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AudioSector-chip amp kits, dacs, chassis

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Questions about integrated amp

I think it was only a matter of time before I started building Integrated amps with a DAC built in. Here's the first one, with USB input:


Peter,

I have been pouring over the DIYAudio posts for a couple of weeks now, trying to decide on how to approach my desired amp project and have narrowed my focus to a combination of the integrated amp you featured in your 4/23/08 post in the Vendor’s Bazaar and the Neil Kaye amp with Squeezebox built in. First, as a mechanical engineer, I can figure out how to put things together pretty well, but electronic design (and testing) has always been a “black art” to me. So I always take the easy route and try building from a kit. I put a mono amp from BrianGT together a couple of months ago and found it very easy (haven’t fired it up yet as priorities have changed), so a NOS DAC doesn’t frighten me too much at this point, but that could change once I got into the project. So my questions are:

1. If I use extra wraps on a toroid to drive the NOS DAC instead of the Hammond transformers, would there be a large number of unused parts from the NOS DAC kit that would not be used? Would bare boards be a better deal in the long run, considering that I would have to possibly pick out components from a schematic? Is a BOM available to help out? Is there guidance available to separate the PCB properly?
2. USB or S/PDIF – The squeezebox has a digital optical output (TosLink?) and a digital coax output (S/PDIF?) on the back of the unit as well as an Ethernet input. I plan on the amp only having the Ethernet input on the back of the amp, with the squeezebox stripped of its case, mounted inside the amp, and the output going directly into the NOS DAC. DAC output directly to the amp boards. I would expect that the logical interface would require the S/PDIF NOS DAC, but would the USB version work as well? Again, my lack of experience in this area shows, so I could really use some advice. The posts that I have read indicate that the USB is easier to work with, but it may not interface correctly. I haven’t purchased the squeezebox yet to take a look inside, so I am only guessing at this point.
3. I would like to build a series attenuator using an Elma rotary switch, but I am having a hard time figuring out which model to use. Percy has kits based on the BV series and the 04-2130. The Elma website shows the 04A2A00 for audio use and it appears to be the same model (due to the PCBs) that you used in your integrated Patek. Do you have a preference? Again, a kit would be nicer here, but mechanically, this doesn’t look that hard. I have found the listing for the resistors to be used (10K I believe) so picking them out would not be difficult. Caddrocks would be nice, but I may have to stick with the Holco H4/PRP assortment.
4. I could not find much info on adding extra wraps to the toroid. Do you use a formula to figure out how many wraps, based on wire gage, to use? I assume that the wraps go through the hole and around the mass of wire and core. I would also assume that the wraps would need to go all the way around the torroid (i.e. 360O). Do you remove the covering or wrap right over it? I have not taken one of the ones I have on hand apart, so I am not entirely sure how they are constructed.

I wanted to thank you for the new thread on building a GC. I have been following it now for a few weeks and will go back to it often for reference. The set-ups and the pace seem to be very helpful. Thanks again for that help.
:bawling: :bawling:
 
1 If you add turns on toroid to power the DAC, the AC module and Hammond transformer are the only parts not installed on DAC’s PCB.

By buying parts separately you will safe some 20%, but then you also need to consider shipping charges from different suppliers, and AFAIK, none of the major suppliers carries BG N 4.7/50 caps any longer ;)

2 I’m not familiar with squeezebox, but it seems like you need SPDIF version of the DAC.

3 I use BV22568 Elna switch from Percy catalog.

4 The info about adding turns to toroid was posted here: http://www.diyaudio.com/forums/showthread.php?postid=1492139#post1492139
and the actual number will depend on toroid type. I didn’t do it all around toroid, but only 1/3 of the core. I made it right over the original plastic wrapping, don’t remove anything, and further insulated it with more tape.

Here's the BOM for the SPDIF DAC:

1000/25 BG STD 2pcs
1000/25 BG NX 2pcs
47/50 BG N 1pc
BNC 1pc A24494
MSR 860 8pcs
Line Filter 2pcs PLK1077
Dale 20R 4pcs
Ferrite Bead 2pcs P9818BK
AN8005 3pcs
AN8008 1pc
10/50 BG N 2pcs
15/20 OsCon 2pcs
4.7/50 BG N 2pcs
0.47/50 BG NX 1pc
330R Caddock 1pc
75R Caddock 1pc
10n Vishay 2pcs 75-KP1830310063-TR
3n3 Wima FKP2 1pc P3332
SN75179 1pc
CS8412 SMD 1pc
TDA1543 1pc
2k7 Riken 2pcs
1k5 Riken 1pc
AC Module 1pc
PCB fuse 1pc 507-1032
 

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I finally got inspiration to raise the digital bar in my system reading the shigaclone thread and got hold of a boomblaster.

