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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 10 May 2021, 13:46

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PostPosted: 26 Feb 2021, 02:44 
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Joined: 13 Jan 2018, 21:33
Posts: 407
Location: australia
The td160 I only recently bought is showing its age but a nice old thing to have. Lucky I have long forgotten how good my linn with a grace arm and supex mc cartridge was.

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PostPosted: 26 Feb 2021, 08:42 
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Joined: 04 Jun 2008, 20:59
Posts: 4370
Location: Arizona, USA
Hi, Ugh. I miss a day and odd things go on. As a designer and long time builder of commercial and diy stuff...I see absolutely no reason to switch off the AC mains neutral. Particularly when the fuse is not in the same line. I am of the opinion that this is about as dangerous as it can get. Only line powered (no isolation transformer) gear is worse. For a preamp that is quiet and pretty easy to build look at the IC based one I posted elsewhere. It can run off a pair of 9 volt batteries and skip the power supply. Mark is doing that so you could look at some of his postings on it. It sounds great, extremely quiet, can use either MM/MI or LOMC cartridges, easy to build if you can deal with ICs (hint use sockets) and the cost is quite low.

Good listening
Bruce

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PostPosted: 07 Apr 2021, 05:57 
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Joined: 09 Aug 2018, 03:15
Posts: 22
Location: Forsbacka Sweden
Hi. This looks really nice! I want to build this one with some changes to the gear I have. I have already several pre stages with White Catode followers (no gain for good matching).Can I just skip the last catode follower stage then? If so can I modify the powersupp for this? I will then not need the highest stage in powersupp. And I will be alright with less heater power I guess... and put the 1uF output coupling cap after ecc83stage?

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PostPosted: 07 Apr 2021, 12:18 
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Joined: 04 Jun 2008, 20:59
Posts: 4370
Location: Arizona, USA
Hi, The cathode follower is used to get the output impedance into a reasonable range and prevent loading on the previous stage. SRPP stages make good voltage amplifiers, but can be non-linear if current is needed. Thus the cathode follower. The Z out of the SRPP is in the order of 20K ohms and should not really feed anything under a 200K input. (some folks would argue that 100K may be OK) Most gear is way lower. The CF Z out much lower and can feed pretty much anything. Since I tend to like designs that have only the components necessary to do the job correctly I recommend not leaving out the CF stage. It is used in all the diy ones I have and is in the commercial proto types. I would still leave the number of filters in the PS. Even with no CF stage you need really good filtering for the first two stages. If the DC is not clean enough you will get more hum.

Good listening
Bruce

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