Help understanding schematic

[munkeyboy]

I picked up this 6V6 beauty at a flea market while traveling.  It's missing the tuning dial pointer, the back and has a mismatch tuning knob.  I was just going to repurpose the iron for SE guitar amp.  But saw that it has a phono input setting.   Looking at the schematic, I was doubtful it would work as is for guitar, but I was wrong and would like to know why.   It sound great with guitar.  And am/fm works too.  Not much output (3watts), but good breakup dimed.  Still have some work to do (it looks to have been recapped with Mallory's, but the filter cap can was not touched  ).

I think it is the complex switch that is throwing me off, but from what I can see there is only the single 6av6 as the preamp for phono.  Am I wrong?

[sluckey]

I think it is the complex switch that is throwing me off, but from what I can see there is only the single 6av6 as the preamp for phono.

That's correct.

[PRR]

You probably think "phono" is 5mV and 47k and a falling RIAA curve.

Up to 1950, domestic electric phono was a lot like a telephone receiver. Fairly high level and "flat" response. Fashion turned to crystal/ceramic needles, again high-level and "flat". In modern terms, these are both hi-Z line inputs.

Yes, a geetar should work there, but sensitivity is lower than customary. Your arm gets a good workout.

[munkeyboy]

So if I wanted to add a gain by replacing 6av6 with new wiring for 6J6 or modding for a 9 pin 12ax7, what can I do for the diodes I'm lossing in the 6av6? If I made changes, I would rather keep the am/fm functions.

[kagliostro]

No need to look for other tubes

in that chassis you have 6AU6 and 6X8 both are tubes you can use to rearrange a more gain preamp for your SE

I'm sure that more than a guy here on the forum can help you to use the tubes you have for your purpose

This is from our friend DummyLoad (may be he can give you more info about)



Franco

[pdf64]

That pot with 3 wipers seems wacky!

[sluckey]

That pot with 3 wipers seems wacky!

There's only one wiper. Pins 4 and 5 are fixed taps, one at 250K, the other at 500K. The 250K tap is connected to a common "loudness" compensation filter to provide better bass at low volume. The not so common 500K tap is also part of the tone network. I've never seen that before.

[munkeyboy]

No need to look for other tubes

in that chassis you have 6AU6 and 6X8 both are tubes you can use to rearrange a more gain preamp for your SE

I'm sure that more than a guy here on the forum can help you to use the tubes you have for your purpose

This is from our friend DummyLoad (may be he can give you more info about)



Franco

Well, I want to keep the am/fm functions if possible.  If I rearrange the other tubes, I will lose those functions.

[sluckey]

So if I wanted to add a gain by replacing 6av6 with new wiring for 6J6 or modding for a 9 pin 12ax7, what can I do for the diodes I'm lossing in the 6av6? If I made changes, I would rather keep the am/fm functions.

Replace the tube diode (only one is being used) with a 1N34.

[munkeyboy]

So if I wanted to add a gain by replacing 6av6 with new wiring for 6J6 or modding for a 9 pin 12ax7, what can I do for the diodes I'm lossing in the 6av6? If I made changes, I would rather keep the am/fm functions.

Replace the tube diode (only one is being used) with a 1N34.

dumb question:  where does the other end of the diode go?  Ground?

[shooter]

believe so, pin 5 is anode , cathode is ground

[munkeyboy]

Cool.   You think something like this will work?

[PRR]

...I would rather keep the am/fm functions.

You have radio where you live???

Then use a JFET booster on the guitar input. Or just an LPB pedal in front.

[kagliostro]

May be you can use/adapt the FET input of the Dumble ODS (that is well documented)

Franco

[PRR]

> the FET input of the Dumble ODS