The official G9 help thread

[Stagefright13]

thanks originalmusician! Some inspiring words are always welcome. I am hoping it will compliment my UA pres. But if it replaces them that is cool too! It just looks like such a fantastic project I couldn't resist it. The circuit boards may be here in a matter of hours I keep checking mailbox lol!

I have read this entire thread AND all the metas about the G9. I like to be prepared. But someone like you obviouslly has more experience with the unit than any amout of reading can afford.

And yes I have a Tat Purusha case on the way. I have no way of silk screening graphics and such...

I did test my power transformers and have 240 volts coming out of the step up one. Is that enough?

And thank you!

 

[Stagefright13]

I would think both HT caps should read the same. However the schematic only shows one channel. Possibly excessive current used by one side that is dropping the voltage? Short or wrong component on one side only? Just guessing. I would thoroughly check the components on the side with less voltage. 30 volts is a big difference. And try swapping tubes from one side to another.

 

[jdr]

One thing I'm unsure of is that my big power caps (c14, c15) don't measure evenly. I have 240v on one and 270v on the other. Does anyone know if this represents a problem?

C14 is before the voltage regulator, so it should have a higher voltage across it than C15. C15, after the TL783 regulator is the HT reservoir cap for the circuit, so something like 245VDC is just what you want.

I did test my power transformers and have 240 volts coming out of the step up one. Is that enough?

The schematic shows 220VAC loaded by the rest of the circuit, so 240VAC unloaded is in the right ballpark.

Enjoy the build!

John

 

[Stagefright13]

oops! your right C-14 IS on the schematic! My bad! And thanks I will be assembling it hopefully Monday if the pc boards come.

 

[originalmusician]

Thanks you guys! I have finally got the grounding scheme correct on this thing, and it runs quiet. I can put it in the rack and actually start using it! Sometimes with these DIY projects, I start to feel like I'm never going to get a piece of gear quite finished, but this baby is done.

Now my mic pre arsenal consists of GT brick, vintage Neve 1272, G9, and Green Pre. I have the stuff around to make a 1290 and a Great River, but seriously, I have to lay off this pre building...and start making some microphones. Ever since I discovered this forum, my girlfriend thinks I'm crazy. Just how many of these strange looking gadgets does a guy really need? But she says as long as it makes me happy, that's the important part. In return, I keep my mouth shut every time she buys a new pair of shoes, which is quite often IMO. LOL :grin:

 

[originalmusician]

[quote author="Stagefright13"]thanks originalmusician! Some inspiring words are always welcome. I am hoping it will compliment my UA pres. But if it replaces them that is cool too! [/quote]

I think the G9 will be a nice compliment to the UA pres and will add variety to your arsenal.

You know, the first project I built here was the Green pre using PTownKid's kits (but I replaced the caps with Wima). As inexpensive and straightforward as that project was, I continue to be impressed with the pres. They have such a nice big clear sound to them. In order to take these away from me, first you would have to kill me.

I feel the same way about the G9 as it relates to its unique characteristics. When I say the G9 is distorted and saturated, I should point out that this is actually rather subtle. I recall one builder saying that the G9 is clean and without saturation and distortion. From my experience, the pre has obvious high-quality tube amp characteristics. I think using the transformers you used you can expect a fairly clean sound with classic tube amp characteristics embedded into it. You might not prefer it on all sources, but when you do prefer it, you will get a real feeling of accomplishment from it. :grin:

 

[Stagefright13]

Well looky here is my New G-9! :

Coming along great. May have it done tomorrow if my missing Wima's come. I ran out of parts and brain cells so taking a break lol. Been working on it all day. Let me know if ya see something goofy in there.

But I would like to say this is my most personally rewarding project yet. I spent weeks reading the threads on here while I was waiting on parts etc.
Thanks so much Gyraf!!!! Having great fun.

:green:

Originalmusician: Tell her as many boxes as these 2 five Foot ten inch racks can hold. And as long as the floor can support them. Well that's what I tell my girlfriend anyway!

 

[originalmusician]

You are moving fast! Where did you get those cool looking heatsinks?

And where are you getting the last of your Wima's from and what values are they? I had trouble finding Wimas that fit.

 

[Stagefright13]

Hey when your computer power supply blows up don't forget to rape it for parts.

