[jsteiger]

Jeff
Curious if it's possible to change the frequency points of a 553?
I love the sound of them and I'd like to customize a couple for specific jobs.
Would it be a matter of R values or something relatively simple or more complex than that?
Thanks

Changing the caps that are in series with the inductors will change the resonate frequency. It is very hard to lower the low band though. I assume you are after altering the mid band? The bandwidth will change since you are only changing the C. I would not go too far from what it is. YMMV.

[jasonallenh]

Jeff,

The site is showing a quantity of zero... is there an ETA for these?

[jsteiger]

Jeff,

The site is showing a quantity of zero... is there an ETA for these?

I am still debating on if I am gonna restock. If I do, it will be after I launch the 3 new EQ's that are in the pipeline.

[jasonallenh]

GASP! I was ready to pull the trigger on a pair...

[jasonallenh]

If I do, it will be after I launch the 3 new EQ's that are in the pipeline.

...and is there an ETA on this?

[jsteiger]

...and is there an ETA on this?

I am right at the tail end of the build pics for the LC25 & LC40. Hope to have those listed at the store over the next few days. The BT50 will be a month or 2 behind. I need to get the parts sorted for those and complete the build guide pictorial.

[jasonallenh]

Mr. Steiger!

I'm following up now that the BT is complete (which looks awesome, btw!!). Will we see the 553F returning?

[jsteiger]

Mr. Steiger!

I'm following up now that the BT is complete (which looks awesome, btw!!). Will we see the 553F returning?

Yes I am leaning towards it. I have been very preoccupied with DAWtomation as well as the new version of the FC526 comp. As soon as I get some breathing room there I will get the missing bits in for the 553F's. Hard to put a date on it though at this time.

[k.steeze]

Hey Jeff!  It's been a few months, casually checking in on the 553F.  I've been patiently waiting to get my hands on a pair    I hope Dawtomation is coming along smoothly! 

[jsteiger]

Hey folks, just wanted to give an update that the new Rev B 553F kits are in stock at the CAPI store.

http://capi-gear.com/catalog/index.php?cPath=22_117_119_170

[Maggot Brain]

Working on my build and going great so far.

Quick question, re: installing the op amp sockets... it says in the build guide to install from the bottom...

Anyone using Louder Than Liftoff Rogue 5's in their builds?

I'm wondering if there will be enough clearance btwn the components and the PCB (the components are on the bottom (pin) side of the DOA), or would it be safer to install the sockets from the top instead?

Thanks in advance.

EDIT: For anyone interested, I took the chance and soldered the pins as instructed... Rogues Fives fit just fine.

[artifactaudio]

Hey all! New 553f user, long time builder/DIY'er

Curiously, I'm running into a wild problem on my first 553f Rev B build; PR6, the 10 ohm resistor on that (I believe) sits on the positive  keeps frying! I've replaced it, switch opamps to a known working one, and up in flames again! I'm hesitant to keep trying as I don't want to damage anything else, but I'm at a bit of a loss! Diodes+Caps on the PSU rails are fine, Transistors on the followers/DT07 are oriented properly,  I'm at a loss! Any help would be appreciated <3

[artifactaudio]

Hey all! New 553f user, long time builder/DIY'er

Curiously, I'm running into a wild problem on my first 553f Rev B build; PR6, the 10 ohm resistor on that (I believe) sits on the positive  keeps frying! I've replaced it, switch opamps to a known working one, and up in flames again! I'm hesitant to keep trying as I don't want to damage anything else, but I'm at a bit of a loss! Diodes+Caps on the PSU rails are fine, Transistors on the followers/DT07 are oriented properly,  I'm at a loss! Any help would be appreciated <3

HAH, turns out the bottom of the voltage follower was too close to the body of the 2503 and shorting to ground. Got both 553f's working now, they sound incredible! Great job Jeff!

[calaverasgrande]

Just finished a 553F a couple weeks ago. It's the newer RevB version.
When I plugged it in, it all worked. Highpass, Lowpass, and the high, mid and low EQ. Though it seemed to not have much headroom?
I left it plugged in and powered up at my studio. And was not able to come back for 2 weeks.
Yesterday I got back to the studio and fired up a keyboard and patched it through the 553F. I wanted to try a string sound.
But when I pulled up the fader I got massive white noise (actually pink noise might better describe it).
I twisted the EQ knobs and they seem to have an affect on the spectral content. So Iassume it is happening up stream of the EQ circuit?
Any help would be appreciated.

[jsteiger]

Always the first question...what 2520 style amp is in it and who built it? Was it tested and known to be working in another module? This is the first thing you need to rule out. 2nd would be to look  for the trouble after the DTO7 receiver amp. This is most likely an active part of the circuit like opamp or discrete follower.

[calaverasgrande]

oops I guess I don't have notifications on.
(turnt on now)
I am using a GAR2520 I built myself.
Fortunately I picked up several when I bought the kit. Suppose I need to build another one now.

I'll make it back to the studio on Friday, so I'll snag the EQ and see if there are any visible solder bridges or reversed components.

[calaverasgrande]

Okay got it back to my bench and took it apart.
Pulled the GAR2520 and it looks like two of the on-end resistors had gotten pushed together and may have been conducting. Hoping the transistors were not fried by this short. Gonna re-assemble now. It will have to wait until I can make it back to the studio to test in the rack. I don't have a PS here or any kind of test jig.
Shoot I should remedy that if I plan on building more of these I guess. 

[calaverasgrande]

Deep Breath.
So I remembered that I'd ordered 3 2520 DOA kits back when I got the 553F kit months ago.
Turned out I had assembled two, so I swapped out the presumably bad DOA for the unused one.
Biked out to my studio, racked it up and fired up the API rack.
After about 3 seconds the red LED winked out and bad smells.
On disassembly I see two burnt out resistors next to the DOA socket.

The DOA has some carbon on it,
but I'm thinking that's just due to proximity to the other two burnouts. I don't see any damage.


Dang it.

[jsteiger]

Burning those 10R's means that DOA has something very wrong on it.

[calaverasgrande]

Well finally got time to put this back on the bench.
Can't believe how blind I am. I missed R14! 
Even found the exact matching 12k4 resistor in my misc resistors bin. Replaced the two 10 ohm soldiers that got liquidated as well.
Made a little test rig during the intervening months. I'll bring it up slowly to see if anything is getting toasty before I try it in my rack.
Also, I'm unclear on the 3 pins and shunt to change the output impedance.
The build doc totally skips these. I've notice elsewhere in this topic you said it was ok to skip for the previous Rev A version. I've reviewed photos of the 553F rev B internals online and it seems about 2/3rds of the builds include it. What does it do? Toggle between old school 600 ohm output impedance and a more modern higher impedance? Is it required for the output circuit?