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Reviews For: Alpha/ETO 91B

Category: Amplifiers: RF Power - HF & HF+6M

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Review Summary For : Alpha/ETO 91B
Reviews: 53MSRP: 2798.00
Self-contained HF linear amplifier covering 160-10M including WARC bands & MARS capable. Manual tuning and band switching.

Capable of continuous operation at peak-rated output of 1500 watts peak power output on SSB, CW, SSTV, RTTY, digital modes and AM with no time limit. If continuous periods of "key down" carrier operation exceed 5 minutes the optional auxiliary cooling fan must be installed.

Drive power nominal 50-60 watts for rated output.

Uses 2 x 4CX800A/GU74b ceramic-metal tubes

Full break-in vacuum-relay QSK system

3+ kVA hypersil power transformer

66 lbs net weight

Product is not in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
N4DEK Rating: 2023-05-25
SUPER FINE AMPLIFIER Time Owned: more than 12 months.
Been more than pleased with my 91b so far. Legal limit with about 25 watts of drive. Very quiet in its operation. Mine has the Peter Dahl transformer installed as well as a set of new tubes so I'll be holding on to this one for a while. Alpha quality just can't be beat!
W8NIC Rating: 2021-05-10
Fantastic!!! Time Owned: 0 to 3 months.
Very efficient for an old amp. Very quiet and puts out 1500++ with only 38 watts drive, and, tube doesn’t overheat. Not only are the tubes still a available, they’re also very affordable unlike the 8877 that will set you back $2000
K6YE Rating: 2021-03-15
STILL AWESOME Time Owned: more than 12 months.
This is my third review (last one was 2013 CE). We moved from Colorado to California in 2015 CE. In 2020 CE, I finally got my station operational. I sent the 91B to Array solutions to be checked. This year, 2021 CE, I put the amplifier on-line and let it idle for a day. I put it in operation and it performed as before - quiet and efficient. Still rocks.

This my second review (first one was in 2008) of an awesome amplifier. I have owned this amp for more that ten years. With the exception of one 4CX800 and a fan failure, it has had no problems. I always look at the newer Alpha amplifiers, but I am so content with this one that is pointless to change. It gives full legal power out, on all bands with 40 watts of excitation, and is very quiet. I also have a Kenwood TL-922 and an Ameritron ALS-600 and while they are fine amps, my nod goes to the 91B. IMHO, the best amp is the one that YOU like to use, regardless of the manufacturer. For me, it is the 91B. Enjoy the hobby.

Semper Fi,

Tommy - K6YE

Earlier 5-star review posted by K6YE on 2008-11-12

I purchased my 91B sometime ago. I drove it over to Alpha and dropped it off for upgrades. (It really helps to live only 9 miles from the factory). When I got it home, installed the transformer, and applied 240 volts, one of the 4CX800s shorted out. I replaced the tube and this baby now cranks out the power.

It will easily exceed maximum legal output so watch the drive power. While the directions seem complex, the actual tuning is straight forward and quite simple. Kudos to Glen and Molly at Alpha for their supreme help in identfying the bad 4CX800 via telephone. How many companies are there that still give personal attention over the telephone sans charges? In addition, they gave me tune procedures paperwork pertinent to my IC-775DSP and FT-1000D transceivers.

I am totally pleased with my amp.

Semper Fi,

Tommy - K6YE
W9BB Rating: 2021-01-22
still fantasic Time Owned: 0 to 3 months.
Well I bought another alpha amp. this one a 91-b , As for all my alpha amps that I have owned (I guess I'm lucky) they all have operated flawless and put out 1500 ++ . In my opinion there is not a better sound than a tube amp on the receiving end of your radio. Don't think twice about buying these older tube amps. Operate them with your head , don't over drive them. The old Eimac tubes will last a long long time . All my alpha amps are quite. DO YOUR HOMEWORK .
KE4AMQ Rating: 2020-11-18
problems Time Owned: 6 to 12 months.
The 91b is a good amp, I am amp poor here I have a few, My commanders are the favs. The only issues with the alphas are service seems like no one want to help if things go wrong. Now it goes into fault when keyed even tried with 20 watts does the same thing fault.........
W0RMS Rating: 2019-07-24
GREAT AMP Time Owned: more than 12 months.
Have had this amp over 5 years no problems at all. It just sits there and makes buckets of power with little drive. The fan is quiet and the displays let you know what is going on. If you do make a mistake (wrong band etc.) it will save you, The only con. I have is the warm up time to come on line. If you find a nice one grab it! WØRMS

W4YB Rating: 2018-01-06
Wonderful amplifier over all Time Owned: 0 to 3 months.
I just picked this amp up from a friend so have operated only at his shack. Very anxious to get it set up in my shack. We were driving it with a Flex 6500 and easily obtained the legal limit with just 25 watts of drive. As others have said it loafs along with legal limit and is a dream to tune. Esthetically I think it’s a 5 also. Not sure if i’ll Ever upgrade but that remains to be seen. I think it’s going to be a dream machine, for me anyway.
NO2C Rating: 2017-05-10
Bought Used - It Failed - Sent to Alpha for Repair - WOW! Time Owned: 3 to 6 months.
I bought the amp used. After about three weeks the transformer failed. The fan also failed. Emailed Alpha and discussed options with Glenn. I decided to send it out to them and have it repaired.

They fixed it up, updated the controls and now it acts like a 99. They sent me an transformer made in the USA and put in a fan made here also.

I now get the full legal output on much less drive.
N6ERP Rating: 2016-11-10
Great Value Time Owned: more than 12 months.
Highly recommended. Simple to operate, it loafs along at legal limit w/ plenty of headroom, fans and relays are quiet, it's almost dummy proof, and just works. Easy to forget you are running an amp. And, people just "hear" you. 4CX800 tubes are rugged, yet inexpensive.

I hear a lot of talk from people saying they are modifying their amps of other brands, adding soft-start, QSK (vacuum relays), soft mounting the blowers to reduce noise, etc. The 91B already has all that..
PA3HGT Rating: 2015-10-20
Great to have Time Owned: 3 to 6 months.
Had this amp for half year but due some "neighbour" problems at my holyday-QTH had to sell it.Implemented all mods in it and when you know how to tune it's a nice amp to work with.Tuning is a bit strange in the beginning but it's ok after when uoy used on it.Plenty of power is available and you won't be dissapointed.
I have on my website a lot of photo's (dutch written,Google translate available) :