Re: FA: Rare ElectroVoice A20C Circlotron Amplifier 290228944649

((It isn't terribly common but it isn't particularly in demand either. My
guess is you have way overpriced it, although an Asian buyer won't care.
But it may not have any Whig Bid power in Asia either. Bret.))


ElectroVoice A20C Integrated Mono Hi Fi Tube Amplifier
Rare working 20 watt Circlotron - in great shape! Item number:
290228944649






ElectroVoice A20C Integrated Mono Hi Fi Tube Amplifier
Previous Picture Stop Play Next Picture
1 of 7
Supersize


Starting bid: US $499.00
Your maximum bid:
US $
Place Bid >
(Enter US $499.00 or more)

Buy It Now price: US $799.00 Buy It Now >



Get up to 6 months no payments Apply
End time: May-17-08 19:30:09 PDT (2 days 12 hours)
Shipping costs:
US $30.00
Other (see description)
Service to United States
(more services)
Ships to: N. and S. America, Europe, Asia, Australia
Item location: Atlanta, Georgia, United States
History: 0 bids
You can also:


Starting time: May-07-08 19:30:09 PDT
Starting bid: US $499.00
Duration: 10-day listing



Meet the seller
Seller: jono-ats( 285Feedback score is 100 to 499)
Feedback: 99.3% Positive
Member: since Mar-23-99 in United States
See detailed feedback
Ask seller a question
Add to Favorite Sellers
View seller's other items

Contact the seller instantly


Buy safely
1. Check the seller's reputation
Score: 285 | 99.3% Positive
See detailed feedback
2. Check how you're protected




Description (revised)
Item Specifics
Amplifier Type : Power Amplifiers Type: Tubes
Brand : Electrovoice
ElectroVoice® A20C Integrated Mono Hi Fi Tube Amplifier
Rare working 20 watt Circlotron® - in great shape!
This ElectroVoice amplifier is a rare piece of audio history, one of
comparatively few that featured the Wiggins CIRCLOTRON® circuit.
According to the manufacturer's literature, "All DC is removed from the
output transformer, allowing class B operation of output tubes. All
switching transients are eliminated, and unusually efficient operation of
the output tubes is realized, resulting in cool optimum operation with
less distortion than conventional amplifiers. This primary impedance of
the output transformer is one quarter of that found in conventional
amplifier output circuits, affording vastly extended range response at
full rated power."

The specifications of the amplifier are really marvellous for its time;
the previous owner measured an outstanding 22 watts of power from the pair
of 6V6GT output tubes. I connected it to my home music sytem, and the
music that emerged was very detailed and life-like. This mono unit
features inputs for magnetic or ceramic phono cartridges, tuner, tape, and
microphone. Adjustable bass, treble, volume, and loudness controls are on
the front. A variable damping factor control is mounted on the side, for
optimum load matching.

Features & specifications include:

* Power Output: 20 watts rated, 40 watts on peaks
* Frequency Response: +/- 1 dB 20 to 20,000 Hz. at full power
* Harmonic Distortion: Less than 0.5% at maximum rated output
* I.M. Distortion: Less than 0.3% at 5 watt; less than 1% at 20
watts
* Hum and Noise: 70 dB below rated output
* Speaker Outputs: 4, 8, & 16 ohms unbalanced; 600 ohms balanced
* Damping Factor: Adjustable between 0.1 and 15
* A/C Power Requirements: 117 VAC 60 Hz. at 1.15 amp maximum
* Dimensions: 10.75 wide x 11.25 deep x 7.375 high
* Weight: 20 lbs net; 26 lbs shipping


Technical notes
Most of the tubes appear to be original, and all test fine on my tube
tester. I lubricated the controls and switches. For an amp of this vintage
(ca. 1956) it is in unusually good condition.

I bought this unit from the original owner, who apparently had replaced
the notoriously leaky "bumblebee" coupling capacitors with good Mallory
parts. To be safe, I replaced the two output tube coupling capacitors with
new polypropylene types. I tested the Mallorys for leakage and found none,
so I concluded the rest of the coupling caps were probably fine.

I also checked the selenium bias rectifier before applying power, and
replaced it with a silicon rectifier, along with the original bias filter
capacitor, for additional protection. I then temporarily replaced the two
tube rectifiers with solid state types, and brought the system up very
slowly with an adjustable A/C power supply. The large electrolytic
capacitors reformed nicely, and I did not notice any heat or signs of
leakage from them.

The new silicon diode replacement had considerably less voltage drop
than the original, and so I installed a 2W 50K adjustable bias control
(see photo) to bring the fixed bias to about -40 volts.

Included with the amplifier is a copy of the SAMS Photofact® and a
copy of the factory specifications and instructions.

Shipping & delivery
U.S. winning bidder pays $30.00 via Fedex Ground in the Continental
USA. International buyers pay freight costs plus 5% additional for
handling.

NOTICE: We reserve the right to accept or decline any bid or order for
any reason.

We appreciate your business. If you have any questions, please call us
at (770) 414-5266.

Select a picture
Larger Picture








00261
What's your Credit Score? 720? 650? Find Out From Experian.


Shipping and handling
Ships to
N. and S. America, Europe, Asia, Australia

Country:
Shipping and Handling To Service Insurance
US $30.00
United States
Other (see description) None
Free
United States
Local Pickup None

Country:
Shipping and Handling To Service Insurance
US $30.00 United States Other (see description) None
FREE United States

--
Message posted using http://www.talkaboutaudio.com/group/rec.audio.tubes/
More information at http://www.talkaboutaudio.com/faq.html


.

Relevant Pages

  • Re: Microwave Oven problem
    ... The first is that its 20 Amp circuit breaker keeps tripping ... Microwave ovens can only produce the max amount of energy, that the tube is ... If you set it to lower power, the tube is turned on-off, some ... Short of tube replacement, these things are fixable. ...
    (alt.home.repair)
  • Re: Finding band borders on the surreal
    ... >>> use a 30 watt solid state amp. ... > A valve amplifier when clipped gives even harmonics, ... gain and not pushing the power section very hard and the tube ampv is ...
    (alt.guitar.bass)
  • Re: Selenium rectifier question
    ... The 1N1239 was a replacement for the ... Then the 5R4 ist a directly heated rectifier ... tube and the 5 Volts AC are the heater power. ... To give the amp tubes time to heat up before anode etc power is ...
    (sci.electronics.repair)
  • Re: Info needed on possible factors affecting signal range
    ... A magnetron is a power oscillator - there is a power ... There is a an amplifier based on the same ... re-evacuate the tube and seal it. ...
    (alt.internet.wireless)
  • Re: RL in Class A SE, an alternative view was Re: Class-A RL determination in SE amps.
    ... "What determines output power of a tube?" ... try an amp built to the other outlook. ... The load value tolerance for SET isn't too bad in fact, ...
    (rec.audio.tubes)