Grounded Grid Preamp Project And Possible Group PCB Buy

[Mark A. Gulbrandsen]

Thanks! Thought I had done the same but couldn't locate it..... You saved the day on this one......

Best,
Mark

 

[seve]

Hi...

Any of you that have build the ground grid with the 6sn7? If so please let me know what you think about it and if you can compare it with the grounded grid with the 12au7 it would be great.

I have read that the wyetech preamps use the grounded grid with the 6sn7, but do you know if the circuit is similar to the circuit posted in this thread? The reason I am asking is that I have read that the wyetech uses a +-200V rail and the circuit posted hear used around +-350V rail. I also think the the wyetech uses more caps in the curcuit if I have studied the picture correct at 6moons. If anyone know the differences between the circuits and how they will effect/change the circuit circuit please informe me thats if there is any difference at all.

Any information will be gladly received.

Thanks
Martin

 

[Mark A. Gulbrandsen]

Any of you that have build the ground grid with the 6sn7? If so please let me know what you think about it and if you can compare it with the grounded grid with the 12au7 it would be great.

I am going to begin gathering the parts this week to build that 6SN7 GG circuit. My experience with 6SN7 in other tube equipment is much better than 12AU7... 12AU7 is much more microphonic than 6SN7. Only military 12AU7 don't seem to suffer from microphonics but they don't sound as nice as something like Tung-Sol 12AU7 does. I don't worry what the final rail voltages are. The original Rosenblatz GG has a raw supply of around 300 volts but is zenered down to about +/- 200 volts. It uses a voltage doubler that is fed by a standard 20 watt 120 volt isolation transformer for each rail.

Mark

 

[rick57]

Any thoughts on how the GG sounds compared to an Aikido; and what would be less expensive?

I think the GG is cheaper ~

(thanks to Bas for these links)
Introducing the Aikido
http://www.tubecad.com/2004/blog0011.htm

Aikido Variations
http://www.tubecad.com/2004/blog0013.htm

Aikido revisited
http://www.tubecad.com/2005/January/blog0030.htm

More Aikido testing
http://www.tubecad.com/2005/January/blog0032.htm

Aikido Enhancement
http://www.tubecad.com/2005/January/blog0033.htm

www.diyaudio.com/forums/showthread.php?s=&threadid=63744

Thanks

 

[rick57]

This GG seems to offer real bang for buck -

Who's in for a group PCB Buy? I am for one!

 

[seve]

I am going to begin gathering the parts this week to build that 6SN7 GG circuit. My experience with 6SN7 in other tube equipment is much better than 12AU7... 12AU7 is much more microphonic than 6SN7. Only military 12AU7 don't seem to suffer from microphonics but they don't sound as nice as something like Tung-Sol 12AU7 does. I don't worry what the final rail voltages are. The original Rosenblatz GG has a raw supply of around 300 volts but is zenered down to about +/- 200 volts. It uses a voltage doubler that is fed by a standard 20 watt 120 volt isolation transformer for each rail.

Mark

Thanks for the reply. Please post your results when you are finished.

Martin

 

[Mark A. Gulbrandsen]

This GG seems to offer real bang for buck -

Actually the Rosenblatz version offers alot of bang for the buck, perhaps an even better ratio of bang to buck....and I've certainly seen and gotten alot more feedback from people that have built his at this point in time. What I will probably do is to build the chassis for the 6SN7 Akaido version with space for the extra tube socket so I can build both of them at different times and listen and judge them. Although I can certainly do measurements they really mean very little as to how something will actually sound. Except for being curious I prefer to let my ears do the measuring.

Mark

 

[pinkmouse]

Mark and I have discussed the possibility of a PCB, and it's certainly do-able. The only issue that complicates it is the availability of appropriate PCB sockets for the valves.

Another project that I'm currently looking at uses valves, and the only way we will be able to make a suitable PCB is to supply the socket with it, as the dimensions of all that I've looked at seem to be slightly different, and incompatible.

I look forward to Mark's results.

 

[rick57]

> Except for being curious I prefer to let my ears do the measuring

Exacto mondo 😉

The only issue that complicates it is the availability of appropriate PCB sockets for the valves.

> So do we next need to agree the most popular valves to use, with perhaps some shepherding form Mark and you?

Let the selection begin . .

 

[pinkmouse]

I'm not fussed about the valves, but I do need the dimensions of the sockets! 🙂

 

[Mark A. Gulbrandsen]

Al - Rick,

Valves are not hard to find in either the US or the UK. Doing quick search on E-Bay will turn up hindreds of either 6SN7 or 12AU7. Which valve we use remains to be heard!! As for which preamp we do the Akaido certainly does not need to be ok'd by its inventor whilst the Rosenblatz GG might need to be although I am more on the side of lets go ahead and do the project anyway since his book is now out of print and the circuit is not patented. I think its high time to share the info with who ever else may be interested in his circuit.... the 6SN7 version is certainly all to similar.

Tube sockets are also quite easy to aquire and available from many sources. Its also quite feesable to hard wire tube sockets to the pcb with short wire leads as is done in many commercial units. This may make the psb a bit mroe universal for anyone to use.

Mark

 

[pinkmouse]

Tube sockets are also quite easy to aquire and available from many sources.

Yep, and they all seem to be slightly different in radius/pin size etc... 🙂

Its also quite feesable to hard wire tube sockets to the pcb with short wire leads as is done in many commercial units. This may make the psb a bit mroe universal for anyone to use.

Good idea. Do you know what the socket bases are perchance, or will they vary with the selected valve?

 

[sklimek]

Its also quite feesable to hard wire tube sockets to the pcb with short wire leads as is done in many commercial units. This may make the psb a bit mroe universal for anyone to use.

Mark

3 6SN7's are quite large compared to 3 12AU7's, hard wiring to the PCB may be a good idea in that it would give the option to someone who wanted the octals on top for space considerations as well as the classic tube chassis look.

 

[VT67]

Picture of an Octal (6sn7) and a Noval (12au7) valve socket for PCB.

Regards

 

[pinkmouse]

That was quick Walter! 🙂

al/can see the future, lots of KrellClones paired up with valve pre's...

 

[rick57]

> It’s feasible to wire tube sockets to the pcb with short wire leads

Is this hurdle now behind us, and flexibility > wider appeal now incorporated?


🙂

 

[pinkmouse]

Well, it does sort of defeat the primary advantage of a PCB, short path lengths... 😉

 

[VT67]

Are there that many components involved that a PCB is needed?
For tubes I prefer P2P wiring, much easier. On which schematic would the PCB designed on?

Regards

 

[jacco vermeulen]

I've used ceramic sockets with goldplated pins only, never low quality pressed sockets.

Yes, i would like to enlist too, i've been keyehole peeping the GG posts from the beginning.

 

[pinkmouse]

The tech side is down to Mark, he just asked me to look at producing a PCB once he has a finalised circuit. I think there is a link to the schema earlier in the thread.