ATC CDA2 Mk I - Noisy/slow CD mech?

[Sean K]

Wondering if Rick at Musicraft or anyone else can advise.

I've just picked up a Mk one CDA2. The CD drive is rather slow to read discs, 10-12". I understand this might be within normal limits for this mech, but I've never had a drive take this long.

The CD drive does seem a little on the noisy side, a low pitched whirring, but not constant like motor noise, more like bearing noise. It seems a little intermittent; it was doing it with one CD but when I reloaded the CD, it stopped.

To put this in context. I've got it on my desk, at work (it only arrived this morning), so it's less than 1m from my ears. I very much doubt I'd notice this when set up at home with sound through the speakers, but if it is a sign of something awry, I'd rather discuss with the seller (who seems a very genuine bloke) asap.

I hope this is normal for this mech, as even through the old pair of old DT331s I keep at work, it sounds lovely, looks great and I really want to keep it; very detailed and with great bass (can't wait to put it though the 50s later)

Cheers

 

[John Phillips]

I've just picked up a Mk one CDA2. The CD drive is rather slow to read discs, 10-12". I understand this might be within normal limits for this mech, but I've never had a drive take this long.

Yes, I have to say that this slow is normal based on my experience. My dealer lent me his Mk1 while ATC were building a Mk2 for me. It was a surprise after having got used to my 2004-vintage Quad 99 CD-P so I had to learn to be a little more patient for a while. The Mk2 mechanism is much faster.

The CD drive does seem a little on the noisy side, a low pitched whirring, but not constant like motor noise, more like bearing noise. It seems a little intermittent; it was doing it with one CD but when I reloaded the CD, it stopped.

To put this in context. I've got it on my desk, at work (it only arrived this morning), so it's less than 1m from my ears. I very much doubt I'd notice this when set up at home with sound through the speakers, but if it is a sign of something awry, I'd rather discuss with the seller (who seems a very genuine bloke) asap.

I can't comment definitively on mechanical noise since the Mk1 was about 3 metres away from me while operating. However I also do not recall it being excessively noisy while I was loading a CD, so clearly I did not notice anything awry.​

 

[AndyU]

I’d give ATC a ring.

 

[Sean K]

Thanks for the info and advice.

Spoke to the NZ ATC distributor; very helpful and reassuring; quite normal for these drives to be noisy and no problem with spares for the foreseeable future, just in case.

 

[John Phillips]

… Spoke to the NZ ATC distributor; very helpful and reassuring; quite normal for these drives to be noisy and no problem with spares for the foreseeable future, just in case.

Excellent. Do enjoy it. I run my CDA2 into SCM50ASLs as well. For my ears it's a very satisfying combination indeed and I hope you find the same.

The only thing I would note is that the CDA2 Mk2 has a very high output voltage but the SCM50A has a default sensitivity of just 1 Vrms. I cannot recall now if the Mk1 also has such a high output voltage.

For my normal classical fare from CD the volume control sits at 09:00. That's OK as channel balance is well maintained and volume is not over-sensitive to rotation of the control.

However when running the TV into the optical socket, 09:00 was too loud. So I got a pair of 10 dB Rothwell XLR pads for the XLR connection, just to move the volume control up a bit. Pads should normally be placed close to the destination end of the connection to avoid being loaded with too much capacitance. But I didn't like to plug these directly into the loudspeakers as there was then a lever that might damage the sockets with a careless knock. So I used a 0.5m XLR lead from the loudspeakers to the attenuators and the main lead from there back to the CDA2.

 

[Musicraft]

I don’t recall the CDA2 being noisy.

 

[Sean K]

Thanks for all the replies and advice.

As a preamp/CD player, it sounds absolutely wonderful, more detailed than the Mytek Brooklyn I was using, including using the internal DAC to process the optical out from Chromexast for Tidal. The analogue input is very quiet, too, taking the signal from my P75, although my cartridge is past its best, so I look forward to hearing it with the Dynavector XX2 I've just bought from Gazjam. It's very dynamic; the attack on string bass and percussion is much more prominent. It's not bass-shy, either!

I can only imagine how good the Mk II sounds if it's an improvement on the Mk I.

Thanks for the tip re: the Rothwell attenuators; it's so loud into my active 50s that there's not much useable travel on the volume control, especially when using the remote.

