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PostPosted: 28 Dec 2013, 00:04 
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Joined: 08 Aug 2009, 03:11
Posts: 2229
Location: Chilliwack, BC
The bigger the iron, the lower the core saturation and the better the bass response and the lower the THD added by the iron.

The Hammond vs. Edcor shootout is one that will be going for a long time and results are Googleable on a variety of experimenter's pages. Hammonds are less efficient and add more THD than Edcor, but have a broader upper-end frequency response for the same size/weight as an Edcor.

IMO, it comes down to your wallet on a 300B OPT ;)

Cheers!

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* Ratings are for transistors - tubes have guidelines*
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PostPosted: 28 Dec 2013, 00:35 
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Joined: 06 Jun 2008, 18:23
Posts: 4944
Location: Australia
I probably favour Hammonds over Edcors but you will pay the price. It's probably not hard to calculate the wattage required for the OPT but from personal experience I have found bigger is better. As an electronics engineer friend told my you can't beat a ton of wire. Big trannis have a ton of wire. He also said more wire more bass.

My 300B draws 90mA per tube at 435V. For sure a smaller OPT would have done the job but probably not as well. On the CRO 3db points are 10hz to 52khz. A small cheap OPT would not test or sound as well. I only wish Edcor would publish current ratings of the OPTs was well as other values.

After all I have said above I have used 10W Edcor OPTs on 5W EL34 amps which had more bass than they should and sounded excellent. Go figure?

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
Website: retro-thermionic


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PostPosted: 27 Apr 2017, 10:46 
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Joined: 16 Dec 2015, 03:05
Posts: 12
I made this amplifier based on the circuit at first page.

I am using metal oxide resistors (blue color). Phillips capacitor for DC filter, RIFA for cathode bypass for 6SN7 and 300B.

Coupling capacitor is CDE Orange Drop (waiting for my K-42Y to come).

Image

Output transformer is local custom made as well as the power transformer. Need to save for better transformers.

The power transformer has 880Vct (higher than the original design).

Not really clean inside the box.

Final photos is like shown below.

Image

To my surprise, the sound produced by this amplifier is so good despite a not so good transformer.

I really enjoy this amplifier.

Thank you very much for the designer.


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PostPosted: 27 Apr 2017, 18:00 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
Nothing wrong with those trannies. Amp looked good. Personal I found the 300B just a little characterless but most would probably like that. If you can try an SE amp with 6L6s. It will surprise.

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Projects: "Lagoon" - tube preamp with cathode follower | "retro-Oatley 6J6" - 6J6 push-pull headphone amp with OPTs | "retro-Hiraga" - Jean Hiraga Le Monster
Website: retro-thermionic


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PostPosted: 30 Mar 2018, 22:10 
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Joined: 13 Jan 2018, 21:33
Posts: 78
Location: australia
aatjitra wrote:
I made this amplifier based on the circuit at first page.

I am using metal oxide resistors (blue color). Phillips capacitor for DC filter, RIFA for cathode bypass for 6SN7 and 300B.

Coupling capacitor is CDE Orange Drop (waiting for my K-42Y to come).

Image

Output transformer is local custom made as well as the power transformer. Need to save for better transformers.

The power transformer has 880Vct (higher than the original design).

Not really clean inside the box.

Final photos is like shown below.

Image

To my surprise, the sound produced by this amplifier is so good despite a not so good transformer.

I really enjoy this amplifier.

Thank you very much for the designer.


Hi, i would like to use similar ventilation inserts you have used around the valves bases for my build of a similar but pcb based design. if you don’t mind, where might I look for a seller of these. Do they provide sufficient ventilation?

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