receivers

[3abill]

I am looking for info on new receivers capable of driving my refurbished AR3a speakers as well as a theatre system. Low impedance capabilities are proving hard to find. I don`t trust my H-K930 receiver any more.

[michiganpat]

try download the manuals for some of the upper end marantz, denon, and onkyo receivers from their websites. I think most are 4 ohm stable

or buy a HT receiver with pre-amp outs, and look for some good 4 ohm stable power amps to run your fronts using the pre-outs, new or used (maybe adcom, carver, phase linear, marantz, etc in the used world)

[genek]

Moving this topic to the electronics forum. I think you'll get more input if the audience is widened to include the KLH and Allison readers.

[bitbandit]

From personal experience, the old technics "New Class A" amps (circa 1980-85) such as SU-V4X, SU-V7X, SE-A5 etc. all drive 3As well and are happy at 4ohm. I have seen McIntosh amps highly recommended by AR lovers but have yet to find one myself to try. I find newer amps sound harsh and bright with the AR speakers and have yet to find anything modern that I like the sound of with ARs.

Hope this helps.

[3abill]

From personal experience, the old technics "New Class A" amps (circa 1980-85) such as SU-V4X, SU-V7X, SE-A5 etc. all drive 3As well and are happy at 4ohm. I have seen McIntosh amps highly recommended by AR lovers but have yet to find one myself to try. I find newer amps sound harsh and bright with the AR speakers and have yet to find anything modern that I like the sound of with ARs.

Hope this helps.

Thank you for your help.I am afraid of old receivers.I`m retiring my HK930 because it stroked my refoamed woofer when I turned it on. I don`t want to worry about blowing my rebuilt AR3a`s. And I want to incorporate the receiver into a theatre system[when I upgrade from a 27 inch crt]

[3abill]

Moving this topic to the electronics forum. I think you'll get more input if the audience is widened to include the KLH and Allison readers.

Thank you genek. Thats the difference between a newbie and an advanced member.I appreciate all the help.

[3abill]

try download the manuals for some of the upper end marantz, denon, and onkyo receivers from their websites. I think most are 4 ohm stable

or buy a HT receiver with pre-amp outs, and look for some good 4 ohm stable power amps to run your fronts using the pre-outs, new or used (maybe adcom, carver, phase linear, marantz, etc in the used world)

Thank you for your knowledgable[sp?]input and taking time to help. I will attempt to download manuals. Who`d a thunk this computation device could be used for more things than e-mails and fb.

[Steven L. Bender]

I am looking for info on new receivers capable of driving my refurbished AR3a speakers as well as a theatre system. Low impedance capabilities are proving hard to find. I don`t trust my H-K930 receiver any more.

Most "new" receivers, with remotes (Sherwood, Onkyo, Denon, etc.) these days have poor design, and some are identical with others behind the flashy front panels (Sherwood & Insignia) almost all come out of China. So you are right low Z / high current designs don't exist. The HK-930 is a very good design, but its mid-1970's output transistors have medium power capabilities, I seem to recall they are NPN-NPN type of TO-3 parts such as the 2SD188's, or something similar, with a Power dissipation (Pd) of about 100 to 125 Watts per transistor.

An easy way to make the power margin and overall reliability factor of the output amplifier much, much higher would be to 1). Substitute more modern TO-3 power transistors such as: MJ15003G, or MJ15024G, or MJ21194G parts which have a 250 Watt Pd. and 2). Replace the old mica type insulators and their 35 year old dryed-up silicone thermal grease, with modern flexi-thermal pads (Sil pad). The old style silicone thermal grease drys out and loses its low thermal resistance over time, which makes the set less reliable as it ages.

These two easy measures - higher power output transistors, and new thermal pads which don't need grease, will vastly increase the reliability of the 45 wpc power amplifier in your older Harman/Kardon 930 to well above any modern receiver that I know of - mostly due to the increased safe operating area (SOA) these modern transistors afford.

Yes, there are other factors and considerations such as power transistor fT and such to worry about, but I believe you are safe in that respect, when using any of the three exact replacement transistors I have suggested.

-Steve

[dynaco_dan]

Moving this topic to the electronics forum. I think you'll get more input if the audience is widened to include the KLH and Allison readers.

Hi Gene

If I may suggest this topic should be in the, Acoustic Research, forum.

A similar to, "suitable receiver requirements for AR-3A's", heading.

This would focus more on the receivers compatibility for his, 4 ohm AR-3A's, which a lot of people know, are really a poor quality receiver and amplifier killer.

This is where probably more owners went for a pre-amp and amplifier combination, clean stable power and not necessarily a super amplifier even.

There is a limited selection of classic receivers that are safe for full use with the AR-3A's.

Have you considered possibly converting to separates?

Not necessarily from the 1960's or 1970's, because most of that equipment may need capacitors and resistors replaced, etc, and OEM parts and substitute parts

sometimes can be difficult, if not impossible, to find.

