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    Building, troubleshooting and testing of these amplifiers should only be
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Grounded Grid Help

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I have decided to build a Grounded Grid Preamp as my first diy Tube project and I have a few questions. It is the Grounded Grid design from " Audio Reality " by Bruce Rozenblit.

My first question is: Can this preamp be built in the style of the Bottlehead foreplay? In other words; can the components be top mounted on a plate and then put in a wood frame? I ask because the few examples I have come across are all in an enclosure.

Secondly, I am using the schematic from page 87 of the above mentioned book, and was wondering if anyone who has built this preamp from this schematic is aware of any mistakes in the schematic, or has any suggestions for minor improvements?

I plan on getting all of the components in the next few weeks and hopefully will start the build soon after the holidays.

Thanks
 
Yes, Thats exactly how I've built a number of them. I used an alumnium top plate on a nice oak base, mine were built for under 100.00 including NOS Tung-Sol toobes. The grounded Grid however is just an OK line stage..... HOWEVER you might want to read these two threads before you buy all the parts..... Then you won't waste time and go through what I did to get where I now am.

Yet another 12B4 line stage, or is the 12B4 better than the Grounded Grid.....


Plus this one........12B4A Linestage
 
Gelder

I have build one as you planning for.
 

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Hi Vangogh,

My 12B4 circuit is based on .Brian Beck's circuit that uses an LM317 as a CSS. This runs the current at 30ma which does indeed place this tube just about in its optimum curve. I am just powering it from a variable H-V bench supply at the moment. I plan on building and testing this circuit later this week. It has very low impedance over a very wide range so it should work very good with the 12B4. Quite number of others have heard this line stage now and most agree its about as good as it gets...

I have not worked with the 5687, however the plate resistance is about twice what the 12B4 is so it might be more confined to use at higher input impedances than my 2's. My GG now resides on the shelf along with all my other DIY line stages.....

Mark
 
Another question

I am putting together my order for the Grounded Grid components. In doing so I have another question.

The original schematic shows two 120 volt transformers in a voltage doubler arrangement, and a separate 12 volt transformer.

I am wondering if I could just get one 200v-0-200v + 12v transformer?
It seems like that would be a lot easier.

If so, how different would the circuit then become?

Thanks
 
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