[justd]

Ya same problem with all sources. Apple TV, sony blurry etc.

Actually i don't have a speaker binding post. But  i'll try your suggestions and report back. Thanks again for all the help.

[bruson2]

Thanks Mboxler,

The hum is coming from the speakers. I am using Mirage speaker OMD 15, OMD 5, OMD C1. Yes it does go away if i remove the interconnects.

I am using a UMC-1 as the pre-amp and processor. I  have tried lifting ground on all the equipments and it is not helping at all. in fact the problem is very peculiar. There is very little hum (almost inaudible) when everything is connected. But as soon as i play the source, and the hum volume increases. The volume of this hum is the same irrespective to the volume on the UMC-1. When i pause the source the and the music stops... the humm stops after a 2 seconds.

So it seems to me that a 50hz, signal is superimposing itself on the interconnects between the umc-1 and the amp boards. Or may be the amps are grounding themselves through the interconnects via the UMC-1 since the amps do not have a ground available to them."
 ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::


It may be an RFI signal, or ground hum, generated by your source or UMC-1 when audio is produced. And your amps without a chassis are picking it up by RF or in the wires.

[justd]

I'll consider that. Most probably it is the umc-1. But since i am testing right now. It is some distance away from my amps. So it could only be affecting the interconnects.

I just read through from page 140. Very interesting.


The hum symptoms also keep on changing. There so many variables. I learnt that even amp temperature is an issue.

This driving me crazy:-). I am thinking of making chart of the various scenarios and then posting here.

[justd]

I was also thinking of using a connexelectronic power supply, since it generates very little EMI. It is rated for 800w. Do you think a single will good for three CDA254.

[john dozier]

Has anyone replaced the tantalun input caps with high quality films? I understand this will change the cutoff freq  but I am using subs and thus can afford to use 1 or even .5 uf caps here. I am concerned abut RF or EMI pick up with the longer leads. Any experience anyone has had would be appreciated. Thanks and kindest regards John Dozier

[wushuliu]

Has anyone replaced the tantalun input caps with high quality films? I understand this will change the cutoff freq  but I am using subs and thus can afford to use 1 or even .5 uf caps here. I am concerned abut RF or EMI pick up with the longer leads. Any experience anyone has had would be appreciated. Thanks and kindest regards John Dozier

I've done it. The longer leads are indeed an issue. Better to do the PS caps mods discussed a few pages back.

[john dozier]

I have now found that the input caps are niobium oxide and are much better sounding than tantalum-in fact pretty much SOTA. Thanks for the input though. Regards

[wushuliu]

I have now found that the input caps are niobium oxide and are much better sounding than tantalum-in fact pretty much SOTA. Thanks for the input though. Regards

Good to know. I really, really wish Tom would just share more info about these boards. Even something like that is an interesting tidbit and good selling point. Sigh.

[john dozier]

I cannot blame Tom, as many other manufacturers are keeping their design and construction techniques as proprietary. There are many countries where patent protection is not worth the paper it is printed on. Intellectual property theft is rampant and if it ever gets on the web, the whole shooting match is down the tubes. Regards

[ratso]

im sure this info i buried in this thread (probably a million times) but that class d website is a tremendous headache. i have, after hours of trying to search it, yet to find which amp or kit to buy. i would like to find a 4 ohm amp that is either 500 + 500W stereo or 500W mono. i would also like to get the kit (minus chassis and connecting hardware). if i could find one on amazon, that would be even better as i have a line of credit with them. for instance, what is this:

[urlhttp://www.amazon.com/250W-Class-Power-Supply-Transformer/dp/B002E6YXL0/ref=sr_1_5?s=electronics&ie=UTF8&qid=1346544898&sr=1-5][/url]

is this in 4 ohms? i cannot find any kit listed on the website that matches up with this? (of course that would be easier if the kits weren't listed under 17 different places and had any kind of accurate descriptions). 

