Updated...Foreplay ll, interested in ps cap mod, how to identify 1st, 2nd and 3rd stage

hron61

hron61

Member
I am interested in modding one of my power supply caps with film and maybe doing the bypass at some point but cant for the life of me find info on the three ps caps 1st thru 3rd stage.
Which is which? I feel like a dummy by not knowing.
Im not very good with electronics and im learning some as i read alot of the thousands of posts here from the begining to now but ive yet to come across one that explains which is which.
A picture would be awesome if possible. Thanks.
 
Well the Foreplay II predates the existence of the Bottlehead forum that's not hosted by the Audio Asylum, so I don't think we can fault you for not being able to find this information. 

The last power supply cap is the 220uF/250V cap that's closest to the 12AU7 tube sockets. 

https://www.mouser.com/ProductDetail/WIMA/DCP4G061007ID4KSSD?qs=RB4whv9F6rw7LG5OrQv1Tw%3D%3D

You could probably glue a pair of these to the chassis plate to use in place of the last 220uF cap (use the black RTV available at your local autoparts store). 
 
Hello and thanks for the info on the ps cap stages.
So, the wima caps sound like something i would be interested in doing next and i think i would prefer that over a bypass.
I read the specs on them and they are quite large indeed but i'll squeeze then in somehow.
I noticed they have 4 leads each, how do they get wired in? Only 2 leads on existing caps.
Again i am learning as i go and value your input and knowledge you provide.


 
If you set your meter to read continuity, you'll find that there are two pairs of leads that are connected in parallel.
 
So if im understanding correctly the other 4 leads dont get connected, just left unhooked?
Is magnet wire needed to lengthen the leads or will stranded wire be ok?
Just never seen in person and by the picture on the website it looks like the leads are super short.
 
hron61 said:
So if im understanding correctly the other 4 leads dont get connected, just left unhooked?
Click to expand...
If there are 4 leads on the cap and you leave 4 leads disconnected, then the cap won't be connected to anything... All you are doing with the meter it to check to see which pair of leads are internally connected together inside the cap.
hron61 said:
Is magnet wire needed to lengthen the leads or will stranded wire be ok?
Click to expand...
I would get some 20-22 AWG solid core tinned hookup wire.  I would not use the magnet wire (it's a pain to work with), and stranded wire is not all that pleasant to work with in situations like this either.
 
Ok im following you now.
Was reading that the 2 leads on each end are connected together internally but I'll double check that when I get them.
I'll get the caps and wire ordered here soon.
 
Ok, im updating this post.
Question for Paul.
The 2 wima caps you recommended total together 200uf and the ps cap is 220uf.
Will being short 20uf affect the sound in any way?
I ordered the updated xo series auricaps and after they are broken in i want to install the wima's in the last stage of the ps.
 
No, 20uF isn't going to make much of a difference. The tolerance on a lot of electrolytic caps is +/-20% anyway, so your 220uF power supply cap could be 176uF and it would still meet its specifications.
 
Great and thanks for the quick reply.
I'll have Mrs. Santa order up a pair for me for Christmas as i have been good this year...mostly. ;)

Have a wonderful holiday season Mr. Birkeland :)
 
Quick question.
The ps caps are polarized, the wima films are not, correct?
Does it matter which direction they are installed?
 
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Great, thanks.
Also received my Auricap 3.0uf 200v XO caps today.
Im hoping to get them installed this weekend.

Something unrelated to these posts is while i was surfing on the used audio gear page on the gig harbor audio website they have a pair of your 838 mono blocks for sale that you built?? Same name as you.
Was it a one off or something you made many of?
I visit his store now and again since im just over the narrows bridge from them.
 
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I've made a few 838 amps over the years, and really I only need one set here, so I've been letting some of the others go.
 
Very cool.
If i had learned audio electronics in my younger days im sure i would have built many amps and preamps as well. So many different circuits to try with different sounds.
Wish things were different but life got in the way and electronics were not in my flight path unfortunately, but great sounding music is. Just got into this hobby way too late, but been listening to music since i was 5.

I do have another question also, another option for the last ps cap i was thinking of too was if i replaced it with a solen film what value uf is recommended?
Im still going to use a pair of wima's first but at some point a solen film may get put in that spot someday instead.
 
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Hi Paul, a quick question if i may.
The last cap in the power supply, i have a bunch of 0.1uf 630v pio duelund caps waiting to be installed in my 300b amp but it will be awhile before i get to that, so i was thinking of using one for a bypass for the time being untill i get a pair of wima's.
Any issue with going from 22uf straight to 0.1uf?
I know about the 10% rule but im curious if that would work also.
 
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There is also a 1% rule, and a 0.1% rule, and a 0.01% rule supported on the web. I think everyone is just guessing. So you'll have to try it and see. There is a calculable effect, but it is tiny, depends on the effective series esistance and inductance of the capacitors and associated wiring, which are rarely available, depend on the layout and wiring and (in electrolytic capacitors) not constant with time.
 
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