Already do that... but its always been more for style than anything else
...and besides the conductive cooling of the copper can be quite refreshing on a hot summer day! LOL.....
Alright, don't gang up on the urban industrial dweller Maybe you can help me learn something instead!
I understand how to calculate the 3db point of a low or high pass filter F= 1/2pi*RC. The examples I can find just have a series resistor and capacitor to ground.
But in the case of input to the F5, or many other amps for that matter, there is also the shunt resistor to take into account. For the "R" in the equation above, how does the 100K resistor fit in?
Would it be 1/2pi*101,000*C? This does not seem right to me.
I know this may be an elementary question, but could not find it here or elsewhere.
I understand how to calculate the 3db point of a low or high pass filter F= 1/2pi*RC. The examples I can find just have a series resistor and capacitor to ground.
But in the case of input to the F5, or many other amps for that matter, there is also the shunt resistor to take into account. For the "R" in the equation above, how does the 100K resistor fit in?
Would it be 1/2pi*101,000*C? This does not seem right to me.
I know this may be an elementary question, but could not find it here or elsewhere.
My understanding is that as long as the 'load' has a much higher impedance than the filter its shunt resistance does not affect the functioning of the filter. In the case of input filters, the series element is usually selected to be quite a bit lower than the load impedance.
In your case, 100k shunt element is not factored into the equation.
Also, a lower shunt element will only affect attenuation, not rolloff (at least talking about ideal components),
In your case, 100k shunt element is not factored into the equation.
Also, a lower shunt element will only affect attenuation, not rolloff (at least talking about ideal components),
The parallel resistor (Zin) should be taken account of when calculating the theoretical roll-off curve.
But the effect when Rseries << Zin is tiny and may be ignored.
I often use 1uF + 1k in series in the hot feed followed by a parallel combination of 91k//680pF as my passband filtering.
But the effect when Rseries << Zin is tiny and may be ignored.
I often use 1uF + 1k in series in the hot feed followed by a parallel combination of 91k//680pF as my passband filtering.
My new dual mono F5
hi
I decided to do a little change my F5 ,to the turbo version
http://www.hostingpics.net/viewer.php?id=173070DSC0860.jpg
because I want cascoding the jfet, doubling the output stage, bigger power supply (2 X 500VA), fast and low loss rectifier ......
The beginning of the change is the case because it will bring two transformer and 4X 100 000 uF capacitor
http://www.hostingpics.net/viewer.php?id=177677DSC0845.jpg
http://www.hostingpics.net/viewer.php?id=511264DSC0859.jpg
http://www.hostingpics.net/viewer.php?id=787696DSC0854.jpg
the pcb
http://www.hostingpics.net/viewer.php?id=410844DSC0855.jpg
the DC protection for speaker
http://www.hostingpics.net/viewer.php?id=618157DSC0862.jpg
And wire it all, the concern is to find the time because of work
http://www.hostingpics.net/viewer.php?id=857931DSC0863.jpg
and .....
http://www.hostingpics.net/viewer.php?id=924531IMAG0004.jpg
http://www.hostingpics.net/viewer.php?id=999979IMAG0003.jpg
Not really finished Yet
it sound beautiful, with better bass
The bias is 2A for each channel and the power supply 2X28V DC
Big thanks to Mr . PASS for the design and for the member of the forum for the help
Excuse-me for my poor english
hi
I decided to do a little change my F5 ,to the turbo version
http://www.hostingpics.net/viewer.php?id=173070DSC0860.jpg
because I want cascoding the jfet, doubling the output stage, bigger power supply (2 X 500VA), fast and low loss rectifier ......
The beginning of the change is the case because it will bring two transformer and 4X 100 000 uF capacitor
http://www.hostingpics.net/viewer.php?id=177677DSC0845.jpg
http://www.hostingpics.net/viewer.php?id=511264DSC0859.jpg
http://www.hostingpics.net/viewer.php?id=787696DSC0854.jpg
the pcb
http://www.hostingpics.net/viewer.php?id=410844DSC0855.jpg
the DC protection for speaker
http://www.hostingpics.net/viewer.php?id=618157DSC0862.jpg
And wire it all, the concern is to find the time because of work
http://www.hostingpics.net/viewer.php?id=857931DSC0863.jpg
and .....
http://www.hostingpics.net/viewer.php?id=924531IMAG0004.jpg
http://www.hostingpics.net/viewer.php?id=999979IMAG0003.jpg
Not really finished Yet
it sound beautiful, with better bass
The bias is 2A for each channel and the power supply 2X28V DC
Big thanks to Mr . PASS for the design and for the member of the forum for the help
Excuse-me for my poor english
Last edited:
I'm going to order all the parts for F5, speaker protector, lightspeed. Can someone take a look to my bom?
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=44cde2a163
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=44cde2a163
Hi all, could anyone clarify the procedure for setting the bias on the F5 for me.
As I understand it you have to set the two pots that are in parallel with the 2.2K resistors that supply the input FET'S 's to minimum resistance and then gradualy increase them in turn until the desired bias is reached, also checking the offset voltage.
Is this correct, or have I misunderstood? At initial start up the input FET's will be connected directly to the +- supply rails with no source resistance? Sorry to be so dumb
Alan.
As I understand it you have to set the two pots that are in parallel with the 2.2K resistors that supply the input FET'S 's to minimum resistance and then gradualy increase them in turn until the desired bias is reached, also checking the offset voltage.
Is this correct, or have I misunderstood? At initial start up the input FET's will be connected directly to the +- supply rails with no source resistance? Sorry to be so dumb
Alan.
Start with resistance turned to minimum position.
In a perfect world you have 3 meters. Set all to DC volts.
Place meter across R11, another across R12, (the source resistors on the outputs) and one on the speaker outputs.
Turn pots (plural) up until you show 0.1V across the source resistors. Once they show some bias, now by adjusting one of the pots, set any DC offset you have to zero.
Once the Offset is zeroed, increase the bias again, to .2 or so, and then remove the offset.
This is a series of steps that will increase the bias, and probably remove some of it when the offset is zeroed. Two steps forward, one step back. This is normal.
Continue to increase bias in .2V steps or so and then zeroing offset.
Once you get it to 0.55V across both resistors, zero the offset again, and let the amp sit for 1/2hr. Lay the lid of the chassis on top, to simulate normal airflow.
After it's all warm and stable, tweak the bias one last time to 0.6V and zero offset. If it makes it all the way to normal bias, button it up and enjoy! Check again in a week.
If it doesn't, (with BL-grade Jfets you likely won't have any problem...) please report back with the maximum amount of bias you can achieve with zero offset.
As for the Jfets being attached to the rails with no source resistance, yes, that's correct. With no resistance there will be no current drawn that way, and they won't turn on.
In a perfect world you have 3 meters. Set all to DC volts.
Place meter across R11, another across R12, (the source resistors on the outputs) and one on the speaker outputs.
Turn pots (plural) up until you show 0.1V across the source resistors. Once they show some bias, now by adjusting one of the pots, set any DC offset you have to zero.
Once the Offset is zeroed, increase the bias again, to .2 or so, and then remove the offset.
This is a series of steps that will increase the bias, and probably remove some of it when the offset is zeroed. Two steps forward, one step back. This is normal.
Continue to increase bias in .2V steps or so and then zeroing offset.
Once you get it to 0.55V across both resistors, zero the offset again, and let the amp sit for 1/2hr. Lay the lid of the chassis on top, to simulate normal airflow.
After it's all warm and stable, tweak the bias one last time to 0.6V and zero offset. If it makes it all the way to normal bias, button it up and enjoy! Check again in a week.
If it doesn't, (with BL-grade Jfets you likely won't have any problem...) please report back with the maximum amount of bias you can achieve with zero offset.
As for the Jfets being attached to the rails with no source resistance, yes, that's correct. With no resistance there will be no current drawn that way, and they won't turn on.
6L6 & Co. are remembering where tutorials are posted
Lol!!!
I've done it so many times it's just easier to type it out than search for it...
alibear meant on drain resistance ( with pots zeroed)
input jfets will draw current , set with their own source resistors (roughly) while their dissipation will be certainly higher than in fully biased amp state
however , that is not dangerous
just to mention - using just two DMMs is enough - one for voltage across (any of two ) output source resistor and one for offset
series bulb thingie for first power up is wise to have
input jfets will draw current , set with their own source resistors (roughly) while their dissipation will be certainly higher than in fully biased amp state
however , that is not dangerous
just to mention - using just two DMMs is enough - one for voltage across (any of two ) output source resistor and one for offset
series bulb thingie for first power up is wise to have
Lol!!!
I've done it so many times it's just easier to type it out than search for it...
not for old geezer like me ......... call it laziness .........
I'm going to order all the parts for F5, speaker protector, lightspeed. Can someone take a look to my bom?
http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=44cde2a163
For comparison this Mouser BOM worked correctly for me. I have suggested the admins include a Mouser, Digikey and/or other BOM on the diyAudio store F5 page - but I guess that might ruffle some feathers.
My F5 BOM
I have suggested the admins include a Mouser, Digikey and/or other BOM on the diyAudio store F5 page - but I guess that might ruffle some feathers.
I'm sure Jason would be interested, it's always a matter of time with those kind of changes, not for any disinterest.
I was referring to supplier or vendor envy/competition not forum admin intent.
Not anything I worry about.
The most important thing in a good and complete BOM is seeing an example of the component to buy... Sometimes you don't have any info on, say, lead spacing, until you see a part listed and then you can see that, as well as dimensions, etc...
BOM are always useful to the hobby builder.
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