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D3a Experimenters Breadboard Project

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#24
I'm with SY on this one, in terms of linearity I haven't seen anything much better than the D3A.. I have used them in power amplifier designs and I use a pair in my phono stage where their noise performance is incomparable - never encountered anything this quiet..

And yes the transconductance can vary massively from one sample to the next, I have my stash of D3A all acquired for around $10 each and all are Halske and Siemens..

I'm also quite a fan of the 5842/417A a device which many have tarred with the same brush.

Doug, I am definitely interested in a board or two so sign me up if I am not too late..
 
#29
I realize now that I should have probably gotten one of these boards. Oh well. Still I have some other experimenter boards that I can try.

I recently picked up some 6J52Ps off ebay on recommendation from Wavebourne. He suggested they were like D3A's. I have some D3A's too, it would be neat to compare.

That reminds me I need a lab supply.
 
#31
dsavitsk said:
Domestic boards are in the mail. International ones will need to wait until Monday -- sorry about that.
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No worries, that will give me time to think about what tubes to try them with (I have a new policy on not listing tubes on this forum, I have noticed how that is driving prices up; lets just say it's between a Russian tube and an NOS TV tube).
 
#38
SY said:
like the provision for a chip resistor as gridstopper.
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Those are actually plate and cathode stoppers -- the grid stopper is full sized 🙁


JoshK said:
Which chip resistors do you like to use for gridstoppers?
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I don't have an opinion -- I like the ones that let me order 2 rather than 10. There is a little in MJ about SMD stoppers, so he may mention a specific type.

I have added some additional information on the website -- specifically some CCS details. Let me know if there is anything else I need to add.
 
#40
Which chip resistors do you like to use for gridstoppers?
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As stated the chip resistors are in the cathode and plate circuits. I usually use some generic 50 X 80 mil (0805) sized chip resistors that I got from a vendor sample kit for grid stoppers.

I may find time to build up one this weekend. I need to evaluate some tubes that are currently on the $1 list at ESRC. There are two weekends left in the $1 sale.

I plan to build a minimal configuration. Grounded cathode, variable negative grid bias from a power supply, triode mode, CCS or resistor plate load.
 
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