AMB Laboratories DIY Audio

[mawi]

I thought it might be useful to share my experience of my β22 build in the hope others might find it helpful, as well as focusing me a little. I don't have a huge deal of electronic experience, but have so far successfully build a CKKIII, mini3 and gamma2 full++. With the group buy of the epsilon 22 I thought it was time to tackle the big one

My intention is to build as reasonably priced as I can 3 channel β22, with the ε22 from the recent group buy and a ε12 to protect my HD800s ... when I get them . Until then, I'm rolling with HD600s . I'm aiming for no more than £600 for the build but I don't want to cut any corners. Time will tell how close I can get to that.

To start off is the link to my BOM for the build.

https://docs.google.com/spreadsheet/ccc ... VFGMldCX1E

This spread sheet covers the parts for the β22, σ22, ε22 & ε12 for the amp, along with a 5V σ11 for my gamma2.

Parts are from the AMB shop where possible (although the sigma22/11 CR devices are in stock with AMB, which I didn't realise when I ordered - they're listed as the Mouser parts in the spreadsheet), as I believe the least I can do for all Ti's hard work is buy all the parts I can from him. Mouser is used otherwise. I'm in the UK, so prices are in GBP where possible. I think the β22 & σ22 BOMs are complete & correct at least for the electronics parts, though I'm not guaranteeing anything so please do double check everything if you use it. The last column on each page contains cut 'n' paste text for the Mouser BOM import tool. The ε12 & ε22 BOMs need a little work.

I'm not going to use 'boutique' components, though it was tempting, but I will probably got for something a little better than the Alps RK27 pot, hence it's not on the order. Hifi-Collective sell a range of pots that I need to give further inspection. Where I can, I've stuck with the top item on the part list suggestions.

I need to get hook up wire, which will probably just be copper, though silver coated for the signal path isn't too expensive, but I'm not entirely sure I'll be able to tell the difference. I'm thinking 18AWG for the PSU to amp umbilical, possible 18AWG for the larger Molex KK terminated interconnects and 24AWG for the smaller. This is something I need to give more thought but again, Hifi Collective have a large are of cable from the basic to the outlandish.

Molex contacts will be tin. Gold was a possibility I guess, but I don't intend on unplugging and re plugging them once built and my solder is only tin/lead anyway so I can't see the significant extra cost is worth it. I'm not one for warm and fuzzy feelings, but if there is an objective benefit to more expensive parts I'm happy to give them some consideration.

The build will be the PSU in a separate case with SpeakON terminated interconnects. I'm currently trying to hunt down a suitable price filter IEC inlet so far with out a great deal of luck though I suspect that's lack of inspiration on my part. I also need a suitable transformer, which may end up being a Farnell own brand - even though Avel Lindbergs EU office is just up the road they charge an arm and a leg for single units.

Audio connector wise, Neutrik heavy duty panel mounts are tempting. The front and rear panel may be from Front Panel Express's sister company in Germany Schaeffer AG, unless I can find a local firm, and Frontpanel designer already has nice templates for the Neutrik holes. The headphone socket will probably be locking. I'm not sure I want to limit the voltage swing with higher R34/R35 values, though perhaps that's better than fried MOSFETs. A locking connector seems like a fair compromised. Having said all of that, these connectors and the front panel milling will be expensive. I may just stick to circular connectors with drill bit sized holes and drill them myself!

For the cases I keep going back to Hifi-2000. I used one for my CKKIII build and it's easy enough to work on, though I don't find them that all that attractive. Otherwise, I'm not sure what other choice I have locally in the UK or EU.

Tools wise, I have a £50 temperature controlled soldering iron with digital display, anti-static mat & wrist band (I've been told I'm paranoid, but better that then fried components), some reasonable quality, though a bit fine, 63/37 solder, flux pen, good side cutters and assorted other tools. Probably nothing much to write home about there, but the same equipment served me well through the Gamma2 & GrubDAC build ( with the help of a stereo microscope ), so I'm sure it'll be fine here as well.

To get a feel for sizings and layouts of the case I'm using Sketchup. I've found it a useful tool for visualisation the space required.

So that's where I am. The AMB shop parts have been order, so I'm committed now. I'll update from time to time as I make a bit of progress, and any feedback or information on your own build, especially if in the UK, would be appreciated. Thanks for reading

[joeyjojo]

Sounds great, can't wait to see it take shape. Good luck

[linux-works]

molex contacts that are gold on the finger part are a lot cheaper. worth it if the posts are also gold.

I hate mechanical contacts. they get noisy over time. if you move things or ship it, that's a weak spot. lock-tite helps but molex-kk is just not a great contact. its 'ok' but it needs babying.

the gold on gold is probably goign to be lessy noisy over years and years (like, decades). the tin will not be as good, imho.

a tiny drop of hot-melt glue can also secure things once you are done (really sure you are done).

I do hate the contacts but I like designing and using them because unsoldering is even worse

[mawi]

Time for an update

The AMB supplied parts arrived a week or so ago. I'd not done a great deal since my first log. Actually having physical parts has spurred me on. My time spent building my first amp, a CKKIII, the gamma2 and mini3 have certainly helped with the process. It's still time consuming to research and choose parts but at least now I know how to navigate the various sites and interpret the relevant information.

