[Trench Recordings]

I built my first of two... gonna test and cmrr adjust tonight.

Questions. what resistor value is best for the cmrr calibration cable ? and how important is my steel case cover. I cant get all the screw holes to line up on the cover. Everything else is installed and the faceplate is on and looking good. Maybe the metalwork on the cover is a touch off ?

-Dave

[jsteiger]

Some of the flanges need a tweak to get them to line up. I would adjust them if you can. The steel is soft and can be adjusted with pliers pretty easily. The value of the R's is not super critical as long as they are a very good match to each other. Anything between 500-ish to 3k should be fine.

[Trench Recordings]

Ok first one tested and seems like everything is working. I couldn't get the cover on and all screw holes lined up. I didn't feel like taking off the knobs, faceplate and boards out just to get the cover on so I left it off.

Silly question, How does the lpf and hpf work ?  Does the freq selector affect them ? I flipped them on and off but didn't really hear a difference. What should I be hearing ? Anyway to test them ?

Other than that it sounds great. Nice mojo !

Thanks,
-Dave

[kante1603]

Hi Dave.

Ok first one tested and seems like everything is working. I couldn't get the cover on and all screw holes lined up. I didn't feel like taking off the knobs, faceplate and boards out just to get the cover on so I left it off.

Sad to hear.It's a tight fit,but it works fine.Maybe washers mounted wrong on the standoffs?

Silly question, How does the lpf and hpf work ?  Does the freq selector affect them ? I flipped them on and off but didn't really hear a difference. What should I be hearing ? Anyway to test them ?

Dave,you need to apply a signal that contains those frequencies to hear or measure anything.
And your speakers should be able to reproduce that too.Maybe your ears don't work good enough where the LPF sits at.
Jeff once answered my questions where those (fix) frequenciies are and at which slope in reply #47:

......Both have a 12 dB per octave slope.HPF is stated as 50Hz and the LPF is stated as 15kHz......

But you can test them pretty easy:Apply some (pink) noise to the eq while eq is active but the three main bands are set to zero (flat).
Monitor the eq output with an analyzer,maybe you have one in your daw or so.Analyzer should be set to no weighting filters!
Toggling the HPF as well as the LPF should show roll-offs at the very low and very high frequency-bands now.

Hope to have helped,

Best regards,

Udo.

[EmRR]

I think I may have had to extend some holes in a cover to get it to fit on. 

[mulletchuck]

I built 4 and none of them have the cover on.    works/sounds fine without it.   

[jsteiger]

The frames sometimes need a little adjustment to get everything to line up. I have built many and get the covers to work every time no problem. You need to verify the fit of the cover before final assembly otherwise it's hard to do and no one wants to work backwards.

[Trench Recordings]

Thanks for the info Udo. I will pink noise it to check. Ouch with the "maybe my hearing isnt good enough comment". lol

I will play with the cover some other time. For now its installed and working

Thanks everyone,
-Dave

[kante1603]

Ouch with the "maybe my hearing isnt good enough ").

Hi Dave,

I didn't want to tell things wrong,sometimes there's still the language barriere and it's a bit hard to find the right words,hahaha........
15kHz is quite high and can be pretty close to what people are able to hear,I'm not refering to the normal loss while getting older but especially the young people nowadays.
A lot of my students certainly do have problems in that frequency range!They are aged around 20 to 24 years,and the older guys here will know why this happens....and it is irreversible!
I'm 50+ but do hear them btw.
So always take care,our ears are the most valuable instruments we audiofreaks have!

But this is completely off-topic now,me culpa

Have fun with these great equalizers (I do),

cheers,

Udo.

[Trench Recordings]

Just an update. I tried the cover from the other kit I haven't built yet and everything lined up perfectly. So the hole are off on that first cover. Not a big deal, I just need to drill the holes out a bit to make it work.

[tonycamp]

Oh happy day!, i wont be able to put them through the paces for a while though

[Unit7]

Finally started the LC53A project and did the CMRR today, with PCB board in my Purple rack and an extra special cable in addition to the CMRR cable.

Used DAW for both signal generation and measuring (Logic Pro -> Fuzz Measure).

Managed to find the lowest point on the variable resistors with approx .25dB difference between my two units, so I hope I'm ok.
Only had one thing I would like to check:
When unit was off (no power) the signal was stable, but with power on the signal started to wobble approx ±0.5dB. Happened with both units and with two different GAR2520s. Is this normal?

(edit: tested same two GAR 2520s in one of my TB550s and signal was stable)
(edit 2: got word from jeff that he sometimes get a ±.25dB fluctuation, so hopefully I'm fine...)

Cheers!
Paul

[Unit7]

Soon ready and again, SO grateful for Chunger's guide! So here's my µ-contribution. I've got it in Word format too, so if you prefer that, or if you find an error please just pm.

[kante1603]

Hi Paul,

great,thank you very much for sharing!

Best,

Udo.

[Axelerator]

Hi Jeff, my lc53a´s are sounding soo nice but building two more seems to time consumpting..so i want to ask about the lc553  :-) !?.any news on them ?
greets,
axel

[jsteiger]

Hi Axel

I need to find the time to put together all the build docs, BOM's, pricing and list them at the store. I have had all the parts since Feb 2012! I just never seem to find enough extra time to get that all handled. One of these days I will get to it.....

[Unit7]

Done! Interesting to compare to Brian's 550s. As I believe Doug mentioned somewhere, the 53As sounds a tad bit more natural/uncolored. First impression is that the TB550s smears transients a bit more, in a way I really like. Guess I'll be looking at two more of each to fulfill my dream of a full eq rack...

A note on Chungers photo guide, regarding joining the main PCB with the CB PCB. As I don't have the tools to measure accurately the way Chunger did, I checked that the screws and standoffs were centered more or less, then had boards laying on the side on my table (to get things straight) while semi fastening the screws and then simply put the joined boards in the chassi to check that holes matched. Worked fine obviously, but I'm interested to hear what other builders say about that.

Ciao!
Paul

[fluxofpinkindians]

I love this EQ and loved building it.

The bypass switch on my build makes a loud pop/click when engaged or disengaged.

Just wondering if this is normal or if anyone had any suggestions as to why ?

thanks to all

[jsteiger]

The bypass switch on my build makes a loud pop/click when engaged or disengaged

There is a small click but typically nothing loud or dangerous sounding.

[sharpeleven]

I love this EQ and loved building it.

The bypass switch on my build makes a loud pop/click when engaged or disengaged.

Just wondering if this is normal or if anyone had any suggestions as to why ?

thanks to all

No audible artifacts when engaging/disengaging here, unless there's a signal present and a considerable low frequency boost/cut applied.

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