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PostPosted: July 17th, 2014, 8:00 pm 
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Joined: July 3rd, 2014, 7:47 am
Posts: 89
Exactly what I was looking for. Can't thank you enough for sharing it

Jeff


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PostPosted: July 18th, 2014, 9:00 am 
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Joined: March 2nd, 2013, 2:43 pm
Posts: 216
Location: Potomac, MD
Welcome aboard, Mike,

Tom is contagious, so beware. He got me to build a pair of woofers--even to the point of helping, of which I am still doing the final steps. And that's not all he got me to build! I am going to try to run these and my Merlins using passive crossovers using a 6-watt 300B SE. The reason is that I manufacture amps and I need to be able to evaluate amps full range. I used to bi-amp, but it was too difficult to make comparisons with amps. Some day I would like to have a 300B shoot-out as there are a number of folks in the group that have made these. I don't currently make a production 300B, but have in the past and may again someday.

David Berning


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PostPosted: July 18th, 2014, 12:13 pm 
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Joined: July 16th, 2014, 3:05 pm
Posts: 19
Location: MD
dberning wrote:
Welcome aboard, Mike,

Tom is contagious, so beware. He got me to build a pair of woofers--even to the point of helping, of which I am still doing the final steps. And that's not all he got me to build! I am going to try to run these and my Merlins using passive crossovers using a 6-watt 300B SE. The reason is that I manufacture amps and I need to be able to evaluate amps full range. I used to bi-amp, but it was too difficult to make comparisons with amps. Some day I would like to have a 300B shoot-out as there are a number of folks in the group that have made these. I don't currently make a production 300B, but have in the past and may again someday.

David Berning

Thanks, David!
It all started with the High Water Sound setup at the last Capital Audiofest. It was not 300B, but it was a single tube SE and I liked it. So I purchased a Chinese 300B SE and gave it a listen. It was "ok" and obviously lacked the power for my floorstanders. But I felt that the thing had a potential, so I decided to build a push-pull class A amp. I'm lucky to have speakers with a very stable impedance (4 ohms going to 3.5 min) so it worked pretty well.

I'm also curious, what the requirements are for an amp to be manufactured, how it is different from a DIY.

As for the speakers, I don't know. They are highly inefficient non-linear devices by themselves and require a lot of effort to sound decent. The cabinets should not make them sound boxy, the crossover gives you linearity in exchange of efficiency, there is a lot of tradeoffs. Besides I'm completely satisfied by my floorstanders so far.

-Mike


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PostPosted: July 20th, 2014, 8:11 am 
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Joined: March 2nd, 2013, 2:43 pm
Posts: 216
Location: Potomac, MD
Quote:
I'm also curious, what the requirements are for an amp to be manufactured, how it is different from a DIY.

-Mike
[/quote]

It depends on where and how you want to sell it. Generally I want to sell worldwide, and CE can be self certified whereas UL cannot and is expensive to have a third party test. The basic things to pay attention to is the application of RoHS compliance (no lead solder, etc), control of RF emissions, control of line-frequency harmonics (power factor correction), and safety (no cabinet holes larger than a certain amount, no exposed tubes, etc.). Line leakage currents must be controlled as related to safety as well. Of course the obvious things like proper fusing needs to be observed and should by the DIY project too. Certain other things come in for certain countries like dual banana posts are a no no in the UK because the power line plugs have the same diameter pins and roughly the same spacing. I like using these posts and will sometimes furnish a safety boot to go over them and/or plug the holes in the posts. As far as exposed tubes, I now make an 845 amp which meets the requirements except the exposed tubes may be an issue if it were pressed. I supply a safety cage, but the user could opt not to install it. Even installed, the vent areas are far bigger than normally allowed. I don't think any 845 amps made by anybody can meet the requirements, and because of the tiny market for these products this safety requirement may be overlooked by inspectors.


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PostPosted: July 20th, 2014, 9:31 am 
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Joined: July 16th, 2014, 3:05 pm
Posts: 19
Location: MD
Thanks, this is very interesting, I did not know that the RoHS compliance was so widespread these days. I wonder now how say BAT sells its stuff in Europe, there is no hint of any cages available for its tube amplifiers.

I checked your website, your stuff is very impressive, I wish I'd known about it earlier. I liked your 845 amp. When I run out of power I have now, I will probably build something along the line but most likely with GM-70.


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