My build spreadsheet has come a long a lot. I'm now using four main suppliers - AMB, Mouser, Digikey and Farnell here in the UK. This has mainly been to reduce costs as prices can vary 100% or more between supplier. Again in the UK, Kustom PC look like a source for hard-to-find-by-the-metre braided cable sheathing - they sell a good range of size and colours of Techflex PET and others. Anything marked on the spreadsheet in bright orange is still for consideration and review (not that other parts won't change as well )

Further purchases have been:

• I wanted a better potentiometer than the Alps RK27 and I've gone for a TKD 2CP-2511. It was a toss up between this and a 10K Nobel AP25. It went with the TKD as the review have been very good pretty much universally, where as the Nobel, while good, has a few middle of the road reviews. Either way, I've bought the TKD privately for about the same price as the Nobel was up for, so I'm happy.
• 18AWG & 24AWG 5 colour selections have been ordered from John's Wire Shop. The order was placed last week and should have shipped yesterday. So that's two parcels to look forward too . the 24 AWG will be for the KK 100 terminal parts and general signal hook up, the 18AWG for the KK 156 and general power.

I've also decided to go for the gold KK crimp terminals. It turns out that all KK terminals are only gold plated at the terminal connection end. The crimp end is tin or brass or similar. I've been able to keep the cost down significantly by using Digikey for those. They have very favourable price break points for the quantity required. That also means gold plated headers (I've also learned no to use tin in contact with gold on my reading journey), which are cheaper at Farnell. The spreadsheet shows all.

The biggest decision has been to take my time. I'd rather this take months and be a good job than a month and me not be happy with the end result. It'll be worth it, I know it will.

The main thing that's taken my time over the last few days has been getting a model done in SketchUp. I find it far easier to work with scale models of the parts, and SketchUp is pretty easy to use. I had just gone for blocks for the main components... then I got carried away



It's been a good chance to learn some modelling and I'm pleased with how it's helped me learn about the parts I'm using and aid in understanding part diagrams and data sheets. I now know more about Molex KK connectors than I ever thought I would .

The model makes good use of components. Changing, say, the length of one screw changes all screw lengths. Most of the parts are sub millimetre accurate on their key dimensions. Some guess work was used for others. I also have models for the sigma22 and the sigma11. Shots of the work in progress of the sigma11 in a Hifi2000 1GX187 case can be seen on my Google+ post. The overall idea was to get the critical heights and clearances in there while making something that can then be transferred to Front Panel Express for the panel work and can be referenced for parts and during the build. For instance, having made the model it became clear to me 10mm spacers were where I was happiest - not least as my previous choice of 8mm meant only 0.5mm clearance of the zobel caps! It also allows me to get a real feel for how the inlet and switch positioning will feel on a final built.
The models still need a bit of a tidy up - the materials are a mess, some components are unique where they shouldn't be and a few other niggles.

The usual disclaimer applies - this is all a work in progress. If you use parts listed on the spreadsheet, for instance, please double check it's right. (and let me know if it's not )

[amb]

That's a very nice (and way cool) drawing!

[joeyjojo]

The Panny caps you can now get from Mouser for the same price. Ti you might want to update that on the parts list.

The price difference on the others seems pretty small (10-20p per item?) - you might in fact save money by getting everything from mouser if the shipping from Farnell is great enough?

I don't work for mouser btw just looking to put in a big order very similar to yours and would like to know the cheapest route.

Lovely model. Your information about 10mm spacers being best is something I was trying to figure out myself, cheers! The total height of the whole thing then is 61.3mm (two spacers, two boards and heatsinks)?

[mawi]

Molex part 08-55-0102 was my initial reason for using Digi-key. At the quantities I'm after, mouser is £0.48 each, Digi-key £0.17. If I were to order from Mouser I'd buy a 100 lot. At their break points, I could get 100 from Digi-key and it'd still be cheaper than Mouser for 28! Having written that, maybe getting 100 makes sense anyway. While I'm not scrimping as such, if I can trim £20 or so off it's worth the effort to me and it's also, to me, worth learning Digi-keys systems for the experience of it.
For both Mouser & Digi-key I'm over the free shipping limit any way and there where some other bits and bobs I needed (WM9999-ND is £7 cheaper among others). Having said that, I know with Mouser the import charge is already covered by them, Digi-key I'm not so clear on.

[joeyjojo]

You're right, Mouser for that part is actually ludicrous. It's £47.62 for 99, or £14 for 100! Thanks for the pointer.

Have you heard good things about that cirmp tool?

[mawi]

There are a number of price breaks along those lines, though that particular one is about the worst for one item that I've seen. If you use Farnell it's worth checking the minimum order as the price will be for 1 unit and the minimum order is 5 or 10 or more.

As for the crimp tool there is the mystery manufacture made 'deluxe' HT-225D which is also available on eBay, and Farnell (datasheet) for twice the price as everywhere else. The Molex branded ratcheted hand tools retail at £200+, so the deluxe moniker might be a little misleading . The Molex datasheet lists the individual parts it's designed for of which none are KK parts. I've been meaning to do more investigation. It's on the list and that line should be bright orange You can crimp the KK terminal with pliers but it's a bit... rough.

Edit: I've just found this discussion on this very topic.
Edit 2: and this one on this very forum

[astrouk1]

I used this IEC inlet filter:

http://www.ebay.co.uk/itm/Schaffner-FN3 ... 758wt_1144

It's made by Schaffner, a very good manufacturer and as well as the filter it has a switch and fuse compartment. It's a good price too, they're normally knocking on towards £30.