API Mic pre (with Yamaha parts) ***COMPLETED***

[khstudio]

Dave, Thanks man:thumb: I will do what you said.

[quote author="3nity"]looks interesting. Instead of racking those pm1000 or 2000 you used the parts for an API??

tell me how does they sound?? better to those yamaha channel strips??
did you ever heard one APi 312?? how do they sound against API??

Good work.....[/quote]

Not instead of the PM1000 or 2000... I already finished the 1000 & the PM2000 is almost done. I'm getting a second channel this week, no sense in paying for a Case, PS and all the work for just one. I like-um in pairs :wink:
& NO, NOT BETTER than the 1000 or 2000... different. They're ALL cool but this API/YAM is just SWEEET :green: I sounds like it would be MUCH more universal than the others & less of a one trick pony.( I take that back, the 2000 is pretty sweet too, but I can just feel the simple API design & LOVE it.) Never heard a REAL API but now I'd love to. I wish you guys could hear this thing. For the first time I feel like it captures what's on the other side of the mic. I think the Yamaha components are pretty good.


mattmoogus
Once again, thanks for the tips :thumb:

Is a volt meter accurate enough?

I'm getting -16.3mv

I forget who said it recently but they said a little won't hurt.

My BIG question is, since I love the way it sounds right now, will it change over time having a little DC on it or will it pretty much sound how it does NOW. Also, will it ruin the tranny in any way... like burn it out?
The low/hi end is sooo nice right now I'm hating the thought of adding the cap but it's better than ruining it all together.
EDIT: OK The more I looked at the schematic I can see that any DC can & probably does travel thru the OT back thru the ground path & could affect things so, IF I ADD AN OUTPUT CAP... WHERE? BEFORE OR AFTER THE FEEDBACK?(normally 20k/120pf)

1 more thing,
I guess it's OK to just hook up the bal I/O of my sound card to this thing while running that ap? The sound cards OUTPUT impedence is ok & won't effect the test :?: Doesn't seem right when the input wants to normally see a low impedence mic, probably 600ohm or less, NO :?:

What is CRO :?:

Kevin

 

[khstudio]

Not to overshadow my last post but,

You guys are probably right about the 2520. I'm really just borrowing the basics as you can see in the schematic I posted. And for they little money these parts cost me it's just sick what I'm able to get out of it.
So far about 6 of my boys picked this pre over all my others... PM1000, 2000, MP20, M80, Topaz pre's on board... I know I know, it's all I've got... right now :wink:

I just love making shit out of scrap parts that is cheap, usefull & kick ass :green:


Kevin

 

[mattmoogus]

16mv is probably too much, but I dont know this for sure. Better to be safe than sorry tho, just put a big cap in there. If you can hear the sound change Id be very very surprised.

The problem is that any DC on the output transformer will reduce your low end headroom and slowly magnetize the core, which increases distortion. Yamaha have caps after these opamps and thats probably why. The other way is to use a gapped transformer like our 1:1:1.

Yamaha put the cap after the feedback point, so Id do the same. If anyone knows better let us know!

You can hook your soundcard to the pre no problems, but you will need a pad in front of the transformer otherwise it will be saturated by the test tones and youll get a huge THD/IMD readings, and perhaps a wrong freq graph aswell. Id copy the pad from the PM2000's +4 gain setting;
220ohms in series with each leg and 330ohms across them.

With the pad in it doesnt matter how low Z your soundcard's output is as it will have plenty of resistance in series with it.

A CRO is a Cathode Ray Oscilloscope - you said you had a valve one? Assuming its all within spec it will be very useful for testing these pres.

Soundguy, hear hear re. your API/Neve sound observation!


M

 

[rafafredd]

16mv is probably too much, but I dont know this for sure. Better to be safe than sorry tho, just put a big cap in there. If you can hear the sound change Id be very very surprised.

I hope it´s ok to give my opinion... :?

