Hi 6L6,
On your terminal strip for the mains supply to the x-former you have the two CL-60 thermistors. In between that is a capacitor. I see from the schematic that it is .0033uF or 3300pF correct? I have not found listed in any BOM or have seen a reference to a part number. Aside from finding a disk shaped blue one at the stated capacitance, I'm not sure what to order.
On your terminal strip for the mains supply to the x-former you have the two CL-60 thermistors. In between that is a capacitor. I see from the schematic that it is .0033uF or 3300pF correct? I have not found listed in any BOM or have seen a reference to a part number. Aside from finding a disk shaped blue one at the stated capacitance, I'm not sure what to order.
You can learn more about X1/Y2 line capacitors here: https://www.mouser.com/datasheet/2/212/KEM_C1065_X1_440%20VAC_Y2_300%20VAC-371221.pdf
Thanks WKCox! Ok, with 120Vac mains, what voltage should I use? 440Vac is the spec in the link you sent. Is that standard for 120Vac? Would 250vac be safe?
Thanks WKCox! That helps and clears it up a bit. Now a question about the voltage rating to use. The link to the data sheet lists 440Vac. My mains will be 120Vac. Would 250Vac be safe? Or is it standard to us 440Vac?
im curious about the F-5, but all these threads and hundreds og pages is a bit overwhelming.
sorry if im being stupid:
1. has anyone got any good sources on cheap chassis from china on ebay? thoes monoblocks in the store were rediculous expensive, like over $600 for the pair? apart from the heatsinks the sheetmetal should be pretty cheap...
2. is the universal powersupply any requirement? wouldnt any shelfware bridge rectifier off ebay work fine? full board with 40-60.000uF caps are like $20-30
i take it softstart etc is a luxary and not needed. one rectifier board, cables, switch and the amps will work fine?
thx
sorry if im being stupid:
1. has anyone got any good sources on cheap chassis from china on ebay? thoes monoblocks in the store were rediculous expensive, like over $600 for the pair? apart from the heatsinks the sheetmetal should be pretty cheap...
2. is the universal powersupply any requirement? wouldnt any shelfware bridge rectifier off ebay work fine? full board with 40-60.000uF caps are like $20-30
i take it softstart etc is a luxary and not needed. one rectifier board, cables, switch and the amps will work fine?
thx
Well, Nelson pass doesnt use a soft start but he almost never shuts his amps off apparently. My electricity bill was $500 last month so I am always shutting it off. If I have a party I just make sure to turn them on 2 hours before. I have had to change like 20 fuses over the last three years, not sure why, but I bet a softstart would help. I built mine according to the specs, but I only wish I would have found some better 10uf caps. F5 is, according to some, sensitive to the quality of your power supply caps. I always wanted to try larger caps as well. From what I have heard larger caps lile 60000uf can have too much bass and sound sluggish. 10000uf is quicker sounding. For some reason I prefer a 5W tube amp on my 15" woofer, and the F5 on the mid and tweeter horns for a clearer and more balanced sound.
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If you don't want to do the soft start, you can use a CL60 thermistor to limit inrush. Once it gets hot the resistance drops and then the behaves as if it wasn't there. I personally would do this especially if you use a big tx and lots of capacitors.
I used a bunch of 22000uf in my f4 psu. 4 per rail. Nothing sluggish about bass. Make sure you get low esr ones though. Maybe larger ones have a tendency go have larger esr, I don't know. Larger esr may lead to sluggishness.
If you don't mind drilling the case yourself you can get the plain case from hifi 2000 which would save quite a bit over buying the deluxe chassis. However for ease, The duluxe and chassis hardware kit are sort of worth it.
I used a bunch of 22000uf in my f4 psu. 4 per rail. Nothing sluggish about bass. Make sure you get low esr ones though. Maybe larger ones have a tendency go have larger esr, I don't know. Larger esr may lead to sluggishness.
If you don't mind drilling the case yourself you can get the plain case from hifi 2000 which would save quite a bit over buying the deluxe chassis. However for ease, The duluxe and chassis hardware kit are sort of worth it.
My research into PSU caps has lead me to the norion that a few experienced builders share, that caps should not be parallelled for the best sound.
The only stupid question is the one you don't ask. 🙂
what version F5 are you thinking of building? Only the F5Tv3 (the really big one) needs 5U/400mm chassis that are mono. All others can be built stereo. A standard F5 as shown in the link below can be built comfortable into a 4U/300mm
Firstwatt F5 amplifier v3 - diyAudio Guides
As for Chinese chassis, most everybody who has tried that has done it once, and then found the hifi2000 chassis to be well worth the cost due to quality and convenience. They are a very nice product.
IF you can do the metalwork yourself, and it's not a large inconvenience, yes, of course it will be less expensive. And will look exactly as you want it to, which is neat. But for 95% of builders, myself included, chassis is always the biggest obstacle.
The PSU board is used mainly for convenience and organization. Yes, you absolutely can make the PSU with different components and it will work perfectly. You DO need to do something about power-up inrush with big capacitors. the CL-60 in the primary circuit as shown on the PSU schematic will do the job well.
What was the rationale behind that? More paraelled caps should be able to deliver more current on demand improving bass (to be honest, it probably only has to be sufficient, there will be a point of rapidly diminishing returns) . You would need a suitably large transformer to make sure they are filled back.
The opinion I've usually heard is that more smaller caps in parallel is better. Eg, 2x10000uf would outperform a single 20000uf.
The opinion I've usually heard is that more smaller caps in parallel is better. Eg, 2x10000uf would outperform a single 20000uf.
The design of the F5 power supply has 3 CL60s in it. No softstart is needed if going by Nelson's design.
I recently bought a chinese chassis and it was cheap and it arrived fast. I then had to tap two holes to the heatsink and cut holes in the back panel. For what I was doing (not a full amp) it wasn't too bad however if I were to build another Pass amp again, which I inevitably will, I would buy the deluxe chassis, the parts kit and all that stuff from the store again because they do such a good job with it and it requires far too many holes and cuts. After going the Chinese chassis route, I now understand the value of the Hifi200 product.
When I built the F5 I remember thinking that I really didn't want to spend all that money on the parts kit and chassis but like I said, I would do it again and not think twice.
Cutting holes in chassis is my least favorite DIYAudio activity. Drilling is fine, but cut cutting for PEM/XLR sucks!
F5 specifies 6Aac (216VA) for the transformer? so most people buy a single 250VA 2x18V for 2 channels then? any point in going higher at all?
I would go a bit higher. I don't think you need to go nuts though. You do want to make sure your tx doesn't saturate and start humming. I think 300 to 400va is probably the sweet spot.
If you can afford it consider the torroidy audio supreme. It's quiet, has a shield and doesn't hum. I previously had a sedlbauer 500va and it hummed. It wasnt much cheaper. I have also had a bunch of others hum too so where possible I will be getting those.
If you can afford it consider the torroidy audio supreme. It's quiet, has a shield and doesn't hum. I previously had a sedlbauer 500va and it hummed. It wasnt much cheaper. I have also had a bunch of others hum too so where possible I will be getting those.
i thought the size caused humming, like the DC resistans of transformers 500VA or higher is less?
over here in scandinavia its all "ulveco" or noratel.
over here in scandinavia its all "ulveco" or noratel.
Ha, there's a bit of debate on that. Anecdotally, that seems to be the case but the general reason seems to be loose windings and magnetostriction. Anyway, my 400va potted torroidy is absolutely splendid. Doesnt hum and I think it made the amp sound a little better too.