A cleanish preamp

[G-Sun]

I've been evaluation my preamp needs a little bit more,
and comparing something like a SSL9K with a G9.
It seems not that different in cost, difficulty and work (considering that much is new to me anyway, and case and psu is a major part of cost)
and I guess I would choose the G9 over the SSL9K 9 of 10 times.

Although a SSL9K would be welcome beside my Hamptone HJFP2 (the HJFP2 is has a little color/bite to it),
I'll think I'll have to check out the G9 a little more

 

[ricardo]

Could you give me the Green vs. Super Green -short story?

Green uses the Cohen i/p with a very crude o/p stage.  Super Green is closer to Cohen, has better parts and some EMI protection.  Both use poor P48V protection.

But the circuit is only one aspect of preamp performance.  I've said the Millenia doesn't have the noise performance of the Cohen but it is still one of the best clean preamps you can buy.

The SCA C84 has excellent EMI & P48V protection and an excellent PCB layout; vital for "clean".  The board kits are a bargain.  I don't think you can buy his excellent bits for the price of the kit.

The PSU & case are expensive for 2 channels but not if you consider the cost of making something like a PSU for a G9.  The case & PSU are vital aspects of preamp performance; especially if you want "clean".  You'll probably end up buying more SCA boards, maybe the transformer & DOA ones to go with your T15 or C84.

Lastly, but definitely not least, I'm impressed with SCA support on their forums.

BTW, G9 is NOT a novice project.

 

[kante1603]

BTW, G9 is NOT a novice project.

Absolutely!

@G-Sunlease try to build some stuff operated at low voltage first-and as said-learn.
The G9 is a tube based mic pre,therefore it is using high voltage.Doing something wrong or do things like trial & error could be the last thing you do forever-no joke!!!
Check how much you know about the basics in electronics and follow all safety rules concerning handling mains power exactly!
Build things like 2 rail psus at low voltage and try to understand how it changes the incoming ac at 230 or 110 volts to the desired dc rails (e.g.what does a transformer do/ my DMM shows a different ac voltage on the secondaries when nothing is connected/what happens in and after the rectifier/what are those big caps for etc.).

Please be careful,

best regards,

Udo.

 

[G-Sun]

@G-Sunlease try to build some stuff operated at low voltage first-and as said-learn.
The G9 is a tube based mic pre,therefore it is using high voltage.Doing something wrong or do things like trial & error could be the last thing you do forever-no joke!!!
Check how much you know about the basics in electronics and follow all safety rules concerning handling mains power exactly!
Build things like 2 rail psus at low voltage and try to understand how it changes the incoming ac at 230 or 110 volts to the desired dc rails (e.g.what does a transformer do/ my DMM shows a different ac voltage on the secondaries when nothing is connected/what happens in and after the rectifier/what are those big caps for etc.).

Please be careful,

best regards,

Udo.

Thanks Udo I'll never take lightly on safety and high voltage. But, I'll have to get into tubes at some stage anyway.
I will consider the G9, but maybe do some other projects first.

 

[G-Sun]

Green uses the Cohen i/p with a very crude o/p stage.  Super Green is closer to Cohen, has better parts and some EMI protection.  Both use poor P48V protection.

Thanks! Supergreen is a not so well documented project, and the pcbs are not easy available, right?

But the circuit is only one aspect of preamp performance.  I've said the Millenia doesn't have the noise performance of the Cohen but it is still one of the best clean preamps you can buy.

The SCA C84 has excellent EMI & P48V protection and an excellent PCB layout; vital for "clean".  The board kits are a bargain.  I don't think you can buy his excellent bits for the price of the kit.

The PSU & case are expensive for 2 channels but not if you consider the cost of making something like a PSU for a G9.  The case & PSU are vital aspects of preamp performance; especially if you want "clean".  You'll probably end up buying more SCA boards, maybe the transformer & DOA ones to go with your T15 or C84.

Lastly, but definitely not least, I'm impressed with SCA support on their forums.

Looks like the SCA C84 with a JLM AC/DC kit and my custom case could be a good option (does it fit in 1U?). Wouldn't be that much cheaper than a G9 with OEP though.

 

[G-Sun]

Has anyone compared the ScA C84 with the SSL9K?

 

[ricardo]

Has anyone compared the ScA C84 with the SSL9K?

SSL 9K is yet another Cohen copy.  More complicated than C84 both of which are more complicated than the original and  less EMI protection.  No P48V protection.  I'll bet Millenia & Earthworks are much closer to original Cohen.

On paper, C84 has less noise.  But real performance factors include exact PCB layout, box & wiring.

The real deciders probably  the protection issues and things like C84 accurate switched gain.

 

[G-Sun]

SSL 9K is yet another Cohen copy.  More complicated than C84 both of which are more complicated than the original and  less EMI protection.  No P48V protection.  I'll bet Millenia & Earthworks are much closer to original Cohen.

On paper, C84 has less noise.  But real performance factors include exact PCB layout, box & wiring.

The real deciders probably  the protection issues and things like C84 accurate switched gain.

Thanks!

 

[G-Sun]

After much back and forth I think I've landed on 2ch SSL9k with JML AC/DC kit, Go between kit with DI, and maybe a case from Par-Metal 1U.

 

[ricardo]

After much back and forth I think I've landed on 2ch SSL9k with JML AC/DC kit, Go between kit with DI, and maybe a case from Par-Metal 1U.

  If there is ever a chance that this will be used with P48V (even with a separate P48V box), install the protection diodes as in the C84 circuit; R31/32, D1-4

 

[G-Sun]

After much back and forth I think I've landed on 2ch SSL9k with JML AC/DC kit, Go between kit with DI, and maybe a case from Par-Metal 1U.

  If there is ever a chance that this will be used with P48V (even with a separate P48V box), install the protection diodes as in the C84 circuit; R31/32, D1-4

Don't think so, as the JML Go Between Kit will give me 48V. Right?

 

[signalflow]

I think Ricardo is saying to add the protection diodes to the input of the SSL9K to make sure that the phantom power doesn't harm the circuit.

But I will say I do not have protection diodes installed on my 8 channel and have never had a problem with them.  The 2.2uf caps at the front of the circuit are there to block DC from entering.  Adding the diodes would just be an additional precaution if your paranoid about such things IMO.

Plenty of people have gone without them and have had success with this build. 

My $0.02,

-Casey

 

[ricardo]

If there is ever a chance that this will be used with P48V (even with a separate P48V box), install the protection diodes as in the C84 circuit; R31/32, D1-4

Don't think so, as the JML Go Between Kit will give me 48V. Right?

Doesn't matter how you get the P48V.  If you EVER have it, you must protect the electronic input stage.  If you keep the SSL C55/69 at 2u2, you can probably leave out the C84 R31/32 but DON'T leave out the C84 diodes D1-4.

You might think MAT-02 is rugged enough to survive a line short with P48V on (eg if a patch cord plug touches chassis, the input caps dump their charge through them).  But what happens is Vbe zeners.  Your preamp may still work but is suddenly forever noisy.

Bortoni, R & Kirkwood, W “The 48V Phantom Menace Returns,” AES preprint 127th AES Convention, Oct09

http://www.thatcorp.com/datashts/dn140.pdf has a simple explanation