DIY Caiman Power Supply Project

[chrism]

Really pleased with the mods that I have completed to my Caiman power supply and have added a few pictures (sorry grotty flash ones) to show what has been done.

I wanted to remove the Murata Super Regs and feed new regulated "linear" supplies instead. The power supply is basically two separate supplies in one box one set at 14.5v and the other at 6v.

The supplies are:

1. Avel Lindberg encapsulated toroidal's giving a 17.5v AC supply.
2. Avondale full wave bridge kit with Schotty T0220 Diodes.
3. Kendeil 10,000uf cap.
4. Avondale pretracking regulator kit.

The 6v supply is fed to 5v Murata point and has a resistor and 220uf cap (under the board) and passes forward bang on 5v. The +ve feed from the 14.5v circuit is cut here also although the 0v grounds are kept common.

The 14.5v supply uses the existing diode and fuse route but I have taken out the 10,000uf cap and just put a tiny film in (not really needed though). Again a resistor and cap has been added at the 12v Murata position. The 14.5v input gives bang on 12v at this point on the board.

The sound, yes different to before. A step forward in smoothness of the high treble notes and more of the "blackness" between instruments. Bass is more controlled but still as deep.

Enjoyed doing the project and feel it was well worth the effort.

What's next!

Regards

[StanleyB]

One question I often get asked by people wishing to try out a different power supply is where to find a suitable DC lead to connect between the power supply and the Caiman or TC-7520. Well I just found one on the MAPLIN (http://www.maplin.co.uk/dc-output-lead-6290) site.

[Maximum]

Yes I bought one of those leads with mine. Unfortunately the spades don't fit on the terminals. In fact not just that, the adaptors that work with it use a different key to identify the polarity which make no sense, one using a diagram showing in/out polarity on either side and the other just with the word TIP on it. After looking around the net for 30 minutes I was none the wiser, picked the most likely way around and tried it. The dac never came on so I promptly turned it off and butchered an old lead instead giving that cable up as a bad job. So best be aware of these issues.

[keiths]

I
n fact not just that, the adaptors that work with it use a different key to identify the polarity which make no sense, one using a diagram showing in/out polarity on either side and the other just with the word TIP on it.

You just line the word TIP up with the polarity you want the tip to be - "+" or "-".

[Maximum]

I

You just line the word TIP up with the polarity you want the tip to be - "+" or "-".

That's the thing, the adaptor kits all come with these on...

http://en.wikipedia.org/wiki/File:AC_adaptor_polarity.png

One on each side, so I matched TIP with the polarity I wanted and it didn't work.

[UV101]

Come on guys, has anyone actually read the 1st post?

Nice work Chris, I'm really pleased that you are getting to grips with all this PSU stuff and making really ace progress!!! How are you finding the TPR's? they will be much better than 78xx regs.

[chrism]

Hi Ian,

Yes very surprised at the lack of interest with the DIY Caiman PSU project. Nice little upgrade over the Murata regs that I had in before. Building two linear PSU's to feed the digital and analogue rails makes sense and removes a level of regulation over all.

I built an identical one for my Squeezebox but had to put a massive heatsink on the digital 5v one. I am now running the SB with three supplies - two 5v linear supplies (one for the new clock) and a cheapo linear for the display only.

Sounds great.

I may have to compare notes about swapping some caps over on the Caiman digital side near the DAC chip. You mentioned Oscon's are worh a go. Any good suppliers of them around?

Best

Chris

[Bassie]

Hello Chris,

I think you are on to something here. I have removed the diode, fuse, big cap, 5V regulator and 220uF+ bypass cap, and replaced that with a diy dual voltage external power supply based on LD1085.

The interesting part was 'tuning' the psu, It has a really big impact on the sound IMHO. 12 to 15V is not critical if you have the passive mod, but the 5V is very sensitive to every little change made. At the moment I have 2x12Vac >> 2x Hexfred (for me more detail) >> 2200uF Panasonic FC bypassed with 0,1 uF Pe >> LD1085 referenced by 100r to two LED's bypassed by 10uF foil bypassed by 6,8nF Polystyrene. (This is the trick! LEDs are a quiet current source, and the bypass caps are in the feedback of the regulator, they invert on your frequency response) >> 470uF 6,3V (tunes bass responce, but at a cost. 150uF minimum according to data sheet) >> XLR cable to box, connected at output of removed 7805 >> 10uF Foil >> 100uF Panasonic FM at the converter. This results in the clearest, most balanced sound so far, after a week of experimenting with the power supply.

I personally feel that this is the biggest upgrade yo can do after the passive mod, without exotic components that is. I have ordered some fixed 5V LD1085 regulators to experiment on a caiman. only decent 15V according to description and the regulators on the board swapped, so I can tell how much difference that alone made, since my DAC is completely hotrodded now.
It was one of the biggest improvements in terms of harshness, my main issue with the 7520. I think I will trade mine for a caiman now and see where that will lead me...very pleased with my little DAC now!

For anybody reading: If you have a linear PSU based on LM317 you can replace the regulator with a LD or LT1085, they are pin compatible, or you can start by bypassing the LM317 according to previous directions first, and zener reference it. This alone will make a difference!

Well Chris, I felt so sorry for you I joined this bunch :lol: Thanks for having me guys!

Marc