Z19 Crossover Update

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




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



LPAD mounted on front panel of chassis :




LPAD side-views :









Next steps :

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

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

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 :








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 :

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 ( http://www.digitalakuten.com/circuits/ralph_amp/ralph-amp.htm), 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 diyaudio.com - 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.













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