[lan]

Well if the regulators are 3.3V or 5V output then post regulator cap of 6.3V would be fine. For things you don't know, just measure them. PCI cards have 12V max so you should be able to get away with 16V most of the time. But there are parts of the 1010 card which I use which goes to the 1820m dock which are higher voltage so it's always wise to check.

 

[ablaze]

hi Ian,
thanks for the advice. I measured across the legs of each cap. Does this look right?

 

[lan]

Well I don't have these memorized or written down so I can't say if they are correct. How am I to refute a measuring device?

 

[ablaze]

I was hoping you'd be able to tell me if they looked right on cursory inspection of the voltages

anyway I was thinking of going full black gates on the card. would it be a good idea if I went with the N series on all the caps on the board? or should I throw in some FKs and what not into the mix?

 

[lan]

Yes by glance it looks about right.

You have Sanyo OSCON already there. Not much point in going blackgate.

I generally like N more than FK. NX > N. NX-hiQ > NX. But you can't fit most FKs and Ns in those holes so it's not as you even could.

 

[ablaze]

most of the sanyos barely fit in there either, but there's always the back of the board haha

anyway, most likely will be selling my oscon-ed 0404 and getting a new board to go full black gates. thanks for the advice!

 

[lan]

Well I meant the leads don't go through the hole not the diameter of the cap. If it's too large, you won't be putting the caps in the front or back.

 

[adfinni]

Quote:

Originally Posted by lan Well I meant the leads don't go through the hole not the diameter of the cap. If it's too large, you won't be putting the caps in the front or back.

Wel im about to order some os-con 10uF/16v SG caps to replace the yellow caps on the diagram. Will they all fit in on the main side, or even through the holes?

Im also getting panasonic direct replacement for the purple 47uF/16V, and red 100uF/25V, caps for direct replacement. Will these fit on the main side and through the holes on the pcb.

Btw. i intend to bypass the output caps, remove and bypass the outputs buffers, then wack on an lt1364 first before changing the caps.

One more thing. how do i measure this offset that everyone goes on about, and what are safe levels????

cheers

 

[adfinni]

Anyone

I really wana know how to measure the DC offset, and what it means. Plus i want to order the caps by tomorrow so they get here early next week.
??

ta

 

[sgrossklass]

A DC offset is a constant voltage superposed to the (AC) signal, relative to signal ground. The voltage level at no output is shifted, thus the term DC offset. If you want to connect headphones or speakers via an amp that's entirely DC coupled, you do not want this to be too large to avoid fried voice coils. The output coupling caps are there to eliminate any DC offset; single-digit mV readings across the cap should be safe (after the voltage gain stage, if any - you don't want it to be amplified, after all). Now coupling caps are not the most linear devices, particularly electrolytics (you need them to have a certain capacity to drive loads down to 600 ohm, and comfortably so) and those particularly when they are not biased (some DC across the cap - like a few volts - reduces the hysteresis considerably; yes, these things can distort like transformers). That they work as well as they do is only due to being overdimensioned quite a bit, thus very little voltage dropping over them in the frequency ranges that interest us. (Try building a simple R-C highpass with a 'lytic and measure the distortion for tones around and below the corner frequency. That won't be looking good even for nonpolar types I bet.)

 

[adfinni]

Quote:

Originally Posted by sgrossklass The output coupling caps are there to eliminate any DC offset; single-digit mV readings across the cap should be safe (after the voltage gain stage, if any - you don't want it to be amplified, after all).

Great explanation, cheers.

So to measure the DC offset on my emu card i should take a reading from a cap that on is the left channel, and one on the right?
Going by the diagram, 9 posts above this one, i should take readings off the green caps next to the '1.2V' lettering (near the two green output buffers) ??

thanks

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[sgrossklass]

Those green caps look right... I just don't know why there are 4 of them there, the card only has 2 output channels after all and the coupling caps for the inputs are further up to the left of U2. I guess there's one for signal and ground per channel then. Oh, and now that I'm looking at the pic... ablaze has already measured the voltage across your caps, 1.2 V in this case. Looks like a decent bias for 'lytics, but not like something one should bridge.

 

[adfinni]

Quote:

Originally Posted by sgrossklass Oh, and now that I'm looking at the pic... ablaze has already measured the voltage across your caps, 1.2 V in this case. Looks like a decent bias for 'lytics, but not like something one should bridge.

ye i thought it was those caps. With regard to the not bridging them above, i thought it was a well know mod that helped the sound and had no risks involved ?

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[bg4533]

Quote:

Originally Posted by adfinni Btw. i intend to bypass the output caps, remove and bypass the outputs buffers, then wack on an lt1364 first before changing the caps. cheers

I played around a little with the LT1364 in E-MUs and other devices. I found the chip has more DC offset than desirable. I can't remember the specifics right now. I would be cautious using this opamp without caps after it.

I originally bypassed the caps in my 0404, but I found that the DAC on the card put out too much DC offset to leave it this way. I installed Blackgate NX coupling caps later. If you are lucky enough to have a DAC with no offset than go ahead and bypass the caps. Most likely you will need the caps though.

 

[adfinni]

Quote:

Originally Posted by bg4533 I played around a little with the LT1364 in E-MUs and other devices. I found the chip has more DC offset than desirable. I can't remember the specifics right now. I would be cautious using this opamp without caps after it. I originally bypassed the caps in my 0404, but I found that the DAC on the card put out too much DC offset to leave it this way. I installed Blackgate NX coupling caps later. If you are lucky enough to have a DAC with no offset than go ahead and bypass the caps. Most likely you will need the caps though.

Oh right, because i thought it was a safe mod that could be done and forgotten about. My lt1364 arrived this morning, so il check the DC offset in the next few days and see if i have to leave the output caps untouched.

Btw, what is a safe DC offset level ?

thanks

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