I can tell you that the ULTIMA project is taking a very sharp turn! I'm going towards BATTERY POWERED tube preamp. How's that? I've just read the reviews of a battery tube preamp in 6suns.com (you know where) and I just could not believe how good that preamp can be, with a U$4000 price tag!
It is SLA powered, uses JJ tubes, Jensen foil capacitors, Panasonic electrolytic, Alps motorized pot and a ver nice chassis. The Jensen caps are placed directly beside the JJ tubes, what a joke! I guess the manufacturer must either being stupid or they just want to suck blood out of their supports for replacing the foil caps in near future.
I can do better than that, for 1/2 the price! I've talked to my hardware (chassis) manufacturer friend and he should be able to supply me a nice chassis, with cryo-option for my tube preamp project. Now that's a good start!
So this is how the new tube preamp project is going to be, with 1/2 the price but better than the U$4000 one for sure!
- NOS Tungsol 5687WA tube
- SLA (2pc - 3pc) battery powered B+/HT
- Mains powered tube filament/heating
- Integrated or exterior charger circuit
- Preamp with OPT from Sowter or capacitor coupled
- Aerospace grade aluminum chassis
- Stepped attenuator or motorized (remote controlled) Alps pot or electronic attenuator with relays + resistors
Needless to say more.
SLA (2pc - 3pc) battery powered B+/HT and mains regulated filament heating
I'm choosing at least 2 SLA, 3 with even better results and drive strength for this preamp. User can select whether to power the tube filament with battery too but optional. The reasons for not using battery for filament are because:
1. The filament draws too much current.
2. Battery heating brings not much effect on indirectly heated triode. Mains
regulated or battery heating sounds almost the same.
3. Prolongs the lifespan of your SLA.
4. Extended play time - a 5AH SLA will last > 200 hours per charge.
Exterior charger circuit
The charger is of little consequences. You choose! I would prefer it to be external so that one can buy any charger off-shelf easily. This will remove additional noise from the inner of the chassis too.
Preamp with OPT from Sowter or capacitor coupled
A good OPT is alway better than capacitor coupled. It eliminates ground loop between your preamp and power amplifier as well. It has lower output impedance to be able to drive any interconnects. Also, I can wire it to be balanced if your power amplifier accepts balanced input. The unit I chosed has a very wide bandwidth of > 10Hz - 60kHz.
Aerospace grade aluminum chassis
Rigid. Low mechanical resonances. Sturdy. Reliable. Non-magnetic. Light.
Stepped attenuator
Others possible but stepped attenuator gives the best sonic results over brush-based pots. Remote controlled attenuator with relay switching is available too but with a premium price as they're not cheap themselves.
That's it! Anyone interested, drop me an email.
Ken
