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Subwoofer plate amplifier for Velodyne sub


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Hey guys. I've been a member for a long time but I've not visitited the forum since my first registration - I can't even remember why I originally created an account. 

A couple of days ago I realised my Velodyne CT100 sub was active but producing no sound. I've been testing different configurations (AV amps, settings, cables, etc) and have concluded that the plate amp is the likely culprit (it lights up but no signal seems to be getting to the driver). 

I'd consider replacing it (after 19 years) but I just finished building a hardwood cabinet with a specifically sized space to house it.

So I'd like to get it up and running again. 

I'll give a local speaker repair place a call tomorrow to see what they can do, but like to explore my options. 

My first guess is that the amp inself isn't an economic repair. I can't see any sign of obviously bulging caps. Does anyone have any thoughts on the viability of having the amp itself repaired? Given its age, I assume replacement boards aren't going to be available from Velodyne. 

Presuming the speaker repair place recommends replacing the amplifier, is there anything specific I should be asking for? I've seen the Dayton SPA250 discussed (the original amp is rated at 150w at 8ohms) so 250w should be adequate. However, it seems to have some potential flaws - a turn on thump and interference hum (I'm using a shielded coaxial cable so perhaps that will prevent the hum?). Are there alternatives I should also be looking at?

The sub is mostly used for home theatre these days, but musicality was the original reason for choosing the Velodyne. I'd like to ensure I replace the amp with something that maintains a similar quality as I'm used to from it.

Thanks,

Tristan

 

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10 hours ago, hopefullguy said:

have seen the ct100 come up a few times on gumtree/ebay over the last couple of years. can pick them up around $150-250.

 

too bad your not in NSW.. https://www.gumtree.com.au/s-ad/lidcombe/home-theatre-systems/velodyne-ct-100-subwoofer/1235550820

 

Thank you. I'm going to get in touch with the seller and see if he'll consider shipping - even if it's just the amp module. 

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10 hours ago, JohnL said:

If you think the cost is worth it............

 

https://www.ebcelectronics.com/velodyne-ct-100-Repair-Service.html

 

It was for my HGS 15........saved myself $1K

 

Otherwise an upgrade is probably better bang for buck.

Definitely worth the cost of repair - but is it worth the cost of 2x international shipping? I'll look into it. Thank you. 

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The circuit on the CT100 is fairly simple compared to the modern SMPS and Class D amplifiers of today .Any good tech should easily repair it .Common faults will be dry joints and dryed up electros .  

Replacing plate amplifiers on subs with after market types is never completely successful as there is some equilization applied to the original circuit to compensate for cabinet size .

 

 

 

 

 

 

 

 

 

 

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On 28/01/2020 at 9:26 AM, mavi said:

The circuit on the CT100 is fairly simple compared to the modern SMPS and Class D amplifiers of today .Any good tech should easily repair it .Common faults will be dry joints and dryed up electros .  

Replacing plate amplifiers on subs with after market types is never completely successful as there is some equilization applied to the original circuit to compensate for cabinet size .

 

 

 

 

 

 

 

 

 

 

I asked locally too and revived a couple of recommendations for a local speaker builder/repairer. I called him up to discuss and delivered the sub to him this morning. He's going to go through the amp checking caps and resisters to ensure they're all within spec and check for dry joints etc. I'll see how he goes. 
Thanks all for your suggestions. 

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The speaker repair guy just called. He found a number of caps that were no longer functional. He's been through and replaced some and put in temporary caps (too big physically) of the right value elsewhere. It's now working as it should and he's placed an order for some correctly sized caps. 
The only issue he's unsure of is the auto-switching. He's not sure how long it should be without a signal before it turns itself off, but hasn't observed that happening yet. Unfortunately that area of the board is covered in hot glue which makes it difficult to test relevant components. 
If it doesn't auto-switch I'll live with that and perhaps find a method to have my harmony remote a switch on its power supply.

He said $100, so I'm well pleased to get it back in action for so little. 
 

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@tritto perhaps worth posting at one stage who the local speaker repair guy is. probably of value to other tassie folk who might fall in same predicament perhaps in the future some time.

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1 hour ago, tritto said:

If it doesn't auto-switch I'll live with that and perhaps find a method to have my harmony remote a switch on its power supply.

 

I have a master/slave power board which allows other components to automatically switch on when my HT receiver switches on (the subwoofer and a few fans in the equipment shelving). There are many stories of the lifespan of subwoofer plate amps being greatly reduced through being left in 'stand-by' or 'auto-switch' mode, whilst using my approach achieves the same result without the accelerated wear on electrolytic capacitors.

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On 30/01/2020 at 4:36 PM, pete_mac said:

There are many stories of the lifespan of subwoofer plate amps being greatly reduced through being left in 'stand-by' or 'auto-switch' mode

Thanks for the tip - just went and turned both my plate amps to "off" on the sub...