Try measuring the DC current throught the transformer primary. It looks like a big core, I don´t think it will lead into any troubles over time with a transformer that big. The DC current is probably very low. It will dependend on resistance and inductance of the transformer, so you better measure it with a cheap multimeter, instead of calculating. It´s probably on the order of some hundreds microamps, so your transformers will work ok for at least the next 30 years without a cap. I say, if you like the sound, leave it.

 

[khstudio]

mattmoogus & rafafredd
Thank You.

I'll be testing it tonite.

Also,
I set my meter to DC & put the black on the GND side & the RED on the inpit side & got -16mv... but earlier in this thread I was lucky to get CJ to comment but he did some crazy math & by the time he got done the actual DC was much lower than I measured. Me don't understand :?

The output tranny I'm using IS pretty big. It weighs about 1 - 1.5 pounds.

OK so over time it COULD change but what about the DC that travels thru the tranny back into the circuit? Do I even need to worry about it. I let it run last night & it didn't blow up & still sound great.

I WILL be trying:
- an output cap JUST to listen to it & see if it ruins a good thing.
- follow matts advise on testing
- & inserting a POT in the feedback to check for a sweet spot/max gain (also while hooked up to the test app to see what's going on)

 

[khstudio]

mattmoogus,
I emailed JLM/Joe about shipping cost & getting the 99v boards without the op-amps, gold pins, relays & associated components.

Basically everything I need but use my trannys & the NE-80200 op-amps.

I emailed on friday but havent received a responce :roll:

I also did the math myself to get a rough idea of cost & it didn't seem to work out. If you subtracked the op-amps, pins & relays from the total listed now it is a litte high :!: Caps, toggles, diode & resistors don't cost that much... I just wanted to get all the parts in one shot. But I'm still waiting for his responce.

As soon as I get a idea of cost, I'm ready to place an order.
I really need the power supplies the most but thought, why not try a few of the Dual 99v boards with my stuff. I have just enough parts to build 2x dual 99v's & 8 od these API/YAM's I'm doing now.

Thanks,
Kevin

If you talk to him & he didn't get my email, could you forward this to him?

 

[rafafredd]

messing with R3 to find a hot spot is a nice idea, but if you only need more gain, try lowering the value of R2, to 100R, 47R or or even 22R. R2 limits maximum gain. The problem here is that you don´t have a big step-up at the input transformer, so you need more active gain. For this, make R2 lower value until you are satisfied with the maximum gain you have.

Also, if you use another value for R3, make sure the pot you are using for gain control isn´t greater than this R3 value. This makes minimum gain not less than 2. Less than 2x gain might be a problem with many opamps. I don´t know about this yamaha... Best would be to use the same value for R3 and pot. Or a little lower pot value to limit minimum gain and make the whole thing more stable.

Just a guess, 22k = R3, 47R = R2, 20k = pot might make you happy, with lots of maximum gain and stable minimum gain.

 

[khstudio]

Do you mean a 20k for the actual gain trim/vol?

I'm not sure if you checked out the schematic I posted but what your saying makes sense...
My R2 is @ 220, didn't have a 200 - so a little loss there.
My R3 is 18k, probably won't hurt to go 20 or 22k there either.

Dude your tips are great, thank you, I'm sorry I have to scrap a good board but as you can see (and I wish you could hear) it's for a good cause :wink:
I'm really going to get a LOT more out of it in the long run.

BTW, I did fire up one of the M1516 strips but this thing is KILLING it.
Not to mention 8 channels of it in a 2 space rack for drums... O yea.
I've been using a Presonus M80 for years on drums. I think this is better.

Kevin

 

[rafafredd]

What´s the value of the gain rim pot you are using. Let´s say it´s 20k. With a feedback resistor (R3) of 18k, you end up with less than 2x (6dB) active gain. That´s really hardly usefull for micing, specially with a low ratio input and makes things a little more complicated for the opamp stability. If if you are dealing with really hot mics and sources, like neumann condenser close on a snare drum, you should include a -20dB pad before the input transformer.

Also, 220 is a little high for R2 with this input transformer. It won´t give you enought gain for many situatrions.

