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PostPosted: 24 Nov 2012, 17:57 
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Please feel free to ask any questions and to post comments about the DIY 6DJ8 (ECC88) Tube Hi-Fi Headphone Amplifier Project in this forum thread.

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Project Link - DIY 6DJ8 (ECC88) Tube Hi-Fi Headphone Amplifier Project

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PostPosted: 02 Dec 2012, 10:39 
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Joined: 13 May 2012, 17:47
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Congratulations Bruce! For sure it sounds amazing. :headphones:
All that is left at this point is a tube eq!
Cheers.


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PostPosted: 11 Dec 2012, 01:57 
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Joined: 11 Dec 2012, 01:52
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Location: Bangkok, Thailand
I've been looking for a project for ECC88 for quite a while, and now my dream comes true :wizard:

However, my knowledge of electronic is almost none (if not sub-zero). Is it possible that you will provide BOM or PCB that will make my life so much easier?

Thanks for sharing this!!!


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PostPosted: 14 Dec 2012, 14:59 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, Pretty much all the parts are standard ones (they are listed on the schematic) and can be obtained from several sources. The three transformers all come from the same place (Edcor - on the web). There is no particular way to build the project. point to point or perf board will do fine. I just used a PCB I had from another project.

Places like Parts Express, MCM, Allied, Mouser to name a few will be able to supply pretty much everything. There are no "premium" parts in the project.

Good listening
Bruce

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PostPosted: 29 Dec 2012, 02:00 
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Joined: 11 Dec 2012, 01:52
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Location: Bangkok, Thailand
Thank you, Bruce. Your advice is appreciated.

I visited another site, where the builder made " ECC88 OTL heaphone amp" using 3 of ECC88 tubes, and found it is very interesting, too. Do you think your design will drive HD600/650 better?

I actually tried to find the diagram where 2 of ECC88 and one of ECC81 tubes are used, the diagram that can be found in Earmax SE. I used to own Earmax SE for a period of time, and impressed with the footprint. Any idea?

Thanks again for sharing.


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PostPosted: 29 Dec 2012, 10:10 
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Location: Arizona, USA
Hi, Related to your question.... There are a couple of ways to connect the output of an amp to the speaker or in this case headphones. There are advantages and disadvantages to each. The three main ones are transformer, capacitor and direct. In a transformer coupled one the primary limitation is the quality of the transformer. The advantages are that it can more efficiently transfer power to the load (impedance matching). In capacitor coupled there are two main limitations, low efficiency and the limitations of the capacitor itself ( response, linearity mostly). In direct coupled the limitations are again low efficiency and also complexity of the circuitry, primarily in the power supply. I chose the transformer as I could get cheap wide band transformers that could be used push pull. Push pull has the advantage of cancellation of some harmonic distortion and inherent good sensitivity to rejecting power supply noise and hum. I wanted a very simple design that would be easy and cheap to duplicate. In capacitive coupled designs there is usually a need for multiple parallel tubes. Parallel tubes do not have the advantages of distortion and noise cancellation and thus make it necessary to have a cleaner power power supply (think more current and added cost and complexity). Additionally, they need to have large quality output capacitors. The capacitors are likely to cost more than the transformers I used. A design with direct coupling will often also require multiple tubes and frequently will be a push pull arrangement. It is probably the best sounding of the types if done well. Unfortunately it is the most difficult to get to behave correctly. There should be no DC at the output, very difficult to do without IC OP amps. It will need a split power supply as well (added complexity and cost).

So now back to the basic question..... Since I have not built the one you mentioned I really can't say which would be better. Most phones only need about 1-10 milliwatts for full output so probably either will do. The one in the project delivers approximately 50-100 mw clean and if you choose higher cost and quality transformers will actually put out nearly 1/2 watt. The transformers specified in the project are really cheap and have good response. In general you could use any push pull transformer that has a primary from about 10K to 20K and secondary windings to match your phones. I considered some much larger ones, but decided that the intent of the project was a "low cost, simple amp" and they would not be suitable.

Good listening
Bruce

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PostPosted: 05 Jan 2013, 04:04 
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Joined: 11 Dec 2012, 01:52
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Location: Bangkok, Thailand
Such a perfect answer to all of my questions, you addressed everything I have in mind. Thank you so much for your advice. :)

Enjoy the music. :headphones:


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PostPosted: 19 Jan 2013, 06:09 
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Joined: 16 Mar 2012, 11:15
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Location: UK
Has anyone in the UK tried building this amp with UK sourced transformers? I like the Edcor transformers but the shipping to the UK is higher than the cost of the transformers themselves! I really fancy building a valve based headphone amp but can't find the transformers in the UK.


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PostPosted: 19 Jan 2013, 06:43 
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Joined: 08 Aug 2009, 03:11
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Location: Chilliwack, BC
Heed wrote:
I like the Edcor transformers but the shipping to the UK is higher than the cost of the transformers themselves!


I think if you used Sowter or Lundahl, you'd find you pay the same quid as you would have for the Edcor :(

Life's a beotch outside of the US for shipping. I live a LOT closer in Canada and doubling the website price for landed cost is pretty darn accurate.

Cheers!

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PostPosted: 19 Jan 2013, 08:09 
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I found the Sowter website and was very happy to have found a UK source. Then I saw the prices......


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