Hi All! First post, so I hope Ya'll will bear with me!
I was hoping someone could give a little experience/advice. I’ve been upgrading a hybrid tube headphone amp that has very limited space, mainly bypassing a few electrolytics and replacing signal path caps with higher grade ones. The headphone amp is a Schiit Mjolnir 2, a hybrid Tube/FET model with plenty of power. One of its design constraints was to use a non-regulated 6 volt supply for the tube heaters, just a simple RC network after the bridge rectifier (coming off a multi-secondary transformer). I'm considering upgrading that. and have been shopping for standalone, regulated PS circuit boards/kits/modules. As space is limited in the amp chassis, it would have to be separately enclosed in an external case. The easiest method to pipe this in would be to remove the original bridge rectifier and caps from the 6 volt heater rail of the headphone amp (thus disabling that secondary tap of the transformer) and hook up directly where the previous RC filter caps were (via an external port). But now I would be tying two separate circuit grounds together, as well as case grounds. So here are a few questions.
The other method, which would be harder (and somewhat irreversible), would be to solder the external supply directly (via the external port) to the tube sockets, but then there is the problem of having to isolate those pins from the main circuit board. It might be able to be done by cutting traces/etc., but this is a 4 layer board and there may be connections or circuit trace routing I don’t know about. . There is no schematic. This method would also make it less easily reversed if I don’t like the results and wish to restore.
The purpose of this parallel supply isn’t per say to change unregulated tube heaters to regulated ones. That improvement would be incidental. Instead, I want to increase the max amperage of the filament circuit. Max current for a 6DJ8 tube is around 325 mA. I want to add flexibility in the type of tubes I can use with the headphone am, to be able to use 6414’s,6829's,E180cc's, or others (w/adapters),up to 500mA. So I’m trying to gain about a 1/4 Amp more heater current or so, about an amp total. Of course, I'd be glad for any benefit regulated filaments would give me, but the main purpose is tube rolling.
What do Ya’ll think? Any experience on something similar?
I was hoping someone could give a little experience/advice. I’ve been upgrading a hybrid tube headphone amp that has very limited space, mainly bypassing a few electrolytics and replacing signal path caps with higher grade ones. The headphone amp is a Schiit Mjolnir 2, a hybrid Tube/FET model with plenty of power. One of its design constraints was to use a non-regulated 6 volt supply for the tube heaters, just a simple RC network after the bridge rectifier (coming off a multi-secondary transformer). I'm considering upgrading that. and have been shopping for standalone, regulated PS circuit boards/kits/modules. As space is limited in the amp chassis, it would have to be separately enclosed in an external case. The easiest method to pipe this in would be to remove the original bridge rectifier and caps from the 6 volt heater rail of the headphone amp (thus disabling that secondary tap of the transformer) and hook up directly where the previous RC filter caps were (via an external port). But now I would be tying two separate circuit grounds together, as well as case grounds. So here are a few questions.
- Would that be SAFE,?
- Would it be stable?
- Would it be prone to noise/hum?
- Would it be advisable to tie the chassis grounds together? Or what grouding scheme would you use?
- I would be removing a load on the secondary winding from the original multi-secondary transformer. Would that effect voltage/current on the other secondaries? Would I need to compensate for those extra voltages/amperages (there are 4 secondary windings on the transformer) since a 6 volt secondary is now unused/unloaded?
The other method, which would be harder (and somewhat irreversible), would be to solder the external supply directly (via the external port) to the tube sockets, but then there is the problem of having to isolate those pins from the main circuit board. It might be able to be done by cutting traces/etc., but this is a 4 layer board and there may be connections or circuit trace routing I don’t know about. . There is no schematic. This method would also make it less easily reversed if I don’t like the results and wish to restore.
The purpose of this parallel supply isn’t per say to change unregulated tube heaters to regulated ones. That improvement would be incidental. Instead, I want to increase the max amperage of the filament circuit. Max current for a 6DJ8 tube is around 325 mA. I want to add flexibility in the type of tubes I can use with the headphone am, to be able to use 6414’s,6829's,E180cc's, or others (w/adapters),up to 500mA. So I’m trying to gain about a 1/4 Amp more heater current or so, about an amp total. Of course, I'd be glad for any benefit regulated filaments would give me, but the main purpose is tube rolling.
What do Ya’ll think? Any experience on something similar?