No, not more diy lunacy

Apologies for what follows -

The dac chip doesn't matter I'm told, but in the past, the following filter and audio output side once fitted as separate items meant far more. I'd suggest getting an Arcam Alpha 5 and tweak that as Les W does - may be easier to separate bits out and there was provision to disable the onboard dac and add the Alpha 6 dac-output board as well.

Oh, and if what you say about the dac chip not being important then why does the £3.43 dac sound so good ? Apart from the big multi legged chip there are only two 3 legged components on the whole board. Rest are just caps and resistors. The two 3 legged components are labelled Q1 (transistor) and P1 (?). I would suggest there is very little of what you would call an output stage in it. There are a number of unused pcb pads including some for an eight legged chip which is not there.

Stu

I loved that mk1 TIS, but I guess even it can’t beat no cable at all Seeing Dave mention the Avondale Arcam Alpha 5 reminded me that Les also modded the CD3 and the CDI. I’m guessing Les likes the TDA1541. Cant fault his taste, cos I still think it has a magic about it.

As I understand it, modern dac chipsets 'do it all' on one package. Even the business part inside a 1541 was pin-head size, the rest being space to fit the pins around it, although I think it ran a bit warm as well from memory of when I had the tops off stuff like this when running.

The cheapo dac has a lower output than a typical CD player, so that could indicate no add-on output buffer. I'm not saying it's a world beate ror anything, but given a reasonable supply behind it, it's as good as many classic mid price players I reckon and once you forget it's there (so your eyes don't dictate the sound quality), i still feel it's pretty darned good! My power supply is a fairly expensive (by usual standards) black coloured fully potted 30VA toroid from RS Components with paralleled 12V secondary's into a similar regulated +DC supply much the same as that in the £40 Chinese supply oft recommended. It's in an abs project box (I can drill abs - just, but not metal)... This was originally a 9V supply for my ceramic cartridge preamp (high input impedance very basic fet buffer stage and I just trimmed it down via the adjustment to 5.1V or so.

Pics of latest mods.


Bypass of cdp anologue output stage. Lifted one leg of red wima 10uf, 100k resistor added to signal 0V and silver wiring to phono sockets

My preamp (or lack of)  Forget the circuitry on the green pcb none of it is used anymore. Signal wires from coupling cap and 100k to 0V go to the potential divider (the black rc55y resistors) and the 0V wiring to a copper bus bar I soldered across the 0V tabs of the crappy phono sockets (removed from a knackered Cambridge audio integrated). So a bus bar rather than a star earth. Four TIS cables go off to the 4 monoblocs. Simplicity 




Pic of the LM317 mods I did on the regs for two of the dac power supply pins. If output voltage required is 5V then remove one resistor and replace with two green LED's in series. Much lower noise and output impedance is the result. I love the glow of these led's, especially when its dark. The clock reg has one on too as has the flea reg for dac internal opamp. Super regs on the output stage had an led each as well but they are history now.




Just gonna do this led trick with the rest of the 5V regs in this player but they are all filtering the supply for digital chips and the laser - I don't expect much difference if any but more green led's is cool  I know none of this is rocket science but hey i'm kind of proud of the sound I have here.

Its all gonna be on one level of the "music centre" i am going to build out of wood and 6mm aluminum sheet for heatsink. I might even dispense with the 3.5's chasis and just use the front panel, swing out tray and motherboard.

If the silent switcher switch mode psu works out then i wont need any transformers, rectifiers caps or regulators. Just a couple of SS boards which are tiny ( fit in the palm of your hand).

Yeah there are a lot of resistors and caps. Only multi legged components are a regulator, the dac chip and a zener diode (which usually only have 2 legs so might have got that wrong).

I also dont know how they make it for that price. Bonkers.

Got mine for €3.43   although i will probably need another by the time i have finished with it. Pity i dont know how to seperate out left and right channel data then i could use one per channel.

If it could go in the 3.5 i would have a stab at wiring it in. It depends what clock frequency has to be used i think. But then this thing can get shoved on the end of all sorts of things. Need to read more (or get out more).

