Blog Pages

7/20/13

PULTEC PASSIVE EQ CLONE

PULTEC EQP-1A 

Just finished building my PULTEC 3U rack enclosure from http://collectivecases.com/pultec.html.
I'm very excited to get started on this project. This will be a clone build of a classic passive equalizer! My printed circuit board came from http://www.dripelectronics.com/.

COST
Rack cost was around $130 not including shipping. The transaction was a breeze. Also, it was shipped in a reasonable time frame considering that when I purchased it they still had to be painted.


FEATURES
1. (2) XLR and (1) IEC power inlet cutouts on back panel
2. Sides are vented
3. No holes on top or bottom panels (You will need to drill those yourself)

TWEAKS
I needed to enlarge the front 4 mounting holes a bit in order to get things to align.

QUALITY
Build quality is very good using heavy gauge steel with an aluminum front panel.
Fit-N-Finish was also good. Note: Make sure to bolt your front panel on first for good alignment.

As always, you will find my build information right here so please stay tuned!

7/5/13

1176 FREQUENCY RESPONSE

BOAT ANCHOR TUBE SCOPE
While making scope measurements I thought I it would be cool to fire up an old Navy vacuum tube oscilloscope and see if I could use it for my images.

But, I changed my mind pretty quickly.

After fighting to get a signal to show up after waiting 15 minutes to warm up, I decided to take the easy road.

But, it certainly makes for a better photo!


TRANSFORMER ABUSE IS NOT A CRIME
Ten hertz at 20 volts peak is absolute hell on small signal audio transformers.

The poor core has to start giving up somewhere! I felt very sad for it but now I'm over it.

Wow! It looks nasty but I'll bet it sounds really cool on some recorded Godzilla foot steps!


CLEANING UP YOUR ACT
This 1176 clone cleans up really fast above 20Hz. This is still at about 20Vpk output!

Seriously though, 20Vpk at 20Hz, this is crazy but fun. That's why we do this stuff !


FROM DC TO LIGHT
O.k., it doesn't do that. But, up to 20kHz and beyond looked really flat.

It started to roll off around the upper end of the audio spectrum.

The peaks are now just under the 20V division mark on the grid.

Again, no one in their right mind is ever going to run it this hot. At least I wouldn't think so...


COMING SOON
Next up will be some DC measurements around the circuit. Stay tuned!