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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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OTL tube power amplifier project
I have been intriqued for some time now with the idea of building an
output transformerless tube audio power amplifier. I have seen schematics of two different versions of this, one in an old 1962 radio book that I have and another on the web which was published in the February 1990 issue of a magazine which I've never heard of call "Glass Audio". One design uses 1682 triodes for the output and the other uses 6AS7's. The 1682 is just a 26 volt filament version of the 6AS7 and so the heaters can be wired in series eliminating a filament transformer. In fact this particular design uses no transformer for B+ either with AC neutral being connected to one side of the chassis. As long as you polarize the plug everything should be ok the article goes on to say, however I don't know how crazy about that scheme I am though. Each design boasts 25 and 35 watts respectivly into 16 ohms with .50 percent total distortion at full rated output. Frequency response is not limited by the transformer and and so extends from 10HZ - 250KHZ on both. The circuit for the 35 watt design is very interesting and can be seen at: http://www.bonavolta.ch/hobby/en/audio/6as7_2.htm#top If I'm going to the trouble to build something though, I would really like to wind up with a unit that can do at least 70 watts or so. By the looks of these designs, perhaps just adding more triodes in the output and beefing up the power supply would do it but I was wondering if anyone else had any further information on this type of project, or had looked into this? Thanks, Lenny Stein, Barlen Electronics. |
#2
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OTL tube power amplifier project
Anything that connects any user accessible parts to the AC line
- Hot or Neutral - is against NEC Code. Outlets are often wired with reverse polarity and faults could also result in full line voltage on the speaker wires or inputs. This is a potantial time bomb both for humans and any equipment it may be attached to. --- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html Important: The email address in this message header may no longer work. To contact me, please use the feedback form on the S.E.R FAQ Web sites. |
#3
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OTL tube power amplifier project
"Lenny" wrote in message om... I have been intriqued for some time now with the idea of building an output transformerless tube audio power amplifier. I have seen schematics of two different versions of this, one in an old 1962 radio book that I have and another on the web which was published in the February 1990 issue of a magazine which I've never heard of call "Glass Audio". One design uses 1682 triodes for the output and the other uses 6AS7's. [snip] This idea gets discussed on rec.audio.tubes from time to time. It might be worth asking there. Frank Dresser |
#4
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OTL tube power amplifier project
Thanks very much. Lenny
"Frank Dresser" wrote in message ... "Lenny" wrote in message om... I have been intriqued for some time now with the idea of building an output transformerless tube audio power amplifier. I have seen schematics of two different versions of this, one in an old 1962 radio book that I have and another on the web which was published in the February 1990 issue of a magazine which I've never heard of call "Glass Audio". One design uses 1682 triodes for the output and the other uses 6AS7's. [snip] This idea gets discussed on rec.audio.tubes from time to time. It might be worth asking there. Frank Dresser |
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