You're welcome -
I've concentrated on the F3 for awhile now, as the way it controls the Coral beta 8 driver (from 160Hz upwards) is outstanding - I've done quite a bit of trying different types of the caps and that strange RC bipassing thing - also ended up with the 8ETH06 diodes (IR product)into a 0.1R - 22,000uF - 0.1R - 33,000uF power supply setup (RCRC). Multistranded wire in this area seems to be useful getting rid of some of the diode and line noise and 1mm silverwire everywhere else.
C9 was changed a bit to 46pF styrene in series with a 70R resistor - seems a weird selection but works like a charm -
C1 is a 22,000uF/40v Siemens Sikorel (thanks to PD) with a whole collection of passengers - a // pair of S+M 64uF/40v B41590 (as C10) and the big Russian 10uF POI (as C8) and a series RC network of 1.8R + 220uF of the Rifa peg124 across that - all this is offboard (no room)
A big surprise was the EI transformer gives a much more relaxed sound to the amp but is "faster" and much "more detailed" than with the larger VA big torroid it replaced - sorry for the vague terms.
Will eventually get around to finishing a properly built F5 for the 12" bass driver - need to complete the pcb with an included C multiplier and a few other details yet.
I've concentrated on the F3 for awhile now, as the way it controls the Coral beta 8 driver (from 160Hz upwards) is outstanding - I've done quite a bit of trying different types of the caps and that strange RC bipassing thing - also ended up with the 8ETH06 diodes (IR product)into a 0.1R - 22,000uF - 0.1R - 33,000uF power supply setup (RCRC). Multistranded wire in this area seems to be useful getting rid of some of the diode and line noise and 1mm silverwire everywhere else.
C9 was changed a bit to 46pF styrene in series with a 70R resistor - seems a weird selection but works like a charm -
C1 is a 22,000uF/40v Siemens Sikorel (thanks to PD) with a whole collection of passengers - a // pair of S+M 64uF/40v B41590 (as C10) and the big Russian 10uF POI (as C8) and a series RC network of 1.8R + 220uF of the Rifa peg124 across that - all this is offboard (no room)
A big surprise was the EI transformer gives a much more relaxed sound to the amp but is "faster" and much "more detailed" than with the larger VA big torroid it replaced - sorry for the vague terms.
Will eventually get around to finishing a properly built F5 for the 12" bass driver - need to complete the pcb with an included C multiplier and a few other details yet.
at 22v, my N channel FETs Q2,3 run about 65c, or course that was in open air. In a chassis, I suppose they are warmer because of the ambient air.
I am continuing to drill holes in my chassis and got the ambient inside temp to 48c in a above room temp listening room. Dont know if this is too unhealthy for the caps or not.
I might order some grill like aluminum for the top, that will help. Still waiting for Elna cap break in, but the amp sounds nice, not as sassy as F5.
I am continuing to drill holes in my chassis and got the ambient inside temp to 48c in a above room temp listening room. Dont know if this is too unhealthy for the caps or not.
I might order some grill like aluminum for the top, that will help. Still waiting for Elna cap break in, but the amp sounds nice, not as sassy as F5.
Sorry CeeVee,
I've been "told off" by the moderator - too many words, apparently!!
Send me you're Silmic &/or Nichicon requirements and I'll send some over to you - can't see a problem. There are quite a few 220uF/63v Epcos Sikorels available on eBay (Germany) and some of the bigger power caps (33,000/63v B41560) - not easy to find at reasonable prices.
JC and TB,
I blocked off some fins on my h/sinks to get the h/sink temp up past 55*C (more detailed and smoother sound, now) but made sure the inside stays about room temp with open grill top, and the shottky diodes are on separate small h/sinks and isolated from the chassis - same for the big Sikorel electrolytic caps and transformer - these all stay below 45*C.
Going to add a simple B1 buffer to the input with a supply feed off the main amp rails.
... Gotta stay outa "sin-bin"
I've been "told off" by the moderator - too many words, apparently!!
Send me you're Silmic &/or Nichicon requirements and I'll send some over to you - can't see a problem. There are quite a few 220uF/63v Epcos Sikorels available on eBay (Germany) and some of the bigger power caps (33,000/63v B41560) - not easy to find at reasonable prices.
JC and TB,
I blocked off some fins on my h/sinks to get the h/sink temp up past 55*C (more detailed and smoother sound, now) but made sure the inside stays about room temp with open grill top, and the shottky diodes are on separate small h/sinks and isolated from the chassis - same for the big Sikorel electrolytic caps and transformer - these all stay below 45*C.
