HA-1 cost

[andrzejpw]

How much would Jan's corda cost to build?

 

[slindeman]

I assume you mean by buying all of the parts yourself. If you buy from Jan I think it is around $250 or so. I just happen to have a list with part numbers that I'm working on. I'll probably build it eventually since I love how it sounds (I have a pre-built one). Note that my list includes an AC/DC adapter rather than a nice internal power supply like the Corda has. Also it has just one level of crossfeed, the lowest.

My list is a budget minded and "keep-it-simple" minded list, so there is no etched pc-board or aluminum case or anything too fancy, just basic parts. If you want it to look as nice as the real Corda you'll save tons of hassle (and money too I would bet) by just buying the kit from Jan. DK stands for Digikey, MS for Mouser, and RS for radioshack.

---------
Corda Amp
---------

Amp
12.32 4 National Semiconductor LM6171 Opamps (DK LM6171BIN-ND)
2.62 1 12mm Panasonic EVJ-C20 10K dual potentiometer (DK P2G1103-ND)
0.21 2 47K ohms 1/4W resistor (DK 47.5KXBK-ND)
0.43 4 10K ohms 1/4W resistor (DK 10.0KXBK-ND)
0.65 6 4.7K ohms 1/4W resistor (DK 4.75KXBK-ND)
0.21 2 2.2K ohms 1/4W resistor (DK 2.21KXBK-ND)
1.33 4 1.5K ohms 0.6W resistor (DK BC1.47KZCT-ND)
0.21 2 1K ohms 1/4W resistor (DK 1.00KXBK-ND)
0.21 2 47 ohms 1/4W resistor (DK 47.5XBK-ND)
0.66 2 120 ohms 0.6W resistor (DK BC121ZCT-ND)
0.56 2 220pF 50V Polypropylene Caps (DK P3221-ND)
2.44 4 10pF 500V Mica Film Caps (DK 338-1061-ND)
-----
21.85

Power Supply
25.96 1 24V 330mA Regulated Linear AC/DC Adapter (Allied 879-1080) or (Newark 16F126)
1.70 1 DC Power Jack Panel Mount 5.5mm/2.5mm (RS In store)
1.65 1 SPST Sub-miniature Toggle Switch (MS 10TA805)
0.27 1 Low Profile Lens Mounts for T 1 3/4 LEDS (MS 593-3000C)
0.35 1 Low Current T-1 3/4 Red LED (MS 512-HLMPD150A)
0.33 1 20.0K ohms 0.6W resistor (DK BC20.0KZCT-ND)
0.66 2 10K ohms 0.6W resistor (DK BC10.0KZCT-ND)
5.24 1 Burr-Brown BUF634 Buffer for Pseudo Ground (DK BUF634P-ND)
3.12 10 .1uF 100V Metal Polyester Capacitor (DK EF1104-ND) for bypasses
9.69 10 1000 uF 25V Electrolytic Caps FC Series (DK P10278-ND) for bypasses
-----
48.97

Natural Crossfeed Filter
0.21 2 2.2K ohms 1/4W resistor (DK 2.21KXBK-ND)
2.56 2 .22uF 50V Polypropylene Caps (DK P3224-ND)
0.32 3 2.2K ohms 1/4W resistor (DK 2.21KXBK-ND)
2.56 2 .22uF 50V Polypropylene Caps (DK P3224-ND)
2.17 1 DPDT Sub-miniature Toggle Switch (MS 10TA815)
-----
7.82

Misc
13.35 1 Hammond Aluminum Panels, Black ABS Case (7x6x2) (MS 546-1598C-BK) (DK HM164-ND)
0.64 4 Rubber feet (MS 517-SJ-5012BK)
5.98 2 Matching Printed Circuit Board (RS 276-170 In Store)
2.58 2 DGS New 2001 Hi-rel 1/8" jacks (MS 161-7400)
2.69 2 Gold Plated RCA input jacks (RS 274-852 In Store)
2.81 1 Knurled Aluminun Knob 1.25" (MS Black 450-6008 or Aluminum 450-6007)
-----
28.05

Total = $106.69

 

[zoboomofo]

Much appreciated slindeman. I'll be needing that list for my next project.