 

Now I've just got to remember to turn them back on :)

 

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Good news. Arthur called to say the amp repair has been completed. $110 all up. 
he couldn't sort out the auto-switch function for a couple of reasons - it was covered in hot glue and he couldn't get a circuit diagram for it. I'll see if I can source a master-slave board as suggested by @pete_mac
Thanks for all your suggestions. I'll post again when I've picked it up and dialled it in. 
Cheers,

Tristan

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On 30/01/2020 at 5:12 PM, tritto said:

Good idea @betty boop. He's Arthur Francis Audio Speakers in Lindisfarne.  No website be he comes up on google. He works from his garage!

Damn, this guy has been around forever, think I visited him 20+ years ago, very knowledgeable

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16 minutes ago, swervyn said:

Damn, this guy has been around forever, think I visited him 20+ years ago, very knowledgeable

He's pretty good. Called me after a few days to let me know he had it running but needed to order parts. I expected another week or two to get the parts in, but the whole job has taken less than a week. 

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3 hours ago, tritto said:

 I'll see if I can source a master-slave board as suggested by @pete_mac

 

Tristan, this one looks to be good quality and reasonably priced:

 

https://www.ebay.com.au/itm/Embertec-Smartswitch-Standby-Power-Controller-for-PC-/122821631791?_trksid=p2349526.m4383.l4275.c10#viTabs_0

 

 

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13 hours ago, pete_mac said:

Thank you. I had seen the embertec, but only the AV version. The AV version is not a true master/slave switch because it actually relies on picking up regular use of an IR remote to remain on. I had rejected that as unsuitable. 
The PC version that you've linked appears to be a proper master/slave. I've purchased it and will report back on how it goes. Cheers. 

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12 minutes ago, tritto said:

Thank you. I had seen the embertec, but only the AV version. The AV version is not a true master/slave switch because it actually relies on picking up regular use of an IR remote to remain on. I had rejected that as unsuitable. 
The PC version that you've linked appears to be a proper master/slave. I've purchased it and will report back on how it goes. Cheers. 

 

Yes, I was a little confused myself at first, but the instructions clarified the differences.  The PC version should do the job nicely! Looking forward to your feedback.

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I picked up the subwoofer on the weekend and it's been great to have some proper bass back in the system. I highly recommend Arthur's services. 
Only one issue remained outstanding - Arthur was not able to repair the circuit that switches on the subwoofer when it detects a signal from the receiver and off 15 minutes after a signal is no longer detected. The sub was on regardless of the signal status. 
As suggested by @pete_mac, I purchased an Embertec SmartSwitch PC. Total shipped cost was about $22. 
it has one master and one slave socket. I have installed it and everything seems to be working as it should. Receiver on and the subwoofer comes on. Receiver off and the subwoofer goes off after about 1:30 minutes. The SmartSwitch has a handy LED that shows if it's on or off. First impressions are that it's fit for purpose. Clap clap. 

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  • 2 weeks later...

Not so good news to report. The SmartPC is not fit for this purpose. 
When my amp is on but resting (between albums perhaps) it’s not drawing enough current to keep the SmartPC from turning off. That would be ok but starting a new album or show doesn’t draw enough current to switch on the slave plug and therefore the Sub. Back to square one. 

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57 minutes ago, tritto said:

Not so good news to report. The SmartPC is not fit for this purpose. 
When my amp is on but resting (between albums perhaps) it’s not drawing enough current to keep the SmartPC from turning off. That would be ok but starting a new album or show doesn’t draw enough current to switch on the slave plug and therefore the Sub. Back to square one. 

 

Bugger - what a shame! Sorry to hear that. The Jaycar master/slave board which I use works perfectly in this application. It's a shame that they are no longer available.

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There are a few master-slave boards still available online, although they tend to be referred to as energy saver boards.

A couple indicate the level of consumption from the master device needed to trigger the slave socket - around 30-35w. The SmartPC doesn't indicate the necessary consumption.

I guess the first step is to buy or borrow an energy consumption meter to see exactly the amp is drawing when being lightly driven or when it is on but silent so that I don't just keep buying master-slave boards that have too high a consumption threshold. That could get expensive paying out $20-$30 for each one plus postage.

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So, I found a couple of master-slave boards online (they’re usually referred to as energy saver power boards) and a couple that indicate they’re switched at about 30-35w of power being consumed by the master device. 
In order to buy with certainty, I borrowed a home energy audit kit from my local council, which includes a power meter. 
When the amp is turned on it peaks at around 70w for a moment, then settles in at around 43w. With tv a low volume that’s where it stays. With tv at our regular volume it sits around 48w. I suspect the SmartPC must be switched at around 45w. The turn on peak was enough to activate the slave, but depending on volume, the power draw wasn’t enough to consistently keep the slave activated..

I’ve ordered a board that’s quoted as switched at 35w. Hopefully that works better. 

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