Does the winking smiley mean I've actually done a really shoddy job? 🙂
Thanks for all the help. I'll go buy some more parts today, a lower valued capacitor and some high powered bolt-on resistors if I can find them in the right values.
Hell no! There are a lot of us who've had more experience, and don't turn out something as good.Saurav said:
Saurav said:
You're welcome 🙂 (careful with the smile)
Now: How does it sound?
Cheers,
Thank you for the kind words. The amp sounds beautiful. Effortless, relaxed, smooth. Compared to my earlier amps (ASL Waves, *excellent* amps for $200, but nevertheless, there's only so much you can do with $200), sounds decay for much longer, where earlier they'd get lost in the hash. I think this amp handles overload situations better too, because on old vinyl, the music seems to be "visible" through the surface noise much better than before. I haven't yet tried any complex/congested music, that's one area where the ASL Waves were a little weak and I expect this amp to be a lot better.
It took me a little while to relax about the 6SL7's plate voltage being 330 where it should have been 300, and more importantly, it's cathode-heater voltage being 94 where the max allowed is 90. It's hard to set the voltage divider for the 6SL7's heater when my B+ is going all over the place with the changes I was making. Once I've sorted my B+ out, it'll be easier to pick resistor values to get the heater at the potential I want. I figured the 6SL7s would survive for a night or two with the heater-cathode voltage being 4% over spec.
You really don't know what your speakers are capable of until you drive them with a good amp.
It took me a little while to relax about the 6SL7's plate voltage being 330 where it should have been 300, and more importantly, it's cathode-heater voltage being 94 where the max allowed is 90. It's hard to set the voltage divider for the 6SL7's heater when my B+ is going all over the place with the changes I was making. Once I've sorted my B+ out, it'll be easier to pick resistor values to get the heater at the potential I want. I figured the 6SL7s would survive for a night or two with the heater-cathode voltage being 4% over spec.
You really don't know what your speakers are capable of until you drive them with a good amp.
LOL! Listening to music, at least for a few days, hopefully, before I start getting itchy again 🙂
OK, I think this should do it:
My current PSU has a 4.7uF cap in the first position, and both voltages are about 20V too high. I found a 3uF 450V myar cap at the surplus store (Aerovox, is anyone familiar with that name?) It was interesting to see Sprague/Wima MKP caps, Dale resistors etc., looking a little dusty and priced quite a bit lower than online dealers.
You can't see it in the scan, but the peak voltage on C1 is 438 and RMS is 345, so I think a 450V cap should be OK here. I spent a long time looking for 600V caps in the 2-3uF range but couldn't find any. I then remembered that the only time I'd seen the voltage go up above 400V was when I had only the 5AR4 in the circuit, so I think this should be fine. Not 100% idiot proof, but I'm sure there are other areas in this amp where an inexperienced user could cause damage.
An externally hosted image should be here but it was not working when we last tested it.
My current PSU has a 4.7uF cap in the first position, and both voltages are about 20V too high. I found a 3uF 450V myar cap at the surplus store (Aerovox, is anyone familiar with that name?) It was interesting to see Sprague/Wima MKP caps, Dale resistors etc., looking a little dusty and priced quite a bit lower than online dealers.
You can't see it in the scan, but the peak voltage on C1 is 438 and RMS is 345, so I think a 450V cap should be OK here. I spent a long time looking for 600V caps in the 2-3uF range but couldn't find any. I then remembered that the only time I'd seen the voltage go up above 400V was when I had only the 5AR4 in the circuit, so I think this should be fine. Not 100% idiot proof, but I'm sure there are other areas in this amp where an inexperienced user could cause damage.
There's nothing quite like reality...
BHC Aerovox is a British manufacturer, they're on the web. Capacitors care about peak voltages, but RMS currents. You need to find out the Equivalent Series Resistance (ESR) of your capacitors (the manufacturers give values at 120Hz), and compare the reservoir capacitor's ripple current rating to the RMS current predicted by PSUD. You can then replace the 2R default values in PSUD, and if you have not already done so, use accurate values for the transformer winding resistance. You need to be very careful with simulations, they're quite useful, IF they are given accurate data...
