[TechAssist] Re: 70 volt line audio amp
- From: "Damon" <damon101@xxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sat, 30 Apr 2005 08:37:21 -0500
Jim is right....the 2nd test after the music test should be the mike/aux
input checks.....that phone line could be hooked up to the wrong style of
input.....just be sure to use the 2 prong adaptor test first and foremost
with PA amps.
Damon Brunger
Telrad Electronics
Fort Wayne IN
----- Original Message -----
From: "becyn" <becyn@xxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Friday, April 29, 2005 12:39 PM
Subject: [TechAssist] Re: 70 volt line audio amp
> Mark,
> As a matter of practicallity, I personally never found some open/short
> condidtion
> down the line to be the problem (although a dead short on a tap seconday
> could do it).
>
> Did you try the mike instead of the output from the phone sys?
> Also, you need to use a lower gain "aux" input instead of the the high
gain
> mic input, otherwise the input will be overdriven.
> There may me some mismatch at the front end causing the distortion.
> Something about all this just doesn't ring true...sorry ;-)
>
> Jim McVey
> McVey Alltronix
> 327 Broadway
> Newburgh N.Y. 12550
>
> "If it doesn't play...
> CALL MCVEY !!!!!!"
> Factory authorized
> service for over 20
> major brands.
> 845 561 8383
> (Last of the Mohegans)
>
> markbrock wrote:
>
> >Yes Jim, I'm hooking up to the 70 volt line port. these amps have a
remote
> >feature, the phone is used as a paging system, this amp is to drive the
> >speakers on the lot and in the shop and wash basin and paint booth and
show
> >room, ( car agency ), there is an auxiliary control for back ground
music,
> >cd, tuner, etc, the phone company controls the music on hold through a
> >different system, this is just for PA purposes only,
> > now back to the original question and I agree with J Silverman,
these
> >systems can be checked with an ohm meter, and 70 ohms is too high,
there's
> >and open tap somewhere, 15 foot on the ceiling I suspect to find an
> >impedance matching transformer, ( like peavey builds ) where you can
> >basically hook up a short or what ever but right before the amp sees it
its
> >isolated by a large transformer, and I strongly suspect when the output
> >shorted and the filter caps blew, it crammed dc directly into this
> >transformer and opened the primary, I'm probably getting enough leakage
> >through it from the eddy urrents that fly around the outside of the 70
volt
> >signal. thats my best guess I'll see Sunday when I tear up the ceiling
of
> >those nice offices and make my accent to the roof..... man I can't wait.
> >I'll let you all know. thanks for the help so far.
> >brock
> >
> >
> >Brock Electronics
> >R.R.4 box 237
> >5208 cr.3385
> >Independence Ks. 67301
> >620-331-0235
> >fax 331-7191
> >
> >markbrock@xxxxxxxxxxxxx
> >Zenith*Philips*Peavey*Fender*Crate
> >we work on all brands,makes,models
> >of anything that plugs in the wall
> >----- Original Message -----
> >From: "becyn" <becyn@xxxxxxxxxx>
> >To: <techassist@xxxxxxxxxxxxx>
> >Sent: Thursday, April 28, 2005 5:26 PM
> >Subject: [TechAssist] Re: 70 volt line audio amp
> >
> >
> >
> >
> >>I'm going to ask a stupid question.
> >>Does the "new amp" have a 70v port output?
> >>If you are hooking up an 8 ohm system to the 70v ,
> >>you will have a MAJOR impedance mismatch.
> >>Essentially, the 70 v is the audio version of the power grid.
> >>Step up the voltage( reduce current) to send long distances in order to
> >>reduce
> >>I^2 *R losses.
> >>
> >>Jim McVey
> >>McVey Alltronix
> >>327 Broadway
> >>Newburgh N.Y. 12550
> >>
> >>"If it doesn't play...
> >>CALL MCVEY !!!!!!"
> >>Factory authorized
> >>service for over 20
> >>major brands.
> >>845 561 8383
> >>(Last of the Mohegans)
> >>
> >>J Silverman wrote:
> >>
> >>
> >>
> >>>70 ohms of resistance sounds high. Amps work into impedance, which is a
> >>>dynamic reflection of the load. DC ohms resistance should be much lower
> >>>
> >>>
> >than
> >
> >
> >>>the impedance number. Since that is a 70 volt line output, the DC load
is
> >>>just the resistance of the transformer windings.
