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In Reply to: RE: Motor Run Caps for the BB Proof Amp posted by Stuben on December 14, 2014 at 06:37:14
Hey Stuben, Garg0yle, Fried,
How 'bout this?
Panasonic or WIMA DC Link 50uf 1KV cap in C1. 12 week lead time.
Any preference between 45uf and 50uf?
Thanks,
Jamie
Big speakers and little amps blew my mind!
Follow Ups:
Jamie,
I haven't used the WIMA offering but folks on the forum speak highly of the product. I did notice that the 5V4 data sheets that I dug up states a max C1 of 32 uf...I'm sure Paul knows this rectifier well enough to exceed. I don't see why you would want to pay and wait for a 1kv capacitor though...I thought WIMA offered a 600V rated product...
Stuben
"I don't see why you would want to pay and wait for a 1kv capacitor though...I thought WIMA offered a 600V rated product..."
Gotcha. Only because it would allow for a different circuit later on.
Thanks Stuben,
Jamie
Big speakers and little amps blew my mind!
Wima also offers the DC Link caps rated for 800 and 900 v.
Mouser has many of them in stock.
Thanks Jim!
Big speakers and little amps blew my mind!
Maybe check with Paul Joppa on that one, as two of the caps after the PS in the schematic are in series, halving their capacity. (They should stay as 100uF to effectively be 50uF)The Ultrapath and the one below it.
I could be mistaken, but double check before you order.
The 267K and the 178K resistors parallel across them appear to set the 180V point. They also seem to be stabilizing the voltages seen by those two capacitors and possibly the meter.
I could be mistaken, but double check before you order.
Thanks, I will check with PJ first.
We aren't talking at cross purposes are we? I mean just one 50uf 1KV cap in C1 and that's all. The first version schem didn't have the C1 cap bypassed with 270K resistors.
Big speakers and little amps blew my mind!
Its almost YOUR choice, can be done either way.If you series two caps ( right after the tube rectifier, as an INPUT cap filter ), the two 270 K 1 Watt Rs across the supply there are necessary, they divide the raw B+ VDC across each cap equally, and they serve a secondary function of draining these caps on turn-off.
If you use a single 800 to 1,000 VDC rated quality WIMA DC LINK film in that one location, you can either add a single resistor, ( equal to the two in series used above, or 540 K 2 Watt ), to act as a drain-down, OR ... you can use NO RESISTOR there what so ever, to totally eliminate the sound of ANY Resistor across the supply.
Drain-down after turn-off will occur in either scenario with the two high value Parafeed resistors, already in this circuit, going from B+ to ground.
I always question "is this part really needed" before I add it to a amplifier's design.
Every resistor / part adds its own sound, none are perfect. The less parts I use, and the simpler the circuit, the less there is to mess with the purity of the presentation. KISS rules.
So, its up to you. Have fun, its going to become YOUR amp !!
Jeff Medwin
Edits: 12/15/14 12/15/14 12/15/14 12/15/14
Hey Jeff,
Thanks for the advice.
"If you use a single 800 to 1,000 VDC rated quality WIMA DC LINK film in that one location, you can either add a single resistor, ( equal to the two in series used above, or 540 K 2 Watt ), to act as a drain-down, OR ... you can use NO RESISTOR there what so ever, to totally eliminate the sound of ANY Resistor across the supply."
There was a DIY type tube amp designer who passed away about ten years ago. One of his trade marks was not using a bleeder resistor. Do you remember his name? He also had a rep for type 45 amps.
Being a novice I will stick with bleeder resistors for a long while. I do remember reading his cite for the concept. It was in the official ham radio manual I believe. Long time ago.
Jamie
Big speakers and little amps blew my mind!
The parafeed resistive network, from B+ to ground, already serves as a bleeder .
Was it John Hogan ?
Jeff Medwin
I wondered that as well about the resistors,
just to clarify, those two resistors (267K and 178K) and the connection to the 2A3 hum pot can be deleted? (If substituted by a 50uF 700V WIMA etc.)
Specifically can the connection right below the "180V" on the schematic be severed?
No !!!
I was just referring to the INPUT CAP, the very first part of the B+ Filter after the tube rectifier. All the parts you mentioned, on the right side of the schematic, need to stay as per Paul's design. \
Jeff Medwin
OK gotcha, the resistor part threw me off.
So I need 1 50uF and 3 100uF per amp then.
I want to cut out decoys made of Styrofoam so I am trying to get the sizes pinned down.
Cheers.
Make the 50 uF input cap an 800 VDC rating. Reliability, conservative operation. Its a stressed part at the start of the filter. Lots happening IN it !!
Jeff Medwin
Yes they are all going to be 700V/800V capacitors.
I might use the Panasonic 100uF 500V for the three other positions other then C1.
I suppose C1 could be a Panasonic 50uF 800V.
As noted by Mr. Steady the Pansonics are cheaper. Whether or not the WIMAS sound nicer, the Panasonics should be better then the Electrolytic.
The cost would be around $200 which seems to be about as good as it gets, especially given my space constraints.
Yes, yes, KEEP C1 at 800 VDC and the others at 500 VDC should be very much OK.
Do not cut yourself short on under-chassis room !!!! Some things are best short, 2 inches or less, RCA jack to driver's grid, silver wire. Silver wire on DC to 2A3 !!! Consider fields, consider layout IN ADVANCE and carefully. PJ gave a good tip on where to locate choke.
Jeff Medwin
Yes I have a general area for the choke and will try PJs trick.
Although not specified, what ever you do, be sure not use any 15A. rated IEC . Use Hubbell 20 A. rated ( Michael Percy ) IEC as a minimum, or better ....Go to Chris VH's web pages and make yourself up decent ( 12 AWG etc ) power cords, perhaps his Flavor 2. " Duster " on the Cable Forum of AA often offers suggestions on cost effective approaches. Have fun.
Jeff Medwin
Edits: 12/16/14
I have already drilled to use a M12 SVT type strain relief for the power cord.
I usually file for IEC sockets but didn't feel like it this time around.
Other then the occasional convenience and looking a little better, I don't really need the IEC socket.
So the pigtail does away with the connection all together.
This does limit the wire to SVT sizes, in my case 18awg as the 16awg SJT wires I had for the IEC sockets don't fit through the SVT pigtail.
I will check it out, although I don't put much credence beyond the usual engineering as far as wires go. I am more concerned with conforming to codes as much as possible.
I mean realistically if one felt the need for 12awg wiring it would make sense to not use the IEC at all, but then comes the challenge of trying to safely secure that thick of wire to the chassis.
Cheers
As you wish.
I am not an IEC fan. Read the Percy catalog on 20 A. IECs, and cable asylum.
On the build I am working on now, I hope to use a Neutrik PowerCon 32 A. device, in lieu of a HUBBELL 20 A. IEC. Look up Thorsten Loesch'S post on that part's use.
Jeff
You know what, I might just have to go with the WIMA caps.The size alone makes them worth a shot. The squarish shape seems to be a more compact fit compared to the Solens or ASC can-caps I was considering.
I will have to reread the the other thread as I know there was some discussion in regards to the different types of WIMA's.
Cheers.
Edits: 12/15/14
Yes for position C1 a 47uF or 50uF @1000V would work.
I think the first version just had a single C1, so didn't have any resistors.
Cheers
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