Re: Re: Re: Re: Re: Re: A LA CARTE........
Yep, as explained to me, a motor start capacitor is only meant to provide the energy necessary for overcoming the centrifugal friction that a motor, like an AC compressor motor, sees at start up. As soon as the circuit senses that the motor is running, it is switched out of the circuit. If the motor can't turn over in a set amount of time, the circuit switches the capacitor out. According to this HVAC tech, a motor start capacitor is nothing more than a glorified electrolytic, i.e., it's a dry capacitor and not an oil capacitor, and is one of the most failure-prone parts in an air conditioner.
EC8010 said:
Yep, as explained to me, a motor start capacitor is only meant to provide the energy necessary for overcoming the centrifugal friction that a motor, like an AC compressor motor, sees at start up. As soon as the circuit senses that the motor is running, it is switched out of the circuit. If the motor can't turn over in a set amount of time, the circuit switches the capacitor out. According to this HVAC tech, a motor start capacitor is nothing more than a glorified electrolytic, i.e., it's a dry capacitor and not an oil capacitor, and is one of the most failure-prone parts in an air conditioner.
Best of both worlds?
How about this..?
Place an octal socket on your chassis in which to use a rectifier tube 5R4 or what ever and wire it.
Take an old octal socket from a bad tube(sorry Frank, one 6sn7 gave its life for this) gut it and place (4) 1n4007 diodes in it. Diode from pin 4 to pin3 and from pin3 to pin 1. Place another diode from pin 6 to pin 7 and pin 7 to pin 1. Jump from pin 1 to pin 8.
Plug it in and use it when and if you want. You can use it to judge the differences between SS and tube rectumfires.
I just made one and plugged it into my Dynaco Stereo 70 amplifier.
As a safety note* I filled mine with silicone to keep my grubby fingers from accidentally touching the diodes.
How about this..?
Place an octal socket on your chassis in which to use a rectifier tube 5R4 or what ever and wire it.
Take an old octal socket from a bad tube(sorry Frank, one 6sn7 gave its life for this) gut it and place (4) 1n4007 diodes in it. Diode from pin 4 to pin3 and from pin3 to pin 1. Place another diode from pin 6 to pin 7 and pin 7 to pin 1. Jump from pin 1 to pin 8.
Plug it in and use it when and if you want. You can use it to judge the differences between SS and tube rectumfires.
I just made one and plugged it into my Dynaco Stereo 70 amplifier.
As a safety note* I filled mine with silicone to keep my grubby fingers from accidentally touching the diodes.
Motor Run Caps
I have been using motor run caps (ASC) for some time in my tube equipment. For me, nothing compares and for the price they are almost free. I purchased some 100uF ASC off of Ebay a while back and redesigned my monos to use 5 of these plus a 20uF on a very short 12guage silver umbilical with one ASC Blue motor run (a special form motor run that ASC USA does - slower winding, much tighter and slow to break in but what a sound! -about 30% increase in cost) internally as the last cap on the B+. There are NO electrolytics in my B+ of the amps. My dac uses these as does my preamp, though the preamp uses 30 and 40uF ASC caps in a beautiful rosewood case.
I stress that the motor run caps are fantastic. I also have used tube rectification for many years. I currently use it in my dac and my preamp in the for of 6X4's for the preamp and EZ81's for the dac. I have also used the 5AR4's in all forms. But I also beleive that solid state rectification done correctly can be as good and has it's place. I use Stealth on my mono amps.
On my dac board I use all Black Gate capacitors (Black Gates must be left on all the time or they self heal and must go through the break-in process again) and I find the BG's excellent.
John
I have been using motor run caps (ASC) for some time in my tube equipment. For me, nothing compares and for the price they are almost free. I purchased some 100uF ASC off of Ebay a while back and redesigned my monos to use 5 of these plus a 20uF on a very short 12guage silver umbilical with one ASC Blue motor run (a special form motor run that ASC USA does - slower winding, much tighter and slow to break in but what a sound! -about 30% increase in cost) internally as the last cap on the B+. There are NO electrolytics in my B+ of the amps. My dac uses these as does my preamp, though the preamp uses 30 and 40uF ASC caps in a beautiful rosewood case.
