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Stage PA Amp 101 question

Member for

4 years 3 months
I have a stereo amplifier. It's a really powerful Ashly that is nice sounding. (Not really important to this topic). Being that it has two channels, can I run a mono mix to front of house (two speakers only @ 8 ohms) on one side of the amp. .And run stage monitors on the other channel ? I have a sneaky suspicion its ok as long as my ohm load is equal on both channels. Or, am I wrong. The amp will handle different loads, I know this. Here is my situation. A friend gave me a stage wedge (15" peavey, 8 ohms). I only have one amp right now. So, what I want to do is run the FOH in parallel at 8 ohms on one side and run a single wedge 8 ohms on the other side. I'm sure this is an annoying stage amp 101 question for most of y'all. So, I apologize for my level of novice knowledge. Will this mismatching of speakers on the two different channels harm my amp ? Are there other imperative reasons why two totally separate amps would be required ? Of course, that is my ultimate goal for later. I just don't want to burn up the only amp I have. Thanks.
MPBWY

Comments

Member for

15 years 7 months

Boswell Thu, 08/17/2017 - 03:03
Most powered PA mixers have switches that allow you to do exactly what you describe: use one channel for FOH and the other for foldback monitors. Solid-state amplifiers, unlike their valve counterparts, do not usually need defined loads. Since the power output stages are normally independent, you can load either or both amplifiers with what you like (down to the minimum specified), so 8 Ohm on one channel and 4 Ohm on the other should be straightforward.

You don't state which model of Ashly amplifier you have, so I can't usefully check if there would be additional problems. Assuming that your model is specified for driving low-impedance speakers directly rather than through 100V transformers, it's unlikely that there would be. The only problem I could imagine would be if your Ashly is one of the older models that were primarily for domestic hi-fi use and did not relish being used as a PA amplifier.

Member for

16 years 9 months

moonbaby Thu, 08/17/2017 - 10:41
Bos,
Having owned I don't know how many Ashly products since 1977, I was unaware that they ever made a home hi-fi amplifier. The first amps I saw them release were the FET series which were about as heavy-duty as anything on the market back in the early 80s. And they weighed a TON!!!

Member for

15 years 7 months

Boswell Thu, 08/17/2017 - 11:12
The reason I mentioned them is that I had a friend many years back who had an Ashly power amp in his hi-fi setup. I remember giving his gear a quick once-over, but didn't pay too much attention to the amp, although I do recall it having binding-post terminals for the speakers. It was the first Ashly product I had seen, and I suppose it's possible that it was one of their lower-end PA amps unofficially modified for home use. My friend had bought it from a US Serviceman on one of the air bases, as I don't think Ashly had a UK dealer back then.

Member for

16 years 9 months

moonbaby Tue, 08/22/2017 - 11:59
What made it "unofficially modified for home use"? Here in the US, states' electrical and installation codes required binding posts (for banana plugs) for power amplifiers. I believe that anyone - Crown, BGW, Yamaha, UREI, even Peavey - who built "commercial sound" amplifiers was required to provide them. They were also spec'd by the FTC (Federal Trade Commission) in their guidelines for measuring RMS output specs of "commercial power amplifiers" in a famous ( at least here in the States) legal ruling. Anyway, Ashley's FET series amps were the first Lucas/THX-approved power amps on the market. Mine were bullet-proof and clean as a whistle...as clean as my McIntosh 2105 home stereo amps.

Member for

15 years 7 months

Boswell Tue, 08/22/2017 - 15:19
moonbaby, post: 452224, member: 22944 wrote: What made it "unofficially modified for home use"?
It's what my friend said the previous owner had done! Exactly what it entailed I do not know. My memory was that we we fighting a putative loudspeaker phasing issue at the time, and having to reverse the speaker leads many times at the amplifier was a lot easier with binding post terminals than with the soldered non-reversible Bulgin connectors that I had on one of my amps of that era.

Member for

16 years 9 months

moonbaby Tue, 08/22/2017 - 16:01
Man, it's amazing how different something as simple as a power amplifier can be so different on one side of the pond from the other side! I don't believe that those are used over here (although Neutriks are these days and they look similar). Those must have been a real pain in the tuckus to swap around!
Sometimes us Yanks have a better idea :)
Peace.