 

[kai_yip]

slindeman,

don't use cheap potentiometer, it will cause noise and unbalanced sound. Used Alps one, can be brought from RS-components.

components in power supply can be cheap, just ensure constant voltage. However, components in signal part have to be high quality.

 

[tangent]

I have some concerns about that parts list, slindeman.

First, you don't give the part number for the DC power jack you got from RS. They sell two: a heavy-duty one (big, basic jack, part# 274-1576) and a cheap closed-circuit job that breaks easily (274-1583). If you want a closed-circuit jack, I recommend you use part number CP-6 from DigiKey instead. It looks almost identical to the RS jack, but it's much smoother and I haven't broken one yet. The heavy-duty RS jack is fine if you only want to run from external power and you have the panel space to accommodate it.

Second, about the panel-mount RCA jacks: you're using them with an aluminum panel, and I assume you'll be putting them both on the back panel along with the power jack. Since the RCA jacks and the power jack are both uninsulated, they end up sharing the same ground. From personal experience, this will not work! You'll have to insulate one of the two from each other. Personally, I'd go with insulated RCA jacks rather than try to insulate the power supply from the chassis, but then, I'd start with insulated RCA jacks to begin with, rather than try to find a suitable insulator after the fact. Or, I guess you could stick the DC power jack on one of the plastic enclosure's sides and let the RCA jacks have the back panel all to themselves. That'll work fine.

Finally, about the protoboard: it probably is wise to get two, but on a bet I'd say you could probably pack the amp onto a single board if you used the dual version of the opamp (LM6172) like Jan does in his amps. Might be pretty tight, though.

Oh, and Kai, about the Panasonic pots: they work just fine. Lots of people use this model. It's small, well-built, and well-understood by a lot of people here.

 

[slindeman]

I'm fairly certain Jan uses the single opamps, not the dual. I know KurtW mentioned swapping in some OPA627s for the first stage in his Corda, so that seems to back me up. My plan was to cut one of the boards in half and use 1 for the power supply, and 1/2 of the other one for each channel of the amp. I've got enough bypass caps there to have some quite close to the opamps for each channel, and some back near the ground driver. If it will all fit on one board I will do it that way, but these kind of things you don't really figure out until you get all the parts and try laying it out. With radioshack I just buy more than needed if there is a question because I can easily return it later without a hassle.

Yeah I'm aware of isolating the RCA jacks (or the DC power jack instead), I just didn't bother adding it to my list. I figured I would get something from the local hardware store. You definitely don't want your input ground connected to your power ground! I was thinking of the big heavy-duty DC Power jack, I've used it before and like it well enough. I don't have the part number written down though. Also I would probably order larger switches because it's not a pocket amp so you don't need the sub-miniatures anymore.

The list is kind of a work in progress, it won't get completed until I get closer to the time when I decide to build it. I'm always keeping lists like this for upcoming projects, many of which I never get to of course.

I update the lists as I see things in the catalogs that I think will work better in the project. I just posted it as an example, and to help people locate many of the parts if they are interested. I've got lists like this for the last 2 amps I built and the one I'm working on now.

 

[tangent]

Oops, yes, the HA-1 does use four single opamp chips. I built one from a kit, but obviously my memory has developed holes since then. I pulled the layout diagram out of the file and indeed, there are four sockets.

As for getting insulators from the hardware store, beware that the vulcanized rubber grommets you can find everywhere actually conduct electricity! (It must be the carbon.) The resistance is high, but it's enough to ground out your inputs. Again I speak from experience.

As for the sub-mini switches, if you've only used Radio Shack switches don't let that influence your purchasing decision. Just like their power jacks, I've broken several RS toggles by tightening the bushing nut too much. Since then, I've been using NKK switches from DigiKey which feel bulletproof. I don't think I could break one of these by over-tightening without using a ratchet! I don't know if this is because NKK doesn't make toggles as small as the smallest ones RS carries or if they're just better. It makes you wonder, though, that you can't get sub-minis from NKK....

Anyway, thanks for posting those lists -- I know I picked a work-in-progress apart, but if someone finds it with a search, I wanted them to find these caveats as well.