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paper in oil capacitor for PSE 845 amp

79.4.157.15
Posted on November 4, 2009 at 09:56:07
845cmax
Audiophile

Posts: 81
Joined: August 7, 2007
 I'm looking for a pair of good 2microF 1250V copper foil paper in oil capacitor for my monoblock parallel single ended 845 tube amp.
Anyone knows where to buy over the Internet at a honest price?
Thanks a lot.

660 VAC Siemens MKV, posted on November 6, 2009 at 07:22:56
PakProtector
Audiophile

Posts: 9949
Joined: May 14, 2002
 hey-Hey!!!,
I found some MKV at 1.5 uF on ebay a bit ago, and seen them since a few times. Very nice as coupling caps. I use a custom PP grid choke so a larger than customary cap is required. In any case I do prefer larger( 1 uF poly/tin for instance ).
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
That's a Big Capacitor!, posted on November 5, 2009 at 10:18:14
Triode_Kingdom
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Posts: 623
Location: Travelin' Man
Joined: September 24, 2006
 I'm just wondering why you need such a large value capacitor. Are you driving this amp into A2? Or is this being used for something besides coupling?
RE: That's a Big Capacitor!, posted on November 5, 2009 at 10:35:43
845cmax
Audiophile

Posts: 81
Joined: August 7, 2007
 In the original project the coupling capacitors specifications were:

2uF, 1250V

The amp is a parallel single ended configuration with one 2A3 and one 5687 as a driver ending with a pair of 845 tubes.
The +Vdc is 1050V.

RE: That's a Big Capacitor!, posted on November 5, 2009 at 13:07:58
Triode_Kingdom
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 Well, bear in mind that I'm not familiar with that specific design and haven't seen the schematic. Generally speaking, I'm always suspicious of overly large coupling caps. Some designers seem to feel that bigger is always better, probably because they've focused only on the low frequency response. However, large caps can cause problems, especially if the time constant of the circuit hasn't been analyzed. The coupling cap charges up whenever peaks cause the following stage to momentarily draw grid current. If the time constant is too long, the cap holds the charge longer than it should. This creates a bias shift and usually results in lengthening the duration of the distortion. Maybe you already know all this, and maybe the circuit has in fact been designed with this in mind. Just thought I'd throw it out for consideration. 2uF is really large.
RE: That's a Big Capacitor!, posted on November 6, 2009 at 07:38:26
845cmax
Audiophile

Posts: 81
Joined: August 7, 2007



Hi. here is the schematic.

V2 = 2A3
V3 = 5687 (originally a E182CC)
V4 and V5 = 845

Bye.

What is the Value of R21/ R18? (nt), posted on November 6, 2009 at 08:10:05
Triode_Kingdom
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Posts: 623
Location: Travelin' Man
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 asdf

RE: What is the Value of R21/ R18? (nt), posted on November 6, 2009 at 08:24:39
845cmax
Audiophile

Posts: 81
Joined: August 7, 2007



here is the component list...

SPICE, posted on November 6, 2009 at 11:13:44
Triode_Kingdom
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Location: Travelin' Man
Joined: September 24, 2006
 Well, I don't see any reason for those caps to be so large. Here's a quick graph of the response of the grid circuit. With a 0.47uF cap, it's down less than 1/2 dB at 10 Hz.
Second that ..., posted on November 8, 2009 at 04:43:01
Naz
Audiophile

Posts: 1186
Location: Sydney
Joined: September 2, 2005
 on so many fronts. 0.47uF would be the highest I'd use.

Naz

here is a 2uf@1000v but I will almoat bet you will be fine because, posted on November 5, 2009 at 07:04:41
Michael Samra
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Contributor
  Since: June 24, 2005
 the voltage most likely won't be nearly 1.2kv on the cap being its a coupler..These caps will easily handle 1200 even tho 1kv is the rating. Military caps are always conservatively rated.
If the power supply waveform isn't pretty,neither is the sound in most cases.
RE: paper in oil capacitor for PSE 845 amp, posted on November 4, 2009 at 10:31:21
danlaudionut
Audiophile

Posts: 3564
Location: Upstate NY
Joined: June 6, 2002
 845

See link below

DanL

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