Fender 5b6 preamp

[M Fowler]

Building a Fender 5b6 preamp only no power amp section.

1/4 out jack and XLR out jack using Edcor WSM 10k/600R line transformer.

Works but not much volume with external power amp.

Any better circuit ideas? 1st schematic is the full amp circuit 2nd schematic is preamp only. Using 6SL7 tube not 6SC7 so pin numbering is different and correct on preamp schematic only version.

Mark

[xtian]

Your schematic is missing the second tridode's plate load resistor?

Anyway, did you do a voltage rundown? Seems like a two stage preamp should generate plenty of volume.

[Milkmansound]

why do you have a volume and level control? Seems redundant to me since the idea is probably a clean tone.

did you test it without the transformer on the output?

Seems like it would work to me but maybe you would do better with a second tube and a cathode follower like the Alembic bass preamp

[M Fowler]

Your schematic is missing the second tridode's plate load resistor?

Anyway, did you do a voltage rundown? Seems like a two stage preamp should generate plenty of volume.

I better change that to 100k on each plate and decrease the cathode resistor to 1k5 on each. I don't have a lot of voltage to play with.

[M Fowler]

Tim I was using that schematic and that is how I have mine wired except for the level control before the line transformer.

I have volume and tone control and final is level control.

I have not wired the 1/4 jack around the line level that I could do.

I do have a unused tube socket available in the chassis to run another tube.

[PaisleyTube]

change the cathode-resistor to 1k5 and the plate-resistor to 100k (if using a 6SL7)

maybe change the tone-cap to 0.02 or lower and change the tone-pot to 1M log

[PaisleyTube]

and.....

split the plates!!!!!!

and...........................

the transformer will load the 2nd stage-output very, very, very (and let's say) very much....................


better drive it with a CF

[M Fowler]

I'm going to change to the cathode resistors to 1k5 and 100k anode.

The preamp is working with more volume without the changes but still I agree changes should be made.

I do have low hum from the line matching transformer I think so I will wire the 1/4 out jack separate from the XLR circuit.

[PaisleyTube]

seperate plate-resistors for each stage in any way!
maybe a larger coupling cap after the 2nd stage but check my earlier EDITED post....

[M Fowler]

Changed to 220k plates and 1k5/25uf cathodes 6SL7.

Changed to full bridge rectifier for more voltage.

Works good now.

[M Fowler]

5b6 toaster preamp.

[Structo]

Cool!

Love that look!

[M Fowler]

Thanks Tom, when asked to build this preamp and saw the toaster I said yes.

[cbass]

That's kickass Mark

[M Fowler]

Cbass thanks I want to hear this preamp in action with pedal steel guitar.