Tube or SS Preamp?

[apexaudio]

Some builds...

 

[still4given]

Some builds...

OK so I now have pins 1, 8 & 9 to ground. Hopefully this is now correct. If so I will etch and build. I already have the counterpoint ready.

 

[still4given]

I etched a board and have populated it. Now I need a PSU. Please take a look at this one and let me know if it will do the job. I basically followed the HV portion of the Counterpoint PSU.

Thanks, Terry

 

[apexaudio]

I etched a board and have populated it. Now I need a PSU. Please take a look at this one and let me know if it will do the job. I basically followed the HV portion of the Counterpoint PSU.

Thanks, Terry

Nice work... you must add RC filters R3,R4,C5,C6 (220R, 22uF on counterpoint schematic) to your PSU and use DC regulated PSU for 6,3V tube heating.
Regards

 

[still4given]

On the counterpoint I had to feed the heater directly with 6.3vac. When I tried feeding it through the regulator, the regulator overheated. The heater works fine with 6.3vac. I will try to rework the PSU to add the rc filter.

 

[still4given]

Is there a simpler psu for this? I don't have enough parts on hand to build that one..

 

[still4given]

Hi Mile,

Another question as I am trying to learn something here. In Counterpoint, R4/C6 feeds pin #1. In this MM circuit, pin #1 goes to ground. Are R4/C6 still needed?

 

[apexaudio]

Hi Mile,

Another question as I am trying to learn something here. In Counterpoint, R4/C6 feeds pin #1. In this MM circuit, pin #1 goes to ground. Are R4/C6 still needed?

You revert pins 1 and 3 on your pcb.

 

[still4given]

That sucks! Serves me right for trying to do mu own layout on a tube circuit. Wasted enough time on this.

 

[jfetter]

That sucks! Serves me right for trying to do mu own layout on a tube circuit. Wasted enough time on this.

No dont give up on it, that is a great concept. Im doing something similar and have been trying to freeze the design but subtle improvements creep in.


I did a point to point first. messy but helped a lot.
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[jfetter]

I have to look at yours more but I use 50v potential with fixed bias. I promise 12au7 and 6sn7 work great with super test reports.

I used cheap 24v supplies in symmetrical arrangment.

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[still4given]

I have to look at yours more but I use 50v potential with fixed bias. I promise 12au7 and 6sn7 work great with super test reports.

I used cheap 24v supplies in symmetrical arrangment.

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Please post your circuit. I would love to see it.

 

[still4given]

Corrected layout

Mile,

Please check this carefully.

 

[jfetter]

Please post your circuit. I would love to see it.

a few pages back, http://www.diyaudio.com/forums/analog-line-level/162125-tube-ss-preamp-8.html#post4878528

 

[jfetter]

Please post your circuit. I would love to see it.

I use dc on the heaters so i sized one 24v for handling that too.
the 200ma 24v open frame are under $2.00. i bought 6 for $13.
Enclosed are safer and have terminal strips go for $6-12 6A

 

[apexaudio]

Mile,

Please check this carefully.

3M9 connect from pin 2 to pin 3...

 

[still4given]

You could have saved me a lot of time and grief if you would have posted this first.

 

[apexaudio]

You could have saved me a lot of time and grief if you would have posted this first.

You do not need new pcb, just cut tracks around pins 1 and 3 on your pcb and revert its with wire jumpers.

 

[still4given]

I made a spice file for the Tube MM. Something is not quite. Maybe someone can look at it.

 

[apexaudio]

I made a spice file for the Tube MM. Something is not quite. Maybe someone can look at it.

You must use 5mV input not 500mV