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Thanks, Peter

This is an interesting and in a way controversial subject, let us to view it in details.

peter foster wrote:

It may be worthwhile to check what transformer is installed in your DA924 because Lavry did change over to torroid transformers from the laminated core power supply transformer.

When I got my unit, it was used; the unit was perfectly operational and sounded flawlessly. I noted still a very slight exuberance in HF and some minor deficiency in lower MF. The HF exuberance was not line with any other DAC I heard – it was absolutely free from any colorations. What is interesting about that exuberance also that it happen ONLY what you feed Lavry from “alien” sources. What you feed Lavry from Lavry own source (AD122) the exuberance did not show itself up and the entire result sound very neutral. Anyhow, I thought that the exuberance was due to some kind of internal miscalibration or fault – sine the unit was not new and I sent it to Lavry for recalibration and testing.  As I remember Lavry charged quite a lot of money to do so (somewhere around $800) and informed me that the unit was OK but still they were able to found that some measurements were not perfect and they we able to set them up according to what they consider they shell be. When I got my unit however I did not notice any change in sound at all but I got a piece with the fact that my DAC operates as it should. I do not remember already now but I believed Dan told me that they had a new transformers and new upgrades that make unit more thermo-stable, I think it was called MK3 modifications or something like that. It was some kinds of controversy about it as I requested them do not do it but they told me that since they have the unit then they insist to do the upgrade. I was not pleased but In the end I told them to do whatever they want just give me my unit back as I was needed to USE it. They did whatever they did, changed the front panel from DB Technologies to Lavry Engendering (it is reportedly a free procedure) and send me my DAC back. I do not know if they changed the transformers – I did not open the unit before but I presume that if they changed so much money than they did something else besides the calibration.  One more thing – I asked than to bypass the analog attenuators that Lavry has between the stages on the back panel and I would like to have as less contaminated signal path as possible.

peter foster wrote:

Also it is a good practice to periodically ship the DA924 to Lavry for recalibration and testing of voltage and frequency.

peter foster wrote:

You may have noticed that when you power it up, it makes you wait a few minutes as it performs a calibration. This is why it may be a good idea to cycle the power once a week."

I do not know about that.  When I was asked them about 24/7 duty they did not told me about it. Also, as I told by Dan and as I understood (that might not be the same) Lavry fully recalibrates itself each 15 minutes. So, if they told about the needs of “cold reboot” then it is possible that during the startup they have some other type of calibrations that are not available during operation. I do not know if it is so and I need to run it with Lavry. I was under impression that the long start up (very annoying) is due to the unit waits until the temperature of internal heater got stabilized…

peter foster wrote:

Dear Romy, advice that I received from Lavry regarding heavy use (6 hours each day) of the DA924 was as follows: "If you really use it that much I would leave it ON but power cycle it one a week. If you don't plan on using if for about 3 days then you should turn it OFF.”

Hm, it does not sound convincing to me. I think it is foolishness to make the DAC in such a small enclosure and then invest time and efforts to fight with the unit overheating. I understand that when Lavry designed it is meant to be use in pro environment and the limitations of the standard pro rack space were critical for Dan. However, in my world I care less about the compliance with pro standards and I did intend to run my DAC 24/7, the way how my Bidat does. I have different listening habits my habits do not permit me to wait 15 min unit my DAC will start up and begin to sound right.  The sound of the NEW DA924++ (with modified PS) is so much more serious then the default DA924 that I might consider in future to keep the DA924++ as the ONLY DAC I use for the whole system, I do not know as now and will make this decision when DA924++ will be fully burned-in and what my new Bidat++ will be broken-in – it will take a month or so…

Meanwhile I did make the provision to enable to run my DA924++ 24/7 with less problems. As you see in the picture above I built a harness for my DA924++ and I run it VERTICALLY with the PS located up the unit. The right part of the unit has the regulars mounted to chassis and this is the only heat-critical part in the unit as I can judge. With vertically positioned DAC, PS atop and the ventilation holes act like a chimney the heat from PS does not go down to the DAC’ circuit board with digital and analog section. Furthermore I keep the right part (in my case of vertical poisoning it is the top part) of the DAC cover, right above PS slightly open and it very effectively removed all extra head from the PS to the air outside the unit. In the long run I would like to keep cover closed and I do not want dust go into the unit, so I bought last week a large heatsink that I am planning attach on the right panel of the init (in my case the top of the unit) where the regulators plate it. I think it will do the job, it not I would add a little fan on the heatsink… In my current setting the bottom of the unit (in my vertical positioning) heated no more then 45C-50C after many weeks of operation that I feel is perfectly reasonable temperature.

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