Power conditioner and attenuator for OR80

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your idol
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Power conditioner and attenuator for OR80

Post by your idol » Sun Mar 25, 2018 10:12 pm

This is my first venture into firebreathing ripsnorting vintage amps and until now Ive always had managable amps. My Rockerver spoils me with loving the juice that pours from my electric sockets and built in attenuation and its a great sounding amp...
... but it aint no OR80 and cant get that sound at all.

So i was tipped off that for a minimal issue lifespan that Id be wise to get some sort of power conditioner for it due to the amount of juice in our US system. Thats cool, happy to buy her a toy if it means she does what I want. The problem is i know jacks#!t about what would be an adequate power conditioner for it.

Secondly I just need some recommendations for a good attenuator so I can milk this amp at a livable volume. There will be live setting use eventually hopefully and I should only need this solution for practice and home recording realistically.

Theres all the info. Help a brother out?

bclaire
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Re: Power conditioner and attenuator for OR80

Post by bclaire » Sun Mar 25, 2018 10:21 pm

What you are looking for isn't a power conditioner. That will offer filtering and spike protection but it's not going to change the voltage out of the wall for you.

What you're suggesting is a voltage regulator that will keep the voltage down to what the amp wants to see. Stupidly expensive... and not a power conditioner.

You might be better off with a good set of output tubes that can handle the higher plate voltages and install a DIVO so the tubes are constantly bias'd....

fiveightandten
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Re: Power conditioner and attenuator for OR80

Post by fiveightandten » Mon Mar 26, 2018 2:07 am

As Billy said, you're talking about a voltage regulator. If your OR-80 is a 90's model, it's not needed. If it's a 70's amp, then it will run cooler if used with a voltage regulator, but it's not necessary. It's much more important to make sure that the amp has a good set of tubes in there, biased properly, and that the caps are in good condition.

If you really want to lower the voltage down, the most cost effective solution for an average user would be something like a Brown Box: https://www.sweetwater.com/store/detail ... attenuator

This does NOT supply constant voltage. But it will lower the voltage so the amp is running in spec. It's not a 'set and forget' device. You have to know what you're doing, and make sure the voltage is in an acceptable range any time you plug the amp in. I have a '71 OR-120. It runs hot off modern wall voltage. I bias the tubes conservatively and just live with it. I run Svetlana EL-34's, which can safely handle the screen grid voltages.


Regarding an attenuator; it sounds like you're going to attempt to play this amp at home. The amp has enough power to kill small animals, and will need to be at those kinds of volume levels to sound proper. As someone who owns a master volume ("Overdrive") model OR-80, IMO even the master volume doesn't let you get proper sound at less than ear splitting volumes. This amp was designed to play stadiums. There's no way I could gig mine these days without an attenuator. Not even close.

I've been through a number of attenuators trying to tame it and retain the great sound. My current attenuator is the only thing I've found that even comes close to the amp sounding proper at low volumes. It's a Fryette Power Station. With this, I can do anything from silent recording, to controlling the OR-80 volume at gigs...from a whisper, all the way up to 50W. It's extremely versatile and works every bit as well as I hoped it would. It's also quite expensive. I bought mine used. Deals are out there.

http://www.fryette.com/power-station-in ... amplifier/

For a lighter budget, I'd recommend a SPL Reducer.
https://www.thomannmusic.com/spl_reduce ... r_266766_0

This is a resistive attenuator, but one of the better sounding resistive units on the market. With resistive units, the sound degrades the more you attenuate. So it sounds terrible at bedroom volumes. With a re-amper unit like the Fryette PS, the sound is consistent at any volume you play at. The caveat of the Fryette is that it's big, heavy, needs to be plugged in, has tubes in it, and it's expensive. The positive of it is that it's the best sounding piece of technology currently available for volume reduction in a live band setting. With attenuation, you have to decide which compromises you're willing to live with.
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Gladmarr
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Re: Power conditioner and attenuator for OR80

Post by Gladmarr » Mon Mar 26, 2018 5:55 am

Your OR80 was built in a day when US wall voltage was like 115-117 VAC. Today it’s more like 120-125 VAC. That turns all the secondary voltages (the voltages inside the amp) up by the same percentage. You need some way to knock the voltage at the input to the amp back down to the old voltage level. There are several ways to do that. Step-down transformers, variacs, there’s a trick where you use a filament transformer to subtract a voltage off the wall voltage, and there’s a method for re-wiring the power transformer on the amp to get closer to the correct voltages inside the amp.

As for attenuators - don’t use ‘em, don’t recommend them. They are a great way to blow your output transformer.

fiveightandten
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Re: Power conditioner and attenuator for OR80

Post by fiveightandten » Tue Mar 27, 2018 9:33 pm

Gladmarr wrote:
Mon Mar 26, 2018 5:55 am
As for attenuators - don’t use ‘em, don’t recommend them. They are a great way to blow your output transformer.
I disagree with this. It may have been the case in the 90's or early 2000's, but attenuators have come a long way. Reactive load units are totally safe for an amp, and are extremely useful. I use a Fryette Power Station with my OR-80 and GRO100 every time I play them. Hell, my 1st OR-80 blew the OT under normal use when it was a few years old. I've been using my 2nd one with the Power Station (OR-80 cranked up full) for over a year and it's been bulletproof.

If you don't feel safe with resistive attenuators, there are plenty of reactive load units (Fryette PS, Two Notes Torpedo Reload, UA OX, BadCat Unleash), and the Weber speaker motor units that are also totally safe.

Fear not! You can get safe and functional attenuators. :mrgreen:
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'71 GRO100 || '96 OR-80 || AD30 || '64 AC-50 || AC-30TBX || Hiwatt DR504 || HI-TONE HT30
LP Standard || LP Studio || LP Custom Lite || Ric 620 || Ric 360 || MIA Tele || SG 61 RI

Gladmarr
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Re: Power conditioner and attenuator for OR80

Post by Gladmarr » Wed Mar 28, 2018 4:15 am

That’s fine if you think so, but if I’ve got a vintage piece that can’t be replaced, I’m not foing to trust it to some goodball, fly-by-night operation to build a cheap resistive load box, and I sure don’t trust many people to build a reactive load box! Most people don’t know what that even means, and some of those people build load boxes.

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