Cap upgrade for amps

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rockdrummer

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Cap upgrade for amps
« on: 24 Jun 2019, 01:53 am »
Hi, I've tried to educate myself, but there is lots to know, so I'm just going to ask.

I have been reading about miflex caps to get but I'm not completely sure which ones.

I want to replace the caps in my bottlehead 2a3 amp, and my Folsom 7297 amp. I would like to lesson the load on the mids. The amps will both be driving 200hz and up, GR Research new super mini's . 200 hz and lower are servo from gr research.
I think I remember hearing the value I need as .046uf.

So as much as I need an education on caps, can someone just advise me on what to put in my amps?

Thanks
Ben

Early B.

Re: Cap upgrade for amps
« Reply #1 on: 24 Jun 2019, 02:04 am »
I'm interested in the same thing for my preamp!

It might be helpful to post pics of the guts of your amps so Jeff and others can advise you on which caps will (or won't) physically fit.

 

galyons

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Re: Cap upgrade for amps
« Reply #2 on: 24 Jun 2019, 03:32 am »
BH Stereomour, Paramounts. Paramours?  The BH amps are parallel feed. So all of them have a parafeed cap to the output transformer. Some also have an interstage coupling cap. So you need to be a bit more specific on what you actually have and which caps you want to replace.  The larger the paraeed cap, the lower the bass response goes.   If you are only driving the lower mids, then, yes, you can use a much smaller, (lower capacitance) cap.

Miflex caps a HUGE, so getting the requisite real estate may  be a challenge. 

I would  post this query on the Bottlehead forum. You are more likely to get quality responses there, perhaps even from the amp's designer.

Cheers,
Geary
« Last Edit: 24 Jun 2019, 02:42 pm by galyons »

rockdrummer

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Re: Cap upgrade for amps
« Reply #3 on: 24 Jun 2019, 04:47 am »
Thanks for the detailed responses.
Here is a photo of my stereomour. At this time, I need to get more details.


Ben

Jeff

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Re: Cap upgrade for amps
« Reply #4 on: 24 Jun 2019, 08:26 pm »
Hi, I've tried to educate myself, but there is lots to know, so I'm just going to ask.

I have been reading about miflex caps to get but I'm not completely sure which ones.

I want to replace the caps in my bottlehead 2a3 amp, and my Folsom 7297 amp. I would like to lesson the load on the mids. The amps will both be driving 200hz and up, GR Research new super mini's . 200 hz and lower are servo from gr research.
I think I remember hearing the value I need as .046uf.

So as much as I need an education on caps, can someone just advise me on what to put in my amps?

Thanks
Ben

Ben,

Hello, welcome to my circle.

Assuming you are replacing the input caps on your Folsom: http://www.soniccraft.com/product_info.php/miflex-kpcu-0033uf-600vdc-copper-foil-polypaper-in-oil-p-5292  They might be back in stock Friday :D

Assuming your Stereomour is using a 0.1uF interstage coupler followed by a 249K load resistor, you would need a 3300pF cap.  No Miflexs are this small.  This is actually a very nice cap: http://www.soniccraft.com/product_info.php/rte-3300-pf-600vdc-p-322  I'd recommend some level of matching.  Now, if you have a 3.3uF on a 4K primary on the parafeed, simply replace the 3.3uF with: http://www.soniccraft.com/product_info.php/miflex-kpcu-022uf-600vdc-copper-foil-polypaper-in-oil-p-5290

It might be helpful to post pics of the guts of your amps so Jeff and others can advise you on which caps will (or won't) physically fit.

A pic is better than nothing I suppose, but nothing beats a schematic.  As for it will, or will not, fit...  You need to take the dimensions, and cut out a piece of card stock or cardboard.  Use it to check for fitment  :wink:

You are more likely to get quality responses there

Surely you jest :roll:  Your thinking of some other circle :lol:

Early B.

Re: Cap upgrade for amps
« Reply #5 on: 24 Jun 2019, 11:40 pm »
Jeff -- try this one:

I have a PBN Olympia L preamp with outboard power supply. The preamp section has 16 Dayton Audio 0.1uF caps in it. Is there any benefit in upgrading some or all of them to Miflex KPAL caps? I realize the Miflex caps are much larger, but I think they'll fit. Unfortunately, I don't have a schematic, only a pic...




Jeff

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Re: Cap upgrade for amps
« Reply #6 on: 24 Jun 2019, 11:54 pm »
Schematic?