The official G9 help thread

[madreza]

I was troubleshooting a friend's G9 and noticed that he had mismatched the Xformers : all input Xformers on 1 channel and Outputs on the other one !
I was wondering if this could damage anything ?

I still have a problem : I have a very low output signal ( maybe 40 db less than my G9 ) on both channels !!!

his HT voltage was very low , i changed a Xformer for a 12V to raise the HT but the pb is still the same !

UP AGAIN
Noone can help me ???

 

[gyraf]

I was wondering if this could damage anything ?

No, not likely.

For error tracing, try comparing signal levels and working voltages between working and non-working units.

Jakob E.

 

[JimiH]

My G9 is almost complete. All it needs is some xlr connectors, some tubes and some power transformers. Quick question, can I get away with 20VA torroids? There is a local supplier but they only do 20VA. Will I scrape through? I am assuming that I will have to go 15+15 and 12+12 if it will even work at all...

 

[Godders]

[quote author="JimiH"]My G9 is almost complete. All it needs is some xlr connectors, some tubes and some power transformers. Quick question, can I get away with 20VA torroids? There is a local supplier but they only do 20VA. Will I scrape through? I am assuming that I will have to go 15+15 and 12+12 if it will even work at all...[/quote]I had problems (and so did others) with low HT voltage with 30VA torroids, I got some 50VA and now everything is dandy.

I think different brands behave differently when used in this way but I don't fancy your chances with 20VA.

Cheers

Nick

 

[kazper]

JimiH If your in the states contact Avel sales department

http://www.avellindberg.com/

There transformers are very inexpensive and there price point breaks at 2 transformers.
I got 8 transformers for a little over $110 shipped for my 1176's and some other projects.

 

[JimiH]

Ok sweet! Thanks everybody.

 

[maxime]

hello all

I had spare time to get into my crosstalk problem on channel 2 my g9. it looks like the C2 (first cap right after the transformer) is likely to pick signal from channel 1. I had 10 dB less crosstalk with the cap soldered under the pcb and laid out parallel to it !
i suspect the channel 1 output tube to act as a source of matter.
do anyone of you think that the tube sockets can have an influence? (mine are ceramic and 3/4 inch high) maybe geometry and layout plays a role in here?


best

maxime

 

[JimiH]

Well my G9 is almost complete. Just need 2 more tubes (well, 4 more, all have is 2 of these damn 40 year old mullards...) and to hook up the outputs and test it fully. I solved my transformer problem (I could only find 20VA units) by using 3 transformers, and it seems to have done the trick rather well, except for phantom. The most I can squeeze out of that is around 27 volts. All my caps seem fine and I'm going nuts trying to find the source of the problem. There is 15V AC before the regulation too. Anyone hazard a guess?

 

[maxime]

did you check diodes and their orientation?

 

[JimiH]

Maxime, you are a genius. I was about to post a reply telling you that I had obviously already done that, but I just ahd another look thanks to you as I thought, ehh, can't hurt, and there you go. D6 is around the wrong way. I haven't changed it yet, but I'll let you know how it goes, as I am sure you are dying to know...

 

[maxime]

glad to hear that!

 

[JimiH]

I meant to say D9 and by the way, it's fixed!!! Thanks a billion!

 

[JimiH]

Well it's all done (I still have only 2 really really old and crusty mullard ecc82's) and after testing it one channel at a time I can say with all honesty and conviction, "holy crap."

I am really inpressed at the smoothness of this preamp. All other tube preamps I have had experience with have all been a bit harsher than expected. This one is as creamy as. Thank to everyone who has helped. I am glad I underwent this endeavour. Even though I coudln't really afford it, it was worth every cent so far. On top of all this I have no issues (except for that one diode - see above) and I didn't even have the high gain oscillation on channel 2... well not yet anyway. This new toy is oh so much fun!

 

[gyraf]

:razz: :thumb:

 

[CurtZHP]

Not sure if this was covered before....

I'd like to use an LED instead of a lamp for the "ON" light. I'm assuming I'll need a current limiting resistor in series with the anode of the LED. Can you recommend a correct value for that resistor?

Thanks!

 

[gyraf]

For a LED fed from 12V, something like 1K or 2K2 / 1W

 

[CurtZHP]

Thanks. Now another question....

I think I screwed up the installation of the phase switch. I have it installed with the "Lorlin" label on the right side (facing the switch), which is how the Gain and Pad switches are installed. Its two positions are 12 o'clock and one click to the right.

Now I'm taking a closer look at the front panel graphics on your website and what I saw made me panic a little. On the site, the phase switch is shown with the "in-phase" position at 12 o'clock and the "invert" position one click to the LEFT. Ooops!!!

When I check the schematic, my understanding is that the switch is rotated clockwise to invert the phase of the output.

Help!!

 

[CurtZHP]

This might be the answer to my previous question.....


Does the output transformer on the G9 invert the phase of the signal?

If that's the case, that would mean that a clockwise rotation of the phase switch would put the output IN PHASE, rather than OUT OF PHASE.

How am I doing so far?? :grin:

 

[gyraf]

..it's easy to reverse the two wires going to the out xlr, if polarity dosen't fit at first..

 

[CurtZHP]

I also realized that it's just as easy (probably easier) to simply reorient the knob on the switch shaft.




How does one say "Duh!" in Danish?