Need recommendation for cathode bypass cap

[andy2]

The current value is 100uf/250V. Could someone recommend a good brand?

 

[SHiFTY]

I have used Nichicon Muse from angela.com before with good results.

That is quite a high voltage rating though, I wouldn't have thought it would need to be that high. What tube is it used on and what voltage is across it? If it is only a few tens of volts, you will be able to get away with a lower voltage rating.

 

[arnoldc]

i would second the Nichicon Muse. I also used Panasonic Tsha and Black Gate Standard.

I would like to try film though, although a friend said that the Black Gate sounded better compared to a Solen on his Airthight 300B.

 

[andy2]

i would second the Nichicon Muse. I also used Panasonic Tsha and Black Gate Standard.

I would like to try film though, although a friend said that the Black Gate sounded better compared to a Solen on his Airthight 300B.

Can you use bipolar cap for cathode bypass? I think the one in the amp is unipolar.

 

[vconsumer]

I suspect that by "bipolar" you mean a non-polarized cap, like a film cap without "+" and "-" terminals. Yes, you can use a non-polarized cap.

 

[rdf]

If chassis permits also consider a polyprop and oil motor run cap. Relatively cheap and excellent quality:

http://cgi.ebay.ca/100-uF-Oil-Run-C...oryZ4662QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

If you decide on this route and it's important to you, this version of ASC sold by the above E-bay dealer has non-magnetic electrode terminals. The terminals of the domestic ASCs I bought from Digikey are strongly magnetic.

 

[Tube_Dude]

If chassis permits also consider a polyprop and oil motor run cap.

I think that is to big and then susceptible to stray noise pick up...only for a output stage, I'm afraid.

In some positions ..."size matters"...

 

[rdf]

"I think that is to big and then susceptible to stray noise pick up...only for a output stage, I'm afraid."

Not at all! The internals are shielded and the terminals are actually quite close together, about 1/2" solder to solder between the inner tangs. Conicidentally I type this while listening to a single stage headphone amp using exactly those caps in an Ultrapath position around a very high transconductance triode, the 6C45-PE. Keeping in mind Ultrapath is reputedly more prone to PS noise than typical layouts the noise spectrum of this circuit constructed on open plywood looks like (hot off the press ):

(post edited for multipull spalling errurs)

 

[andy2]

I have used Nichicon Muse from angela.com before with good results.

That is quite a high voltage rating though, I wouldn't have thought it would need to be that high. What tube is it used on and what voltage is across it? If it is only a few tens of volts, you will be able to get away with a lower voltage rating.

Shifty,

Here is the schematic.
http://www.geocities.com/hai_vu1/schematic.JPG
I am not familiar with tube amp so not sure why the rating has to be that high. The amp uses two 300B per channel which results in 22W.

 

[refference]

Hi andy2 ,

I saw the schematic diagram of your amplifier , and the value of cathode by-pass caps of output tubes is absolutely correct .

You can try another brand to see if it results in the sound's improvement . but don't try to change the rating ( uf and WVDC ) .

Try to use brands like Nichicon , Nipon Chemical , etc.

Regards

Carlos

 

[i_should_coco]

Being as this is a PP design, you could always try leaving the caps out. I don't like caps though, and find that leaving them out often brings benefits.

Cheers,
Pete

 

[refference]

Hi coco ,

Sorry to say it , but I disagree entirely .

The caps are for cathode by-pass of OUTPUT stage , you can't
leave them out of circuit , because the cathode bias resistor , is
900 ohms , so you will experiment a great decrease in the
bandwidth response , mainly in the bass frequencies .

Best regards

Carlos

 

[i_should_coco]

Hi coco ,

Sorry to say it , but I disagree entirely .

The caps are for cathode by-pass of OUTPUT stage , you can't
leave them out of circuit , because the cathode bias resistor , is
900 ohms , so you will experiment a great decrease in the
bandwidth response , mainly in the bass frequencies .

Best regards

Carlos

Oops! Actually, what I forgot to say was you would need to join the cathodes together just above the cathode resistor. This has the effect of introducing some differential action (though I admit, the resistor doesn't make for a great current source).

Works just fine on my KT88 amp. Bass is just fine and sounds better like that than with individual resistors & bypass caps.

This will require good tube matching in the absence of any individual bias adjustment.

Of course, this changes the operation of the circuit somewhat, but is easy to try. If you don't join the cathodes together, then I would agree with you.