6N3/6N6 headphone amp using PCB.

[Ryssen]

Just an FYI for those who asked... I now have a board for 9AJ as input (6N1P 6DJ8 6CG7 etc) instead of 6N3...

Have you had time to listen and coompare the 6N3 and 6CG7?
Just so I get a hint on wich to choose..?

Edit: I guesse you have to use differente resistors with 6CG7??

 

[Ryssen]

2Pc Gold plated ECC88 6922 6DJ8 instead 6N3 5670 tube converter adapter | eBay

 

[kodabmx]

They both sound good to me. 6CG7 would use 430R or 470R in place of 240R but you can just plug them in and use them if you don't mind running them hot.

In reality, the topology linearizes the tubes by running one against the other if that makes any sense. The distortion tends to cancel so it doesn't really matter which tubes you pick.


FWIW, I'll make a version for 12A*7 since some people seem to like them more and they are easier to get in some places. Hell, I might even make it selectable by jumper.

If anyone wants a version for another tube, let me know and I'll make one.

 

[Ryssen]

Hell, I might even make it selectable by jumper.

Souns nice!

I found 2 peaces of 2C51 in my drawer I will try first.

 

[kodabmx]

Since the 12AU7 and 6N1P are the same pinout except the heater, the 12AU7 version is created. The jumper idea would have required far more work than just having another version.

Now to send it off for production to test it

 

[Ryssen]

work in progress...:

 

[kodabmx]

Nice!

My work in progress testing the 9AJ version

 

[kodabmx]

Just an FYI - The 12AU7 version of the PCB came today!

 

[Ryssen]

Starting it,but I have a hum from hell.
Du you use DC heaters on your build?

 

[baudouin0]

Before you blame heater make sure you rectifier currents go back straight to the transformer keep this loop away from you signal ground. Looking at you photo that copper T off to the caps looks wrong.

 

[Ryssen]

Tell me how should i go with it?

 

[baudouin0]

Ok the idea is that the current from the transformer should flow through the rectifier, the main reservoir cap and back to the transformer so that is does not develop a voltage into your signal ground wiring. There is a good paper on this on eliminating hum loops but I can never find it - I wish Mr Moderator would put it on the forum.

 

[Ryssen]

ok ,I´m using a SMPS 12v-280V does it have anything to do with it?

 

[kodabmx]

I'm using DC heaters. As long as you run the heater wiring properly, AC should work. Is it 50Hz or 100Hz hum? If 50Hz, check your signal grounding. 100Hz would indicate bad power filtering.

I've used that exact boost module. I've had some bad oscillation but never "hum".

 

[baudouin0]

Found it


http://hifisonix.com/wordpress/wp-content/uploads/2019/02/Ground-Loops.pdf


Its towards the end. If your not sure what to do try and bring your grounds all back to one point.

 

[SCD]

wow, thank you baudoui0:
That is a really good power point presentation. I am sure to refer to that a lot.

 

[SCD]

question for Koda:
I was digging through my collection of salvaged transformer and came across a nice pair of 120:12vac @ 7amp units. I was thinking of converting them to 12vdc then boosting it up for use in this project. Does this make sense or is there a better way to go from 12vac to 250 - 300 dc.
Thanks
still waiting for tubes.

 

[kodabmx]

You could do that.

I use 9V-0V-9V FW rectified to 11.6VDC in my monoblocs and use DC boost converters from that.

You could also just run 120:12:120... Delon the 120 to get ~300VDC, and use 12VAC for the heaters but it seems like a waste of a rather large pair of transformers.

 

[rongon]

Tell me how should i go with it?

Here's another, simpler explanation geared towards tube amplifiers. I found it easy to understand and informative.

The Valve Wizard

--

 

[Ryssen]

So I dissconnected the trafo from the SMPS and connected it to my bench powersupply.
The result...dead silent .
So there i have it, I´m begining to think it´s the trafo itself. It is patually rewind and after 20minutes it gets to hot to touch.