Again, based on your schematics, try this:

R3 = 22k, R2 = 47R and pot (gain trim) = 20k. This is a good combination for me. Max gain will be aprox 60dB, minimum aprox 16dB, counting input transformer. If you need less than 16db, use the pad.

If you find maximum gain is too hot or unstable with this config, try R2=100R.

I hope it made sense. Do you have the parts on-hand available to try this? If not, look in your channelstrips. There might be some of the resistor and pots values there, just for a try.

I've been using a Presonus M80 for years on drums. I think this is better.

yes, most most most probably yes...

 

[soundguy]

[quote author="rafafredd"] If if you are dealing with really hot mics and sources, like neumann condenser close on a snare drum, you should include a -20dB pad before the input transformer.[/quote]

Its my experience that if you are using any kind of stepup input transformer, *any* kind of mic on a snare drum or a guitar cab is going to have a real good chance of overloading the opamp if you are playing at rock volume.

dave

 

[khstudio]

[quote author="khstudio"]mattmoogus,
I emailed JLM/Joe about shipping cost & getting the 99v boards without the op-amps, gold pins, relays & associated components.

Basically everything I need but use my trannys & the NE-80200 op-amps.

I emailed on friday but havent received a responce :roll:

I also did the math myself to get a rough idea of cost & it didn't seem to work out. If you subtracked the op-amps, pins & relays from the total listed now it is a litte high :!: Caps, toggles, diode & resistors don't cost that much... I just wanted to get all the parts in one shot. But I'm still waiting for his responce.

As soon as I get a idea of cost, I'm ready to place an order.
I really need the power supplies the most but thought, why not try a few of the Dual 99v boards with my stuff. I have just enough parts to build 2x dual 99v's & 8 od these API/YAM's I'm doing now.

Thanks,
Kevin

If you talk to him & he didn't get my email, could you forward this to him?[/quote]

I really need a responce on this pretty soon. I just sent another email.
I know the guy is busy but I am a customer. :green:

 

[khstudio]

[quote author="rafafredd"]What´s the value of the gain rim pot you are using. Let´s say it´s 20k. With a feedback resistor (R3) of 18k, you end up with less than 2x (6dB) active gain. That´s really hardly usefull for micing, specially with a low ratio input and makes things a little more complicated for the opamp stability. If if you are dealing with really hot mics and sources, like neumann condenser close on a snare drum, you should include a -20dB pad before the input transformer.

Also, 220 is a little high for R2 with this input transformer. It won´t give you enought gain for many situatrions.

Again, based on your schematics, try this:

R3 = 22k, R2 = 47R and pot (gain trim) = 20k. This is a good combination for me. Max gain will be aprox 60dB, minimum aprox 16dB, counting input transformer. If you need less than 16db, use the pad.

If you find maximum gain is too hot or unstable with this config, try R2=100R.

I hope it made sense. Do you have the parts on-hand available to try this? If not, look in your channelstrips. There might be some of the resistor and pots values there, just for a try.

I've been using a Presonus M80 for years on drums. I think this is better.

yes, most most most probably yes...[/quote]

Excellent info :green:
My pot is 25k right now... I've been testing it with a SM58 so far. I need phantom for my u87's, etc...

I DO have plenty of parts laying around to try this and will as soon as I test it in it's current state with the test software... I'll be back with some data.

Hey, how do you do the math to get the gains.
I want to learn how. If your saying my gain is only 6db now then something off. Example: When I max this thing out it matches my Presonus setting of +50db & hits my LA-2A(set @ my normall, use to settings) Very hard with plenty of gain. Could it be the 25k pot :?:

Thanks for your help,
Kevin

 

[Greg]

khstudio: I'm not trying to be an asshole, but please be patient, seriously. Sometimes you make it seem like your studio is going to crash and burn if you don't get an answer. When I e-mail Joe, it usually takes him a few days to a week to respond depending on how busy he is. When you write things like, " I NEED to know!" you sometimes come off as being pushy... at least to me. All the info here is given for nothing... always keep that in mind.

Not trying to jump your shit but see the big picture...

Happy DIY !!!

