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CVR AMPS (AGAIN!) |
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Earplug 
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Joined: 03 January 2012 Location: Europe Status: Offline Points: 7752 |
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 Topic: CVR AMPS (AGAIN!)Posted: 13 January 2026 at 12:50pm |
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Some guys I know that run a sound system here went & splashed out on a few CVR amps a few months ago. They have:- 1 x D-1502 1 x DSP 3004 1 x DSP 3304 They've had a few problems, so brought them here for me to take a look. I've done a bit of poking around & basic scoping of the outputs, etc. My initial impression is that the outputs are horribly dirty, with a lot of residual oscillation coming through & the outputs not tracking the input that well.  Is this normal with these amps, or have these guys been very unlucky? |
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Earplug
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Posted: 14 January 2026 at 9:21am |
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I've also noticed a slight "clicking" noise coming from the SMPS transformers on the DSP 3304. Is that common? |
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snowflake
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Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3443 |
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Posted: 14 January 2026 at 5:01pm |
that's normal apparently but can't say i've noticed it on the four channel models I have. |
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Earplug
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Posted: 14 January 2026 at 5:16pm |
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Ok. I thought so, but the owners are worried. They are thinking about asking for a replacement, but bought in China, so good luck on that one. I'm not sure how much of a guarantee they'll have there. And it is very slight. Hardly noticeable, especially if the fans are running. |
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snowflake
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Posted: 15 January 2026 at 8:59am |
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interested in your comments about oscillation - how bad is it, and is it above the audio band?
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Earplug
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Posted: 15 January 2026 at 9:22am |
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Ok. Like I said, a slight clicking, almost like a relay that isn't engaging properly. Before opening the amp, I actually thought that it may be a relay, but obviously not. It is very quiet, almost unnoticeable, especially when the fans kick in. The owners have contacted the seller to see what they say. I no longer have the amps as the guys needed them for the weekend. I'll let you know if there are any comments from China... EDIT:- Oh yeah - my advice to the guys was to sell the amps & try get something better. They would obviously love to buy some Powersoft, but beyond their budget. Funnily enough, there are a few heavyweight Crests (MA5850's & CA's) on sale on one internet site here. They would be a lot better for them, but obviously weigh a lot more... Edited by Earplug - 15 January 2026 at 9:29am |
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jacethebase
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Joined: 23 September 2009 Location: Somerset Status: Offline Points: 5837 |
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Posted: 15 January 2026 at 12:38pm |
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I have loads of VZ5002’s left! Send them my way.
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www.wedding-production.co.uk
www.stage2sound.com |
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Earplug
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Posted: 15 January 2026 at 2:03pm |
I image that they would be interested - but import tax & courier would be a PITA -- unless you want to come down for a holiday!!  |
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snowflake
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Posted: 15 January 2026 at 2:09pm |
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consensus seems to be that the ticking noise is the PFC circuit operating. Did your scope measurements of the output show up any other problems?
"the outputs are horribly dirty, with a lot of residual oscillation coming through & the outputs not tracking the input that well." |
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Earplug
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Posted: 15 January 2026 at 3:38pm |
Ok. The outputs were bad. I can't remember which amp it was, but I was getting over 2.5v of oscillation at around 250kHz on one, but all had substantial residuals and some ugly wave forms when pushed. "Pulsing" a sin wave though them showed a lag in the output, i.e. the rails were collapsing a lot when pushed. Also, the 2 DSP models did have some phase shift, but I really didn't have the amps here long enough to do much more. The main problem was that the guys were getting shocks off the racks! I traced that to a bad lead on their distro, no problem! Edited by Earplug - 15 January 2026 at 3:39pm |
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kedwardsleisure
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Posted: 15 January 2026 at 5:15pm |
That's not going to push much current through a speaker voice coil at that sort of level! |
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Kevin
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snowflake
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Posted: 15 January 2026 at 11:13pm |
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I'm no expert but if there is a 12dB/oct output filter at about 50khz then at 250kHz it will be about 20dB down from the peak RMS voltage of the 3302 of 162.5V.
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Earplug wrote: