I need to build a power supply.
I need about 20 to 25vdc on the output mosfet.
currently I have 4 68mF 50vdc caps (quite large). bridge rectifier (what type should I use?)
I just need a power transformer.
any ideas?
I need about 20 to 25vdc on the output mosfet.
currently I have 4 68mF 50vdc caps (quite large). bridge rectifier (what type should I use?)
I just need a power transformer.
any ideas?
A 18VAC transformer that can handle the current, yes.
I guess this is for your choke loaded follower project, right?
I´d suggest a 2x18VAC >300VA toroid transformer.
Use one secondary per channel, 2x3A is easier to handle than 1x6A.
I guess this is for your choke loaded follower project, right?
I´d suggest a 2x18VAC >300VA toroid transformer.
Use one secondary per channel, 2x3A is easier to handle than 1x6A.
yes it is
ok 2x18vac it is then. 10A winding for each???
rectifier... which should I use??? regular bridge?
68,000 cap / choke / 68,000 cap. per channel.
10-30mH choke, low DCR. does digikey or parts express have one?
ok 2x18vac it is then. 10A winding for each???
rectifier... which should I use??? regular bridge?
68,000 cap / choke / 68,000 cap. per channel.
10-30mH choke, low DCR. does digikey or parts express have one?
Yes, two 18V 10A windings will be fine. If you want 27V rails (as mentioned in the thread about the amp) you´ll need slightly higher voltage, say 20-22VAC.
A regular but big bridge. 35A is fine.
I´ve read somewhere that one always should have more capacitance after the choke than before it. Ringnings and stuff I guess.
I guess Hammond has suitable ones.
A regular but big bridge. 35A is fine.
I´ve read somewhere that one always should have more capacitance after the choke than before it. Ringnings and stuff I guess.
I guess Hammond has suitable ones.
Hi Audio Geek,
Do not resign from soft-start circuit if you plan to use toroid trafo and large capacity. This simple circuit will reduce big curents charging capacitors on start-up and avoid from accidential fuses blow.
Regards,
Marek
Do not resign from soft-start circuit if you plan to use toroid trafo and large capacity. This simple circuit will reduce big curents charging capacitors on start-up and avoid from accidential fuses blow.
Regards,
Marek
choke input or cap input????
which should I do????
recommendations for the choke either way?? part numbers etc...
Thanks!!
which should I do????
recommendations for the choke either way?? part numbers etc...
Thanks!!
You might not want to mess around with choke input filters.
Works fine electrically, but finding a choke that doesn´t buzz is not easy. They need to be big (as in BIG), too.
Been there, done that.
A suitable choke for LCL filters might be this one:
159ZG 15mH 4A
Say, 2 x 22000uF - 159ZJ - 4 x 22000uF. Per channel.
If you want to run two channels on the same rail, double up the capacitance and use a 159ZL choke instead.
Make sure that the caps (at least the ones prior to the choke) can handle some heavy ripple currents.
Dirt cheap? Nope, but if this is a serious project you won´t regret spending some hard cash on the caps.
Speaking of caps, put some film caps (1-10uF) across the `lytics.
A 10nF/10R serial network across each diode in the rectifiers is nice, too.
Works fine electrically, but finding a choke that doesn´t buzz is not easy. They need to be big (as in BIG), too.
Been there, done that.
A suitable choke for LCL filters might be this one:
159ZG 15mH 4A
Say, 2 x 22000uF - 159ZJ - 4 x 22000uF. Per channel.
If you want to run two channels on the same rail, double up the capacitance and use a 159ZL choke instead.
Make sure that the caps (at least the ones prior to the choke) can handle some heavy ripple currents.
Dirt cheap? Nope, but if this is a serious project you won´t regret spending some hard cash on the caps.
Speaking of caps, put some film caps (1-10uF) across the `lytics.
A 10nF/10R serial network across each diode in the rectifiers is nice, too.
With a capacitor input filter the output voltage is about 1.4 x the transformer AC voltage and you can pull about 60 DC watts for every 100 transformer VA's.
With a choke input filter (provided the choke inductance is greater than a reasonable minimum value) the output voltage is about 0.9 x the transformer AC voltage and you can pull about 80-90 DC watts for every 100 transformer VA's. Under very low load the DC voltage rises toward 1.4 x the transformer AC voltage.
With a choke input filter (provided the choke inductance is greater than a reasonable minimum value) the output voltage is about 0.9 x the transformer AC voltage and you can pull about 80-90 DC watts for every 100 transformer VA's. Under very low load the DC voltage rises toward 1.4 x the transformer AC voltage.
Yes, choke input filters presents a nicer and easier load for the transformer. Sine shaped current draw instead of the spiky mess drawn by capacitors.
caps I have are:
I have these:
Nippon Chemi-Con
U32D 105C
50V 68000uF
0022L 63
+ POSITIVE
I have four of these total and want to use them.
2 per channel.
not sure about ripple rating on these.
I have these:
Nippon Chemi-Con
U32D 105C
50V 68000uF
0022L 63
+ POSITIVE
I have four of these total and want to use them.
2 per channel.
not sure about ripple rating on these.
Use them!
If you don´t want to take chances, put them after the choke and buy some others for the "before choke" position.
You can also put one or two smaller caps close to to the Mosfet, 1000uF or so high quality low impedance stuff.
Remember, an amp is never better than it´s power supply!
All the amp does is to modulate whatever comes from the PSU.
If you don´t want to take chances, put them after the choke and buy some others for the "before choke" position.
You can also put one or two smaller caps close to to the Mosfet, 1000uF or so high quality low impedance stuff.
Remember, an amp is never better than it´s power supply!
All the amp does is to modulate whatever comes from the PSU.
Actually it isn't! Sorry. The bigger the choke the closer the current from the transformer approximates a square wave!!! This should be even better than a sine wave because it spreads the current more or less evenly across the whole half cycle instead of concentrating it in the centre like a sine wave. Remember, The resistive losses in the copper vary according to the square of the instantaneous current so a square current waveform packs the most energy per half cycle for a given copper temperature.Fuling said:
Choke input or Pi-filter
You guys are confusing a choke input filter powersupply and a PI-filter.
For the first you need a minimum value for the choke depending on the continuous current while the latter will work with something like 2.2mH though I am currently using 15mH in my Ampzilla.
See f.a. Transistor Circuit techniques by G.J. Ritchie, Chapman & Hall, Third edition page 183 and:
http://db.audioasylum.com/cgi/m.mpl?forum=tweaks&n=27698&highlight=elso+choke&r=&session=
http://db.audioasylum.com/cgi/m.mpl?forum=tweaks&n=36470&highlight=elso+choke&r=&session=
http://db.audioasylum.com/cgi/m.mpl?forum=tweaks&n=41191&highlight=elso+choke&r=&session=
I guess the Cello power amplifiers had a huge choke input filter, at least that is what they claimed. The choke was as big as the transformer!
You guys are confusing a choke input filter powersupply and a PI-filter.
For the first you need a minimum value for the choke depending on the continuous current while the latter will work with something like 2.2mH though I am currently using 15mH in my Ampzilla.
See f.a. Transistor Circuit techniques by G.J. Ritchie, Chapman & Hall, Third edition page 183 and:
http://db.audioasylum.com/cgi/m.mpl?forum=tweaks&n=27698&highlight=elso+choke&r=&session=
http://db.audioasylum.com/cgi/m.mpl?forum=tweaks&n=36470&highlight=elso+choke&r=&session=
http://db.audioasylum.com/cgi/m.mpl?forum=tweaks&n=41191&highlight=elso+choke&r=&session=
I guess the Cello power amplifiers had a huge choke input filter, at least that is what they claimed. The choke was as big as the transformer!
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