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Pictures of your Tube Amplifiers


henry4841

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On 9/6/2020 at 8:22 AM, Backfire said:

 

Regretfully, my constructions tend to be rather utilitarian in comparison to some of the beautiful ones built by others!

There are historically renowned artists, architects, designers, and engineers whose works focus strongly on exactly of what you speak!!!  I have taught art and art history for 30 years (now retired), and the fascinating relationship between form and function was always a very important topic of discussion.

 

An amplifier, regardless of how well-dressed-up, machined and polished its chassis may be, is worthless without the circuit inside.   The 6C33C is one tank of a triode.   Very interested in your OTL.

 

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9 hours ago, dwilawyer said:

Interesting,  what is it?

 

A bread-board of this circuit, created by an retired EE audio friend of mine. Frustrated with the price of interstage transformers along with lousy bandwidth and goofy ratios, he experimented using a cheap Allied SE to PP interstage transformer connected as SE to SE.

 

Square waves ring like crazy, until one bridges the interstage with the 0.1uF capacitor.

The cap more or less brute forces the interstage to give better bandwidth, or gives the best of both worlds. (advantages of cap coupling and interstage coupling)

 

It's a circuit that makes SET luddites cringe. But it will output a decent square wave at 30kHz, with strong bass at 30Hz.

The 6EA7/bridged Allied IT front end circuit can run upwards of 120 volts peak to peak if I recall...I could be wrong. It's rather difficult to clip this amplifier for what it is.

 

post-6643-13819853605856_thumb.jpg

 

6EA7 Allied IT 2A3 amp circuit.JPG

 

Personally, I think John Warren won this thread...

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On 9/6/2020 at 11:22 AM, Backfire said:

The first is my everyday amplifier, a conventional type of OTL amplifier using 6C33C output tubes.  I quite like the second one too; again OTL, using 6082 output tubes.  The novelty with this one is that there are no transformer

 

very impressive ,four   6C33C   could deliver125 watts/8 ohms  ,  I 'm thinking this is  a 25 -30 watts amp  x 2  -/  question for you ,  you  are only using 1 power supply in this setup , any advantages versus 2

 

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5 minutes ago, RandyH000 said:

very impressive ,four   6C33C   could deliver125 watts/8 ohms  ,  I 'm thinking this is  a 25 -30 watts amp  x 2  -/  question for you ,  you  are only using 1 power supply in this setup , any advantages versus 2

 

 

Yes, the 6C33C OTL is about 25W into 8 ohms.  I'm just using the single power supply for the two channels, if that's what you mean.  The big toroid on top is 117-0-117 secondary, for the main positive and negative HT supplies for the output tubes, and also, with voltage doubling, for the input and stages driver.  There are a couple of smaller toroids under the chassis, for the heaters.  The main HT transformer is a bit of an overkill in terms of power handling, I think.  I don't have any problems with it.  The design of the OTL is based on one by Tim Mellow; it appeared in Audio Express, February 2010.

 

The power transformer for that other OTL is a bit bigger, and sits in my front garden...power-transformer-s2.thumb.jpg.a7c86ebc15e457e52f07f54deb741916.jpg

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On 9/7/2020 at 1:09 PM, Marvel said:

Personally, I think John Warren won this thread

I know I needn't apologize, and I'm really not....but sorry, John.  I will say what you did is cleanly soldered, with nicely dressed leads.   In my view and experience, the P-to-P folks have it quite easily.  As if this were a race or a competition; which sure, in good fun why not...

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My former 45 amp, built on a mounting bracket from a used shipboard keyboard in 1997, schematic was from an article in Glass Audio. The power transformer burned out once, I replaced it, then stripped it when Maynard came out with the Lil Sweetie schematic. Not the best layout here, the parts had to fit the available space.

IMG_5358.JPG

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1 hour ago, erik2A3 said:
On 9/7/2020 at 4:09 PM, Marvel said:

Personally, I think John Warren won this thread

 

I know I needn't apologize, and I'm really not....but sorry, John.  I will say what you did is cleanly soldered, with nicely dressed leads.   In my view and experience, the P-to-P folks have it quite easily.  As if this were a race or a competition; which sure, in good fun why not...

 

Not my quote, but I agree with it. John designed the boards and layout and worked out more of the circuit.

 

I appreciate the nice/ beautiful work by those who do the PtP builds, too. Maynard's be at the top of that class. 😉

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BTW Bruce:  The extra octal socket in the Moondog top-plate is not 'overkill' per se.'   W. Labs made use of the same chassis plate that was used for the Laurel 300B, which required it for the additional octal valve used in that design over the Moondog.  So, maybe we can substitute 'overkill' with....I dunno....frugal, perhaps? ;)  

 

I know I mentioned this many moons ago, but hey....so what.

 

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11 hours ago, Davecv41 said:

My former 45 amp, built on a mounting bracket from a used shipboard keyboard in 1997, schematic was from an article in Glass Audio. The power transformer burned out once, I replaced it, then stripped it when Maynard came out with the Lil Sweetie schematic. Not the best layout here, the parts had to fit the available space.

IMG_5358.JPG

Tell members about how they sound to you. 

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2 hours ago, henry4841 said:

Tell members about how they sound to you. 

Details have faded over the last 20+ years, but I don't feel this schematic was well designed. I got about 30 minutes out of it connected to a pair of HIIs when the high voltage winding in the power transformer opened. It had been over a year since I ordered it from Antique Electronic Supply, so well out of warranty. I wrote a letter with a copy of the schematic to AES explaining what happened, and got a reply from Mr DeFir, the owner. He analyzed the circuit, and said one winding was overloaded, but the other was not, so he felt the transformer was good in the circuit. (I was in the Persian Gulf at the time, he had been a tron chaser in the navy in WWII, and his son was still on active duty, so it was a nice letter.) I ordered another transformer and replaced it, and got it going again. I have 1967 Khorns, and while the sound was clear, it was not a strong amp, which I partly blame on having to run the high voltage winding thru a resistance to drop it. (The gold ones in the picture are in series, so there was no fighting between unmatched parallel parts.) After several years of listening, it developed a hum, so I shelved it, not wanting to invest the calories in it. When Maynard put out his Lil Sweetie schematic, I took the amp apart, reusing just the aluminum chassis and the Hammond 1615 output transformers. There's probably a couple hours of work left before it's ready to fire up. There are now two mono amps on the chassis.

  I am not put off by the 45 tube in the least, in fact, I'm still looking for a better schematic. This amp sounded good.

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