I stress that the motor run caps are fantastic. I also have used tube rectification for many years. I currently use it in my dac and my preamp in the for of 6X4's for the preamp and EZ81's for the dac. I have also used the 5AR4's in all forms. But I also beleive that solid state rectification done correctly can be as good and has it's place. I use Stealth on my mono amps.
On my dac board I use all Black Gate capacitors (Black Gates must be left on all the time or they self heal and must go through the break-in process again) and I find the BG's excellent.
John
I have purchased from this person on Ebay and she is very nice to deal with. The price of the 100uF caps is only $9.50. I purchased 18 from her. Great shipping and I love the sound. The B+ is fast quiet and the caps are trouble free.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4662&item=3855529457&rd=1&ssPageName=WDVW
John
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4662&item=3855529457&rd=1&ssPageName=WDVW
John
That inefficient? Oops
OK,
I did some playing with Power Supply Designer. I knew I would lose volts with a tube rectification system but I didn't know how many! I can get 392+ VDC with SS rectification and a 300-0-300 Hammond (apparently, I'm still a little lost on the rated vs. actual output thing). That is with a CRC filter with 50uF first cap and 100uF second cap. I need 400VDC for my B+ so that looks pretty close. I'd be 400VDC+ with a 315V trafo.
Using tube rectification and a CLC filter I need a 350-0-350 transformer to get 398+ VDC. I can do a little better maybe with a full-wave tube rectifier but that of course means 4 tubes since I'm planning mono-blocs. I wonder how I'll fit it all on a chassis!
I would still like to do tube rectification but have to give it a second (and third and fourth probably) look.
Am I going about this the right way? My KT88 will probably be biased at 75mA. Since it is class A that should also be about the max draw. Add to that a 6N1P or as Frank suggested an ECC88. I am sizing the PS to be able to deliver 150mA minimum. Do these numbers (and those above) look at least approximately correct?
OK,
I did some playing with Power Supply Designer. I knew I would lose volts with a tube rectification system but I didn't know how many! I can get 392+ VDC with SS rectification and a 300-0-300 Hammond (apparently, I'm still a little lost on the rated vs. actual output thing). That is with a CRC filter with 50uF first cap and 100uF second cap. I need 400VDC for my B+ so that looks pretty close. I'd be 400VDC+ with a 315V trafo.
Using tube rectification and a CLC filter I need a 350-0-350 transformer to get 398+ VDC. I can do a little better maybe with a full-wave tube rectifier but that of course means 4 tubes since I'm planning mono-blocs. I wonder how I'll fit it all on a chassis!
I would still like to do tube rectification but have to give it a second (and third and fourth probably) look.
Am I going about this the right way? My KT88 will probably be biased at 75mA. Since it is class A that should also be about the max draw. Add to that a 6N1P or as Frank suggested an ECC88. I am sizing the PS to be able to deliver 150mA minimum. Do these numbers (and those above) look at least approximately correct?
Re: That inefficient? Oops
Use 6CJ3's. Cheap, quiet, tough as hell, and a much lower voltage drop than all but mercury's.
Ditto everyone else's comments re the oil caps. My system has nothing but GE oils in the PSU's.
For PSUD, I always just set the load as a CCS for th quiescent draw of the tubes. Very close in PP, and close enough in SE.
Also look at this
Sherman said:
Use 6CJ3's. Cheap, quiet, tough as hell, and a much lower voltage drop than all but mercury's.
Ditto everyone else's comments re the oil caps. My system has nothing but GE oils in the PSU's.
For PSUD, I always just set the load as a CCS for th quiescent draw of the tubes. Very close in PP, and close enough in SE.
Also look at this
Re: Re: That inefficient? Oops
Thanks for that link. It helps me clarify my thinking on caps and chokes.
Also it turns out (duh... but I really didn't know) that the valves I've been looking at are full-wave rectifiers anyway so that helps and doesn't require the extra space I thought I'd need.
So after reading that page and re-doing my PS I think I have something that will work-
350V--->valve rect--->50uF--->5Hchoke--->100uF
Looks like about 408VDC which I think is close enough for jazz.
Brett said:
Thanks for that link. It helps me clarify my thinking on caps and chokes.
