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Creek CAS 4040

Mike P

Mike P

Trade: Pickwell Audio
Yesterday I took ownership of a lovely clean example of a Creek CAS 4040 S3.

It previously belonged to my best friend and was purchased new by his father in 1991/2 so I know the history of the amp from new.

I've coveted this little amp for 22 years since I first heard it playing through some big ol' Leak sandwich speakers and finally it's mine!:D

It now has pride of place in my 'second system' in the dining room. hooked up to a classic TDA1541 based Sony CDP and Wharfedale Diamonds it sounds just a great as I remember.

20180108_141429[1] by Michael Pickwell, on Flickr

Gotta love that turquoise lettering!

20180108_141441[1] by Michael Pickwell, on Flickr

20180108_141447[1] by Michael Pickwell, on Flickr

20180108_141513[1] by Michael Pickwell, on Flickr

20180108_141534[1] by Michael Pickwell, on Flickr

Phono section. Nice to see polystyrene caps.
20180108_143057[1] by Michael Pickwell, on Flickr

20180108_143106 by Michael Pickwell, on Flickr

20180108_143116 by Michael Pickwell, on Flickr
 
It is all working as it should but since it is 27 years old I'm thinking a re-cap would be a wise precaution.

I plan to strip it down soon to make a list of the parts that'll be needed.
 
Nice! A fine little amp! For some reason, I never liked the turquoise lettering, but the amp, yeah!
 
I had the original and the S2. In fact I still have the S2 and can't bring myself to sell it, great little amp!
 
Yes, a lovely little amp and Creek are a very helpful bunch. Mike Creek himself once penned for me a wiring diagram for voltage conversion of UK version to North American over his coffee break!
I wouldn't be too hasty to recap, as these are run well within their thermal limits, especially so with the heat sink being external to the enclosed chassis.
If your friend and his father didn't leave the amp turned on 24/7 Naim style then it may very well need nothing more than a DC offset check and possible adjustment.
My S2 measured fine and only needed the pots exercised back to quiet operation. Other than that I re-seated the fuses and cleaned up the input/output sockets.
 
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Just a word of caution, I recently acquired a Creek 4240 and the two main power supply capacitors which appeared to be original (date code for 1994) were rated at 35v whilst the actual voltages on the supply rails were +/- 38.5v - not ideal! Your 4040 is over 25 years old and I'd certainly advise changing at least the main power supply capacitors.
 
misterc6 said:
Just a word of caution, I recently acquired a Creek 4240 and the two main power supply capacitors which appeared to be original (date code for 1994) were rated at 35v whilst the actual voltages on the supply rails were +/- 38.5v - not ideal! Your 4040 is over 25 years old and I'd certainly advise changing at least the main power supply capacitors.
Click to expand...

Thanks for the 'heads up'.

In mine the two big smoothing caps are indeed 35v rated. I don't have the schematic for the S3 but the circuit diagram for the S2 indicates +/-30v on each rail. I'll certainly check though to be on the safe side!

Unfortunately I've already ordered 35v replacements so hopefully the rails will measure at close to +/- 30v.

The two big 6800uF smoothing caps out of mine measure:
6298uF and 3.8 Ohms ESR
6030 and 1.77 Ohms ESR

20180110_132059[1] by Michael Pickwell, on Flickr
 
An interesting observation I've made is that there are several instances where the capacitors don't match on each channel.

C5 and C105 (1uF 50v) are from different manufacturers.
CP5 and CP6 (1uF 50v) also from different manufacturers.
C14 and C114 (2.2uF 50v and 100v) so from different manufacturers and different voltage ratings!

Now I realise that electrolytic capacitors are low tolerance components and that functionally it'll make no difference but I still find it weird. I would certainly never do the same myself.

Here's an example. Note the different colour bands (one black and one dark blue). That's because the cap on the left is a Rubycon and one on the right it is a Taicon.

20180110_103918[1] by Michael Pickwell, on Flickr
 
I have a question about the decoupling caps for the pre-amp section. Here's the scenario:

The main smoothing caps post rectifier are 6800uF.
For the pre amp section there are a pair of 7815 and 7915 voltage regs. These supply the three opamps.
Immediately before each reg is a 100nF ceramic (rail to ground) and after each voltage reg is a 1uF electrolytic rail to ground.
The op amps have some small ceramic local decoupling caps (I haven't checked TBH but probably 100nF).

So there's only the 1uF decoupling caps near the regs plus the local ceramics by each op amps on both the +15v supply and -15v supply.

I'm tempted to add a bit more decoupling capacitance after the regs. Say increasing the 1uF electros up to 22uF (or more).

I'm also tempted to swap the local decoupling caps at the op amps to 100nF polyester (more linear).

