Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plumcrazyfx on February 17, 2018, 03:10:58 pm

Title: Looking for transformer for SE 6CL6 amp.
Post by: plumcrazyfx on February 17, 2018, 03:10:58 pm

I want to build a small practice amp in the 1-3watt range.  Wondering if anyone has already done the math - Probably looking at a Hammond 269AX for the power transformer.  Going to connect it to on of those $10 Eminence 4ohm 6 inch speakers you can get from Parts Express.  Thanks.

Title: Re: Looking for transformer for SE 6CL6 amp.
Post by: shooter on February 17, 2018, 03:19:37 pm

here's the data sheet;

http://tubedata.milbert.com/sheets/093/6/6CL6.pdf

at 250vdc plate looks happy with 7.5k OT primary, guessing anything 5-8k will get you by

Title: Re: Looking for transformer for SE 6CL6 amp.
Post by: plumcrazyfx on February 17, 2018, 04:27:03 pm

Thanks.

Title: Re: Looking for transformer for SE 6CL6 amp.
Post by: PRR on February 18, 2018, 01:54:19 pm

> Hammond 269AX

250VAC CT. Will give 160V DC with two Si diodes, 110V DC with a vacuum rectifier, 320V DC with a full wave bridge.

With presumed 150VDC on 6CL6, we can get 60mA peak at the knee, so idle at 30mA. The plate swing can be 150V 30mA to 50V 60mA, peak swing 100V 30mA. This comes to 1.5 Watts rms in 3,300 Ohms. At 150V P and G2, G1 needs 3V bias for 30mA, so 100r cathode resistor. A single pentode ahead would make a ton of drive. A dual triode will need added loss to not be too-too-hot.

Assumed 300V B+ gives 25mA for full Pdiss. Swing down to 50mA 40V. 260V 25mA swing is 3+ Watts in 10.4K load. 3.5V G1 at 25mA is 140 Ohm RK.

Cheapest to meet your 1-3W spec might be Fender Reverb transformer with any tube to work at 300V 20mA. That's not a heavy-bass transformer but neither is the proposed 6-inch speaker.

Title: Re: Looking for transformer for SE 6CL6 amp.
Post by: plumcrazyfx on February 18, 2018, 07:10:43 pm

I was thinking of going the 2 diode route for the 150V and making the preamp a 6SJ7, 6J6, 6au6, or 5879 since I have a ton of them.

Title: Re: Looking for transformer for SE 6CL6 amp.
Post by: plumcrazyfx on February 19, 2018, 05:51:10 am

So with a 3300 @ 150 volt I'm probably best going to go with the 2500 tap on a 125ase?