Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: TIMBO on November 06, 2010, 02:05:21 am

Title: OT Question
Post by: TIMBO on November 06, 2010, 02:05:21 am

Hi guys, Putting a little amp together. I've got a magnetic components 15w SE OT and it has two primary taps 5K and 8K.The amp has a single 6L6GC .What tap shall i use?? Thanks

Title: Re: OT Question
Post by: LooseChange on November 06, 2010, 05:48:30 am

6L6=5K, 6V6-9K.  But try them both for tonal excitement.

Title: Re: OT Question
Post by: TIMBO on November 06, 2010, 04:50:46 pm

Thanks for the reply LC. So it might be useful to add a switch to allow the use of both types of tubes?? Would the existing resistors/caps allow for a simple tube change?? Thanks

Title: Re: OT Question
Post by: PRR on November 06, 2010, 08:55:22 pm

For 6V6 6L6 EL34: ten times the cathode resistor.

5600 ohm load.

_IF_ the cathode resistor is correctly choosen!!


Or--

You got like 450V B+. Say 400V across the tube.

6L6GC is rated 30W. Pretend this is safe. 30W/400V is 75mA. 400V/75mA is 5333 ohms. Your pentode's optimum power-output load will be in-sight of this value.

This is all scatter-shot. Transformer is just a lever. The real load is the speaker. An "8 ohm" speaker will be 7 ohms near 400Hz, 9-15 ohms over much of the guitar band, and 50 ohms at bass resonance.

You can't hurt an SE amp by trying different impedances.

This amp is NOT suitable for happy 6V6. Connect pin 1 to pin 8 and try EL34.

Title: Re: OT Question
Post by: TIMBO on November 07, 2010, 12:37:04 am

Thanks guy's, ive just updated the schem.