Run 6X5GT or 6BY5GA Rectifier

[Lou]

Describe the improvement pls, The rectifier is separated from all the audio by a low pass filter,
whose frequency is well below any audio content, Preamps are always Class A, voltage regulation is normally not an issue.

Or perhaps just something to look at, 😀

Don has since made this mod public and is even outsourcing his newest amps and preamps, so he won't mind me posting here now.

Don said; "We are modding so that you can use a 6BY5 rectifier tube. I am sick of paying tons for a Bendix 5852 so I did some reading and the old 6BY5 will work and sound much better. Well, at least 10% to my ear. The Bendix and the 6X5 tubes have a 70 mA current delivery rating. The preamp draws about 30-35 mA so they have lots of headroom, but the old 6BY5 tubes will deliver about 175 mA. So they have well over twice the current capability and this really rich sound results. The 6BY5 draws about 1.6 amps from the filament supply vs. 0.6 for the 6X5, but it doesn’t matter at all since the preamp has a 2.5 amp winding that is driving it. So your transformer is more than large enough to handle it. I think you will hear the difference right away. So here is how to do it, but don’t publish it anywhere. This is my new money making mod."

 

[brucebosler]

So ??? What is the mod… just tie the pins together as mentioned previously ?

Thanks

 

[grovergardner]

Yes, that is all you need to do.

 

[brucebosler]

thanks, I have an sp-14v 12-2020 circuit board with pins 3-4 and 1-8 already tied together.

so that's all that needs to be done? ..

I looked at a friends that was done by Sachs which has 3-4 but also 1-8-7 tied together , which puts the cathode at B+.. any ideas about that?

thanks

 

[grovergardner]

Maybe it it reduces hum? No idea. Seems to defeat the the purpose of warm-up delay.

 

[brucebosler]

right, you see preamp and power amp filaments raised above ground to a potential close to the cathode, but this seems odd

 

[grovergardner]

Yeah, that doesn't make a lot of sense. Maybe this was Don's "secret formula," but I'd be tempted to snip it. ;-)

 

[Tubesaregreat]

6BY5 is a baby GZ34. Huge step up from a 6X5

 

[brucebosler]

I sent Sachs a message thinking he might share his thoughts now that he no longer modifies these but he did not respond.

I sent the SP14 guy a message about using a 6BY5 and his only response was "the SP14 is designed for use with a 6X5 rectifier". Which seems a bit odd since the pins are already tied together so it will work with either. In any case, I'm using a BY5 at the moment.