not, its flux might be an issue for me and bunch of others guys since I have no must space available in chassis to manipulate with its "quite" placement.Thanks for the help with my post on March 09.
An additional question on my F5T build.
The Diy F5T boards have a through hole size that allows a max size 20AWG wire for the power supply feed and speaker output.
This seems kinda small to me.
Is this sufficient for the currents needed for the supply and load?
Second question is in regards to power supply resistive vs inductive filter (CRC vs CLC)
The suggested series resistive filter has a much lower series DC resistance than any of the inductive filters I have found. How does this affect the output impedance of the power supply?
An additional question on my F5T build.
The Diy F5T boards have a through hole size that allows a max size 20AWG wire for the power supply feed and speaker output.
This seems kinda small to me.
Is this sufficient for the currents needed for the supply and load?
Second question is in regards to power supply resistive vs inductive filter (CRC vs CLC)
The suggested series resistive filter has a much lower series DC resistance than any of the inductive filters I have found. How does this affect the output impedance of the power supply?
Please have a look at the chokes made by Hammond, for example their 153-159 Series:
D.C. Reactors or filter chokes (153-159 Series) - Hammond Mfg.
I have used 159ZL (44 mOhm) for a stereo PSU, and 156B (70 mOhm) or a mono PSU (basically because four 159ZL wouldn't have fitted into my case
)Best regards,
Claas
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Bias stopping at 11.5mv?
I finished building the F5T vs with cascode and I'm setting up one channel and it set up just like it mentioned in the build guide with one pot adjusting the bias and the other adjusting the offset. The problem is the 5k pot reaches it's maximum turns at around 11.5 mv.
I'm using FQA16N25 and FQA12P20's the input fets are matched and the output mostfets are tested on my Peak Atlas and P's are matched to P's and N's to N's.
I was wondering if I need to change the values of P1 and P2 or do I have another problem. Heatsinks are not warm at all so I don't think the MOSFETS are really turning on?
I finished building the F5T vs with cascode and I'm setting up one channel and it set up just like it mentioned in the build guide with one pot adjusting the bias and the other adjusting the offset. The problem is the 5k pot reaches it's maximum turns at around 11.5 mv.
I'm using FQA16N25 and FQA12P20's the input fets are matched and the output mostfets are tested on my Peak Atlas and P's are matched to P's and N's to N's.
I was wondering if I need to change the values of P1 and P2 or do I have another problem. Heatsinks are not warm at all so I don't think the MOSFETS are really turning on?
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** 6L6 beat me to it.
Try increasing R5 & R6 up to 2k. It could be the gate threshold is a little higher for the FQAs. Don't forget to return P1 & P2 to zero before powering up again.
It's not really one is bias and the other offset. They're both bias adjustments, one for N channel and the other for P channel. After turning up say P1 and then you turn up P2 until you get zero offset, it means the N and P channel bias currents are in balance, which gives a zero voltage at the output.
Start with around 200-250 mV and let it cook for while with the cover on. Then go back and increase to around 300 and let it cook again. Then go a little closer to your goal, let it cook, and so on until bias and offset is stable at the desired level. (should be around 350 mV)
TJ
Try increasing R5 & R6 up to 2k. It could be the gate threshold is a little higher for the FQAs. Don't forget to return P1 & P2 to zero before powering up again.
It's not really one is bias and the other offset. They're both bias adjustments, one for N channel and the other for P channel. After turning up say P1 and then you turn up P2 until you get zero offset, it means the N and P channel bias currents are in balance, which gives a zero voltage at the output.
Start with around 200-250 mV and let it cook for while with the cover on. Then go back and increase to around 300 and let it cook again. Then go a little closer to your goal, let it cook, and so on until bias and offset is stable at the desired level. (should be around 350 mV)
TJ
^^ All good advise ^^
To reiterate the bias procedure;
What's important - Iq (measured as the voltage across source resistors; the Mosfet bias) must be very low , offset is irrelevant in this moment .
Now turn one pot one turn ( assuming that you have multiturn pots) then turn other pot one turn. Continue, one turn at a time on each pot until something happens.
Observe voltage across resistors and output DC offset.
Proceed one then second pot , again just one turn
Observe Iq and offset
Again one turn + one turn
Now you are probably in range when you can see which pot is pulling offset in right direction - to 0 . It will feel like one of the pots is controlling the bias on both sides, and the other is controlling the DC offset.
It’s best to increase the bias a bit, and then zero the offset. As you zero the offset you will decrease some of the bias, so it will be two steps forward and one step back. That action is normal.
As you increase the bias and zero the offset, remember to always keep the offset near zero. If you run out of turn on the pots, determine your max bias, with zero offset. (It’s useful for troubleshooting)
Proceed iteratively with pots , while you set - say - 75% of desired bias, with zero offset.
Now - put lid on box and let it cook for a while - until you get thermal equilibrium on heatsinks
It's best to use wire/clips to leave those voltmeters in place ;
Open the lid , up bias to - say - 90% of desired one ,while maintaining offset
Put lid on , let it cook.
Check again.
If all is OK - move voltmeters for Bias and offset to other channel and repeat procedure.
Use it few days at 90% of desired bias , then check and set to 100%
Remember - temp. equilibrium with lid on is important
To reiterate the bias procedure;
What's important - Iq (measured as the voltage across source resistors; the Mosfet bias) must be very low , offset is irrelevant in this moment .