If something blows up here I even keep the wire sometimes lol. I like to recycle stuff. If it breaks make sure ya open it up and see what will fit in the scrap bin. You may be surprised. As I was. I have a "Vintage" collection of heatsinks now.

Getting the Wima's from Mouser. They frequently upgrade my orders now to 2nd day air for free so I stickin' with them. Just type in Wima in their search. If ya do that in Digikey NOTHING comes up. Hopefully all will be well tomorrow I am close and anxious...

For some reason I never got the .22uf's and the 2 10 uf's. The BOM I used was off by quite alot but not too far. I had some spare parts to get this far.

:green: :thumb:

 

[Stagefright13]

WOW It works perfect! I think my heart rate went up a bit when I powered it on... :roll: But it passed the smoke test and the voltages looked good so I plugged a mic in and OMG sounds great!! I haven't tested it in the studio yet. BUT at first sample I believe it may crush my Universal audio 610's. I'll do a shootout tomorrow.
Pics are here:

Thanks again for everyone's help. It is as always greatly appreciated!

 

[MATTI]

Considering making this but for more gain I
would put 1:10 input transformers instead of OEP´s, possible?

Matti

 

[gyraf]

Yes, possible.

But you could run into too-much-gain, i.e. overloading of the input stage with loud mics.

It's all a balance in these simple designs.

Jakob E.

 

[MATTI]

I´m quite amatourish but if I skipped the "line in" and
used different resistor values for use it as a mic pad, say
-15db or make an separate switchable t-pad input attenautor pefore the pcb. ( now that I looked at the schem. )
Just speculating at this stage...

Thanks

Matti

 

[Stagefright13]

It has plenty of gain as is. With an SM7 shure mic and a fairly powerful singer I had the knobs like 70 input and 60 output.

 

[MATTI]

Ribbons, VO work?

Matti

 

[originalmusician]

The OEP transformers are inexpensive and result in 60+db of gain. By contrast the Groove Tubes Brick only has 50db of gain and is still considered usable.

A G9 with OEP's might need more gain when using certain classic ribbon mics (I've heard that some require 70db of gain, but I do not own any such beasts). My experience is that the G9 has plenty of gain when using my voice as a source for my cheap Chinese Apex 210 ribbon mics. The Groove Tubes Brick is a gain wimp in comparison, thus I only use it on certain sources.

 

[Stagefright13]

If using a modern DAW as your input it has Mucho gain. It will bury your VU in Protools. (If that is what you are using) AND your external converters. I find in my motu and Logic the same thing is true. I really can't see why anyone would ever want 70db gain! You would have to attenuate that to get a good sound.

It sounds great as is and the commercial version I am sure is STELLAR!

And I do 78% VO and will be using it for that on Thursday...

But I don't use ribbons and if you need massive gain for quiet sources and insist on a ribbon it may not be for you. And why in God's name would you use a ribbon for VO??? Weak output and terribly flat. Not the kinda thing a good announcer would want when he says "Come one Come All, Smoking Hibachi Burnouts! It's Atco Raceway!!!"

And if you ever heard that don't tell anyone it was me.

 

[MATTI]

Easy, easy my friends!
I just cannot see any harm from some extra gain...
As a former film sound recordist I´m used to have
70-80 db of gain -if needed.
My main mic for the moment Is a Chinese tube mic
heavyly modified and with a sweet Dale "M7" capsule,
no extra gain needed for that.

Regards
Matti

 

[Stagefright13]

Sorry I got off track. You will find it useful for VO and other things. But if your time is Valuable you would be better of buying a real one from Gyraf. Honestly. It is expensive for parts and the time involved is quite high. Buying a unit from Gyraf may be more cost effective. And it will be the Premium one!

Sure gain is ok until you have ridiculous amounts like you are suggesting and then you need more cables and an atty to get the mic amp in the nice balance of working some.

You recording to tape or DAW I have at least 1 of each?

Good God 80 db of gain? What is that useful for lol. Just kidding ya maybe someone needs a HUGE noise floor.

And you may very well know what that gain is needed for. I am just goofing with ya.

And I kinda pissed one of my monitors went south. Hard to mix without the 2 screens... Maybe I was taking it out on you if so I am very sorry!

 

[MATTI]

I was thinking of some 5 extra db´s with a different input transformer,
nothing insane (this time).
The other alternative could be New York Dave´s Mila or...

Cheers ;-)
Matti

P.S. I could have your Eisen rack as a compliment ,-)