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 NEW  Bruce Heran outlines the details and construction of his simple DIY 6DJ8 (ECC88) Tube Hi-Fi Headphone Amplifier Project.

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 Post subject: 5678 sub mini tubes
PostPosted: 08 May 2009, 20:29 
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Joined: 06 Jun 2008, 14:03
Posts: 272
Location: Tulsa, Oklahoma
Ok I got a line on a few of these little 5678 pentode tubes. anybody know of anything I can do with them? maybe a little headphone amp or something like that.
Steven A.
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 Post subject: Re: 5678 sub mini tubes
PostPosted: 08 May 2009, 22:12 
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Joined: 03 Aug 2008, 20:22
Posts: 386
Location: Denver, Colorado
I built a couple of headphone amps with a similar tube the 6088, looking at the datasheet they have pretty much the same pinout. My construction was a little crude but it was a nice little project, I made one with mosfet outputs and the other with an opamp out. Just be real careful with testing these bad boys as i killed a soundcard by reversing the input and output, then turning it on. Most of these little hybrid amps have a nice little inrush when you power them up so never power up with you headphones plugged in etc etc. All in all it was fun to build.
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 Post subject: Re: 5678 sub mini tubes
PostPosted: 06 Jul 2009, 06:27 
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Joined: 06 Jun 2008, 18:23
Posts: 3784
Location: Australia
Guys

I juts got into these babies only a few days back. I have built two preamps so far and find they punch way above their weight.
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Projects: "Parley" - Tube preamp with Pass B1 buffer | "VoXConcentriC" - Beyma high efficiency 12" speakers | "Black Lace" - all Ozzie tube 6V6 Power amp - old school
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 Post subject: Re: 5678 sub mini tubes
PostPosted: 06 Jul 2009, 12:22 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
Looks good Mark. Do the dampers help much?

Did you try stealing the signal before it goes to the opamp / headphone driver? You should be able to drive high impedance sources that way. If that works well, you could box it up with RCA outputs (signal before the opamp / headphone driver) and then take the output after the headphone driver to a headphone jack.

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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 Post subject: Re: 5678 sub mini tubes
PostPosted: 08 Jul 2009, 05:51 
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Joined: 06 Jun 2008, 18:23
Posts: 3784
Location: Australia
Yes the rubber grommets seem to make a huge difference. I will build my own design with no output buffer/driver. Yet to come. I want to make the portable valve headphone driver first.

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Projects: "Parley" - Tube preamp with Pass B1 buffer | "VoXConcentriC" - Beyma high efficiency 12" speakers | "Black Lace" - all Ozzie tube 6V6 Power amp - old school
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 Post subject: Re: 5678 sub mini tubes
PostPosted: 08 Jul 2009, 12:36 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
Hi Mark, have you compared the OPA2134 vs the stock headphone driver chip with your Grado SR80?

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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 Post subject: Re: 5678 sub mini tubes
PostPosted: 08 Jul 2009, 16:46 
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Joined: 06 Jun 2008, 18:23
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Location: Australia
Gio

I'm not always an A & B man but right from the start realised I had a better chip for the task intended than they provided. I intend to build the headphone driver version so I will get a chance to CRO them and listen. These days I'm doing a lot of listening through my new Phiaton MS400s (carbon fibre shells-closed back). Good but not as good as the Grados or audio-technicas.

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