I had a much longer listening session last night and despite what I said about feeling reassured re: the transport noise, I still think it's louder than it should be. As I said, I've never heard a transport that's so noisy in use; the ARcam 7, Naim CD 3.5 and CDX and various Marantz's were virtually silent in operation; at most, a high pitched whine that could only be heard with the speakers muted and my ear next to the unit.

I was playing Leonard Cohen, Popular Problems very quietly last night and could hear the 'rumbling from the drive from my listening position.

I'll contact the seller and let them know my concerns and give ATC a ring tonight. It's a real bummer, as It sounds fantastic and potentially very inconvenient, as I've just sold my Mytek and NAC72 (first time in 20 years I've owned no Naim!), so will be without a preamp. Bugger.

Thanks again

 

[Sean K]

Very helpful conversation with ATC last night. The upshot is I'm not reassured that the drive is as it should be.

Seller was very understanding about it and I'm sending it back for a refund. I understand ATC have spare drives for these, so I imagine it will be back in great shape soon.

I'm now without a preamp but seriously thinking about ordering a mk2 on the strength of how good the mk 1 sounds. Everything just sounds more defined; the difference that makes to timingis great fun,

Re the attenuators: They'll certainly be necessary for fine control with the remote, at least, which is hard at the moment. I don't think I've had the volume past 9.00 yet.

 

[AndyU]

It might also be worth asking ATC themselves whether the input sensitivity of the speakers can be changed. Some of the pro models have adjustment; it might just be a matter of adding/changing a resistor or two in the amp pack somewhere. Ben Lilley is a good guy to talk to.

Alternatively, Canford have a range of XLR in-line attenuators.

https://www.canford.co.uk/CANFORD-IN-LINE-ATTENUATORS

 

[John Phillips]

It might also be worth asking ATC themselves whether the input sensitivity of the speakers can be changed. Some of the pro models have adjustment; it might just be a matter of adding/changing a resistor or two in the amp pack somewhere. Ben Lilley is a good guy to talk to.

The amp pack on most/all non-pro models does have a couple of holes giving access to trim potentiometers. One adjusts bass boost and the other reduces sensitivity from 1V to 2V. The manual shows which is which and which end of travel is the "reference position".

However please note that although trim-pots are IME robust if you are mechanically sympathetic, they are intended for "set-and-forget" adjustments. If damaged they are a manufacturer repair. So if they get used just be careful. Especially not accidentally trying to force them beyond an end-stop. And don't make adjustments too often.

I have trimmed my SCM50ASLs to the 2 V sensitivity end of the adjustment, as well as having the 10 dB XLR attenuators. I have seen people write that attenuators adversely impact sound but I haven't heard this in practice using either the trim-pots or the attenuators or both. I did, however, make sure the extra output impedance the attenuators inevitably add to the source did not interact badly with cable capacitance to create a low-pass filter.

 

[John Phillips]

Alternatively, Canford have a range of XLR in-line attenuators.

https://www.canford.co.uk/CANFORD-IN-LINE-ATTENUATORS

I would be very wary of using these. They seem to be intended for use in matched impedance audio systems with either 200 Ohm or 600 Ohm source and load impedance. If so, that's unlikely to be suitable for this situation. The Rothwell pads are not designed to be symmetrical and impedance matched. They are asymmetrical and present a suitable but different impedance to both the source and the load sides.

I do know from examining the Rothwell internals that they are suitable. However I am sure there are others like that if necessary.

 

[AndyU]

I would be very wary of using these. They seem to be intended for use in matched impedance audio systems with either 200 Ohm or 600 Ohm source and load impedance. If so, that's unlikely to be suitable for this situation. The Rothwell pads are not designed to be symmetrical and impedance matched. They are asymmetrical and present a suitable but different impedance to both the source and the load sides.

I do know from examining the Rothwell internals that they are suitable. However I am sure there are others like that if necessary.

Sorry about the duff recommendation for attenuators, I’ve never used them. I do however remember JohnW - he of the infinite tap length MDAC2 project - casting aspersions on the Rothwell attenuators ..

https://pinkfishmedia.net/forum/threads/mdac-first-listen-part-xxviii.147081/#post-2149839

 

[John Phillips]

Sorry about the duff recommendation for attenuators, I’ve never used them. I do however remember JohnW - he of the infinite tap length MDAC2 project - casting aspersions on the Rothwell attenuators ..

https://pinkfishmedia.net/forum/threads/mdac-first-listen-part-xxviii.147081/#post-2149839

WIth apologies for the thread drift … I think JohnW is correct and I hadn't seen that issue or thought about whether it has any significant impact. Actually I think the situation with the ATC amp pack is slightly different to the one JohnW has, but I will get out an old envelope and scribble on the back to think about it.

