I assembled the first prototype switchboard PCB,
powered it up and.... nothing. No output voltage... well, there is...
about 2.0 Volts.
And not only that, the IC chip, inductor, and even the regulator were
all getting HOT... very HOT!
I couldn't understand why...
At first I thought maybe I made a mistake when I redesigned the PCB and
moved parts around.
So I opened up my CAD software and checking my schematic and PCB
design...
Then I noticed the IC chip was facing south on my CAD layout! I build
the prototype with the IC facing north! (which is what I usually do... I
always design with the IC notch facing north.)
So I went back to my workbench and removed the IC chip and re-inserted
it in the proper way.
Power up again, and nothing.
Hmmmm.... maybe I fried the IC chip.
So I got a new one from my tube and insert it, making sure the IC notch
is facing south.
Power up and VOILA!... we have power! The DC-DC converter is working!
Adjusted the trimmer for a 48V output and so far, looking good. No
"frying bacon" noise, nothing getting hot or warm.... everything fine
and dandy.
Some pics.
It will do 48V output for as little as 7.5V input.
Feed it 5.0V DC, and it will do 35V output.
Not bad.
Next time is marrying the switchboard and the main preamp board.
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It's alive! Works on the first power-up! I'm very pleased.
As for the sound, initial impressions:
A bit punchy on the bass.
Tighter low end.
Smooth high freq response.
It could run on 3 Volts!!!
I forced myself to build the TS2 prototype last
night, even though there are still some pending orders.
Happy to say the TS2 redesign is a much better improvement in the build
time. Finished assembling this board in about 2 hours time!
I haven't powered up this baby yet, so don't know yet how it sounds.
I don't have the new TS-2 switchboard ready for this, so I think I'll
just jury-rig the wiring for the phantom power, polarity reverse
switches.
We have prototype PCBs!!!
from this...
to this...
Haven't built it yet... too busy with other stuff.
Sent the prototype PCB Gerber files to the
factory.
Now we wait... and wait... about a week before we get the finished
boards back.
This is just the motherboard. When I get this back, I'll rework the
switchboard. (I want to make sure all the holes and dimensions are
aligned.)
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A flash of inspiration... I found a smaller
footprint output transformer I can use... so I created an Eagle part
library for that. (Tip: use a digital caliper when creating part
libraries)
After some creative rearranging of parts, and I made this.
This is just the motherboard. Measuring about 6" x 6".
Ch-check it out!
2 Input Transformers - NEW FEATURE
2 Output Transformers - NEW FEATURE
Gain and Trim knob for each channel
2 VU Meters
4 Full size XLRs
Relay Controlled switching - NEW
FEATURE
Bigger DC Converters - NEW FEATURE
... and better PCB layout by re-arranging parts.
Also, reduced the number of molex connectors from the original (7) to a
single 10-pin Molex! That will be a big time-saver.... plus the use of
PCB mounted XLR Neutrik Jacks.
I also have a smaller daughterboard that contains the 48VDC converter
and soft-start phantom power, plus all the switches. I haven't
re-worked on that yet.
The TS-2 has been getting some traction
recently... and I'm thinking maybe it's time to revisit this product
again and do a Revision B.
The first TS-2 design was very good, and I love the sound of it! (Of
course, it's based on the SC-1mk500 and SC-1mk2 preamps, but in a
smaller form factor.)
But assembling a single TS-2 unit takes up a lot of time/manpower
and with the small profit I have on each unit, it's a losing
proposition. I'd come out ahead if I DON'T build a TS-2!
So to fix this problem, I'd need to raise TS-2 prices, or reduce my
production cost, or a little bit of both. For now, I'm going to
concentrate on reducing production cost. With today's economy, it may
not be smart to raise prices (unless that price increase brings with it
additional features that the original TS-2 didn't have.)
Question: So what can I do to reduce production cost?
Answer: Reduce the time/manpower to build a TS-2 unit.
Question: How can I reduce time to build a TS-2 unit?
Answer: Good question...
I'm thinking of several possibilities.
1. Through automation. Using SMD parts and pick and place machines. Ask a manufacturer to build the boards for me.
Cons: A little on the expensive side, and requires a lot of capital. I
think 100 boards is the minimum. Assuming it will cost $50 per board
assembly fee, 100pcs is a staggering $5000!
And I doubt it will cost only $50 per board... maybe closer to $100.
And that's just the labor. The cost of parts for 100 boards is not
included yet.
2. Minimize "wiring". Yes, soldering wires to the PCB board and
connectors, and jacks take a lot of time. So if we can get rid of
"flying wires", then that will reduce a lot of time and labor. So as
much as possible, use PCB mounted jacks, switches, LEDs, etc...
everything should be soldered to the PCB. No more hookup wires, if I
can avoid it!
3. Reduce the number of PCBs. Right now, the original TS-2 preamp
has 4 PCBs. A motherboard and a switchboard, and 2 VU meter PCBs.
That's a lot! And of course, there are hookup wires to connect all 4
PCBs to each other (see #2 above). So I need to reduce the number of
boards required to build a TS-2.
I've upgraded my PCB design software last year, to allow me to make the
bigger boards. Unfortunately, the TS-2 board design was prior to my
software upgrade.
Now, with the ability to make bigger boards, I think I'll be able to combine more functions in a single board.
We've got plenty of real estate space FREE!
What else...
Revision B will also give the user the option to have INPUT
TRANSFORMERS! So that will be cool! Maybe even add a switch to bypass
Input Transformer. Hmmm... I'm getting too far ahead here.
So that's my goal.... redesign the TS-2 preamp to minimize wiring,
combine more functionality in a single board, and add some new
features.
Wish me luck!
DIY Preamp boards lined up for final assembly  and finally, Burning-in of preamps before shipment... Shown are some SC-1mk500, X-12mk500 and X-72mk500 preamps in 500 Series Lunchbox format. 
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