[sharpeleven]

Two more Love Childs alive and well here.

Everything went well with the build except the calibration part left me scratching my head for a while until I figured it out. you basically have to build two cables for the cal procedures and the rest is easy.

The LC's sound good! I got blisters from turning those knobs...!

All red dot op amps. Lows feel a bit loose, mids/high are very smooth sounding.

thanks, Jeff, for creating yet another great tool!!

Just would like to refine my earlier statement about the low band. By "loose" I didn't mean to question the sound quality in any way. "Lush" might be a better way to describe what I'm hearing. It's definitely not the tight/controlled low end & focus you might get with eg. some of the pultec type EQs. The LC53a always sounds very big and lush in comparison. Highly useful imo. Sounds killer on close micd piano!

[Unit7]

My 2nd pair ready! Hoping to see more in stock soon for my final 3rd pair and my DIY 500 rack filled with 53As and Horvitz's 550As.

Found that the sorting sheets I posted earlier are working fine, so Jeff please feel free to link or use them anyway you want.

Also, inspired by Horvitz's 550 build manual, on the four 53As I've built I've only soldered one pin on the Greyhills until the faceplate is on. Makes things a bit more flexible me thinks. Seems to be a good idea to handle tenderly before fully soldered, especially when installing the stop pins. But if there's another downside I should be aware of please educate me.

[Unit7]

Problem with one of my new 53As. All is ok except that 7k shelving is boosting/cutting on/from a much lower frequency than 7k. It sounds like it's still shelving (not peak) but sounds more like 200hz or 400hz than 7k. I'll open up and look for obvious errors, but meanwhile it would be great to get directions on which Greyhill pins and components that are in the 7k shelving path.

[jsteiger]

Problem with one of my new 53As. All is ok except that 7k shelving is boosting/cutting on/from a much lower frequency than 7k. It sounds like it's still shelving (not peak) but sounds more like 200hz or 400hz than 7k. I'll open up and look for obvious errors, but meanwhile it would be great to get directions on which Greyhill pins and components that are in the 7k shelving path.

Scroll back thru this thread. I think Chuck or someone had a similar problem. It was traced down to a bad cap. See if that is the case for you and let me know. I will send a replacement pronto.

[Unit7]

Problem with one of my new 53As. All is ok except that 7k shelving is boosting/cutting on/from a much lower frequency than 7k. It sounds like it's still shelving (not peak) but sounds more like 200hz or 400hz than 7k. I'll open up and look for obvious errors, but meanwhile it would be great to get directions on which Greyhill pins and components that are in the 7k shelving path.

Scroll back thru this thread. I think Chuck or someone had a similar problem. It was traced down to a bad cap. See if that is the case for you and let me know. I will send a replacement pronto.

Thx! Found the posts at pg 7 from both Chuck and Electrobumps. And I seem to have the exact same issue. I removed C23 and issue is gone. I presume this points at C23 and that I don't have to put it back to test w/o C25?

I'm waiting for 53As to be in stock again for another pair, so if you don't need to get this out of the way I'll remind you to put the new cap with that order. No sweat.

Follow up question: I guess this indicate a high percentage of bad 0.0068µF polystyrene caps? In that case, what would we be hearing if the other 0.0068µF cap (C28) was bad?

[jsteiger]

Yeah for some reason I have had a bad few. Only a few though. If they are bad, they are shorted internally. There should be no "in between".

[yosh]

Hi,
I'd like to double check my CMRR calibration results. I used a DMM to measure ACV at negative side of C2 and ground. The lowest value I can get is about 60mV. This is with the 1K pot turned fully clockwise. At fully counter-clockwise the value is about 162mV. As I turn the pot clockwise from 162mV the voltage slowly drops until it reaches 59-60mV. At no point in the travel of the pot does it dip below 59-60mV. It seems like from what I read about CMRR calibration that 60mV is high. I should be able to get it within 0.1-0.2mV, right? I tested with a known good opamp. I double checked all resistor placements. I double-checked my results with another DMM and an oscilloscope. I'm an experienced builder and understand troubleshooting so I don't think I missed anything obvious, but you never know, if I did, this wouldn't be the first time. By the way, I'm building two units and have the same results with both. Anyone have any ideas? Or am I misunderstanding something and this result is acceptable?