[wushuliu]

im sure this info i buried in this thread (probably a million times) but that class d website is a tremendous headache. i have, after hours of trying to search it, yet to find which amp or kit to buy. i would like to find a 4 ohm amp that is either 500 + 500W stereo or 500W mono. i would also like to get the kit (minus chassis and connecting hardware). if i could find one on amazon, that would be even better as i have a line of credit with them. for instance, what is this:

[urlhttp://www.amazon.com/250W-Class-Power-Supply-Transformer/dp/B002E6YXL0/ref=sr_1_5?s=electronics&ie=UTF8&qid=1346544898&sr=1-5][/url]

is this in 4 ohms? i cannot find any kit listed on the website that matches up with this? (of course that would be easier if the kits weren't listed under 17 different places and had any kind of accurate descriptions). 

Yes 250w into 4 ohms, 125w into 8 ohms, 500w bridged 8 ohms. That is the 254L. I agree, the website is still confusing and some of the amps still don't have full specs listed : (

[runemaster]

Hi all. I own 2 SDS-224, each running in bridge mode. I was playing it in a minute, and then a channel when mute. Upon checking, the amp main board does not have the usual blue LED lit up, and the heat sink is quite warm. The other unit is running fine. When I switch the ON/OFF switch to OFF, the usual amber LED does light up, but when I switch it back to ON, no LED, no sound. I've checked all connection, reconnect them as well, still the same. I initially thought that it was over heating, but I tried it again after a 20 minutes break ( I turn off the main power ) and still the same symptom. Anyone encounter such a problem before?

Thanks

[justd]

I just wanted to understand.

All these amps are basically power amps. Most of them do not have volume control.

So if I have preamp. And attach These amps to it. A 120 watt amps will sound twice as loud as a 60 watt amp. For the same volume level of the pre amp.

I have a cda224 and cda254. But I don't seem to get difference in loudness.  Am I missing something.

[john dozier]

Twice as much power is only a 3db increase, which is barely audible. To be twice as loud you need a 10db increase which would require a 1000 watt amp in your situation ( and new speakers after you have blown your current ones) Hope this helps explain what is going on. Regards

[srb]

Twice as much power is only a 3db increase, which is barely audible. To be twice as loud you need a 10db increase which would require a 1000 watt amp in your situation

10dB is a power ratio of 10X, so compared to a 60W amp, a 600W amp would be twice as loud.
 
Steve

[john dozier]

Decibels are a log function. Compared to 125 watts, 250watts is a 3db increase, 500 watts is a 6db increase, and 1000 watts is a 9db increase. Regards

[firedog]

Twice as much power is only a 3db increase, which is barely audible. To be twice as loud you need a 10db increase which would require a 1000 watt amp in your situation ( and new speakers after you have blown your current ones) Hope this helps explain what is going on. Regards

You're right about the 10db increase, but a 3db increase should be quite noticeable. It's about a 30% difference. Typical humans can easily perceive a 1db difference in volume.

[john dozier]

I agree although ear training and frequency also play a part in audibility. I was just replying to a the comment that he could barely hear a difference (if any) between two amps with different power outputs. Regards

[srb]

Decibels are a log function. Compared to 125 watts, 250watts is a 3db increase, 500 watts is a 6db increase, and 1000 watts is a 9db increase.

Understood, but he was comparing the expected volume increase from the 60W amp to the 120W amp, so relative to the 60W amp, 120W = 3dB increase, 240W = 6dB increase, 480W = 9dB increase and 600W = 10dB (twice as loud) increase.
 

You're right about the 10db increase, but a 3db increase should be quite noticeable. It's about a 30% difference. Typical humans can easily perceive a 1db difference in volume.

I'm not sure about 'easily', but in any case, I can hear a 1dB increase when paying close attention, the majority of people can more easily hear a 2dB increase and certainly most everyone can hear a 3dB increase.
 
Still, that difference will be harder to discern at lower settings of the volume control than higher ones.
 
Steve

[justd]

Thanks for explaining guys...i thought that a 6db increase would tantamount to doubling of perceived sound level.

Actually i have two 254s and one 224. I am using these to drive my 5 home theatre speakers. The woofer is being powered by behinger pro amp.

Since the rear satellites are smaller speakers i have connected them to 224 and the rest three to the 254. But i have rotated the speakers on the amps without any perceived  difference in volume level. But know i know why. 

how are other members approaching multi-channel setups.