The official G9 help thread

[audiophreak]

  and just to be clear, no matter the outcome of the second G9, the first one stays " AS IS "    'cus it sounds feak'n  fantastic !

 

[Janou]

Thanks for all informations, and thanks Jakob and Gustav  

It work great, only think i'm not sure at 100% is the wirring below. I use mono jack with this...

Other pictures now, it's normaly finished  ;D

 

[Morrow]

I've been going through the thread and searching, but I can't find an answer to this (though I hope I didn't just miss it):

At Position 11 (highest gain) on ONE of the channels, the gain actually decreases, and there is a pop. Both channels seem to function perfectly and identically up until that point.

I replaced the switch, measured R11-R14, and swapped the tubes as well as C7, but no change. Any ideas?

Thanks, I love the sound of this guy!
Chris

 

[Morrow]

Oh, also I checked the continuity of the wire going from C7 to R12 and it was good. While I was in there, I reheated a bunch of the joints in that neighborhood with the iron in case of cold solder joints. Still no fix.

 

[audiophreak]

Hi All,
        Sorry to butt in, I finished my G9 6 months ago and am extremely happy with it. Just today I was listening to a CD thrugh it and at some point the low end on the right channel dropped out    there was no indication of something wrong, no noise or pop, just I noticed that there was something missing, and when I checked it out, no bottom end on the right channel, signal was coming out, just no bottom end  :'(  swapped outputs and it followed, so its not the amp or speakers.

  The unit is and has been in a rack, so I don't think anything got jostled.

  any thoughts on were I might start to trouble shoot this ?


    Thanks in advance,
                              Chip

 

[1954U1]

Have you tried with the DI?
If using the DI there is bottom end, and your input is an OEP, maybe your transformer has been magnetized by some DC [coming from the CD player?].
It happened to me with a 1176's input OEP feeded by dirty synths.
[edit]to demagnetize it: 0-3V 3V-0 sine at 30Hz[/edit]

I'd try also to swap tubes.

 

[audiophreak]

    Thanks ... 1954U1 ..

        I was leaving my office when I noticed this, had no time to start digging in, I will definitely check out the DI input and I was also thinking about the tubes. I wont get back till Monday, I'll report back what I find.

    Thanks again,
                      Chip

 

[sjekkih]

Hi! I have a question about the sound of the G9. I finished mine a couple a days ago and was hoping to get the tube sound like on old rap vocal recordings (mid 90's, NAS, Jay-Z). I know they have a tubepreamp (maybe alsp a tube mic) and set the gain so high that the tube clips and unlike transistors it creates a warm distortion sound, rather than the clipping sound in transistor preamps.

Anyways I can't get my G9 to make this distorition. I have a condenser mic, not a tube mic, will I need that too? Is the gain on the G9 to low, or must it be a class A micpre? This DIY preamp says it can create a distortion when driven hard, and is class A. (http://www.soundskulptor.com/uk/mp66.html)

I would like to color my recordings a lot, harmonics, distiortion etc. can I do this with my G9? Change som resistors or something?

Best regards,
Vegard

 

[flintan]

Have you tried cranking the first gain up high with the second set low?

You could  build a pad to put after the out transformer. http://www.csgnetwork.com/decibelattenuatecalc.html

Or maybe you could put another pot before the transformer, after C13. I have not finished my G9 yet so i can't say what is the best or how it would sound.

 

[1954U1]

The G9 isnt made for big saturation effects, its always clean.
It seems like you want some real distortion.. so you can try a design without NFB loop.
See this thread:
Preamp that saturates vocals/Instrument on loud passages
Btw the MP66 SoundSkulptor pre is based on the circuits that you can see on this thread, e.g. the Gates and the NYD one-bottle pre no-feedback versions.
Note that you must be logged to see the attached schematics of NYD 1bottle versions.

Back to the G9.. quickly looking at the schematic, dont know if I'm saying total BS, but I'd try to increase the R10's value, maybe that will lower the NFB loop, thus increasing THD.
If that works, you can add a pot in series to R10.

 

[sjekkih]

Yes I tried setting the gain at max and the out low, but the G9 is too clean

I will try changing R10. I understand the NFB loop consept now, but what is this talk about pads and pots at the output transformer?

BTW, is there a big difference between a tube mic and a regular condenser one?

Thanks for the guidance

 

[stanz]

Noise issues with new input transformers.   