 

[khstudio]

[quote author="Greg"]khstudio: I'm not trying to be an asshole, but please be patient, seriously. Sometimes you make it seem like your studio is going to crash and burn if you don't get an answer. When I e-mail Joe, it usually takes him a few days to a week to respond depending on how busy he is. When you write things like, " I NEED to know!" you sometimes come off as being pushy... at least to me. All the info here is given for nothing... always keep that in mind.

Not trying to jump your shit but see the big picture...

Happy DIY !!![/quote]

This is not the first time you've said this to me & you're the only one. Is this all you have to add to this topic?
BTW, JLM is a business & with most businesses you can order their products very easily. The instructions on JLM's site say to email for shipping.
No offence but if I have to wait a week or two for a responce forget it.
I am VERY excited about getting some of their stuff...that's all.

Not to mention I'm building shit for other people & they want to know too.

So you say I come off pushy to you... I'm not even talking to you. :roll:
Let Matt yell at me if he want... I really just posted it again so it wouldn't get lost. I kinda know Joe is busy (Cause he told me) that's why I'm asking Matt, so I DON"T bother Joe (That's what Joe told me to do)

Get it.
I like these guys here & I'm definitly not trying to piss them off.

FYI, I've had about 4-5 PM's of people saying they want to do the same thing with their Yamaha parts & that they're enjoying this thread.

Thanks for the input :wink:

 

[khstudio]

Greg, I ended my post with this: :green:

NOT
:evil:

------------------------------------

MATT, I'm sorry if I seem pushy :wink:

BTW, I didn't see a price for the PM2000 EQ board & after listening to my PM1000 again tonite, I am REALLY interested in that mod.
How much are they?
& is it both mid bands or just the High mid?

Thanks,
Kevin

 

[jspartz]

Very cool information here. Keep it going. I have a couple extra Yamaha block opamps and a pair of 2503 output transformers (group buy from the forum a while back). I think that this would be a great project for them. I am curious how well the JLM boards work out for you. That would make life very nice.

Jason

 

[rafafredd]

If your saying my gain is only 6db now then something off. Example: When I max this thing out it matches my Presonus setting of +50db &....

mmm...

I mean, MINIMUM gain should be set to 6dB or HIGHER, for stable operation with a wide variety of opamps. For this, you nee to use gain pot smae value of R3. With a higher value, like you are using, you get MINIMUM gain LESS than 6dB. That´s most of the time not good with many opamps. I don´t know this YAMAHA opamp, but I don´t see a logical reason to use minimum gain less than 6dB. So, like I said, using a 22k R3 and a 20k gain pot sets MINIMUM gain to a little MORE than 6dB, and this is even better for stability.

For setting MAXIMUM gain, you should LOWER R2 for MORE maximum gain. With a 22k R3, I think 47R is a good point of MAXIMUM gain. But make sure layout is well done and all audio connections are shielded, for using it at high gain and stay stable.

As you see, the problem is in the extreme settings.

 

[rafafredd]

Hey, how do you do the math to get the gains.
I want to learn how.

man, there´s SO MUCH in a google search...

http://www.pic101.com/op_amp.htm
http://www.uoguelph.ca/~antoon/gadgets/741/741.html
http://sound.westhost.com/dwopa.htm
http://www.dself.dsl.pipex.com/ampins/webbop/opamp.htm

I shouldn´t post it as you might get lazy, but here it goes:

http://www.pic101.com/opamp_calc.htm

and so much more...

 

[khstudio]

I'm sorry man, I'm just so rapped up in this pre & this thread I'm probably not searching around as much as I should

I really can't thank you guys enough for taking the time to help me. :thumb:

I'm working on the circuit changes now...

 

[soundguy]

[quote author="khstudio"]This is not the first time you've said this to me & you're the only one. Is this all you have to add to this topic?[/quote]

If you want to be accurate about it, greg is the only one who has gone out of his way and BOTHERED to post something about it.

There is a universe of difference between your statement above and mine below which perhaps you should consider.

This place and its people are cool, find the flow.

dave