Van Waarde inspired OTL headphone amp

[Mars]

Hi headamp lovers

I am doing a build of the Van Waarde OTL. If anyone is interested, I'll post some photos and info.

http://gilmore2.chem.northwestern.edu/projects/showfile.php?file=waarde1_prj.htm

I am going with the tube recto option and the amp has some line out/bypass functions.

[ghostinthemachine]

I built a similar circuit a while ago - works a treat!

[GradoMan]

Keeping an eye on this thread.

Do you have an estimate of total cost involved, yet?

[iondb]

Yes, it would be nice to follow the build. An estimated price would also be nice. Maybe one day I can try this one..................

[Mars]

Here is a picture of the design; ours will also have only one chassis (for both power supply and pre-amp):



Let us look at the schematic:



So design is simple and effective: voltage amplifier dc connected to a cathode follower and out to you headphone.

Power Supply: here we follow Ying Mingyao's idea of a tube rectifier, with the associated capacitor value changes



It all seems simple, so what is standing in our way?

Have a look at the specified parts values for the circuit:

PARTS LIST (AMPLIFIER)

      P1 - Potentiometer 100 k logarithmic stereo (ALPS RK-27112)
      R1 - 1M ohms, 1 Watt carbon resistor
      R2 - 33 ohms, 0.5 Watt metal film resistor
      R3 - 47K ohms, 1 Watt carbon resistor
      R4 - 820 ohms, 1 Watt carbon resistor
      R5 - 4k7 ohms, 5 Watt wire-wound resistor
      R6 - 3k3 ohms, 10 Watt wire-wound resistor
      R7 - 10k ohms, 0.5 Watt carbon resistor

      C1,C2 - 220 uF, 400 V electrolytic capacitor (Nichicon)
      C3 - 220 uF, 100 V electrolytic capacitor (Nichicon)
      C4 - 0.22 uF, 250 V MKT (DDR stock)

      V1 - E88CC (Brimar)
      V2 - 6AS7G (RCA)

Please note:

      C1, R5 and C2 are shared by both channels.

PARTS LIST (POWER SUPPLY):

      L1 - Inductor 10 H, 90 mA, 270 Ohm
      GZ37 rectifier
      C1 4-8uF 400V

We'll do a redesign of the power supply and then proceed to do layout.

[iondb]

Very nice.  Thanks for the effort put into this to share the build with us tube-noobs

[Mars]

Hi Heads 

Here's some pics of the build:

[alternativeroute]

That looks excellent! 

Out of interest, what was the thinking behind the tubes on the corners of the chassis?

[Prince]

Wow - that looks cool Mr Mars...Beautifully finished..

[Mars]

"what was the thinking behind the tubes on the corners of the chassis?"

I wanted to explore some design ideas I have seen in high end equipment  

Like these fancy pancy designs

[iondb]

That looks really nice!!!!!!

How does it perform sound wise?

[Mars]

A good question  It is not wired up yet...

[GearSlave]

That looks real cool! In fact, I was going to go for a similar look for my phono pre.

[iondb]

A good question  It is not wired up yet...

 

[Mars]

I am now onto the next incarnation of the Van Waarde OTL headamp. A few changes: I am going to follow the Wheatfield design:



For those interested in the costs, have a look at what the laser cutters quoted me: this time the chassis is made of 2mm aluminium and the design is a regular box with a size of 250x355mm.

This is the quote for the box (bent and welded) without the paint job. That will be added once the aluminium box is done.

<quote>Thank you for your enquiry. We take pleasure in offering the following goods/equipment:
 Item                              Description                             Mat'l    Mat'l C.O.M. QTY  Unit Price  Total Price
                                                                          Grade    Thick             (Excl. VAT)  (Excl. VAT)
MAR019-00000048-1        COVER PLATE          1200H4   02.0mm   No    1       R 36.81         36.81
MAR019/00000048-2        HEAD AMP ENCL      1200H4   02.0mm   No    1      R 787.40        787.40
Comments:
 WELDING INSIDE AND OUTSIDE
 STRIP FINISH WELDING
 COVER PLATE AND BOX SEPERATE                                  Subtotal                         R 824.21
                                                                                 VAT                              R 115.39
                                                                               Total Net Price                  R 939.60 <unquote>

It looks like the chassis for the headamp is going to cost around R1200.