My DDAC Case

I built a 12 chip DDDAC a little while ago, its been sitting naked on the shelf while I decided what to do with it case wise.

While looking for a case for my compact chip amp I came accross the hammond 1455 enclosures.

These extruded cases have internal grooves to hold circuit boards, which by happy coincidence hold a DDDAC board perfectly...

A plan was born....

Here is what I came up with



The case although width wise is right is not available with the correct height for a DDDAC module. However in the larger widths it has a slide off panel. This I took a drill, junior saw and a set of miniture files to to "open up the bonnet" 50's Hot Rod style.

I fashioned holes the right size and shape for the DAC's cooling tower.

From light alu sheet I cut and brushed a strip which folded makes a vanity screen/shield for my chips. I am going to work on the shape of this further.

I am delighted with this DAC. It replaced my Cambridge Audio DAC1 and is sweeter, more musical, more dynamic etc etc. I cant really express by how much. I am using it with a Skynet 8080 SMPS. I get these at real good prices via an Ebay contact. It seems a good PSU. NUUK recomends it for chip and D class Amps. It seems to fit the DDDAC well. I was on a budget and I don't think I did badly.

I used Sonicaps bypassed with Vishay 1837 0.01uf caps on the output. This seems to give me a sound I really like. This plays through 4 gainclones into my Mission 753's in a passive bi-amp setup.

I am supposed to be re-ripping my music collection to lossless. The difference in quality is suddenly transparent. Mpegs dont cut it with this DAC. You know instantly you are listening to compressed music. Lossless on the other hand sounds amazing. So far I have only ripped 20 CD's in 6 weeks or so. I am listening and relistening to every one each time!

I will be shortly upgrading from 1 DAC module to 3. The case has space and I think will look cool.



I will have a set of stepped cooling towers, increasing in height from front to back..

Here are a couple of more piccies of the DDDAC





The last gives an idea of scale, as well as showing my reward... A lovely cup of Tea and a route through my so far ripped music collection..

john65b said:

You don't like the Black plastic bezel? I prefer the enclosures with a bezel.

Too bad the largest of these perfect model 1455 is only 8" x 6".

A pic of the 1455 - UCD180 Monoblock. Too bad I sold her off to build a UCD400...too pretty.

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I hummed and hawed a bit before deciding to go without the bezel. I wont throw them out in case I change my mind.

I agree its a very pretty little case. I dont do imperial, but for those that are bi-lingual, the case I used is 220mm by 100mm 8" x 4" (I think)

Its very neat in size. This will hold a 120VA torroid.

dddac said:

I always get mails on what case to use and requests for examples etc. The style and type of cases I use for my DDDAC and other projects (see my Website ) are machine tooled by Schaefer and therfore pretty expensive and also not everyones taste and certainly not budget

So I believe this is a great example, how with relative litte means, a very nice solution can be found....

I will include these on my website if you don't mind ?

doede

Click to expand...

That would be a great honour...

I will mail you with the origionals... Birthday present by the way is going to be another DDDAC module...

Ah I see someone well placed to answer this has stepped in. Sorry Ricoch for being so tardy in my reply..

Well, I just got a year older, and my present from the family this year was guess what? Another DDDAC module.

I couldn't wait to get started, so over a couple of nights created stage 2 of my project.

Here are the piccies... Starting inside.



You get an idea of my lack of skill in these pictures, but the camera is being quite cruel. In RL the work looks less messy.

I have yet to add the better RCA plugs that arrived the other week. They are insulated plugs which I hope will drop the already low sound floor a little lower.







So how does it sound? I have to admit to a couple of things here.

First of all some clumsiness, I had an issue with clearance in my tower. In fact I have mounted the usb module too high. I tried to shorten the highest point on the board, The metal tag on the lm8706. Of course I broke it.

Hidden in those pictures is an off board lm317 which I rigged up to replace the 7806. Works fine though getting the right values from my resistor collection was a challenge! If I am going to squeeze in a third module, I am going to have to lower the usb section and fix up the back plate.

Second admission. In my excitement to get the second stage up and running I tried out the dac before I had completed the mod to the case to allow the lid to be put on.

I auditioned the dac first with one stage then with the second. I imediately got more detail with the second stage installed. however I found the top end was a bit confusing, it seemed as if there was too much detail. The top end also had become hard sounding. Dynamics seemed to have suffered as well. I racked my brains for a while as to what could have caused this. I reckoned it was either the change to metal film resitors in the IV stage or the system needed to bed in.

I left it powered up for a day and a half (My girlfriend expects to see me occaisionally) and came back with less tired ears.

Still the top end was the same. The dynamics seemed a little better. My ears were telling me though that the extra detail was not coming from the recordings. I had a better idea where the problem lay.

I got to work on the case lid. Cutting out the apeture for the tower using my bench press drill and the minature files. Popping it on the sound imediately and dramatically improved. The noise floor dropped back down and the dynamics that I love from the dddac reappeared. Most dramatic of all was the top end detail. High hats became softer, more realistic and beautifully detailed.

I have not had a chance to go through a good selection of music to really enjoy the second stage equiped DDDAC but even listening to a few well known tracks I can tell that the second stage is a welcome addition.

eledora said:

could you tell me how the machine work?

Click to expand...

Basicly its a USB Digital to analogue converter.

In a little more detail the USB section of the DAC takes a signal from your PC and converts it to IS2 format.

This is then processed by 24 (in my case) DAC chips in parallel. By using lots of chips you average out conversion losses. Hence this DAC does not use any other error correction or oversampling (referred to a NOS-Non oversampling), it sends the signal more or less straight to your amp without any correction. There are also no op amps after the DAC.

The idea is that you get very direct conversion of the digital signal. This many have observed gives a very engaging sound. I would tend to agree.

I bought the modules as a KIT from this site.

DDDAC site

There is much more detail on the site about the design etc.

Well worth building if you are looking for a fantastic source.