 

[hifi-dog]

When I needed to drop voltage into an Atc integrated Ben Lilly recommended a t pad rather than the usual l pad arrangement as it matches impedance better.

 

[ex brickie]

Do you have the unit back yet from ATC? I bought a s/h SIACD unit recently and the transport was very slow and noisy. I sent it back and the transport was replaced under warranty (and this was a 5 year old unit - ATC have great warranties)

It is still slow - that's just how this one is. But less noisy...

Most importantly - a very good sound for an all in one unit

 

[Sean K]

Thanks again for the helpful advice and comments.

John Phillips - Mine are an older pair of 50's upgraded to SL spec and swapped in the ATC tweeter, but they don't have the trim pots on them.

ex brickie - I sent the unit back to the seller for a refund so I am sure it will be up and running again soon.

I managed to score a pair of -10db Rothwell attenuators en ebay for half the cost of a new pair, so that looks to be sorted, although I will double check with ATC what they recommend prior to using them.

Anyway, on the strength of how good the mk1 sounded simply as an analogue preamp (I was very impressed side by side with a Mytek Brooklyn and a NAC72/HC), as a DAC (optical output from Tidal/chromecast) and the CD player, I think I'll take advantage of weak sterling and get hold of a Mk 2.

 

[John Phillips]

Sorry about the duff recommendation for attenuators, I’ve never used them. I do however remember JohnW - he of the infinite tap length MDAC2 project - casting aspersions on the Rothwell attenuators ..

https://pinkfishmedia.net/forum/threads/mdac-first-listen-part-xxviii.147081/#post-2149839

I have done some sketches of the interface and some sums. Yes JohnW is right for three-resistor "U-type" attenuators like the Rothwell. They do reject unwanted common-mode signals less than the wanted differential signal. And yes, a 4-resistor version will do the more accurate job.

But there's probably no need to worry, at least for low values of attenuation like 10 dB.

More technical for anyone interested. You do lose some attenuation of unwanted common-mode signal (& noise) but the input's common-mode rejection should still see off any unwanted common-mode signals (if any are present) unless the situation is already marginal. The ATC amp-pack's specification says "10 kOhms per leg" input impedance. So the circuit with that input impedance and the 3-resistor U-type Rothwell attenuators (three 8.2 kOhm 1% metal film resistors) looks like a hybrid between the 3- and 4-resistor attenuator. Wanted signals go down by 11.6 dB and unwanted common mode signals go down by 5.2 dB. So, you do lose 6.4 dB from the interface's effective common-mode rejection.

Now I know (thanks @AndyU) I may get round to modifying my Rothwell attenuators to 4-resistor versions to see if it does make a difference after all, even though I suspect not.

 

[Woodface]

How good is it as a CD player? I am seriously thinking about going for a one box solution. I currently have a cdx/xpas2 feeding a 252/supercap/250. Quite like the idea of active speakers with a simple fron end.

 

[John Phillips]

Re the attenuators: They'll certainly be necessary for fine control with the remote, at least, which is hard at the moment. I don't think I've had the volume past 9.00 yet.

I also found the ATC remote control to be somewhat coarse for volume setting at the bottom end of the potentiometer range.

However FYI I set up my Harmony Elite remote control handset/hub to control the CDA2 as well as the rest of the A/V system. Programmable Harmony remotes have a setting that can shorten (or lengthen) memorized IR control pulses. I use it on the shortest setting for the CDA2 and that's much better for setting volume. The Harmony remote control system does take some time and effort to learn and set up, though, so it's not going to suit everyone.

 

[Sean K]

I also found the ATC remote control to be somewhat coarse for volume setting at the bottom end of the potentiometer range.

However FYI I set up my Harmony Elite remote control handset/hub to control the CDA2 as well as the rest of the A/V system. Programmable Harmony remotes have a setting that can shorten (or lengthen) memorized IR control pulses. I use it on the shortest setting for the CDA2 and that's much better for setting volume. The Harmony remote control system does take some time and effort to learn and set up, though, so it's not going to suit everyone.

Yes, that's just what I found - only a problem late at night, when trying to make small adjustments at low volumes.