I have a big three stage all SET amplifier in place with three separate anode supplies and six heater supplies. I split it into signal part, filament supply part and anode supply part and connect everything with umbilicals. When I still had the floor space and no kids I had everything on wheels.
Yeah, nothing wrong with small amps but the bigger ones are simply more fun!
Rod,
Excuse me for being lazy and not doing thorough search but do you have a heating solution for a quad of push pull 300B.
I have 2 off sets Plitron Power and Output trannies and Chassis etc ready to go for HiFi Monoblocks..
Cheers,
Ian
Excuse me for being lazy and not doing thorough search but do you have a heating solution for a quad of push pull 300B.
I have 2 off sets Plitron Power and Output trannies and Chassis etc ready to go for HiFi Monoblocks..
Cheers,
Ian
Hi Ian,
I assume you mean 2-parallel push pull per channel?
I certainly have solutions for it in any way they are combined.
For 2-parallel, if the cathode point is the same place for each of the parallel 300Bs, you can share the regulator - but the downside there is that the individual bias of each 300B must be made on the grid, if you want to have it individually adjusted; otherwise one filament rregulator per 300B, and slight variation of the cathode resistor.
Else - let me know if I guessed wrongly!
I assume you mean 2-parallel push pull per channel?
I certainly have solutions for it in any way they are combined.
For 2-parallel, if the cathode point is the same place for each of the parallel 300Bs, you can share the regulator - but the downside there is that the individual bias of each 300B must be made on the grid, if you want to have it individually adjusted; otherwise one filament rregulator per 300B, and slight variation of the cathode resistor.
Else - let me know if I guessed wrongly!
Yes,
2 parallel push pull per channel.
I have Menno/Guido bias servo boards to handle the Bias BUT that needs separate cathode current sense resistors (0V side) for each 300B (each board handles 4 output tubes so 1 in each monoblock).
Can I still share the regulator on each of the push pull sides such that I need just 2 regs for each monoblock?
While the Plitron Power Tranny has 6.3V @ 6.8 Amps heater winding that will end up driving Preamp/Phase Splitter and I will need (I believe) a dedicated supplementary tranny for the 300B filaments.
Thanks,
Ian
2 parallel push pull per channel.
I have Menno/Guido bias servo boards to handle the Bias BUT that needs separate cathode current sense resistors (0V side) for each 300B (each board handles 4 output tubes so 1 in each monoblock).
Can I still share the regulator on each of the push pull sides such that I need just 2 regs for each monoblock?
While the Plitron Power Tranny has 6.3V @ 6.8 Amps heater winding that will end up driving Preamp/Phase Splitter and I will need (I believe) a dedicated supplementary tranny for the 300B filaments.
Thanks,
Ian
Hi Ian,
Sharing the filament supply (of any type) effectively shorts (or applies low R across) the cathode points of all the DHTs involved in the share.
So if there are individual current-sense resistors for bias adjusment, the controller won't set each bias correctly.
If you have grid bias with current-sensing in the anode supply, you might adjust the grid bias individually, while all the cathodes are at ground. In this case, the PUSH and PULL sides might have one regulator each.
Sharing the filament supply (of any type) effectively shorts (or applies low R across) the cathode points of all the DHTs involved in the share.
So if there are individual current-sense resistors for bias adjusment, the controller won't set each bias correctly.
If you have grid bias with current-sensing in the anode supply, you might adjust the grid bias individually, while all the cathodes are at ground. In this case, the PUSH and PULL sides might have one regulator each.
How much delay is advisable between heating of normal preamp tubes and B+ coming on? I am having the first pondering of trying a transformer coupled DHT preamp and wondered if having an indirectly heated rectifier (like an EZ80) in the power supply would give enough of a start up delay.
I think it's best to wait for the filament voltage to be within a few percent of the nominal. Time depends on the type. Original types were rapid - many of the new production use hard tungsten instead of Nickel (or even Platinum-Iridium in some 1920s filaments). These take a LOT longer to warm up.
My preferred solution for this is now an (open-loop) anode supply stabiliser, with a power-follower that waits for a counter timeout (programmable delay). Slow rise time, also programmable.
This eliminates the need for expensive items like valve rectifiers& chokes, and sounds much better, with the effective output impedance down to a few ohms, and µV level 100Hz spurs.
My preferred solution for this is now an (open-loop) anode supply stabiliser, with a power-follower that waits for a counter timeout (programmable delay). Slow rise time, also programmable.
This eliminates the need for expensive items like valve rectifiers& chokes, and sounds much better, with the effective output impedance down to a few ohms, and µV level 100Hz spurs.
I can confirm. The thoriated tungsten filaments in my T20/TZ20 amps wakes up in a few seconds when fed from the regulators.
My JJ 300Bs on the other hand takes ridiculously long time, at the first test run I thought the filaments were broken.