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The Christiansen "DG" 300B Amplifier Build Thread

post #1 of 632
Thread Starter 
Warning: Finished AMP Spoiler! (Click to show)

This thread take through the details of my journey to get here:






Note #1:  Any input is welcome.  I especially went to hear about your experiences with 300B and 6N6P valves.


I am about to build Tom Christiansen's "Damn Good" 300B valve amplifier.  It will be customized to support headphones.



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Note #2: I like to call tubes "valves".  That's what they were called when they were invented.




I own a Schiit Lyr, a Schiit Bifrost (uber) and LCD2 cans. The Lyr is a hybrid amp that has a SS output and a valve pre amp.  It utilizes 6DJ8 valve variants.  After collecting for a while I have settled on La Radiotechnique 1965 E188CC’s and 1959 Valvo, Hamburg PCC88 D getters.  I’m delighted with these and I’m done rolling Lyr valves.  (I still love the thread)  Hence, I am moving to an all valve amp.  I also like building things so Tom Christiansen’s DG 300B filled the bill.


Tom provided me with a great deal of assistance redesigning a valve tester.  It's now based on the EICO 667.  This is a parallel project to the 300B build.  (I will also update the progress on this thread.)   Tom's an EE that specializes in precision analog circuit design and has designed amplifiers at National Semiconductor.  The power supply is, IMO, the most critical component in audio gear, double that for valve audio.  I am a hopeless bumbler that is trying to learn electronics along the way.  I do have decent intuition. 


Before finding Tom's site  I was bumbling my way around different valve tester design.  I was working with various transformers and getting nowhere, but I learned a lot.  That led me to Tom’s power regulation products.  The 21st Century Maida Regulator, for high voltage, and the Filament Regulator for, well, filaments.


21st Century Maida Regulator:


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Filament Regulator:


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The one I built.






I built both of them complete with 0805 package SMD components.  I never thought I could do that but after watching Dave Jones EEVBLOG solder series, it wasn’t too difficult.   They both work great!  They fixed a lot of design issues and provide nuts-on voltage from the secondary’s.  Both the Maida and the Filament Reg are used in the 300B build.  The best suggestion I got from Tom is to scrap the tester design I was working on before I electrocuted myself.  It utilized an autotransformer with mains in the circuit.  The EICO 667 design is bumbler friendly.


The schematics, BOM’s, and complete circuit explanations for all Tom’s designs products can be found at his site.  http://www.neurochrome.com/audio/  There’s enough information that you can build your own boards.  It’s much easier to buy them from Tom for a modest price.  The BOM’s have DigiKey part numbers for every component.


I will fill ya’ll in on all the costs along the way.   I don’t expect this to be a bargain basement amp.  But come on’ the board is only $165 and that includes the $25 Maida board and the $20 Filament board. A very reasonable first expenditure.


On with the build.

Note #3: I have decided to call it the "Damn Fine" 300B 


I will not stray away from the 300B BOM (much).  So here are the 300B components I've ordered so far.


Power Transformer:  ClassicTone 40-18069  $122.00


Output Transformer:  Electra-Print custom wound L3500.  5K ohm @ 100ma to 60 ohm, 10 Watt.  This will support my LCD2’s   $200 each.  Two required.  $400



The capacitor specs. are Solen and Cornell Dubilier.  So it’s a North American amp. 


That IS more than enough for a first post, and if you’ve read it, I appreciate it.



I had a suggestion to put the schematics in the first post.

You will see these again.














Edited by sceleratus - 8/17/13 at 8:50am
post #2 of 632

Excellent! Thanks for all the help by the way. gs1000.gif Adding this thread to my favorites, really looking forward to seeing it finished. 

post #3 of 632




-HK sends

post #4 of 632
Originally Posted by HK_sends View Post




-HK sends

Ditto! This should be interesting... smile.gif



post #5 of 632

Looking forward to a very interesting build.  Good luck! beerchug.gif

post #6 of 632


post #7 of 632

Really nice- good luck!

post #8 of 632
Thread Starter 

Today I finished ordering all the components for the Damn Fine 300B with the exception of the 300B and 6N6P valves.  There are close to 150 components.  The enclosure will be custom made and it is in the design stage.


