My New Crown XTi 1000s Are Here!!

[Erik Mandaville]

[]

[SWL]

I presently use XTI's to power my RF-7's. This weekend I will be checking out some RF-7's powered by 35wpc VRD's.

What differences can I expect to hear?.............seriously.

It's been four days now..........I wish I never went and listened to those damn VRD's.[:'(]

[Duke Spinner]

Fan ..Tastic ..

glad ta hear ya liked Craig's product ....[]

we are lucky to have Craig,, 'an MD ... here ..

'an ..

of course ... the Dukester, too .....[]

[jwc]

SWL

Please tell us more!

jc

[SWL]

Tomorrow I'm gonna try the XTI's bi-amped using the DSP for the first time........should be interesting.[*-)]

[Erik Mandaville]

"Power surges and ground bounce transients usually do more damage passing through a power stage to components beyond than damage to the power supply itself. Spikes and switching transients create energy up in the 1-2 mhz range and are best filtered by RFI/EMI suppression where power enters the equipment before it is rectified. Once this HF energy gets into any equipment, all bets are off as to damage, with CMOS devices being the most sensitive to this sort of damage, other SS devices right behind. Crown has EMI filtration on the XTI's power input."

Good point, although bets don't necessarily have to be off. If Crown doesn't install RFI/EMI filters on the AC input into the component, it is in fact possible to do that if one has access to the Hot, Neutral, and Ground legs of the AC line. The same can also be done on the high voltage secondary before it's rectified -- meaning on the AC rather than DC side. Simple brute force line filters can be made, the chokes for which quite easily wound by hand, and for more severe cases of overload, MOVs can be installed across the power transformer primary. I use them on all the amplifiers I've made. That Crown uses such suppression devices on the input is really not so uncommon; and depending on individual levels of present RFI/EMI, can be helpful -- they have for me in the past. I've also had reasonably good quality ripple filter capacitors run just under their rated working voltages for years without problems. Having some head room is of course never a bad thing; I'm just saying I haven't had problems due to overload of the kind/tolerance mentioned above.

For those who don't have this kind of electronic working ability, which would almost certainly void any warranty, there are an assortment of devices available that can be used.

Erik

[Erik Mandaville]

Moreover: As far as the filter section goes off the full-wave bridge, would it not be a correct assumption, considering that you have two capacitors in series with one another that are in parallel with the load, that the effective working voltage of that combination will provide double that of each single capacitor? Obviously the value of capacitance would be cut in half, but since the concern mentioned above had to do with the robustness of the power supply, maybe there is not such a cause of concern with respect to that aspect of the design. It also seems there has been some effort to equalize the voltage between the two capacitors.

Erik

[Erik Mandaville]

"I replaced them with high quality 50V caps just to be safe in case there WAS a power surge while I was using the amp."

Obviously didn't 'hurt' to do that. However, those series-connected capacitors comprised essentially a single cap that, as shown in the helpful schematic of the PSU, wasn't even seeing half of its rated voltage. It's obvious Crown knew what it was doing.

Erik

[Kudret]

Mark,

Is it possible to use those in tube amps as well? I have several of those and could put them in my SETH.

RFI/EMI protection certainly isn't the special province of pro equipment. I was using these in preamp power supplies 4 years ago.

Kudret

[Don Richard]

You have to select them based upon the AC power drawn. The one I show there is a Qualtek # 858-01/003 rated at 1A/120V. They make much larger ones in 3A, 5A and perhaps higher too. As a "rule of thumb" use the rating of your fuse as a guide. If you have a 3A fuse, use a 3A filter, etc. There are many brands, price levels, sizes etc.

Using these on vacuum tube gear should make such gear nearly immune to damage from surge and transients.

Don

[Kudret]

Thank you, Mark.

Kudret

[SWL]

I presently use XTI's to power my RF-7's. This weekend I will be checking out some RF-7's powered by 35wpc VRD's.

What differences can I expect to hear?.............seriously.

It's been four days now..........I wish I never went and listened to those *** VRD's.[:'(]

Careful there Scott- - it's addictive.

Tell me about it!!

[NOSValves]

I just hope he gets there before more hearing damage acures.......[]

[SWL]

Uh........wut?

[NOSValves]

A joke... that is what the [] is for.

To me listening to a pro amp like the Xti would be painful.

[SWL]

A joke... that is what the is for.

To me listening to a pro amp like the Xti would be painful.

I was joking as well..............as in my hearing may already be shot!! []

[SWL]

As far as my XTI system goes.........I think I'll be ok.........just as long as I don't listen to any more tubes.[]

My Peach sure is getting lonely in my second system though............Did I just say that?[]

[Cut-Throat]

"BTW, have you directly compared your XTi to the D-series amps?"

I'm not Don, but I'm working on it.

Dean,

I might have missed something, but I see your XTi's up for sale on Audiogon. Did you prefer the D45 amp?

Also totally unrelated crossover question -- If I was to attenuate my Modified Type 'A's from -6 db to -9 db - Would I keep the swamping resistor at 15 ohms, or would I have to do something else? - Or am I asking something with too complicated an answer?

[Erik Mandaville]

Mark:

I would have actually done the same as you regarding the voltage tolerance of those caps. I was just pointing out that there have been times in the past where capacitors I was using in power supplies were operating for years at very near their max rating without any problems or failure.

On that ground connection: There are a few power supplies in the past I've seen where that common node was intentional as a way of sort of balancing out the voltage between the two capacitors. What I remembered later about those was that I think there were very high values of resistance in a circuit associated with that connection that maintained the advantage of the doubled power rating of the series connected capacitors. My dad confirmed that, as well. He said he's seen this on some sort of test equipment (or some such 'thing') he made.

You are right on the capacitor relationship/connection, and I stand totaly corrected on that.

I wanted to respond to the picture you posted of the integrated line filter on one of your components. That is exacty one of the devices I was referring to in the post above. Suppression takes place immediately -- a point the other contributor to this (I can't remember his name right at this moment) made as well. However, even if the XTi doesn't have EMI/RFI/transient filters on the AC supply, there are still things people can do to take care of the problem -- if there is a problem. It doesn't have to be a 'throw your hand's up in the air' and quit sort of syndrome.

Erik

[Erik Mandaville]

I mentioned a small filter on the AC high voltage secondary, and the following picture indicates that. Note the two high voltage film caps connected between the AC side to the star ground.