Member for

9 years

DonnyThompson Wed, 08/23/2017 - 03:07
Boswell, post: 452226, member: 29034 wrote: It's what my friend said the previous owner had done! Exactly what it entailed I do not know. My memory was that we we fighting a putative loudspeaker phasing issue at the time, and having to reverse the speaker leads many times at the amplifier was a lot easier with binding post terminals than with the soldered non-reversible Bulgin connectors that I had on one of my amps of that era.
Interesting.... So were you getting speakers with internal connections being reversed? Sounds similar to that time period when UK mic cables were wired differently (pin hot) than US-made cables?

Member for

15 years 7 months

Boswell Wed, 08/23/2017 - 04:45
DonnyThompson, post: 452230, member: 46114 wrote: Interesting.... So were you getting speakers with internal connections being reversed? Sounds similar to that time period when UK mic cables were wired differently (pin hot) than US-made cables?
These were speaker cabinets that he had built himself and fitted with bought-in drive units. As I remember, what we eventually found was that the problem was due to the red dot on the terminals of one of the drivers signifying pull rather than push. Once we had established that using a 1.5V battery and chocolate biscuit suspended on a piece of cotton to detect the motion, we got the whole speaker system phased up correctly. Why the chocolate biscuit? We had been having a cup of tea with a pack of biscuits, and it turned out the teaspoons were magnetic and didn't give reliable results when suspended close to a drive unit. Obvious, really.

Member for

4 years 3 months

Raymond Wed, 08/23/2017 - 06:35
moonbaby, post: 452158, member: 22944 wrote: Bos,
Having owned I don't know how many Ashly products since 1977, I was unaware that they ever made a home hi-fi amplifier. The first amps I saw them release were the FET series which were about as heavy-duty as anything on the market back in the early 80s. And they weighed a TON!!!
That's what I have. The FET type with the huge toroidal transformers in it. Yes, it is ridiculously heavy.

Member for

7 years 9 months

paulears Wed, 08/23/2017 - 09:57
Treat any properly designed amp as two separate ones in one box - They really don't care what comes in or goes out as long as you don't reduce impedance lower than the spec says is ok.

Donny - we never had a problem with cables, it was the equipment - Shure, in particular swapped hot and cold - but our XLR cables were always 1-1, 2-2 and 3-3. You got the occasional phasing problem, but the big killer was where balanced systems were unbalanced by shorting the - down to ground - and adding a Shure mixer, shorted out the audio on some badly put together systems.

Member for

4 years 2 months

Cedric Thu, 09/07/2017 - 15:05
Raymond, post: 452092, member: 50745 wrote: I have a stereo amplifier. It's a really powerful Ashly that is nice sounding. (Not really important to this topic). Being that it has two channels, can I run a mono mix to front of house (two speakers only @ 8 ohms) on one side of the amp.....And run stage monitors on the other channel ? I have a sneaky suspicion its ok as long as my ohm load is equal on both channels. Or, am I wrong. The amp will handle different loads, I know this. Here is my situation. A friend gave me a stage wedge (15" peavey, 8 ohms). I only have one amp right now. So, what I want to do is run the FOH in parallel at 8 ohms on one side and run a single wedge 8 ohms on the other side. I'm sure this is an annoying stage amp 101 question for most of y'all. So, I apologize for my level of novice knowledge. Will this mismatching of speakers on the two different channels harm my amp ? Are there other imperative reasons why two totally separate amps would be required ? Of course, that is my ultimate goal for later. I just don't want to burn up the only amp I have. Thanks.
MPBWY
I do that all the time using all sorts of mismatched speakers on different sides. as long as it's a trus discreet stereo amp, the only time one side knows the other is there is when you hit the switch that says something like, "Combine for mono". Each side has its own load capasity and as long as you don't exceed either one, you'll be fine.

Member for

7 years 9 months

paulears Fri, 09/08/2017 - 00:21
Concur 100% - I've been treating proper amps as two in a box for years, and as long as you take proper precautions against stupid connection issues, all is well. For quite a while, I had one side of a 2500W amp running two subs in a theatre, and the other side running 3 Three Watt speakers in a room for paging! Swapping the speakons could have interesting results - but that aside, the amps are perfectly fne.

Many can continue to be used when one side is actually faulty - so if you lose once channel - totally dead, very often you can continue to use the other one. They share power supplies, but apart from that, most are separate.
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