After reading the entiretiy of both threads, I've decided to take the plunge and start on my first DIY amp project with the UCD modules. I already have 4 33,000uf 75v Sprague caps (one per rail) and am planning on purchasing 2 38v 600VA (~53-56v after rectification) toroidal transformers to make monoblocks- does this sound about right? I know the caps might be a little bit of overkill, but I got a great deal on them.
In terms of soft start, is there any problem with just running a resistor parallel to the on/off switch, bypassing it so that the capacitors stay partially charged all the time? Is there any reason to discharge caps other than safety? Are there any poblems with using a circuit breaker rather than a power switch and fuse?
On a more practical note, I will be going out of town on March 14th, once I place my order, how long would it take for the modules to reach me here in New York City? I assume that the shipping is fairly quick, given the rates, but it is a fairly short time frame. Would I recieve the package before I leave or would it be safer to wait until I get back?
Anyway, I am happy to be joining this thread- I am amazed by how much I've learned from the people on this site.
Best,
Larry
In terms of soft start, is there any problem with just running a resistor parallel to the on/off switch, bypassing it so that the capacitors stay partially charged all the time? Is there any reason to discharge caps other than safety? Are there any poblems with using a circuit breaker rather than a power switch and fuse?
On a more practical note, I will be going out of town on March 14th, once I place my order, how long would it take for the modules to reach me here in New York City? I assume that the shipping is fairly quick, given the rates, but it is a fairly short time frame. Would I recieve the package before I leave or would it be safer to wait until I get back?
Anyway, I am happy to be joining this thread- I am amazed by how much I've learned from the people on this site.
Best,
Larry
Hi Larry,
It isn't a good idea at all to leave your caps partially charged all the time. What will happen is they will reform at the lower voltage seen across them, so you'll turn it on one day and when they explode you'll find they became ~10V caps. Such a resistor could be a fire hazard on it's own, in my opinion it's just not a good idea.
Also caps have a certain lifespan for which the hours would be counting away continuously even as you were not using it, probably a good reason why you wouldn't want to just leave it on all the time either. Anyway the real cause of inrush is the transformer itself.
I think you can use up to 42 volt secondaries, 40 would be a safe bet.
I see no reason why you couldn't use a breaker as an ON switch, but I don't think it negates the use of a fuse, why not have both?
Best Regards,
Chris
It isn't a good idea at all to leave your caps partially charged all the time. What will happen is they will reform at the lower voltage seen across them, so you'll turn it on one day and when they explode you'll find they became ~10V caps. Such a resistor could be a fire hazard on it's own, in my opinion it's just not a good idea.
Also caps have a certain lifespan for which the hours would be counting away continuously even as you were not using it, probably a good reason why you wouldn't want to just leave it on all the time either. Anyway the real cause of inrush is the transformer itself.
I think you can use up to 42 volt secondaries, 40 would be a safe bet.
I see no reason why you couldn't use a breaker as an ON switch, but I don't think it negates the use of a fuse, why not have both?
Best Regards,
Chris
I've read somewhere that the UcD's seem to draw a little current even in "stand-by" or "mute" - it might be enough to discharge the caps slowly, I'll test this soon.
What I did notice is another problem - if you turn mains power, and the UcD's are running of the caps, when the voltage drops, there is a really eerie sound coming from your speakers.
In a good design you should disconnect the /on from the ground at the moment the mains power goes down.
I was thinking about using a soft-start and add an extra relay to switch the /on.
I just don't know how fast the soft-start relays "reset" when the power goes down.
Or maybe a mains switch with 4 contacts (don't know the english term... dual-pole?) but it seems dangerous to route 220V so close to the mute signal.
What I did notice is another problem - if you turn mains power, and the UcD's are running of the caps, when the voltage drops, there is a really eerie sound coming from your speakers.
In a good design you should disconnect the /on from the ground at the moment the mains power goes down.
I was thinking about using a soft-start and add an extra relay to switch the /on.
I just don't know how fast the soft-start relays "reset" when the power goes down.
