Hi all,
I'm building a 2xKT88 UL bass amp. The PT is a MM P4550JT-G3, 510vdc B+ ( PT was given to me for servicing a couple of amps for a friend ). The OT is a A431S Dynaco clone ( Freaking huge! )
I emailed MM asking for a recommendation regarding a safe max amount of filtering on the first stage ( UL, so both the plates and screens ), but hadn't received a reply, so I thought I'd ask you fine folks!
I originally planned 200uf or 300uf for the first stage, 100uf for the phase inverter, 50uf each for the remaining two stages. ( I'm using ARS Marshall style can caps, and the chassis is Weber's Marshall 100 watt clone ).
Then I saw some warnings regarding putting too much capacitance on the first node, and a suggestion for using a Pi filter in place of the large 1st node.
Obviously, if going the PI filter route, I'd want to keep the choke's resistance as low as possible.. I have a Hammond 193H, rated for 5H@200ma., with 65 ohms of resistance. Does anyone feel 65ohms is too high? The configuration would be; Full wave recto, 100uf/5H/200uf, then plates/screens.. then as described above for the rest of the supply..
The only real downside I can see to going the PI route is finding a place for the choke ( The Dyna OT really is big, taking up most of the mounting area of normal OT and choke ).
I should mention this amp will be used in jazz/pop small venue situations. High volume is not a priority.
Any thoughts or suggestions?
Thanx!
Bill
I'm building a 2xKT88 UL bass amp. The PT is a MM P4550JT-G3, 510vdc B+ ( PT was given to me for servicing a couple of amps for a friend ). The OT is a A431S Dynaco clone ( Freaking huge! )
I emailed MM asking for a recommendation regarding a safe max amount of filtering on the first stage ( UL, so both the plates and screens ), but hadn't received a reply, so I thought I'd ask you fine folks!
I originally planned 200uf or 300uf for the first stage, 100uf for the phase inverter, 50uf each for the remaining two stages. ( I'm using ARS Marshall style can caps, and the chassis is Weber's Marshall 100 watt clone ).
Then I saw some warnings regarding putting too much capacitance on the first node, and a suggestion for using a Pi filter in place of the large 1st node.
Obviously, if going the PI filter route, I'd want to keep the choke's resistance as low as possible.. I have a Hammond 193H, rated for 5H@200ma., with 65 ohms of resistance. Does anyone feel 65ohms is too high? The configuration would be; Full wave recto, 100uf/5H/200uf, then plates/screens.. then as described above for the rest of the supply..
The only real downside I can see to going the PI route is finding a place for the choke ( The Dyna OT really is big, taking up most of the mounting area of normal OT and choke ).
I should mention this amp will be used in jazz/pop small venue situations. High volume is not a priority.
Any thoughts or suggestions?
Thanx!
Bill
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