BHC Aerovox is a British manufacturer, they're on the web. Capacitors care about peak voltages, but RMS currents. You need to find out the Equivalent Series Resistance (ESR) of your capacitors (the manufacturers give values at 120Hz), and compare the reservoir capacitor's ripple current rating to the RMS current predicted by PSUD. You can then replace the 2R default values in PSUD, and if you have not already done so, use accurate values for the transformer winding resistance. You need to be very careful with simulations, they're quite useful, IF they are given accurate data...
I should have done that before I wired everything up, I realized that yesterday. I should be able to get a proper reading with the rectifier out of the circuit though, the CT to ground shouldn't make a difference to the resistance seen by the DMM. I measured the choke's DCR and updated my model with it. I'll look up the capacitor's ESR.
That's good advice.
I found discussions about their motor run caps. They seem to be a pretty decent quality manufacturer, based on the opinions I read.
Hmm. Here's what the cap says:
Aerovox
AFPS 3 uF
K/450 VDC
Assembled in Mexico
It has 00-48 along one edge. The cap is a 1" long plasticy cylinder with an oval cross-section. Both ends are a blue plasticky material. One lead comes out the center of the oval end face, the other lead runs along the outer surface of the cylinder (I can see the lead under the wrapped cover with the lettering). This lead also has a green line marked in by hand over it.
I can't find an AFPS series on their website. Does the green line mean that's the side which goes to ground? Since that lead's on the outside, I would assume that's what it means?
It kinda looks like the middle cap in the top row here, except the ends are blue:
Looking through the tables, all the 3uF caps here have similar ESR and ripple current ratings, so I'll use these. Does anyone have any idea what the green line means?
Here's the HTML catalog: http://www.aerovox.com/catalogs/arpt_afpt/index.htm
Aerovox
AFPS 3 uF
K/450 VDC
Assembled in Mexico
It has 00-48 along one edge. The cap is a 1" long plasticy cylinder with an oval cross-section. Both ends are a blue plasticky material. One lead comes out the center of the oval end face, the other lead runs along the outer surface of the cylinder (I can see the lead under the wrapped cover with the lettering). This lead also has a green line marked in by hand over it.
I can't find an AFPS series on their website. Does the green line mean that's the side which goes to ground? Since that lead's on the outside, I would assume that's what it means?
It kinda looks like the middle cap in the top row here, except the ends are blue:
An externally hosted image should be here but it was not working when we last tested it.
Looking through the tables, all the 3uF caps here have similar ESR and ripple current ratings, so I'll use these. Does anyone have any idea what the green line means?
Here's the HTML catalog: http://www.aerovox.com/catalogs/arpt_afpt/index.htm
The green line means "outer foil" and should be connected to the lowest impedance to ground. That means that if you are using it as a coupling capacitor, the foil goes to the output of the preceding stage.
Thanks. That's what I thought it meant, but it's better to check than make assumptions 🙂 Reading Morgan Jones' book helped me to understand a lot of stuff I always read about caps but didn't understand the reasons behind.
Hi Saurav;
Your amp is really looking good!
Just a couple comments, while I'm waiting for the paint to dry on a CD stand that's under construction:
1. I really wouldn't get TOO hot and bothered if a 10w wirewound resistor dissipating 2 watts gets hot. That's normal. OTOH, it's best to keep things cool for the longest lifespan on the other components in the amp (particularly electrolytic caps and and carbon comp resistors) so switching to heat sinked metal finned resistors would be a good move. EC8010 definitely gave you some worthwhile advice there!
2. Valves are pretty darn tough customers! A little extra voltage won't necessarily hurt anything, unlike SS equipment. I'd be more concerned about an excess of overall plate dissipation than a little extra voltage (particularly if it's not arcing or otherwise misbehaving). Even so, I've been known to allow an extra tenth of a watt dissipation on output valves without losing sleep. To each his own....
