Metropoulos Forum

Lets see if I have this down.

Lets say 50uf filter caps. If I go up in value (60-80uF) there will be more filtering...so less noise and the amp will get "Tighter".

If I go lower... to say 20uf ... the amp will loosen up and filter less noise.

When saying Looser tighter I mean letting more (or less) frequencies by


Am I getting this?

The difference between 50uF and 80uF is negligible, but you do have the right idea as far as the looser/tighter feel. It also depends on which filter caps you are talking about (power, screens, PI). Your comments about "less noise" and "more frequencies" isn't really accurate though.

I'm no expert but some of the other guys will no doubt help explain things for you.

Will a GZ34 survive a 50w marshall?

I believe you should not use more than 50uF on the mains after the GZ34 you may get away with a Mullard GZ34 up to 80uF, ie a doubled up 40.

100uF (ie typical JMP 50 set up - the first can is parallel 50uF) is a big no-no .

I think you will find Novosibirs words of wisdom here somewhere

chubs wrote:Will a GZ34 survive a 50w marshall?

From where you'll take the 5V heater voltage for a GZ34 in a JTM50?

Larry

I am building this amp from scratch. The heyboer 50w PT I am using has the 5v tap.

I want to find a good setup that will allow me to switch from SS to Tube rectification. I will be using a DPDT switch... SHould I use a 5U4 ?

I want to the tube recto to really be different from the SS. What tube/ cap can compbo would do this for me?

chubs wrote:I am building this amp from scratch. I want to find a good setup that will allow me to switch from SS to Tube rectification. I will be using a DPDT switch... SHould I use a 5U4 ?

I want to the tube recto to really be different from the SS. What tube/ cap can compbo would do this for me?

I am doing the same thing, but I am using a JTM45 PT. Larry reminded me that 60uf is max for a GZ34 recto, (the cans I had were +/-20% - might have even been 30%. So with the tolerance, you could exceed the 60uf max on the recto tube. So I wired two 80uf cans in series, giving 40uf filtering. It also boosts the voltage to 900v to handle the higher voltage from the diodes. Not sure if that is the perfect way to handle this, but it sure looks good on paper. I am wirinig it up with the recto first, then I am going to fire up the amp. Then I will wire in the switch and diodes. Good luck!

Jack

Steve (SDM) gave me another trick

If you use a DPDT switch to go from Tube to SS rectification, use the other side of the switch to jumper (or remove jumper) on the first cap can... Going from 100uF (SS) to 50 Uf when is Tube mode. Basicaly remove one can fromthe equation when in Tube mode.

Pertty smart is you ask me...

The tolerences on the 50uf can make it exceed the 60uf max for tube recto. Not sure in the real world if this will kill the tube or what, but on paper it has the potential to exceed the max.

Also, you could have surges that exceed 500v that over time can kill the cap. What voltage is your can rated for?? Mine were 450v.

Jack

chubs wrote:Steve (SDM) gave me another trick

If you use a DPDT switch to go from Tube to SS rectification, use the other side of the switch to jumper (or remove jumper) on the first cap can... Going from 100uF (SS) to 50 Uf when is Tube mode. Basicaly remove one can fromthe equation when in Tube mode.

Pertty smart is you ask me...

Do you have a schematic for that ?

Here is a layout.

Basicaly when switching to tube rect you are breaking the jumper between the 2 50/50 caps