Also it turns out (duh... but I really didn't know) that the valves I've been looking at are full-wave rectifiers anyway so that helps and doesn't require the extra space I thought I'd need.
So after reading that page and re-doing my PS I think I have something that will work-
350V--->valve rect--->50uF--->5Hchoke--->100uF
Looks like about 408VDC which I think is close enough for jazz.
jamato8 said:
John,
Thanks for contributing! This being my first tube rectified power supply and the cost being far more than a SS PSU I would like to get it right. I can't imagine being able to do this without this forum!
My plan, after using PSU Designer (Duncan Amp Tools) was to only have two caps on the high voltage, a smallish 50uF immediately after the rectifier and a larger 100uF after the choke.
From what I can see in PSUD if I use a 5 Henry choke between those caps my B+ is the right voltage, the right current and it appears to be very smooth. The choke is also providing filtering and is relatively large considering these will be monoblocs. I could of course either increase the value of the second cap or add additional caps. The caps are ASC oil run caps.
The cost of caps from the eBay source mentioned earlier is very reasonable so I don't have a problem either adding caps or increasing their size if necessary.
Which brings up another question- given the choice of a single large cap or a couple of smaller one which way would you go? Intuitively I would think one big cap would be better; less hookup wire, fewer solder joints and one less component to fail; however none of this is very intuitive to me!
This will be fine, providing the tube rectifier used is able to deal with 50uF. Some aren't. Check the specs.Sherman said:
Using oils, it's not going to make any real difference. Don't get too caught up in wire 'quality' at this stage. Connect it all up correctly, get it working right, and then play with differing wires if that's of interest to you. An extra wire and/or solder joint is irrelevant, and none of the components mentioned so far aren't likely to fail in the circumstances you're going to use them in.
General agreement here, but I'd still go with 100u or so if you have it.Sch3mat1c said:
Smaller caps will usually have a higher ESR, so paralleling a number of smaller caps to get the same value as one large one may not give you an effective lower impedance. And lots of smaller caps can be more expensive, or cheaper than one large one; depends on type model, manufacturer and source. Lots of small oils also take up a lot of chassis real estate.markp said:
I find that using more micro farads, to a point, gives better bass impact. I also find that using a few of a smaller value is "faster" than one large cap, but this again depends on the cap. ASC discharge very fast and I have spoken with ASC about this to try and figure out why. They have a different internal connection than most everyone else. They actually solder where as most other manufactures use a different method that possibly changes the rate of discharge. I have a Sencore capacitor analyzer and I can check ESR and the ESR of the ASC caps is very low. If you run a few of these in parrallel it is almost non measurable. But ESR also changes with frequency and this is the reason some people bypass with a .1 or .01 uF. But I no longer do this as I find it can mess up the frequency and if you start off with good quality caps to begin with you are better off not to.
John
Hi,
Most other manufacturers use us process called "shoupage" (in French, don't know the correct English term) which is similar to a weld.
Soldering should make for a slightly better contact (more reliable when stressed) but the discharge time of the cap into a given load won't change one iota for it.
There are formulas to calculate that anyway.
The trouble with using multiple caps in //, even from the same manufacturers and with the same nominal electrical data, is that they are all slightly different.
This won't be much of an issue if only a few are used but can potentially lead to odd resonances when alot of them are put in //.
Bypassing an already good cap with a smaller value only makes sense if you'd put that smaller value cap right next to the load where it would do the most good.
Results may vary according to the type of load and the class of operation it's working in.
Cheers,
Most other manufacturers use us process called "shoupage" (in French, don't know the correct English term) which is similar to a weld.
Soldering should make for a slightly better contact (more reliable when stressed) but the discharge time of the cap into a given load won't change one iota for it.
There are formulas to calculate that anyway.
The trouble with using multiple caps in //, even from the same manufacturers and with the same nominal electrical data, is that they are all slightly different.
This won't be much of an issue if only a few are used but can potentially lead to odd resonances when alot of them are put in //.
Bypassing an already good cap with a smaller value only makes sense if you'd put that smaller value cap right next to the load where it would do the most good.
Results may vary according to the type of load and the class of operation it's working in.
Cheers,
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