Now turn one pot one turn ( assuming that you have multiturn pots) then turn other pot one turn. Continue, one turn at a time on each pot until something happens.
Observe voltage across resistors and output DC offset.
Proceed one then second pot , again just one turn
Observe Iq and offset
Again one turn + one turn
Now you are probably in range when you can see which pot is pulling offset in right direction - to 0 . It will feel like one of the pots is controlling the bias on both sides, and the other is controlling the DC offset.
It’s best to increase the bias a bit, and then zero the offset. As you zero the offset you will decrease some of the bias, so it will be two steps forward and one step back. That action is normal.
As you increase the bias and zero the offset, remember to always keep the offset near zero. If you run out of turn on the pots, determine your max bias, with zero offset. (It’s useful for troubleshooting)
Proceed iteratively with pots , while you set - say - 75% of desired bias, with zero offset.
Now - put lid on box and let it cook for a while - until you get thermal equilibrium on heatsinks
It's best to use wire/clips to leave those voltmeters in place ;
Open the lid , up bias to - say - 90% of desired one ,while maintaining offset
Put lid on , let it cook.
Check again.
If all is OK - move voltmeters for Bias and offset to other channel and repeat procedure.
Use it few days at 90% of desired bias , then check and set to 100%
Remember - temp. equilibrium with lid on is important
I had some 4.7 k dales and I tried it with those and it biased up without any problems. I set it at around 250mv and it behaved well.
I noticed the pots are very sensitive so I will drop the R5 and R6 resistors down to about 3k tomorrow.
6L6 I did print those procedures out before I began testing and I also read through the build guide, I don't think I made it through enough of the thread to see the bias issue being discussed. Anyway, thanks.
I noticed the pots are very sensitive so I will drop the R5 and R6 resistors down to about 3k tomorrow.
6L6 I did print those procedures out before I began testing and I also read through the build guide, I don't think I made it through enough of the thread to see the bias issue being discussed. Anyway, thanks.
Well, I finally settled on 2.3k resistors for R5 and R6 and everything is working as it should.
I just have a few questions that I hope one of you could answer for me.
I'm guessing that the bias would not come up to where it needed to initially because I had not achieved my VGS-on voltage and the larger resistor solved that problem?
I ran the amp for almost an hour and a half with the bias at about 300mv with my top cover on but not screwed down my heat sinks measured about 46C I was planning on bringing about to about 350mv after a couple of days and I was wondering what operating temperature I should keep it below? I had read someone said about 55C but I wanted to make sure.
Also, I was wondering about using a speaker protection unit, is it a necessity?
I just have a few questions that I hope one of you could answer for me.
I'm guessing that the bias would not come up to where it needed to initially because I had not achieved my VGS-on voltage and the larger resistor solved that problem?
I ran the amp for almost an hour and a half with the bias at about 300mv with my top cover on but not screwed down my heat sinks measured about 46C I was planning on bringing about to about 350mv after a couple of days and I was wondering what operating temperature I should keep it below? I had read someone said about 55C but I wanted to make sure.
Also, I was wondering about using a speaker protection unit, is it a necessity?
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I'm not sure if it is Nelson article that you have linked as I can't open it? I did go back and read his article and that is where I had read the 55C rating it was some time ago and I had forgotten where I had seen it. I think my temperature will drop a couple of degrees when the top is actually screwed down to help dissipate more heat? Anyway, it did on the honey badger I built.
The other questions about the VGS voltage of the outputs and speaker protection were not addressed unless I missed them?
The other questions about the VGS voltage of the outputs and speaker protection were not addressed unless I missed them?
Yes. You weren't getting enough Vgs voltage to 'turn on' the mosfets
to the level required. It's usually a combination of jfet Idss on
the low side/mosfet Vgs on the high side. Also my recollection is that
the Fairchilds has higher threshold Vgs than the IR parts.
As for speaker protection, none of the FW designs has them. So
whether to add one will depend on your personal level of comfort.
If it'll makes you sleep better then just add one, and you can get
back to enjoying the music.
Cheers,
Dennis
Thank You, Dennis, my JFET's are a bit low at 7.4ma idss and my P MOSFETs have a VGS-on of 4.28 so that makes sense. I have not had much luck finding input pairs at the recommended 8-10ma suggested.
If Nelson doesn't use the speaker protection I'm sure it's alright. I will just cook them for a couple of days more to make sure the bias settles at a nice and stable state. Then I plan to enjoy the music for a while.
I know that I worry too much, unfortunately, it's my nature.
If Nelson doesn't use the speaker protection I'm sure it's alright. I will just cook them for a couple of days more to make sure the bias settles at a nice and stable state. Then I plan to enjoy the music for a while.
I know that I worry too much, unfortunately, it's my nature.
I may be wrong on this, but there isn't actually an official FW version of the F5 Turbo. It is an extension of the original F5 design, which Nelson revised on demand to provide more output power/current.
I strongly recommend a speaker protection circuit in a circuit like this. The diodes may cause runaway even at idle, and under load/heat they are capable of vaporising a voice coil in a millisecond.
Or, build with a dummy load and test against every possible adverse condition before connecting a real load.
I strongly recommend a speaker protection circuit in a circuit like this. The diodes may cause runaway even at idle, and under load/heat they are capable of vaporising a voice coil in a millisecond.
Or, build with a dummy load and test against every possible adverse condition before connecting a real load.