Welcome, Guest. Please Login or Register
Decware Audio Forums
11/22/14 at 21:47:31


Pages: 1
Send Topic Print
delayed connection of outputs (Read 887 times)
mma
Verified Member
**




Posts: 8
delayed connection of outputs
07/29/13 at 16:01:19
 
I am using my SE84 amp as the top end to a biamp setup, and I am using a MiniDSP crossover.

In order to keep this system from popping badly, I have been sequencing the turn on of the various components manually.  

However, to return the operation to a one-button turn on/off approach, I have built two Vellman speaker relays, and plan to use these to strictly provide a 6 second delayed connection of the amplifier outputs to the speakers.

This is intended for both the SE84 and the MOSFET amp I am using for the bass section.

The Vellman kits provide load resistors for when the relays are open, but advise to not use these for amplifiers that are set up for split supply.

I would like to simply use the relays to open and close the (+) lines of the amplifiers (both the SE84 and the MOSFET) to the speakers.  The delay, as I said, is 6 seconds.  This is well before the output tubes begin conducting, from a cold turn on.

Will this work and be safe for the amps, or should I consider another way of sequencing the turn on?

Thanks!

Mike
Back to top
 
 
  IP Logged
dank
Seasoned Member
****


pair of dual 18
Imperials

Posts: 275
Re: delayed connection of outputs
Reply #1 - 07/30/13 at 02:01:37
 
Mike

Tell me a little more about your setup and maybe I can help.  I'm not too interested in make/model just function.  I assume there are two stereo amps, the Zkit1 (SE84) and another solid state (mosfet) amp.  Is the miniDSP crossover between the source and the two amps, feeding the (L & R) highs to the Zkit1 and the (L & R) lows to the mosfet amp?  Do you then have 4 speakers: one L hi, one L low, one R hi, and one R low?  Would "each speaker relay" then be able to switch both the hi and low speaker on one side (double pole)?

What power up sequence do you have to follow now to prevent the loud pop?  Where is the pop coming from, the mosfet amp connected to the two speakers you are using for the lows?

Dan
Back to top
 
 
  IP Logged
mma
Verified Member
**




Posts: 8
Re: delayed connection of outputs
Reply #2 - 07/30/13 at 13:55:09
 
Dank:

You have it pretty much right.  The MiniDSP is a two channel, 4 output digital crossover, and the preamp outputs go into it, and the four outputs drive (2) woofers (bass horns) and (2) tweeter horns.

I am using Vellman K4700 'speaker protectors' that provide two functions: one is delayed turn-on via relays (I have two of these units, for a total of 4 relays).  The relays sit between the amplifier and the drivers.  The second function is to prevent DC from reaching the drivers.  I do not use this function, but rather, am only intending on using the relay contacts themselves.

The reason I have gone this direction is that the power up of this system is at present, too complicated for my wife to deal with on a regular basis (and truth be told, annoying to me, too, to have to follow each and every time).  The problem surrounds the MiniDSP powering up and then powering off, and the transients that come through to the amps.  Good sized pops on all four drivers.  Sometimes good enough to dislodge pictures from my walls.

My concern is that, in the arrangement I have conceived, all four amplifier channels (2 on the SE84 and 2 monoblock Mosfets ) are coming on with no load for approximately 6 seconds, after which the relays close and the loads are applied to the amplifier outputs.  This gives ample time for the MiniDSP to boot and become stable.  And, the SE84 does not really produce output for many seconds after that (owing to tube warmup).

I just don't want to damage the amps when they start under no load, even if it is only 6 seconds.

I may use the relays to switch SCR relays to apply the AC to the amps- this will used the K4700's to now sequence the power on/off instead of connecting the loads.  However, I still would like the MiniDSP to be the last guy off in the chain, delayed by as much as 15 seconds (to give the SE84 time to leak down).