In trying to improve the low end for my G9, I swapped out my input transformers from an OEP to an Edcor XSM600/15k. Before, it sounded great with no noise problems at all. I simply mounted the transformers to the side of the chassis nearest the previous loctation of the input transformers on the PCB. First I patched it in with a twisted pair, then went to a shielded cable, but both yield a very noisy pre amp. I have pretty much narrowed it down to the transformers. Unplugged the input cable from the board, but it is still noisy. As soon as I plug a cable into the inst jack, it is silent as one could hope, and plays a bass fine, as one would expect. The only thing between these two pints in the circuit is the relay for the line/mic/48v sw, and the transformer. Ther cable run from the circuit board to the transformers ar about two inches. I did not connect the shield to anything, but I did hook them up to a clip to try and see if grounding them would help. No luck.

The transformer is a center tap on both Pri and Sec, so I just hooked up the outer leads (1&4 5&8) to the + & - side of the respective pri and sec holes on the PCB. The transformers are a lot bigger than the OEP. Not sure if that is an issue or not.

Transformer specs.
http://www.edcorusa.com/Products/ShowProduct.aspx?ID=329

Any ideas what I might have missed.

 

[audiophreak]

Hi All,
        I started to troubleshoot my G9 today, sent CD audio in thru front directs and everything sounded fine, then for the hell of it, I went thru a pair of IMPs and the xlr inputs as before, and it also sounded fine ...after letting it play for an hour or so, the low end must have dropped slowly out of the right channel again. 

    I swapped output tubes and both channels sounded fine again, let it play for 3 more hours, still sounds fine. :

  I'm thinking it might be the right ( now left)  output tube as the low end just kind of slips away but not sure, could I be loosing a cap? I guess I'll have to wait till it does this again, and I hope it does, because I cant stand not being able to find the problem, and the unit not reliable.

  anyone have any ideas?

    Thanks,
              Chip

 

[stanz]

So, in doing some digging around, is the edcor XSM a suitable input transformer? Is this transformer susceptible to noise due to lack of shielding?

 

[1954U1]

Hi All,
        I started to troubleshoot my G9 today, sent CD audio in thru front directs and everything sounded fine, then for the hell of it, I went thru a pair of IMPs and the xlr inputs as before, and it also sounded fine ...after letting it play for an hour or so, the low end must have dropped slowly out of the right channel again. 

    I swapped output tubes and both channels sounded fine again, let it play for 3 more hours, still sounds fine. :

  I'm thinking it might be the right ( now left)  output tube as the low end just kind of slips away but not sure, could I be loosing a cap? I guess I'll have to wait till it does this again, and I hope it does, because I cant stand not being able to find the problem, and the unit not reliable.

  anyone have any ideas?

    Thanks,
              Chip

Thats weird.. erratic malfunctions are the worst.
if its still the same ch also after swapping tubes, maybe its a leaking cap  C2/C3/C4/C5/C10/C13..
At this point, if I were you I'd start desoldering the caps, both channels, searching for differences [leaking?],
then resolder all of them with inverted channels.
So at least you'll know if its a cap.

Keep us informed!

 

[shabtek]

@stanz, xsm are  rated 2.5 watt (line level) but may still be usable . edcor does offer mic input transformers; mx series. I have no experience using either as a mic input transformer. shielding may be an issue, try different positioning.

 

[gemini86]

I've been thinking about using edcor iron as well, shielding them with some diy moly sheet cans. Anyone tried them in the g9 yet? I'm going for a budget build here and the price is about right...

 

[audiophreak]

Hi All,
    Well..... it happened again, no low end on the right channel, so I swapped input tubes this time, was o.k. for awhile, then no low end on the right channel again 
I noticed that when I power down the unit for a minute then fire it up again, the low end comes back, so I listened to the right channel only to see if I could hear exactly when and how the low end goes away, it did after an hour or so, and it just kind of faded away over a couple of seconds. Twice I shut it down with the CD still playing and power amp still on,  and when I flipped the switch off on the G9 the low end came back instantly and stayed that way until the G9 faded out ( caps draining ? ) .

Anyone have any Ideas, if not I think I'll start with what 1954U1 suggested. I'm still such a newbie.. ;D

 

 

[Matthew Jacobs]

Audiophreak, I'm sorry to hear you are having these strange bass drop outs with your unit.

I hope you get to sort it out.

Best of Luck

Keep us updated.

J

 

[1954U1]

Hi All,
    Well..... it happened again, no low end on the right channel, so I swapped input tubes this time, was o.k. for awhile, then no low end on the right channel again 
I noticed that when I power down the unit for a minute then fire it up again, the low end comes back, so I listened to the right channel only to see if I could hear exactly when and how the low end goes away, it did after an hour or so, and it just kind of faded away over a couple of seconds. Twice I shut it down with the CD still playing and power amp still on,  and when I flipped the switch off on the G9 the low end came back instantly and stayed that way until the G9 faded out ( caps draining ? ) .

Anyone have any Ideas, if not I think I'll start with what 1954U1 suggested. I'm still such a newbie.. ;D

Ah, so, being maybe power supply related,
I'd try first to swap C25 and C125.