> >>>Jerry Silverman
> >>>Greentron Inc
> >>>4 Newland Ave
> >>>Greenville SC 29609
> >>>Fax/Phone 864 232 3889
> >>>mail to: greentron@xxxxxxx
> >>>----- Original Message -----
> >>>From: "markbrock" <markbrock@xxxxxxxxxxxxx>
> >>>To: <techassist@xxxxxxxxxxxxx>
> >>>Sent: Thursday, April 28, 2005 2:43 PM
> >>>Subject: [TechAssist] Re: 70 volt line audio amp
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>>brand new amp, works fine with one speaker and a mic, on the bench,
but
> >>>>when attached to the phone system, has distortion, I tried to blame
it
> >>>>
> >>>>
> >on
> >
> >
> >>>>the phone co because if I disconnected them it worked ok with one
> >>>>
> >>>>
> >speaker,
> >
> >
> >>>>no there pointing back at me, I need more ammo before I go further,
> >>>>
> >>>>
> >wish
> >
> >
> >>>>
> >>>>
> >>>I
> >>>
> >>>
> >>>
> >>>
> >>>>had a spare amp to try out. old amp has blown output ic and one of
the
> >>>>
> >>>>
> >>>>
> >>>>
> >>>two
> >>>
> >>>
> >>>
> >>>
> >>>>filters popped its lid, I was just wondering if this 70 ohms of
> >>>>
> >>>>
> >>>>
> >>>>
> >>>resistance
> >>>
> >>>
> >>>
> >>>
> >>>>was going to be way off base , but apparently doesn't surprise
anybody
> >>>>
> >>>>
> >>>>
> >>>>
> >>>yet,
> >>>
> >>>
> >>>
> >>>
> >>>>so I'll go a little farther.
> >>>>Brock Electronics
> >>>>R.R.4 box 237
> >>>>5208 cr.3385
> >>>>Independence Ks. 67301
> >>>>620-331-0235
> >>>>fax 331-7191
> >>>>
> >>>>markbrock@xxxxxxxxxxxxx
> >>>>Zenith*Philips*Peavey*Fender*Crate
> >>>>we work on all brands,makes,models
> >>>>of anything that plugs in the wall
> >>>>----- Original Message -----
> >>>>From: "becyn" <becyn@xxxxxxxxxx>
> >>>>To: <techassist@xxxxxxxxxxxxx>
> >>>>Sent: Thursday, April 28, 2005 9:43 AM
> >>>>Subject: [TechAssist] Re: 70 volt line audio amp
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>Divide and conquer !
> >>>>>
> >>>>>Have you bench tested the amp with a 1Khz sine?
> >>>>>It sounds more like the amp than the line.
> >>>>>Many of those mutiple speaker setups have the taps set for a
> >>>>>watt or less, so underpowering isn't an issue.
> >>>>>
> >>>>>Jim McVey
> >>>>>McVey Alltronix
> >>>>>327 Broadway
> >>>>>Newburgh N.Y. 12550
> >>>>>
> >>>>>"If it doesn't play...
> >>>>>CALL MCVEY !!!!!!"
> >>>>>Factory authorized
> >>>>>service for over 20
> >>>>>major brands.
> >>>>>845 561 8383
> >>>>>(Last of the Mohegans)
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>markbrock wrote:
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>>>ok, whats the limit of resistance I can have at the amp using a 70
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>volt
> >>>
> >>>
> >>>
> >>>
> >>>>>>line, I have around 70 ohms, unit is very distorted, 40 watt
system
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>about
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>15 speakers, old unit burned up, they bought a new one and its all
> >>>>>>distorted, then they called me, I figured someone hung a regular
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>speaker
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>on the line but that would be closer to 16 or less ohms, is 70 ok
?
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>they
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>>>may be under powered but it worked fine for 10 years previous.
thanks
> >>>>>>brock
> >>>>>>
> >>>>>>Brock Electronics
> >>>>>>R.R.4 box 237
> >>>>>>5208 cr.3385
> >>>>>>Independence Ks. 67301
> >>>>>>620-331-0235
> >>>>>>fax 331-7191
> >>>>>>
> >>>>>>markbrock@xxxxxxxxxxxxx
> >>>>>>Zenith*Philips*Peavey*Fender*Crate
> >>>>>>we work on all brands,makes,models
> >>>>>>of anything that plugs in the wall
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
>
>>>-------------------------------------------------------------------------
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