The official G9 help thread

[Deepdark]

Little update. I changed the grounding scheme and it helps a lot. Main board exit into the first input XLR, and it's pin 1 is connected to the chasis tab. IEC is connected at the main bolt, as near as possible from the iec inlet, as we should always do. there is a remaining little hum with headphone at max. I'll try again rotating the power transformer and will also change the grounding around C14 and C15. They share the same ground wire but aren't, hierarchically speaking, supposed to connect at the same place. There is a resistor between them, if ywe look at the schematic. So I'll try to wire C14 to the same ground point as the resistor and C15 will connect at the gnd connection of the board, as it is already. I'll let you know if it helps even more. 

 

[Deepdark]

Good developpement.

I changed again the grounding to test something else. Basically, as the schematic recall, ground exit at input xlr pin 1 to the chassis. So, instead of simply strapping pin 1 of input xlr's to the chassis lug, I run a wire from input xlr's pin1 to teh main IEC bolt. That's it. It corrects the little ground loop I had. Now, there is a little minuscule hum that is stable, no matter we change the gain. Probably I could get rid of it with proper transformer rotation or carefull tube selection.

 

[Deepdark]

The only complaint I would have is that I used an full aluminium case, and the panel are on the thin side. So vibrations carry easily to the tubes when we Knock on the front panel. I Wonder if putting some rubber ring on the tubes would attenuate the vibration.

 

[Audio_Ape]

Hello,

I hope I'm posting this at the right point.
I am at the moment planning to build a G9. Additionally, I am probably also going to include that in my bachelor project.
And for that I need an estimated timeline.
So a question to all the DIYers here: If you have all parts, how long does it take (in hours) to assemble the whole G9?
Would be great, if someone could give me an estimated amount.

Thanks!!
Kind regards
Nik

 

[Deepdark]

hmm I would say that about 10h to asemble the pcb and all the wires needed would be a rough estimate

 

[burglar]

Hi Guys,

I'm about to start my build.  I have a few questions including some sourcing.  I like to use Farnell due to free delivery here in the UK:

- I cant seem to find: 47KB (LOG) POT, 6MM

- I cant find : 10K TRIMMER 5x10MM.  Plenty of 10k trimmers but what does 5x10mm mean?  How many turns do I need?

- power transformers.  The first nees to be 220v to x2 15v secondaries.  Does the second transformer need to be specifically a step up transformer or can I use a standard 220v to x2 12v secondaries in reverse?

- I have x2 180uf 450v caps here, these will be ok instead of 100uf 350v?

 

[Deepdark]

Hi Guys,

I'm about to start my build.  I have a few questions including some sourcing.  I like to use Farnell due to free delivery here in the UK:

- I cant seem to find: 47KB (LOG) POT, 6MM

- I cant find : 10K TRIMMER 5x10MM.  Plenty of 10k trimmers but what does 5x10mm mean?  How many turns do I need?

- power transformers.  The first nees to be 220v to x2 15v secondaries.  Does the second transformer need to be specifically a step up transformer or can I use a standard 220v to x2 12v secondaries in reverse?

- I have x2 180uf 450v caps here, these will be ok instead of 100uf 350v?

- 6mm is 1/4inch. Pretty easy to find: http://ca.mouser.com/ProductDetail/Bourns/PDA241-SRT02-503A2/?qs=sGAEpiMZZMtC25l1F4XBU7IVlqK8DuF3rrrTImKrTvQ%3d
Here it's a 50K, it should be ok

- You can use both single or multiturn. You can look at something like that: http://ca.mouser.com/ProductDetail/Bourns/3362P-1-103LF/?qs=sGAEpiMZZMvygUB3GLcD7k%252bod3ZqvEIQboRRPdOKB6M%3d

- In reverse. It's the way we all do it

- Try it out. I personnaly installed 2x 470uf. Maybe you'll be ok with 2x 180uf

 

[JingleDjango]

I used this type (not this particular pot). It still fits if you bend the middle leg out.
Regarding power transformers, for Jakob's commercial units I wonder if he's getting a purpose-built transformer made? Just curious.

 

[Harpo]

- 6mm is 1/4inch. ...

A 6mm diameter knob will not fit on a 1/4" pot shaft. The other way round (1/4"knob on a 6mm pot shaft) most likely will result in an eggwise off-center rotation.
1/4 inch = 6.35mm

 

[Deepdark]

why not using 1/4inch knob?

 

[Deepdark]

http://ca.mouser.com/ProductDetail/Bourns/PDA241-SRT00-503A2/?qs=sGAEpiMZZMtC25l1F4XBU7IVlqK8DuF3W65b0TSwtRs%3d

 

[burglar]

Ok cheers folks,

found what i need on farnell.  I don't suppose you can shed any light on the toroidal transformers?  does the second on have to be wound so the secondary is 230v as a step up?

I don't suppose there's a record of the polyester cap lead spacings is there?  I'm looking to buy Wimas but don't have the board in hand.

 

[Deepdark]

the second toroid just need to be a 120/240 primary to 12v secondary. You strap it in reverse, so the 15v from the first one feed the 12v of the second

 

[Deepdark]

- 6mm is 1/4inch. ...

A 6mm diameter knob will not fit on a 1/4" pot shaft. The other way round (1/4"knob on a 6mm pot shaft) most likely will result in an eggwise off-center rotation.
1/4 inch = 6.35mm

You're right, my fault  ;D

 

[burglar]

These seem cheap as chips from Maplin UK.  Are they likely to be pants at this price?  I see don audio have toroidals specifically for this project that cost 180 euro for the pair! 

Do I spend the extra??

http://www.ebay.co.uk/itm/2x15V-50VA-Toroidal-Transformer-Dual-Primary-Secondary-Windings-Thermal-Fuse-New-/201228066205?hash=item2eda209d9d:g:HRwAAOSwQJhUd0I-

http://www.ebay.co.uk/itm/2x12V-50VA-Toroidal-Transformer-Dual-Primary-Secondary-Windings-Thermal-Fuse-UL-/191428486249?hash=item2c9206e469:g:-RAAAOSw7ThUd0HW

 

[Deepdark]

I used Triad transformer from Digikey. 50VA each. One is 120-240/15V and the other is 120-240/12V. Here are the models: 237-1333-ND and 237-1332-ND

Hope this help

 

[burglar]

Thanks guys, you've all been a great help 

 

[Harpo]

...I see don audio have toroidals specifically for this project that cost 180 euro for the pair! 

Do I spend the extra??

https://www.don-audio.com/G9-Audio-Power-Trafo-Sec-230V-12V-12V-Integrated-Shielding
You only need one of these mains transformers for a G9 build, not a pair.

 

[burglar]

Why is there also a dual 15v secondary especially for the same project?

]https://www.don-audio.com/G9-Audio-Power-Trafo-Sec-230V-15V-15V-Integrated-Shielding_1[url][/url]

 

[Harpo]

Why is there also a dual 15v secondary especially for the same project?

https://www.don-audio.com/G9-Audio-Power-Trafo-Sec-230V-15V-15V-Integrated-Shielding_1
*url edited

pro: +48VDC for phantom power from voltage-tripler is archievable. The tripled voltage from the other type of transformer 12VAC winding will be within phantom voltage requirements (+48VDC +/-10%), but on the low side, maybe leaving you some volts short. Hardly ever a concern, but YMMV.
con: a LOT more wasted heat in the +12VDC voltage regulator for the filament heater supply, calling for massive heatsinking of the 78S12 vreg, higher cost, not in stock, ...
Maybe ask Don.