Or maybe a mains switch with 4 contacts (don't know the english term... dual-pole?) but it seems dangerous to route 220V so close to the mute signal.
Hello Yves
I've a new (very small!) pcb design in progress to connect automaticaly the /ON pin to GND when main power is switch on and disconnect the /ON pin when main power is switch off.
I don't know if this design will be running well, i'm going to put the schematic on line this evening. (you'll be able to tell me your opinion about it)
😉
I have a couple of amps in seperate boxes. What would be interesting is to switch all of them to standby and on through an external connector. If one were going to design a little PCB for switching the amp from the main power, it would also be interesting to be able to switch it via the external input....
Or perhaps given this is DIY stuff it's best just to switch off the mains to all the amps at the end of every day anyway...
Or perhaps given this is DIY stuff it's best just to switch off the mains to all the amps at the end of every day anyway...
Hi ewildgoose 😉
or maybe the best thing will be to switch on the amp automaticaly when having input signal and switch off the amp after a small delay when no input signal...
or maybe the best thing will be to switch on the amp automaticaly when having input signal and switch off the amp after a small delay when no input signal...
Don't use a main switch at all.
Use a low voltage circuit to switch a couple of relays, one for the /on signal (delayed), two for the main power (one for low current and one delayed main on)
Then put a nice little on/off switch in front 😀
add a third secondary for 12v or so, or a small transformer will do?
Y
Use a low voltage circuit to switch a couple of relays, one for the /on signal (delayed), two for the main power (one for low current and one delayed main on)
Then put a nice little on/off switch in front 😀
add a third secondary for 12v or so, or a small transformer will do?
Y
A question of gain...
If you have:
* 5 speakers, with the same sensivity
* 2 UCD400 modules and 3 UCD180's that have the same input gain
Will I have problems to use these speakers in a surround setup?
If I set the levels for each speaker on my pre-amp at a certain db level, will an increase or decrease in volume be identical for all speakers or will the relative volume change? (I would think the UCD400 would raise faster in "volume", but this is wrong?)
My surround setup consists of two 200W main speakers and three 120W speakers of the same family, with the same sensivity - however the "small" ones are an easier load and have lower max volume.
Thanks for clearing this out!
Yves
If you have:
* 5 speakers, with the same sensivity
* 2 UCD400 modules and 3 UCD180's that have the same input gain
Will I have problems to use these speakers in a surround setup?
If I set the levels for each speaker on my pre-amp at a certain db level, will an increase or decrease in volume be identical for all speakers or will the relative volume change? (I would think the UCD400 would raise faster in "volume", but this is wrong?)
My surround setup consists of two 200W main speakers and three 120W speakers of the same family, with the same sensivity - however the "small" ones are an easier load and have lower max volume.
Thanks for clearing this out!
Yves
Hi,
That's too big an IF I think.. don't think they have the same gains. Check their data sheets at the hypex site, ucd400~20dB and I think the 180 is ~26dB.
Hope that helps ya.
That's too big an IF I think.. don't think they have the same gains. Check their data sheets at the hypex site, ucd400~20dB and I think the 180 is ~26dB.
Hope that helps ya.
I think if you ask Jan-Peter nicely he will supply the various UCD modules with whatever gain you request?
So it is, according to the data sheets they're both 26dB, I swear the UCD400 was just over 20, that must have changed as well with the latest version.
Right on.
Right on.
OK, that should make a nice sounding 5 channel setup 😀
Now I'm considering whether to buy a nice receiver as "pre" or go the other way and build a passive pre-amp.
Amps is one thing, but a nice processor can't be done DIY
Now I'm considering whether to buy a nice receiver as "pre" or go the other way and build a passive pre-amp.
Amps is one thing, but a nice processor can't be done DIY
yves, we're sort of doing the same thing. I'll be adding another channel to my current 2ch ucd180 amp so it has three channels. I'm currently gathering parts for a 2ch ucd 400. That should be a nice ht setup. I already have a rotel rsp-985 (dts & whatnot surround pre).
