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JEL 2a3 Deluxe schematic clarification?

T

tbreid0

New Member
I am sorry if this is the wrong location...or if this has been discussed ad nauseum. If so, please direct me elsewhere.

I have been confused about the JEL 2a3 deluxe schematic(s) I have been able to find online (here and elsewhere). My confusion is...all of the schematics I look at have the 6SN7 coupled from it's PLATE to the 2a3 (common cathode). However, it seems as if all of the discussions, etc. that I read state that the 6SN7 is coupled to the grid as a cathode follower. I am uncertain if I should trust the "schematics" or the "discussions". Also, if anyone knows where I can find a schematic showing the "cathode follower" approach...I would appreciate it.
 
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There are several versions of JE Labs 2A3 SE schematics out there, including SRPP versions (implemented by Skunkie Designs in this manner), and lots of good as well as nonsense discussions being generated these days. Please provide links to specifics.

I don’t recall any non-SRPP version using a 6SN7 cathode follower. The first triode (76 or 6SN7) is typically direct coupled to the second 6SN7, which in turn is capacitor coupled to the control grid of the 2A3. The SRPP version use the two triodes of a 6SL7 and one could argue that the 2A3 grid is driven by the cathode of the top triode. I’d say get a proven, reliable schematic and stick to it.
 
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A search of his site and "2A3 deluxe " doesn't turn up anything, so I think this is someone else's term. I would recommend looking up his post on the SRPP 2A3 and comparing that schematic to what you have. I think the confusion is a result of other people referring to his 2A3 deluxe without it actually existing by that name.

jelabs.blogspot.com

SRPP SE2A3 Circuit Redux

jelabs.blogspot.com jelabs.blogspot.com
 
Are you thinking of a "Grounded Grid" amplifier?

They are the Only cathode driven tube amplifier I've ever seen.

Search for cathode driver tube amp and 2A3 amp and it comes up with nothing...

Grounded Grid.

Holy crap they are running a 6L6 at 700 volts!

How TF does that work, Also the operating frequency is 2 Mhz...

tuned_5.gif
 
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Thank you all for the replies.

IMG_0131.jpegThis is the schematic I was looking at (while reading discussions about how the 6SN7 is used as a cathode follower/unity gain) connected to the 2a3 grid. Since this schematic does NOT show it in a “cathode follower” configuration, I was confused.
 
Buck Rogers said:
Are you thinking of a "Grounded Grid" amplifier?

They are Only cathode driven tube amplifier I've ever seen.

Search for cathode driver tube amp and 2A3 amp and it comes up with nothing...

Grounded Grid.

tuned_5.gif
Click to expand...
I have not seen this (or any grounded grid). Thank you for the info.
 
Selmerdave said:
A search of his site and "2A3 deluxe " doesn't turn up anything, so I think this is someone else's term. I would recommend looking up his post on the SRPP 2A3 and comparing that schematic to what you have. I think the confusion is a result of other people referring to his 2A3 deluxe without it actually existing by that name.

jelabs.blogspot.com

SRPP SE2A3 Circuit Redux

jelabs.blogspot.com jelabs.blogspot.com
Click to expand...
Thank you. I think the “deluxe” term refers to the 76/56 driving 1/2 of a 6SN7. I am hoping to build an amp that will use my 56 tubes.
 
spantou01 said:
There are several versions of JE Labs 2A3 SE schematics out there, including SRPP versions (implemented by Skunkie Designs in this manner), and lots of good as well as nonsense discussions being generated these days. Please provide links to specifics.

I don’t recall any non-SRPP version using a 6SN7 cathode follower. The first triode (76 or 6SN7) is typically direct coupled to the second 6SN7, which in turn is capacitor coupled to the control grid of the 2A3. The SRPP version use the two triodes of a 6SL7 and one could argue that the 2A3 grid is driven by the cathode of the top triode. I’d say get a proven, reliable schematic and stick to it.
Click to expand...
Thank you. This helps. I posted the schematic I was looking at below.
 
tbreid0 said:
Thank you. I think the “deluxe” term refers to the 76/56 driving 1/2 of a 6SN7. I am hoping to build an amp that will use my 56 tubes.
Click to expand...
I think references to driving from the cathode are people referencing the SRPP version, as clearly the one you posted certainly doesn't do that. If I was building a JELabs design I would use JELabs as my source and not forum discussion from various people. Good luck with it!
 
Now I remember it was Troels Gravesen of Transcendent Audio designed a Grounded Grid preamplifier.

His page has an interesting experiment on coupling caps, Worth a read.

Grounded Grid preamplifier

If your building a SE 2A3 amplifier the schema you posted is fine.
 
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an SRPP is sort of a weird looking thing, its driving from a plate and from a cathode at the same time, so I can see why it might be explained in a confusing way.

I always get mixed up between mu followers and SRPP. They are very similar looking.
 
Selmerdave said:
I think references to driving from the cathode are people referencing the SRPP version, as clearly the one you posted certainly doesn't do that. If I was building a JELabs design I would use JELabs as my source and not forum discussion from various people. Good luck with it!
Click to expand...
Selmerdave said:
I think references to driving from the cathode are people referencing the SRPP version, as clearly the one you posted certainly doesn't do that. If I was building a JELabs design I would use JELabs as my source and not forum discussion from various people. Good luck with it!
Click to expand...
Thanks
 
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