To make things complete I ordered Peters DAC, not realizing I had to do SMD on a 28 feet chip. I now know a little more about SMD soldering then I did before making the order, but it did not come easy to me.
I have built the dac, checking connections to every pin of that CS8412, powered it up ( no noise, no smell) and tried two different spdif sources.
There is a signal in there somewhere, but its mainly what I believe is discribed as "static". Crakcle and pops and no fun at all.

Did I fry the CS8412, struggeling with solderwick techniques and what not ?

Is there any way I can check this ?
 
Peter Daniel said:
Check the signal on pins 1 and 2 of TDA1543 (BCK, WS). You should see high frequency square wave. If those are missing, most likely CS8412 is no good.

Please forgive my ignorance, but that sounds like something I would do with an oscilloscope ?

I do have a Honeytek 615 that can measure 10Hz - 200kHz but I never used it for that. Do I measure between pins or between one pin and DGround ?

Edit : The Honeytek measures Hz on Voltage or Current. I guess I want the Hz of V. But again, between pins or between pins and ground ?
 
Hi Peter.

I've just about got all the parts together to build the DAC now. Due to cost/availability considerations I've had to go for lesser quality components than desirable i.e. Panasonic FA's for PSU caps, Elna Cerafine in certain positions instead of Black Gate etc.

Just wanted to ask you about the Panasonic line filters. Are they 2 x 0.6mH each? I noticed they are rated 3-amps, but would 2-amp filters perform just as well? Reason I ask is I can get a couple from Farnell here - different make but look OK.

Cheers,

- John
 
Chip and DAC project...

Hi,

I have purchased the nice PD kits (chipamp and DAC) and are planning a project: On housing including both amps, volume and DACs. Inputs are only digital.

Layout:
I would like to make the ultimative layout inside the common cabinet. The must be two digital inputs, one coax (high priority) and one optical.
The wires from analog out from the dac goes to volumepotentiometer (10K Noble) and directly to input on amps.
Using two 500VA dual 20V winding transformers and dual rectifiers

I have the following questions:

Where is the shortest connection most critical, from dac to volume potentiometer or from volume to amp boards?

How do I best implement dual digital inputs and switching from frontplate? I would like to use BNC input for the coax input and optimize wiring/impedance to 75ohm.

Is it better to have long wires from transformer to rectifier board or long wires from rectifier to amp board?

How do I place toroid trafos for best performance regarding to placement of boards?

Is it ok to wind new secondaries for DAC on amp toroids? If so, what type of wiring? Shall I wind one on each trafo or two on one of them?

:)
 
Hi,

A similar project has been described here: http://www.diyaudio.com/forums/showthread.php?postid=1491212#post1491212
Of course, certain aspects of design are dependant on chassis type, controls placement ind input/output connectors location.

I would suggest placing the potentiometer as close to amp boards as possible.

The example of optical input implementation is attached. It's best to use a toggle swith close to both inputs and select them from rear panel. If you really need to do it from front panel, you may consider a relay.

Place the rectifiers close to tranformers and run longer wires to amp boards.

The transformers don't affect amp boards much, place them in a way to make chassis well balanced.

I did wind additonal secondaries for DAC on amp's toroid and used 20ga Cardas solid core enameled wire for that purpose. If you have two toroids it may be recommended to ad one secondary on each: I'm not sure how much those secondaries affect the performance of the amp, but it's better to have both channels run in a same way.
 

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Switch off thump with multi-channel amps

Peter,

I have finally built my pair of four-channel amplifiers for my Linkwitz Orion speakers using the premium LM3175 kits; after trying some SMPS units I have gone over to transformer based power-supplies. On Mid/Tweeter amplifiers I am using the Polish transformers you recommend (and Use), for the bass amplifiers I am using some equivalent Airlink trannies. I have no hum and the sound is excellent - however I am getting a thump when switching off the psus. I do not have any of the Grounds connected to earth or the chassis and therefore this would seem to be the problem.
What I would like to do is connect grounds / earth / chassis as per your Pateks - but I think this will give me a problem. Each side (left/right) has two power supplies (one transformer plus one rectifier board) each of which powers two amplifiers. The V+, V- and PG+, PG- from each amplifier board goes back to the psu, the boards are mounted on connected copper bars.
Will I get an earth loop if I establish one point on each side (left/right) to be the Star-Ground Central for that side, then connect all the board grounds (except SG) to this point and then connect this to the copper bars using a 10R resistor and then run a large ground wire from the copper bar to one of the earths of either power supply?

Re-reading this it seems unclear - I will try to draw a circuit diagram and upload it.

I must say that I was not expecting the amplifiers to go as loud as they do (plenty for me) nor to control the bass units as well as they do - I am very impressed and pleased.

Thanks

Alan
 
A customer contacted me today with an enquiery regarding Mac and my USB DAC:

My understanding is that the Mac must "see the USB device" in order to control the volume. Do you know whether your USB DAC shows up as device for sound output AND whether Mac computers can control the volume? (With the toslink connection, Mac MIDI software options for volume control are not selectable.)

Anybody familiar with the issue?
 
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