I will also be using the 2ch ucd400 amp for normal (stereo) listening. Problem is that the rotel has a pretty clear sonic signature and I don;t want that when i'm listening to cds or lps. I'm planning on making a simple passive pre with a normal input selector and volume control but in addition to that it will have a passthrough-input. I'll connect my surround pre to this one so when i'm watching movies i'll be able to control the whole thing with the remote that came with the rotel and still have the benefit of a nice'n clean passive pre for normal listening.
I will also be using the 2ch ucd400 amp for normal (stereo) listening. Problem is that the rotel has a pretty clear sonic signature and I don;t want that when i'm listening to cds or lps. I'm planning on making a simple passive pre with a normal input selector and volume control but in addition to that it will have a passthrough-input. I'll connect my surround pre to this one so when i'm watching movies i'll be able to control the whole thing with the remote that came with the rotel and still have the benefit of a nice'n clean passive pre for normal listening.
I use a PC as the processor and digital crossover. Brutefir is used to do convolution and I get 6 channels of analogue out the back of the PC.
Volume control is done using a variable attenuator - if you get the cheapo maplins ones you can dismantle the stereo ones and reassemble as a multichannel. I have an 8 way DACT that will be used in version 2...
Sound quality is excellent. With room correction switched in you compensate for a whole host of problems due to speakers and room. See here for some more details on DRC:
http://www.duffroomcorrection.com
Volume control is done using a variable attenuator - if you get the cheapo maplins ones you can dismantle the stereo ones and reassemble as a multichannel. I have an 8 way DACT that will be used in version 2...
Sound quality is excellent. With room correction switched in you compensate for a whole host of problems due to speakers and room. See here for some more details on DRC:
http://www.duffroomcorrection.com
I think about going for a Pioneer Elite TX56/Ax5-AiS + 2xUcd400 for mains.
If the quality is not good I'll go 5xUcD.
OK, I won't be using the amps in the receiver, but I don't care - for this money it's impossible to buy a processor with all the bells/whistles & quality found in the Elites.
I'm dreaming about Anthem AVM30 also, but that is so expensive.
I wonder if room correction is really something worth paying for?
Y
If the quality is not good I'll go 5xUcD.
OK, I won't be using the amps in the receiver, but I don't care - for this money it's impossible to buy a processor with all the bells/whistles & quality found in the Elites.
I'm dreaming about Anthem AVM30 also, but that is so expensive.
I wonder if room correction is really something worth paying for?
Y
Yves Smolders said:
Don't wonder. Do something about it...
The author of DRC (Denis Sbragion) reckons that with the latest (unreleased) version of his software he can EQ his system "flat" both in direct sound and also over the first 200ms in the reverberant field.
["Flat" in this context should be taken to mean "whatever target freq and phase response you would like".]
If that isn't totally mind blowing then I don't know what is....
Consider that the room probably adds 5-10dB of boost to various frequencies and you get the idea that the amp is not the weakest link in your hifi chain - probably either the speakers or the room are. You should try to use traditional room treatments as far as possible. Once you have reached the limits, then DRC style software takes over and does a pretty good job of improving your room.
In my case the imaging leaps out beyond the speakers. The image stabilises between the speakers. Instrument placement is suddenly very precise. Incredible bass!
So what's this got to do with a UCD amp anyway... Well I used to use a Meridian 557 power amp, and found that using room correction was "good", but tended to suck a little of the life out of the music. I speculated that the amp was not meaty enough for the job and was clipping to some extent. The UCD (and the Zappulse) have been extremely impressive and have really let the room correction filters shine through
Personally I rate room correction as one of the most important things to "buy". Speakers and a room are up their at number 1. CD player is at the bottom, and the amp is just something which is beefy enough to connect the room correction stuff to the speakers... Controversial, but impressive results.
Nearly all the big manufacturers are starting to think about room correction to some extent now. Expect to see basic stuff fitted as standard on all systems in 10 years time...