I have also considered gin-ing up a microcontroller sequencer that does this (delayed power on for the amps, delayed turn off for the minidsp).  That would solve the whole matter, but would take a bit more time to conjure.

Thoughts?

-M
Back to top
 
 
  IP Logged
mboxler
Senior Member
***




Posts: 85
Re: delayed connection of outputs
Reply #3 - 07/30/13 at 14:28:59
 
Hi Mike

Glad I caught your thread.  I'm experimenting with a similar setup, but using Marchand XM1 boards.  I, too, have to turn on the XM1's first, and last, to prevent a massive POP.  Fortunately, I have everything hooked up to a power conditioner the has delayed outlets with 5 second delays.  I was considering the MiniDSP to be able to delay the signal to the high amp (I have Klipshorns, and the bass lags the top end).  Didn't realize the MiniDSP took a while to boot up, although that makes sense.

Sorry for the rambling.  Can the MiniDSP's be left on 24/7? That is an option I have with the XM1's.  No pops if left on all the time.

Thanks, Mike
Back to top
 
 
  IP Logged
mma
Verified Member
**




Posts: 8
Re: delayed connection of outputs
Reply #4 - 07/30/13 at 14:44:30
 
Mike:

I recognize your name from the Klipsch forums.  My bass section is Klipschorn (actually, Speakerlab factory builds of their K, with K-33E drivers).  My tweeter section is Altec 288 + EV HR6040 CD.  I cross at 350, and use the Le Cleach configuration.  Extremely satisfied with this setup, never looked back.

I don't know if the MiniDSPs can be left on 24/7.  I don't see why not, but I suppose one would need to test this out.  You are right, this would solve the issue.  Maybe I need to think that one through a bit more.

I know Furman sells a sequencing power conditioner (pretty expensive, though, for what it does, at least for my tastes) that probably would do what I need.

This on/off sequencing problem (general problem of active crossovers, esp. digital) is one of two that plague the active crowd.  The second one is how to do the gain when multiple amps are in use.  I've seen some pretty exotic setups all working to provide a single volume control for things like the behringer 2496 series crossovers, for example.  The MiniDSP does this with one pot, and that is nice.

Power sequencing, though, continues to vex.  Thanks for the creative tip!

-M
Back to top
 
 
  IP Logged
dank
Seasoned Member
****


pair of dual 18
Imperials

Posts: 275
Re: delayed connection of outputs
Reply #5 - 07/30/13 at 22:43:21
 
I don't know of any amp built today that will be damaged if run with the speakers disconnected.  I have heard, but have not experienced, that some poorly designed tube amps had this problem way back when and that's where the rumor that amps could be damaged when run without a load started.  You should have no problem with a 6 second delay.  

That said, if it were me I'd nix the in-line speaker relays and build the power on sequencer controlling the power to all the various parts of your system.  Ever use a Picaxe processor?  They are VERY easy, VERY cheep, and quite powerful.  I've built half a dozen little Picaxe boxes that I use around the house for a variety of functions.  In addition to switching a relay to get switched power they are very good/easy at temperature and IR remote...So you could easily turn your sequencer on/off with a universal remote set to Sony codes.


Dan
Back to top
 
 
  IP Logged
mma
Verified Member
**




Posts: 8
Re: delayed connection of outputs
Reply #6 - 07/31/13 at 02:32:52
 
Dank:

Thanks for the comments- I was suffering from the old tales (evidently, as you point out) that tube amps, left unloaded, were susceptible to damage.  I figured the Mosfet amp would tolerate 6 seconds.

Never-the-less, I do like the power sequencing better than the speaker switching.  I have not used Picaxes, but have used AVRs and my favorite, because it is so simple to program and deploy, Propellers, in many projects.  I figure to either do a quick n dirty propeller based power sequencer, or find a Furman PS-8R on Ebay.  Probably the latter, if I can find one at a decent price.

-M
Back to top
 
 
  IP Logged
Pages: 1
Send Topic Print