An almost DIY 6DJ8 Linestage

[JesseG]

Hi all:

Thought you guys might get a chuckle out of my latest adventure.
I just finished a remote control linestage using 6DJ8s. All of it in a really nice cabinet donated by a friend (Thanks Scott ) and made from some beautiful old-growth Yellow Cedar - what else for the BC Coast, eh!

I am listening to it as I write this and it sounds awsome - very open and detailed with excellet extension in both extremes.

About 9db gain. The 6DJ8s are running at a B+ of 160v with only 5V on the heaters. Input impedance is 250k and output impedance is 22K. I think they call the configuration 'cascode' but I am not sure excatly what that means. One tube per side, with only 2 Rs and 2Cs in each channel. Can't get very much simpler than that .

The schematic is



This is part of a full preamp I found on the web. I'm not sure where it comes from or who designed it - my thanks to whoever it is.

Here is a photo of it - just finished (sorry for the blurries).



A few more images to follow...

Jess

[JesseG]

Next Photo:



This shows the layout of the inside.

Dont get alarmed by the bright RED - the top and bottom plated are made from a recycled road sign

[JesseG]

Now, the remote IO and Vol control board - this is a kit from DIY Gene.



It works a treat and cost only $45 for the 4-input version. It comes with a nifty little remote and gives you 4 inputs plus tape monitor, volume and mute. I call that neat!

[JesseG]

Last one:



Here it is in my system. Sounds very, very good and all up cost about $90 (thanks again, Scott).



Happy Listening to all

Jess

[doorman]

Nice work, Jesse. Hope you bring it to next yrs DIY fest @ Chez Dave's.
Don

[planet10]

Cool jesse,,, it isn't a cascode... a cascode has the cathode of the top tube connected directly to the anode of the bottom tube, and the top tube's grid is grounded... what you have is an SRPP.

http://www.tubecad.com/may2000/

This circuit has a cascode in a long tail pair configuration



dave

[JesseG]

Just wanted to add (been listening to this box for about 4 hours now) that the bass of this linestage is astonishing!

I have a Velodyne ULD12 sub-woofer aand I have never heard it working like this before. I put up the AT series 40 mike into the PC=based RTA to measure the bass lines from Nora Jones "Come Away With Me" and the new Allison Krauss & Robert Pland vinyl - "Rising Sand" - hot damn - I am getting solid response down to 25hz. And, I can hear the notes and texture of the electric bass.

Now this is a suprise - a very welcome one.

onward and upward!

[JesseG]

what you have is an SRPP

Thanks for that Dave - I am slowly learning about this stuff. If it keeps going like this, I will be building s lot more

Jess

[planet10]

Originally posted by JesseG
If it keeps going like this, I will be building s lot more

I warned you decades ago it was addictive... now that you have happily fallen off the wagon...

dave

(PS i seem to remember a little chipdip phono stage you were going to throw together for me)

[vinylkid58]

Originally posted by JesseG
This is part of a full preamp I found on the web. I'm not sure where it comes from or who designed it - my thanks to whoever it is.

This is one of many possible variations for a Symmetrical SRPP Preamplifier based around the 6DJ8 / ECC88 / E88CC family of tubes. The SRPP circuit has also been referred to as a SEPP, Totem Pole, Mu Follower, Mu amplifier and Cascoded Cathode Follower. The original name for this circuit is a Balanced Direct and Alternating Current Amplifier (Maurice Artzt, Radio Corporation of America, February 9, 1943, Patent 2310342).

I'm sure Maurice would be proud of your implementation Jesse, very nicely laid out too. The road sign is a nice touch.

Jeff