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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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It is currently 28 Oct 2020, 12:57

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PostPosted: 08 Mar 2020, 14:22 
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Joined: 06 Apr 2009, 10:08
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Minarai wrote:
But, I am posting because I realized I'm not certain I can use the output transformers I bought or if so, exactly how to wire them. They are Hammond 125J (datasheet attached).
Woodo is correct. The schematic you posted in single ended. The Hammond 125J is a push-pull output transformer. You need a sindgle ended transformer for you circuit. Either a Hammond 125BSE of 125CSE (http://www.hammondmfg.com/125SE.htm).

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PostPosted: 08 Mar 2020, 14:43 
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Got it. Thanks. I think it was the 10k:32ohm spec that threw me off. But that is the same ratio as 2.5k:8, so it does what we need?


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PostPosted: 08 Mar 2020, 18:03 
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Minarai wrote:
... so it does what we need?
Yes.

For a 2.5kΩ primary use the white wire with 8Ω speakers and the yellow wire with 4Ω speakers.

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PostPosted: 14 Apr 2020, 13:35 
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Joined: 15 Feb 2020, 18:53
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well folks, I have at last, finished it.
It has a little hum, but it actually sounds quite good! Exceeds expectations. Not a lot of volume, but perfectly enough for my small kitchen/dining.

I made every conceivable design mistake a person could shy of causing the project to fail. I would never build a chassis/ housing like this ever ever again. In my defense, it is cobbled together from things I've had lying around for years and wanted to use up. And i learned a lot.

I did not implement every suggestion made, (the signal ground is not isolated and there is no filter was used on the mains).

But I greatly appreciate all the input. I certainly couldn't have done it alone.

For my next project, I have a few other oddballs laying around... two VOM 8810 amps, for example. I got one for free and foolishly paid a little money for another thinking I could use them for monoblocks. A little research has revealed that these are generally not considered good enough quality for HiFi stereo applications but are reasonably well liked for guitar amps.

Perhaps I will start a thread about those next.


Thanks again,


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PostPosted: 14 Apr 2020, 18:03 
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Joined: 13 Jan 2018, 21:33
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Location: australia
Bringing something old back into service gives a good feeling. Are the voltages and current what you expected? Bruce’s suggestions may help eliminate hum you observe. There are some excellent grounding philosophies in the technical resources library on this site that have helped me on my project. How efficient are your speakers. This may have some bearing on the volume level if the amp is achieving reasonable output. When i changed from 85db @ 1 watt 1 metre to 89 dB speakers this made a discernible difference in volume although the former was loud enough when cranked up.

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