I have never owned a Macintosh or early Marantz receiver or any other piece of their equipment, I believe that Tom Tyson really likes them.

Well made, built like a battleship, durable and ultra stable would be probably be an appropriate comment, not inexpensive by any means, even used.

An AR receiver or AR amplifier might also be a consideration.

The stabliity using the AR-3A's is one issue with the fluctuation of less than 2 ohms in the upper frequencies to 35 ohms in the lower woofer range.

An extremely popular classic speaker today but fussy who feeds it.

Just a thought for today.

[Steven L. Bender]

Thank you for your help.I am afraid of old receivers.I`m retiring my HK930 because it stroked my refoamed woofer when I turned it on. I don`t want to worry about blowing my rebuilt AR3a`s. And I want to incorporate the receiver into a theatre system[when I upgrade from a 27 inch crt]

Hi, 3abill -

In reading your above comments, I'm just not quite sure what you mean by: it stroked my refoamed woofer when I turned it on.

Did it smoke (destroy) your woofers or just made one or both of them slowly move in, then out (or vice-versa)?

Often older receivers have a pair of large value capacitors in the plus and minus power supplies - the Twin Powered Harman/Kardon 930 actually has four large caps because it has separate, dual power transformers, and dual everything else after the power cord and power switch.

If these big capacitors in the main power supplies happen to charge up at slightly different rates, it causes a temporary DC offset which results in a large excursion, slow woofer movement at turn-on, and possibly a thump at power turn-off. Usually this is not a major cause for concern, but what it does indicate is that those four caps are getting to have increased ESR's (internal series resistances) and at different rates, after 30 to 35 years (and much like the mica pads and dried up silicone thermal grease I already mentioned in my prior response) one should now consider that they should now be replaced.

Just so you know, for more than the past ten years I've made several upgrade kits available which I call: Amplifier Rebuild Kits using specialty output transistors and designed for both the vintage Harman/Kardon Citation 12 power amplifier; and also for the vintage Dynaco Stereo 120 power amplifier. Each of which updates and rebuilds these amps at a different level of rebuild, to bring them twenty plus years into the future for better sonic performance and increased circuit reliability. My Citation 12 kits include four new power supply caps, as well as replacing the original 4 Amp bridge rectifiers (which often show cracks in the surface) with bridges rated at 25 amps. There is probably no reason one of my Citation 12 Rebuild Kits could not be applied to a Harman/Kardon Twin Powered 930, since the power amplifier section of that vintage receiver, is almost exactly the same electrical circuit, but using slightly lower voltages and Japanese transistors throughout.

If you want further information, do a Google or Bing search using the following string (use highlight, copy, and paste) Bender+Harman+Kardon+Rebuild will very likely get five or more links within the first page of results that will bring you to my Rebuild Amplifier web site pages on exactpages.com

-Steven

[Steven L. Bender]

Hi Gene

If I may suggest this topic should be in the, Acoustic Research, forum.

A similar to, "suitable receiver requirements for AR-3A's", heading.

This would focus more on the receivers compatibility for his, 4 ohm AR-3A's, which a lot of people know, are really a poor quality receiver and amplifier killer.

This is where probably more owners went for a pre-amp and amplifier combination, clean stable power and not necessarily a super amplifier even.

There is a limited selection of classic receivers that are safe for full use with the AR-3A's.

...

An AR receiver or AR amplifier might also be a consideration.

The stabliity using the AR-3A's is one issue with the fluctuation of less than 2 ohms in the upper frequencies to 35 ohms in the lower woofer range.

An extremely popular classic speaker today but fussy who feeds it.

Just a thought for today.

Well, I'd really worry about the Original AR Receiver or AR Amplifier some 30 years later.

First of all, while it was a great set in its day, and it may still be a great set now, there were factory redesigns that were MANDATORY UPGRADES to eliminate severe bias problems with the power amplifier and the original bias pots, which would lead to amplifier and transistor failures.

Secondly the thermal shutoffs used on the heat sinks can be another problem, with a mechanical operation, they can exhibit an intermediate resistance and in effect fail to protect. I've measured half a dozen of them after 20 years of use, and none of them was actually properly functional.

Third, the AR Receiver and Amplifier has way too small heat sinks, and their early single diffused homotaxial type slow output transistors, which are electrically effectively in parallel with the TO-66 drivers (which are faster) at low powers can cause a thermal runaway situation too easily driving low-ohm loads like the AR-3A.

This situation can cause a transistor to short, putting 44 Volts at several amps through the woofer, and its series inductor. Suffice it to say that can set the woofer on fire. It has been known to have happened in the past (rarely). Still, 30 years later, I'd strongly think the reliability of the AR Receiver is, on average, very much worse than it was during production some 30 years back.

So use fuses and more fuses, and more speaker line fuses if you intend to drive a power hungry AR-3a with a vintage AR Receiver or AR Amplifier. A word to the wise should be sufficient!

-Steven