Thursday, May 10, 2012

Z19 Crossover Update

Further progress : Layout of components traced out on graph paper :
IMG 0989

Mounted all the components with tie-wrap on PC Board for one channel : IMG 0991

LPAD mounted on front panel of chassis :
IMG 0994

LPAD side-views :
IMG 0997

IMG 0996

Next steps :
  • Mount speaker binding posts
  • Repeat above steps for second channel
  • Wire components on both boards as per schematics

Wednesday, May 9, 2012

Z19 external crossover upgrade for Altec Model 19

Now that the D3A phono build is up and running (albeit, it is still a WIP), I have now emabarked on the next project - the Z19 crossover project based on the Zilch (RIP)'s design from Audiokarma fame . I have all the materials for the build :

1) Two 12"x8" Hammond Chassis

2) Crossover components from Soniccraft ; Below is my order
Soniccraft order
3) 2x 8 ohm LPAD
4) Terminal blocks, PCB Laminate, Speaker binding posts, Neutrik 4P male/female XLRs, 18GA hookup silver coated copper teflon coated wire

I based my layout on this design, courtesy AK member billyunderhi :

Here is the mockup :

Layout 1

Layout 2

I traced the components on a graph paper, so I can replicate the layout accurately on the other build Next Steps :

  • bore holes on PCB laminate
  • mount components on PCB and tie wrap
  • bore holes on chassis for speaker binding posts and speakon
  • bore holes for LPADs
  • bore holes for terminal blocks

Z19 schematic for reference :

604 8H Mod19 Ckt

Sunday, May 6, 2012

6B4G Push Pull Amplifier built by Min Yang

Quoting Min Yang :

6B4G Push Pull Interstage Coupled Push Pull Stereo Amplifier

Built for Nikhil Suvarna of Redwood City, CA

Completed on 2/01/12

Those that follow my work would be familiar with my affinity towards buidling single ended amplifers, e.g. about 90% of my builds are single ended amplifiers. Having said, here is a build that might change that a little.

When Nikhil approached me to build this amp based on Ralph Powers schematic (, the first thing I did was to study the schematic. I have to admit, the circuit was by far the simplest PP circuit I have laid my eyes on. That was good. I like simple. I also read the following remarks by the designer, and I quote, "So you wind up with a sound that is not quite single ended and not quite push pull, but instead one that borrows the best from both worlds." I had to see for myself what that sounded like. See below for my comments:




Nikhil provided me with all the tubes and those beautiful Sansui 1000A output transformers. The Sansui tube amp legacy still lives on through Hashimoto products.



I replicated the circuit faithfully with an exception of the interstage transformers. The original circuit calls for the LL1635, but as per Kevin's (K & K Audio) recommendation I went with the LL1692A (25mA version) and it seemed work nicely.
My overall impression of the amp is very positive. I was trying to figure out what Ralph was saying about combining the best of both SE and PP and I seemed to have an idea what that might be. The amp has a plenty of the SE finese in the high to mid frequencies but with a lot more gusto at the lower frequency. The amp also sounds very balanced. It almost sounded like a very powerful 45 amp minus the speaker unfriendliness. I also love how simple the circuit is, e.g. no phase inverter tube to wire, no NFB, no bias circuit, etc. If you're looking for a relatively simple amp to build that will give you a hi fi performance, I would really give this amp a chance. Happy listening! Min

D3A phono complete (almost !!)

This project took the longest time to complete, but it is finally done (almost).Still need to tweak for the input impedance - right now the default loading is at 50K. Maybe use a linear pot like Edwin did on his initial phono stage designs. My initial impressions are that it is quiet for a tube phono stage (no low-freq hum). It is also detailed sounding maybe a littled tipped to the high frequency, but I think I might be able to workaround with changing the loading impedance. This project is collaborative effort on - the shunt regulated high voltage power supply is designed by Salas in Greece, the phono stage is designed by Andrea Ciuffolli in Italy and the PC boards designed by Quanghao in Vietnam. I'm using an enclosure from par-metal - nothing fancy but does the job for this project.
DSC 0403

DSC 0404

DSC 0405

DSC 0406

DSC 0407

Some features I need to incorporate in the future :
  1. Toggle Switch MM & MC
  2. Install Altec 15095A
  3. Loading option using a Dual Linear 100K Pot or Stepped Attenuator
  4. Re-orient the phono board

Saturday, April 28, 2012

D3A Phono Build - 0427

Connected Phono Board to PSU and hook'ed up to input and output RCAs Found that the on the input side, the "GND" silkscreen was reversed. Banged my head trying to find out why I wasn't getting sound only on one the left channel. Found that I had not connected B+ to the right channel. DOH !!! Ahh.. finally got sound out of both channels ! Amazing detail thru the Stax Lambda headphones using the iRIAA and iPhone. iPhone -> iRIAA -> D3A phono -> T-Amp -> Stax Lambda == Smiley Face

Next steps :
  • Re-orient boards

  • Run all joints thru a round of solder

  • Install resistors on the secondary after parts get delivered

  • Try mounting 15095A in the chassis for MC functionality (possibly MU metal shielding)

  • Install switch for switching between MM/MC

  • Install shielded hookup wire
  • Heatsink solution for MOSFETs if they don't run cool even after installing the power resistors on and dropping B+ to 200 (current set to 220V)

Thursday, April 26, 2012

D3A Phono Build - 0426

Tasks Completed :
  • Bored hole for power switch on the face plate ; used 0.7" drill bit
  • Completed wiring for power switch
  • Completed extending secondary heater wiring
  • Tested power on with switch - tested okay
  • RCA female plugs are painful to tighten. Looking at Neutriks :
    • D3a techshop 4 D3a techshop 1 D3a techshop 3 D3a techshop 2

        To Do :
      • check ground wiring
      • use hookup wire to hook RCAs
      • solder terminal posts
      • connect to main D3A phono board ; test B+, H+ voltages
      • connect iRIAA and test

Wednesday, April 25, 2012

D3A Phono Build

@TechShop - Powered up SSHV board... changed Heatsinks.. Power Resistor 470K to 1K/20W - Set output voltage to 220VDC @ 5Kohm load - 6.3VDC okay Heatsinks for both IRF9610 and IRF840 continue to be hot...Looking at changing to a bigger 4"X3" aluminum plate. Need to check all voltages as per the note Things to do : - Extend 6.3V secondary winding - Power switch on Front Panel; drill hole - RCA connectors - Shielded hookup wire - Silkscreen rear panel