Am I Missing Something?

[amandarae]

Hello guys,

It's been almost a year since I bought my TSE board and I am just about to start to build the amp. I try to catch up reading through the site again and I have a question.

For the "Power Transformer" requirements, the literature says: " ...needs to provide 640 or 650 volts center tapped at 150mA or more, 5 volts at 2 amps, and 6.3V at 4 amps"

5842 draws 0.3 amps(x2)and 300B draws 1.2 amps(x2) for a total of 3.0 amps.



My power transformer have the following specs:

120V/240V primary! 380-320-55 (bias tap) -0-320-380 at 200mA. 6.3VCT at 3.5A for power and input tube filaments! 5V at 3A for rectifier tubes. 5VCT at 1.5A for 300B filament.

Is the power transformer good enough for this project?

Regards!

Abe

 

[Parafeed813]

No personal experience with his products, but I love to read about Tubelab stuff.
One thing is clear for me: George puts any and all valve types in his amps. That is where the 6,3V@4A 'requirement' comes from: so you can use 6,3V power valves as well. Two KT88s plus drivers would need about 4A. Since you use 300Bs, you don't need a lot of current @ 6,3V.
Do check the actual voltage at the lower current consumption: there are power transformers that give higher voltages when loaded lighter than their rating.

 

[amandarae]

No personal experience with his products, but I love to read about Tubelab stuff.
One thing is clear for me: George puts any and all valve types in his amps. That is where the 6,3V@4A 'requirement' comes from: so you can use 6,3V power valves as well. Two KT88s plus drivers would need about 4A. Since you use 300Bs, you don't need a lot of current @ 6,3V.
Do check the actual voltage at the lower current consumption: there are power transformers that give higher voltages when loaded lighter than their rating.

Thank you for a great explanation! I am only going to build this amp as a dedicated 300B amp, so it's a go. I thought I missed something from my reading. Thanks again!

Abe

 

[Tubelab_com]

George puts any and all valve types in his amps......KT88s plus drivers would need about 4A.

Good guess, but not technically correct. Yes, I have stuffed just about anything into a TSE, but I usually use external power supplies to do it.

The parts list and transformer requirements are written for the specified tubes only. So why do you need a 4 amp transformer for 3 amps worth of tubes?

The TSE is designed for DHT's and uses DC heating on all of the tubes to achieve near zero hum, and eliminate a listener fatigue inducing 60 Hz IMD issue present in ALL AC heated DHT amps. Rectifying the output of a transformer causes the current drawn from the secondary to occur in short pulses. This increases the losses and the heat in the transformer.

Power transformers made in the last 15 years or so have been cost reduced and tend to run hotter than a similar transformer made long ago. I specified a 4 amp transformer so that just about any 4 amp transformer can deliver enough voltage to operate the regulator properly, and not get too hot. If the voltage is too low the regulator will not remove all the ripple, causing hum.

If you already have the 3.5 amp transformer, try it. It will probably work OK. I have a 3.5 amp transformer in one of my amps and it works just fine. It is a Hammond and they are known for putting out excessive voltage though.

 

[amandarae]

Good guess, but not technically correct. Yes, I have stuffed just about anything into a TSE, but I usually use external power supplies to do it.

The parts list and transformer requirements are written for the specified tubes only. So why do you need a 4 amp transformer for 3 amps worth of tubes?

The TSE is designed for DHT's and uses DC heating on all of the tubes to achieve near zero hum, and eliminate a listener fatigue inducing 60 Hz IMD issue present in ALL AC heated DHT amps. Rectifying the output of a transformer causes the current drawn from the secondary to occur in short pulses. This increases the losses and the heat in the transformer.

Power transformers made in the last 15 years or so have been cost reduced and tend to run hotter than a similar transformer made long ago. I specified a 4 amp transformer so that just about any 4 amp transformer can deliver enough voltage to operate the regulator properly, and not get too hot. If the voltage is too low the regulator will not remove all the ripple, causing hum.

If you already have the 3.5 amp transformer, try it. It will probably work OK. I have a 3.5 amp transformer in one of my amps and it works just fine. It is a Hammond and they are known for putting out excessive voltage though.

I see. It is the "Angela Universal Power Transformer" that I have.

Thank George!

Abe

 

[Doc Jr 8156]

That is what I been using for more than 3 years for my 300B TSE although I overreacted on the heatsink. No hum whatsoever. You can listen if you want. Godspeed.

 

[amandarae]

That is what I been using for more than 3 years for my 300B TSE although I overreacted on the heatsink. No hum whatsoever. You can listen if you want. Godspeed.

Cool! On a side note, did you change the grid resistor on yours to 1K CC type too?

 

[Doc Jr 8156]

Yes I did, if I'm not mistaken. The value and rating was adjusted to compensate for higher B+ tranny. Godspeed.