Thanks in advance!
Josh

edit: I am using 478.8 ohm resistors out of the signal generator.

[jsteiger]

What frequency are you using? What DMM is it?

[yosh]

400 Hz as recommended. It's a Fluke DMM. Just discovered I had a bad test lead. Now I'm reading 50mV at full counter-clockwise with a slow and steady drop to 22.5mV at full clockwise.

[jsteiger]

Something does not seem right with those results. The low spot is usually about 5-7 turns CW from the center which is the starting point when the trimmer is untouched. Do you have another way to test? DAW maybe?

[yosh]

Yeah, I'll probably finish the build then take these to my studio and test them there with the DAW. Thanks!

[Drumbreak]

Hey all!  I was wondering if anyone has tried, or if it's possible to put the EA 1166-500 output xfrmr in one of these babies.  The primary side of the 1166 is a 200ohm load, compared to a 75ohm load on the 2503.  I'm not sure if loading the circuit that much is possible or good.
I have been borrowing a friends BAE 1073d, which sounds extra smooth in the upper mid-range compared to the more up front mids of the LC53a.  I really like both flavors with their similar inductor sound, but thought a Neve style output would change the flavor for another veriety.
Thanks, and cheers!
Brendan

[Tiotever]

Hi, I'm new to the community. I've built 4 preamps, and I'm totally hooked!  I've started 2 LC53A's and didn't realize in advance that I would need to calibrate them.  I'm reading all of the information, and without really understanding any of it, I think I will eventually be able to pull it off.  But with my current limited understanding of Ohms law and electronics in general I'm wondering if I might be better off finding someone in the LA area that can help me through these first 2 babies?  Hope I'm not breaking a DIY code here,...but I'm glad to pay an hourly rate to get these calibrated so I can finish them off before a session early next week.  Seems like a really good way to learn too!! If anyone's got any suggestions in my area please let me know.  In the meantime I'm gonna keep building these suckers..  Cheers!

[jsteiger]

It's pretty easy to do if you use my test jig. There are even instructions on the board's silk screen. http://classicapi.com/catalog/index.php?cPath=22_117_185

[Tiotever]

Hey Jeff,  Thanks for the response.  I ordered the extension jig bundle last night before posting.  Hopefully its going in the mail soon.  I'm gonna give it a shot.  Cheers! 

[jsteiger]

Yup. Already packed and leaving here in about an hour. 

[Tiotever]

Question about the cable build required to do the calibration.  The outputs on my DAW that i plan to generate the test tone with only have 1/4" TRS outputs.  Can I make my cable with one side 1/4" TRS and the other the side XLR male (with the matched resistors)?  Or perhaps another option would be to make both sides XLR and use an XLR to TRS adaptor for the DAW output side.  Will both of these options work?

[jsteiger]

If you use my test jig there is no need for a special cable. Just follow the steps on the test jig.

[Tiotever]

Well that just goes to show how well I understand what I'm about to do.  Going to my workspace now to build my jig, and go fully calibrate.   Will I need 4  or 2 alligator clips attached to my DMM?  As of now I only have the 2 probes that came with it.  Btw thanks for the prompt shipping!!

[jsteiger]

Well, with the test jig built and inserted into your 500 rack, LC53A module connected to the test jig, you will need to send a sine wave signal to the input of that 500 slot (XLR or whatever, depending on your rack). If you can monitor an unbalanced signal with your DAW, (set a channel up to record enable) I would just use the DAW instead of the DMM. If you use a DMM, you can just clip your probes on. If you need to make a cable for your DAW, you will need only 2 alligator clips. I think 'Chung has pics of that part in his build pics.

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