I have created a Dropbox folder to put all the schematics, BOMs, Photos, and Specs.  I will update the post as I add material.  Presently there are:


·      300B Schematic parts BOMs and Photos

·      21st Century Maida Regulator Schematic, parts BOM, and photo

·      6.3V and 5V Filament regulator Schematic, parts BOM and photo

·      1950 Western Electric 300B valve specification

·      Christensen Damn Good 300B Amplifier internal and external photos

·      List of expenses.


I will close with a photo of the interior.





post #9 of 632
Thread Starter 




I finished the 21st Century Maida High Voltage Regulator while waiting for the 300B boards and components to arrive. I thought I’d show some of my soldering, I rate it ok, and provide some great soldering resources for those how don’t think they can solder.


First off, if I can solder, you can solder.  Despite persistent hand tremors I got it done.  First watch the Dave Jones, EEVBLOG, 3-part video on Youtube.  They are a bit long but well worthwhile esp. if you want to solder surface mount components.  Dave has even more advanced videos as well.  Who knows, you might want to hot-rod your Lyr some day.


Part 1 is about The Right Gear and Solder.  This is where I learned about 0.38mm 5 core solder. That alone made it worth watching.  I also picked up a Hakko FX-888 Solder station.  This is a can’t miss tool.  Heats up quick and amazing control and tip cleaning.  An articulated desk, arm magnifier and a small Panavise is also essential.  There is also great information on solder wick and solder suckers to correct your mistakes or remove components.  I was familiar with solder suckers but did not know about solder wick....Yes this is basic.


Part 2 is basic thru-hole component soldering.  I picked up more things I didn’t know.   Prior to this, when I had to solder something, it was very hit and miss.  Cold joints.


Part 3 is soldering SMD components.  I never believed I could solder a component that is 1.18mm wide.  






Same for LM22673 Ti switching regulators.



  They have 8 feet very close together.  Simply watch Dave’s video and you can do it.  Some of my work isn’t the prettiest but I had no solder bridges.  Dave shows you how to fix them anyway.  


Here’s the finished product (less heat sink):






Filament board.  Don't laugh,  it works..  The black spots are shadows off the shiny solder...biggrin.gif










Here's what's on the way:




Edited by sceleratus - 6/22/13 at 2:43pm
post #10 of 632

Looks great! I remember when I tried to custom make a PCB with ferric chloride, copper clad, and a sharpie. It was fun but looked very sloppy. Btw I have the same caliper. That thing is a great tool. 

post #11 of 632
Thread Starter 
Originally Posted by PinkLed View Post

Looks great! I remember when I tried to custom make a PCB with ferric chloride, copper clad, and a sharpie. It was fun but looked very sloppy. Btw I have the same caliper. That thing is a great tool. 


I'll be making a PCB for the valve tester.  It's a parallel project, but most of my attention is on the 300B.   There are some new etching techniques that appear to be better than ferric chloride.  The name of the process escapes me now.


I'm using DipTrace to create the schematic (for the tester).  It produces the board trace from the schematic automatically.  I don't know that much about the circuits so I'm re-creating a few in LTspice to simulate and try to understand their function.  Again, this is more like a kit project.


I could not live without a set of calipers.  I have an inexpensive set that has a 1/64th fraction table.  I use those a lot.

post #12 of 632
Thread Starter 

I'm looking for wisdom and recommendations for 300B and 6N6P valves.

If you have any experience with these I love to read about it.

post #13 of 632
Thread Starter 

I was not going to write about my plans for the enclosure but I can’t keep a secret.  I’m really stoked and I think it will look interesting.


The enclosure will be wood, have an antique style, and be made from walnut, mahogany, or rosewood.  Think “Old Cigar Humidor”.  I have a good friend that has been making custom kitchen cabinets for 30 years.  


I will plate the top panel, either nickel or copper.  For the controls I did some shopping on eBay …




post #14 of 632
Thread Starter 

Boards and components arrived today.  I inventoried all the components and started to work on the driver board.

8 components mounted, 65 to go.




post #15 of 632
Originally Posted by sceleratus View Post

I'm looking for wisdom and recommendations for 300B and 6N6P valves.

If you have any experience with these I love to read about it.

"Western Electric=holy grail of the 300B" according to my friend who has a Grant FidelityA535 amp.

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