• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

OTL designed by Glen Orr AudioXpress

I just built this amp. Started listening last night. Very nice sound, nice and clean with nice mids. Although I am not a fan of the 12AX7 overall in this design she is not coming across as bright as the most recent OTL I built which you cab find in this thread:

http://www.diyaudio.com/forums/tube...signed-tim-mellow-4-6c33c-20.html#post2384643

Would love to hear comments if anyone else has built this OTL. This design is a modification of an old OTL design from the 50's I believe and RCA 25 Watt amp.

Thx

D

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Here is the last page of the article and my testing rig build up. The power supply in the pic that is at the top center is a regulated PS that is running the 450vdc lines. The 155 plus/neg PS is on the board and from that I am also getting the -70vdc and -225vdc supplies.
 

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:cop: I've removed the AX article- this is copyrighted material. If you have Ed Dell's written permission to post those scans here, let me know and I'll put them back.

No problem Sy sorry about that was not thinking. The schematic in the article is not under copyright so I should be able to post solely that correct? It is from a public schematic for years now as its origin. Thx
 

taj

diyAudio Member
2005-02-23 8:49 pm
It wouldn't really matter how you distributed the article, it would be a copyright violation if it's done without permission of the owner. All you can legally do is 'refer' to the article and hope people get it from the publisher. Or that the publisher makes it available.

The copyright for the old schematic has probably expired, but you never know without investigating. The Gutenberg Project is currently taking some flack for publishing books they thought were copyright free, but were in fact bound by copyrights that had been renewed.

..Todd
 
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dwhitf

Member
2008-05-20 12:11 am
Please list the transformers

desperateaudio

What are the transformers your using? need a simple stereo unit for the office.
dwhitf

sorry miss this
The power supply in the pic that is at the top center is a regulated PS
 
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1. Glen Orr has no patents in audio and based on patent law he could not patent the amp in this article.

2. Based on copyright law there is no copyright issue here as I understand it.

3. AX is a DIY mag and all this does is bring attention to a mag that could only profit from people seeing this and taking notice that the mag has value and then having those folks subscribe. This is an article from 6 years ago. The methods used to modify the amp in the article by Glen Orr were developed by others which are patented, so would AX and Glen Orr owe them money?

We need to apply some sensibility here.

I will reach out to Mr. Orr today and discuss the matter with him.
 
I have not recived a call back from Mr. Orr yet but will try again on Monday.

I have been listening to the amp now for 3 days an it is as close to my rebuilt NYAL OTL3's in sound as any other otl I have built has come to sounding as nice. Great stage solid bass. Mellow sound but clean. I am currently using 5 NOS NIB GE 6AS7GA and they do sound better then my NOS NIB GE 6080's but not by much. You want a nice DIY OTL I suggest you build this amp.
 
Lighten up!

What is so sad IMHO is that the moderators, in a zealous attempt to protect some imagined intellectual property (consisting of some non-patentable simple tube circuits) choose to stifle discussion and learning rather than promote it by removing links to circuits that some members want to simply discuss. :rolleyes:

From the article it sounds like Mr. Orr has much better things to do with his time than concern himself with unauthorized publication of "his" circuit. All the guy did was make some modifications to an already existing circuit.

BTW, there are 5 (yeah, FIVE) caps in the signal path of this amp, one of them a large electrolytic. I'm not trying to insult Mr. Orr, he's obviously a talented individual, but really all he did was cascade several stages and couple them with caps. Tim Mellow's design looks a lot more elegant, although I have no experience with either amp.

I have never before in any DIY forum seen a circuit that was not patented or in commercial production removed by the moderators. They even removed the man's name from the post - I had to dig just to find that.
 
Tim Mellow's design looks a lot more elegant, although I have no experience with either amp.

Well as you know I have built both.

I would agree that on paper the Tim Mellow's amp is more elegant but I have to say the Orr amp is sweeter in sound and is much more even in the curve of HZ distribution over the entire spectrum to my ears. But again yes the Mellow's amp certainly does many things very nicely.
 

SY

diyAudio Moderator Emeritus
2002-10-24 10:19 pm
Chicagoland
www.SYclotron.com
:cop: desperateaudio and sampleaccurate: I have removed a link to a pirated version of a copyrighted article which has been pointed out to me. You did not get permission from AX to reprint and distribute it. Your understanding of copyrights and IP is severely flawed and I would advise members to ignore it. This is not subject to dispute.
 
:cop: desperateaudio and sampleaccurate: I have removed a link to a pirated version of a copyrighted article which has been pointed out to me. You did not get permission from AX to reprint and distribute it. Your understanding of copyrights and IP is severely flawed and I would advise members to ignore it. This is not subject to dispute.

Sy greatly appreciate your point of view but since the law is part of my profession I must disagree with you on the other level but its your show so do what you feel is right.