3. If you really want to get a 'lotta bang for the buck' improvement (literally), you could put a .1uF "X" class 250VAC UL Listed safety cap** in as a mains RF filter. My 2A3 improved surprisingly with such a tiny little tweak - enough so that I now have it as a standard feature on all my amps.
4. For the best air circulation, you ought to put some sort of feet under your amp's chassis so that air can flow up from beneath. In conjunction with a few strategically placed vents, it's a cheap way to help cool things down.
Enjoy your amp!! 🙂
All the best,
Morse
**For the record, under no circumstances should a non-"X" rated safety cap ever be used in a mains filter - any other capacitor type is a potential fire hazard in this application. Personally I have had excellent results with Panasonic X2 caps that are designed specifically as interference filters. They're about a buck apiece from Digikey.
Your amp is really looking good!
Just a couple comments, while I'm waiting for the paint to dry on a CD stand that's under construction:
1. I really wouldn't get TOO hot and bothered if a 10w wirewound resistor dissipating 2 watts gets hot. That's normal. OTOH, it's best to keep things cool for the longest lifespan on the other components in the amp (particularly electrolytic caps and and carbon comp resistors) so switching to heat sinked metal finned resistors would be a good move. EC8010 definitely gave you some worthwhile advice there!
2. Valves are pretty darn tough customers! A little extra voltage won't necessarily hurt anything, unlike SS equipment. I'd be more concerned about an excess of overall plate dissipation than a little extra voltage (particularly if it's not arcing or otherwise misbehaving). Even so, I've been known to allow an extra tenth of a watt dissipation on output valves without losing sleep. To each his own....
3. If you really want to get a 'lotta bang for the buck' improvement (literally), you could put a .1uF "X" class 250VAC UL Listed safety cap** in as a mains RF filter. My 2A3 improved surprisingly with such a tiny little tweak - enough so that I now have it as a standard feature on all my amps.
4. For the best air circulation, you ought to put some sort of feet under your amp's chassis so that air can flow up from beneath. In conjunction with a few strategically placed vents, it's a cheap way to help cool things down.
Enjoy your amp!! 🙂
All the best,
Morse
**For the record, under no circumstances should a non-"X" rated safety cap ever be used in a mains filter - any other capacitor type is a potential fire hazard in this application. Personally I have had excellent results with Panasonic X2 caps that are designed specifically as interference filters. They're about a buck apiece from Digikey.
Done that already. I had one left over from a previous project when I ordered 2 of everything, forgetting that the power supply parts list was common to both channels.
Done that already too 🙂 Though the feet aren't very big, because there's only so much contact area for the glue to hold on.
I got a lower valued filter cap, and that's brought my B+ down to something that I think will be fine. I picked up a couple of 100 ohm 40W resistors too, I might throw one of those in there. They're not as nice as the cathode bias resistors I have in my amp, but they do bolt on to the chassis, and it looks like the metal will help dissipate heat.
That's good advice. I'll probably write down all my voltage measurements tonight and do the calculations. So far I was just trying to get them close to the values in the schematic.
X-CLASS.
Hi,
Actually, while I fully understand your warning, you can use any filmcap as long as you're aware that X-class caps are rated for AC voltage service and other filmcaps such as coupling caps are rated for their DC blocking service.
So, generally speaking a 600VDC rated cap shouldn't have any trouble working at 115/240 VAC.
What you have to be aware of though is that some, not all, X-rated caps sometimes contain a resistor as well, which make them more ideal for snubber service at the primary side of a xformer or across rectifier diodes for instance.
Cheers,😉
Hi,
Actually, while I fully understand your warning, you can use any filmcap as long as you're aware that X-class caps are rated for AC voltage service and other filmcaps such as coupling caps are rated for their DC blocking service.
So, generally speaking a 600VDC rated cap shouldn't have any trouble working at 115/240 VAC.
What you have to be aware of though is that some, not all, X-rated caps sometimes contain a resistor as well, which make them more ideal for snubber service at the primary side of a xformer or across rectifier diodes for instance.
