Help a noob build a ZV9

[neil_kaye]

Hi,
I am in the process of building my first Pass DIY amp. I have searched the listings for answers to many of the questions that I have with varying levels of success. So i thought i would start a post where i might be able to ask specific questions regarding "a beginners guide to the ZV9" and as other people build their ZV9 they might add questions to this post... an informal wiki.

1. My first questions relates to capacitor C7 as labelled on Veterans boards. I would like to use either a Kimber 1uf or Solen 1uf cap. The Kimber's are polarized. How would i determine the correct orientation. It appears that they run in parallel to the 10,000uF cap. If this is the case do i attach the +ve leg of the 10,000uf cap to the +ve leg of the Kimber?

2. Star grounding: Do i star ground from the PCB ground, output ground and rectifier ground all to the chassis. If this is the case and i am using 400v 35A GBPC rect. bridge, where would i star ground on this as there are only tags for live and neutral?

3. Would a 3amp slow blow fuse work with this project?

4. Has anyone used Artic Silver 5 Polysynthetic Thermal Compound to attached JFET's to heatsinks iinstead of mechanical screws. It seems like a good solution and is used extensivley in the computer industry.

Thanks
Neil

[Zen Mod]

Originally posted by neil_kaye
Hi,
I am in the process of building my first Pass DIY amp. I have searched the listings for answers to many of the questions that I have with varying levels of success. So i thought i would start a post where i might be able to ask specific questions regarding "a beginners guide to the ZV9" and as other people build their ZV9 they might add questions to this post... an informal wiki.

1. My first questions relates to capacitor C7 as labelled on Veterans boards. I would like to use either a Kimber 1uf or Solen 1uf cap. The Kimber's are polarized. How would i determine the correct orientation. It appears that they run in parallel to the 10,000uF cap. If this is the case do i attach the +ve leg of the 10,000uf cap to the +ve leg of the Kimber?

2. Star grounding: Do i star ground from the PCB ground, output ground and rectifier ground all to the chassis. If this is the case and i am using 400v 35A GBPC rect. bridge, where would i star ground on this as there are only tags for live and neutral?

3. Would a 3amp slow blow fuse work with this project?

4. Has anyone used Artic Silver 5 Polysynthetic Thermal Compound to attached JFET's to heatsinks iinstead of mechanical screws. It seems like a good solution and is used extensivley in the computer industry.

Thanks
Neil

1. yes-same polarization as main (10KuF) cap

2. make your star ground on filter cap,wire all grounds independently to this point,and connect chassis to it via thermistor

3.depending what size of xformer and main cap bank you intent to use

4. old ways,good ways........mebbe one day you'll must change that part ,from any reason.......computer industry is more "use it ,throw it if doesn't work anymore"

[neil_kaye]

Originally posted by Zen Mod



1. yes-same polarization as main (10KuF) cap

2. make your star ground on filter cap,wire all grounds independently to this point,and connect chassis to it via thermistor

3.depending what size of xformer and main cap bank you intent to use

4. old ways,good ways........mebbe one day you'll must change that part ,from any reason.......computer industry is more "use it ,throw it if doesn't work anymore"

Thanks for responding zen mod.

1. What is the filter cap and what is a thermistor?
2. The xformer is 250VA per channel with 4 10,000uF caps for the main bank

[Zen Mod]

Originally posted by neil_kaye



Thanks for responding zen mod.

1. What is the filter cap and what is a thermistor?
2. The xformer is 250VA per channel with 4 10,000uF caps for the main bank

1. filter cap is your main bank
2.you can try with mentioned fuse,but I have some doubts that you'll need bigger one


thermistor..........resistor with (in this case) negative temp. coefficient.....with current ,resistance decreases.........just chill out some time and read those Pass's manuals little more .......

[thomaseliot]

Originally posted by neil_kaye
What is the filter cap and what is a thermistor?

Hi Neil,

a thermistor is a special resistor that offers a resistance when it is cold. When it becomes hot, after a few seconds, resistance drops near to zero. It is used here as inrush current limiter: what make fuse blow at startup.

I got two Digikey p.n. 570-1032-ND: current limiter inrush 10ohm 5A



The problem is where to place them.

I would put the two thermistors before the transformer, between live and safety gnd, and between neutral and gnd, respectively.

But Zen Mod says to put one between chassis and star ground. It's not clear to me how does it works.

Ciao

P.S.

The star ground point mentioned by Zen Mod is the negative pole of the first 10000uF capacitor of the PS pcb. As we both use Veteran's boards, we have two PS boards. So I would better have the star ground point on the chassis, between the two PS, and connect there filter caps grounds, safety ground, input and output signal grounds.

[Zen Mod]

thermistor between audio and safety ground is to prevent ground loops and-in case of any mains related failure-to allow path for fuse ......fusing

[neil_kaye]

thanks...
When i built my gainclone i used a standard 10ohm resistor to isloate the signal ground from the chassis ground. I guess a thermistor is a better option for the Zen amps.
Been recieving some of the chassis and VU meter parts... exciting times ahead.

[Dennis Hui]

Hi Neil,

You may also want to have a look at Figure 6 of the
ZV4 article ( http://www.passdiy.com/pdf/zen-v4.pdf )
It shows the use of a thermistor and diode bridge
for softstart and groundloop isolation purposes in an
unregulated power supply which is also suitable
for the ZV9.

Cheers,
Dennis

[moe29]

Hey Neil,

Since you asked for help, i would recommend building the original Zen amp first. It's a well documented project, and your chances of finishing it with a working amp are high.

Sure, the ZV9 is a more refined amp, and probably even sounds better than the original Zen. But the Zen amp is a great learning experience.

If i can't talk you in to building it, at least read all the Zen articles leading up to the ZV9. Good luck and have fun

(and buy big heat sinks)

[steenoe]

I would put the two thermistors before the transformer, between live and safety gnd, and between neutral and gnd, respectively.

Thomas, that does not sound as a good idea, if I understand you correctly. If you use the Thermistor as an inrush current limiter, you must put 1 Thermistor in series with the hot (live) lead. I usually solder the thermistor directly to the hot leg on the AC-inlet socket. Dont ground the hot lead through a termistor, which will be as good as a short
Nothing wrong with connecting the circuit GND to chassis ground through a Thermistor though

Steen