You’ll likely get the odd light-hearted comment, but hopefully nothing more. I hope they realise there’s no point in having it all neat and tidy whilst you’re experimenting. You’d probably be ten steps further back, or limiting yourself due to space constraints.

Yeah its good to have the freedom to poke the iron or probe anywhere you like at a moments notice    Had a few comments on pfm, just wait til they see my speakers 

I promise i will tidy it up one day, just for you Jammy. No wiring looms though.....that i a no no.

I quite like my avatar, have a few similar. A nice rack would be good though 

Yes Dave that is the plan but plans are constantly changing. I need to draw the line eventually otherwise it will never get "finished". 

Thing is my mind is always racing on to the next thing. What if i did this etc etc.Current thoughts are centring around not having any interconnects at all. This requires some srious thinking about getting all signal circuitry close together and the power supplies out of the way but not too far away. Think dac output and phono stage straight into source selector and volume control. And then straight into 6 channels of power amplification. Connections as short as poss without causing other problems like crosstalk.

Speaker design is more or less sorted just need to build the final thing.
LP is still a bit up in the air
Phono stage sorted
CDP nearly there
Preamp section has been decided on
Power amp choices are almost there. 6 channels using nva boards and separate psu's for front end and output stage. Just 4 channels to build

Not much to be getting on with eh ?


I dont think the people who frequent pfm audio room read the forums i post on. They dont even read the diy room on pfm.

Still loving my CD3.5 with out output stage  A much more honest and natural sound with more detail to boot. Who would have thought it ? Still occasionally think about adding a cathode follower buffer but I am more than happy the way things are now driving a passive volume control.


Valve output stage for a Naim CDS anyone ?  See here

One for Andrew - Sonneteer Alabaster tweaks here      its the same guy !

Been looking into the digital side of the CD3.5 and cdp's in general. Laser is the thing to worry about. Found some info on cleaning the inner workings of it but wouldn't bother until it started playing up. Cleaning the sled runners and adding a smear of new plastic safe grease can cure some skipping problems. Phillips transports don't need any adjustments generally.

The 3.5 uses a TDA1300 combined laser supply and RF amplifier (has its own LM317 reg in the swing out tray. This sends the signal down the flexible ribbon cable to the main board. Ribbon cable is not the best way to send these signals and if so they need a ground line between each. I need to check what Naim have done here. There are a few dc power lines coming down the ribbon cable to the LM317 reg and the swing out tray sensor which tells the player when the draw has been closed which in turn tells the laser to read the TOC. There are other lines as well from some of the other IC's on the main board. Everything is talking to each other.

The power drivers on the motherboard are two TDA7073AT which control the sled, motor etc. These have a LM317 each but one of these regs is used to pre regulate the 5V LM317 in the swing out tray. So either Naim thought that clean power was essential for the laser or that the reg on the swing out tray would be dropping too much voltage and get too hot. Which shall it be ?

There is a PIC ram chip loaded with Naim written software. This gets its own LM317 reg at 5V. SAA7376 is a combined servo processor and decoder. A huge 64 pin surface mount chip with connections running all over the shop. Gets three dedicated 5V lm317 regs and two or three reference feeds from one of the 9.375V regs which also supply one the TDA7073 power drivers. Not sure what the significance of this is.....yet. The i2s signal is transmitted from the SAA chip to the TDA1305 dac via 3 data lines. The dac is pretty self explanatory and has three separate power pins which I have mucked about with quite a bit  . I got rid of the inverter chip and its reg many years ago when I put a pfm flea powered tentlabs clock and dedicated psu in, so wont mention that apart from to say it distributed the clock to the decoder and dac.

Display takes a feed from one of the 9.375V regs which also power the power driver chips. Might shove a dedicated reg in for the display and get it off sharing with a power driver. Anologue stage has gone so I don't need to worry about that anymore 

People say don't bother messing with the digital side of the player as Naim have it pretty well sorted already and their are no improvements to be had. Being the inquisitive type I might have a bit of a play...…...well ya know how it is  Scary stuff this digital malarkey .