Cheers,😉
Hi Frank;
Sorry about making my posts look like the boiler plate on the bottom of a contract, but we live in a litigious society and I just like to play it safe!! 😉
One thing to add is that I always put my "X" caps after the fuses. That way if they do fail catastrophically, I've got something to "catch" it.
Anyway, my understanding is that "X" caps are designed to take powerline spikes without failing, and when they do fail, to fail open rather than closed. Also, the small supply of 'em I have over here are all potted in fire retardent materials. They're really pretty imposing things!
Personally I would spend the $1 or so on the 'real deal' and not worry, but to each his own!!
All the best,
Morse
Sorry about making my posts look like the boiler plate on the bottom of a contract, but we live in a litigious society and I just like to play it safe!! 😉
One thing to add is that I always put my "X" caps after the fuses. That way if they do fail catastrophically, I've got something to "catch" it.
Anyway, my understanding is that "X" caps are designed to take powerline spikes without failing, and when they do fail, to fail open rather than closed. Also, the small supply of 'em I have over here are all potted in fire retardent materials. They're really pretty imposing things!
Personally I would spend the $1 or so on the 'real deal' and not worry, but to each his own!!
All the best,
Morse
Hi Morse,
No problem.It is always best to use the appropiate part for the task at hand.
No arguing there.
Same to you,😎
No problem.It is always best to use the appropiate part for the task at hand.
No arguing there.
Same to you,😎
Whilst I welcome you back Frank, I must take issue with your suggestion of using non x-rated and y-rated caps in mains filters.
These certified components are manufactured specially for this purpose, and have special features. A few are:
A guaranteed max leakage
Self healing
Max value
Flamability and gas safeguards
But most importantly, they are subject to a strict QC.
Whilst other caps may be as good, there is no guarantee and no certification.
Cheers,
These certified components are manufactured specially for this purpose, and have special features. A few are:
A guaranteed max leakage
Self healing
Max value
Flamability and gas safeguards
But most importantly, they are subject to a strict QC.
Whilst other caps may be as good, there is no guarantee and no certification.
Cheers,
RE:SAFETY POLICIES.
Hi,
Thank you for the welcome back.
I'm certainly not going to argue about the obvious.
Surely, I wouldn't spread this old fox trick through the forum so, let's just disregard it and stick to the appropriate parts as I suggested.
Fair enough, I suppose it's only reasonable to assume that you know what you're doing...so, do I but it would be unfair to assume the same of all the pundits...
No big deal,😉
Hi,
Thank you for the welcome back.
I'm certainly not going to argue about the obvious.
Surely, I wouldn't spread this old fox trick through the forum so, let's just disregard it and stick to the appropriate parts as I suggested.
Fair enough, I suppose it's only reasonable to assume that you know what you're doing...so, do I but it would be unfair to assume the same of all the pundits...
No big deal,😉
Morse....
Morse, maybe I am too late. I was going to mention I found a body painting private shop, locally, who does professional baked on (I forget what you call it now) for cheap, like $25.00.
My painter does race cars for the local Peoria racers. If you are still looking, I found mine by going to the paint shops and asking around.
Hope this helps Morse.
Steve
Morse, maybe I am too late. I was going to mention I found a body painting private shop, locally, who does professional baked on (I forget what you call it now) for cheap, like $25.00.
My painter does race cars for the local Peoria racers. If you are still looking, I found mine by going to the paint shops and asking around.
Hope this helps Morse.
Steve
PAINT IT BLACK.
Hi,
Steve, you're one helluva fellow.😉
Here's what I do if I feel that I can't get professional results by doing it myself:
I call upon a garage that has a bodywork spray cabin and tell them the paint has to withstand high temperature and has to be scratchproof.
Upon which they usually suggest an epoxy powder coating which does all of the above.
Cheers,😉
Hi,
Steve, you're one helluva fellow.😉
Here's what I do if I feel that I can't get professional results by doing it myself:
I call upon a garage that has a bodywork spray cabin and tell them the paint has to withstand high temperature and has to be scratchproof.
Upon which they usually suggest an epoxy powder coating which does all of the above.
Cheers,😉
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