Going to add a simple B1 buffer to the input with a supply feed off the main amp rails.
... Gotta stay outa "sin-bin"
Well, it sounds a bit more layed back so far on the top end, maybe less treble emphasis on my build. I have a 47uf elna silimic as a bypass for C1, but no c8, I wonder if this would bring in a tad more 'air' if I put a good small cap here.
I just dropped in the Fairchilds without any other adjustment. I had a bunch of them around from F5 project, so I used them. They may need to be adjusted, but so far everything works. I would probably swap to IR's before trying to make sure the fairchilds work. I think in the F5, people who used Fairchild or Vishay IR's did not need to do any further adjustments.
I just dropped in the Fairchilds without any other adjustment. I had a bunch of them around from F5 project, so I used them. They may need to be adjusted, but so far everything works. I would probably swap to IR's before trying to make sure the fairchilds work. I think in the F5, people who used Fairchild or Vishay IR's did not need to do any further adjustments.
Hi James,
Don't really understand why you would be told off, except publicity to commercial operators..., but on all other respects you were exemplary.
As far as the Sikorels go, i already got the big 'uns for the power supply, my alternatives were Nichicon Superthru's but only 15000uF.
As far as the Silmics go ...i got a bag from ebay and am checking if they are genuine or not:
Sacrificed 2 in the name of science, took out their innards and compared with the genuine article....ripping the "paper" will be the ultimate test if all else looks genuine ( looking for the silk fibers...).
Got brown and gold ones as well as black and gold !!! ...one off them, a 220u/100V was a little dry already ( yellowing )...compared to the 220u/63V one which was snow white.
Ebay has it's down sides...
I'll post some pictures later...might be helpfull for other's.
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output cap question
I know that that topic of the output caps on the F3 has been flogged, BUT here's my question.
If the output cap acts as a first order filter cap, why the 15mF? Even if I were to use a 2Ω speaker, 8mF would give a 10Hz -3dB point. With an 8Ω speaker, that would be 2mF. Since most people are running fullrangers, a 25Hz -3dB point would be reasonable... requiring only 800uF.
Is this 15mF value just overengineered for the application, or am I missing something obvious?
I know that that topic of the output caps on the F3 has been flogged, BUT here's my question.
If the output cap acts as a first order filter cap, why the 15mF? Even if I were to use a 2Ω speaker, 8mF would give a 10Hz -3dB point. With an 8Ω speaker, that would be 2mF. Since most people are running fullrangers, a 25Hz -3dB point would be reasonable... requiring only 800uF.
Is this 15mF value just overengineered for the application, or am I missing something obvious?
Hi,
I'm planning to start my F3 build next days...
A few open questions:
1. Why do I need the 100Ohm resistance against ground after the output cap? I thought a much bigger resistance would care for leak currents...
2. In the power supply, we have NTC1 connect the caps to ground.
- Which device is used (CL60???)
- Why don't we connect the caps direct to ground???
3. I got a quality 750VA toroid having 2x18V So I will use it for stereo. Do I use 2x CL60 in series to reduce power on surge? Or do I need a conventional shut in circuit?
Dirk
I'm planning to start my F3 build next days...
A few open questions:
1. Why do I need the 100Ohm resistance against ground after the output cap? I thought a much bigger resistance would care for leak currents...
2. In the power supply, we have NTC1 connect the caps to ground.
- Which device is used (CL60???)
- Why don't we connect the caps direct to ground???
3. I got a quality 750VA toroid having 2x18V So I will use it for stereo. Do I use 2x CL60 in series to reduce power on surge? Or do I need a conventional shut in circuit?
Dirk
Sorry, can't help you... but maybe you can help me?
Do you know for any F3 PCB source?
Thanks in advance & cheers,
Hi Dirk,
Naah, no not too trivial, in fact the negative feedback (C9 + R2) is taken from the output over R10. To dampen switch on/off effects (especially when not using any further load) looped back on the gate of Q1 especially offset (due to capacitor leakage) you really need to have R10. Of course you're free to play with this.
-I have connected the capacitors direct to ground. Be aware of mains ground currents not running through you're signal ground! There's no reason to use a NTC when you have both a low potential on Neutral and Ground. Nowadays we tie all the grounds together (EMC en Lowvoltage regulations).
-My advise: always short your inrush limiters after switching in. The internal impedance of the powersupply will drop; improving impulse response of the amp! You can easily check this by measuring the ouput impedance of the power supply; placing some 50Ohm, 50 W resistors on the DC rail. First one, then two. An ideal PS will hold the voltage. When using CL 60's you will notice the voltage drop over the NTC...
Have fun constructing!