Your thoughts please.
 
Mike P said:
An interesting observation I've made is that there are several instances where the capacitors don't match on each channel.

C5 and C105 (1uF 50v) are from different manufacturers.
CP5 and CP6 (1uF 50v) also from different manufacturers.
C14 and C114 (2.2uF 50v and 100v) so from different manufacturers and different voltage ratings!

Now I realise that electrolytic capacitors are low tolerance components and that functionally it'll make no difference but I still find it weird. I would certainly never do the same myself.

Here's an example. Note the different colour bands (one black and one dark blue). That's because the cap on the left is a Rubycon and one on the right it is a Taicon.
Click to expand...

I wouldn't worry too much about this, it was much the same at Naim - the component bins on the production lines could contain devices from several manufacturers. In your case the capacitance value is correct for each position and all have above the required working voltage.

Most 7815/7915 regulator circuits that I see have 100nF or 1uF decouplers so I'd probably stick with the value Creek used.

I've not yet found a circuit diagram for the 4040 but I do have one for the 4140s2 and the MM phono section of that shows 100nF decoupling capacitors on the NE5532 so changing to that may be a good move.

Going back to my 4240 the circuit diagram has the rail voltages at +/- 35v so using 35v devices is not good practice especially as the mains voltage has a +/- 10% tolerance anyway.
 
misterc6 said:
I wouldn't worry too much about this, it was much the same at Naim - the component bins on the production lines could contain devices from several manufacturers. In your case the capacitance value is correct for each position and all have above the required working voltage.
Click to expand...

I figured as much and I know that in practical terms it won't make a difference since electrolytic caps are usually something like +/- 20% tolerance anyway.
 
Mike P said:
Thanks for the 'heads up'.

In mine the two big smoothing caps are indeed 35v rated. I don't have the schematic for the S3 but the circuit diagram for the S2 indicates +/-30v on each rail. I'll certainly check though to be on the safe side!

Unfortunately I've already ordered 35v replacements so hopefully the rails will measure at close to +/- 30v.

The two big 6800uF smoothing caps out of mine measure:
6298uF and 3.8 Ohms ESR
6030 and 1.77 Ohms ESR
Click to expand...
Your capacitors are failing. ESR always rises long before the capacity falls with age and is the parameter that matters. I would expect <<1 Ohm from a reservoir capacitor
 
Am I correct in assuming that rising ESR causes a given capacitor to gradually become more 'reluctant' to accept a charge? In effect, slowing the recharge time/recovery rate to full uF capacity?
 
All finished.

20180112_093836[1] by Michael Pickwell, on Flickr

20180112_094801[1] by Michael Pickwell, on Flickr

Here's a summary:

  • All electrolytic capacitors replaced with the only deviation from factory spec being that I increased the capacitors on the output of the two regs from 1uF to 47uF (1uF just seems like a really measly amount of decoupling to me).
  • Local decoupling caps around the three op amps 'upgraded' from 100nF ceramic to more audiophile friendly 100nF polyester film.
  • Source selector switches, fuses, headphone socket and speaker connectors etc cleaned with DeOxit.
  • Volume pot, balance pot and tone controls relubricated with a drop of Faderlube.
  • Bias checked and readjusted.
  • Everything dismantled and cleaned.
The main voltage rails measured at +/- 30.7vdc so perhaps a touch closer to the 35v max rating of the smoothing caps than is completely ideal but since the last ones survived for 27 years I'm not going to lose sleep over it. I may swap them out for some higher voltage rated ones in the future.

I can provide a BOM if anyone wants it.
 
Nice job!

I've opened Naim amplifiers which hadn't been serviced in 40 years of life. They had 40v capacitors on 39.5v volt rails and were working fine so I would have no concerns about 30.7v with 35v capacitors.

Here's the 4240 that I've just been working on. I replaced two reservoir and two decoupling capacitors, and the balance and volume controls which were noisy and didn't respond to treatment. I also cleaned all the switches and connectors.

IMG_0077 by Malcolm Connah, on Flickr
 
misterc6 said:
Nice job!

I've opened Naim amplifiers which hadn't been serviced in 40 years of life. They had 40v capacitors on 39.5v volt rails and were working fine so I would have no concerns about 30.7v with 35v capacitors.

Here's the 4240 that I've just been working on. I replaced two reservoir and two decoupling capacitors, and the balance and volume controls which were noisy and didn't respond to treatment. I also cleaned all the switches and connectors.

IMG_0077 by Malcolm Connah, on Flickr
Click to expand...

Nice work Malcolm.

It looks like there are far fewer electolytics inside the 4240 than there are in the 4040.
 
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