Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Misc Schematics and Layouts => Topic started by: pnadora on March 22, 2016, 09:00:12 am
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Hallo, I am new to the forum but already learned a lot from reading through some threads :icon_biggrin:
I am planning on building an EF86 based preamp and was evaluating different ways to include a fender style eq-section. First planned to use the Ef86 in V1 and use a cathode follower to drive the tone-stack, but now I saw that the matchless clubman uses a pentode in V2 with great results. I found a thread about the EF86 version of the clubman via the search function, but sadly the links to the layouts are dead. In the schematic library here is only the 6SH7 version as well.
Can anyone help me out with the wiring of the EF86 version? Also any opinions on the CF vs Pentode as V2 to realise the tone-stack are highly appreciated :)
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I have never seen a confirmed reengineered schematic of the EF86 version but I have read a build report in a German amp building forum where a member built a Clubman clone with 6V6s and the EF86 preamp. He first used the AC15 values for the pentode and later switched to the values recommended by ValveWizard, and at the same time changed the parallel input stage from Ra = 10k to 56k (more like a MAZ jr.) and reported that he liked that better than the original configuration.
I considered building one too but built a Chieftain instead.
Good luck,
Stephan
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Look at this thread here: http://el34world.com/Forum/index.php?topic=9640.0 (http://el34world.com/Forum/index.php?topic=9640.0)
It has some wiring ideas for an EF86 in the second gain stage.
You can also look at my HoSo56-OD and look at how I have the 5879 set up in the OD channel.
http://el34world.com/Forum/index.php?topic=20016.0 (http://el34world.com/Forum/index.php?topic=20016.0)
With respect, Tubenit
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In the schematic library here is only the 6SH7 version as well.
You could probably use that circuit with an EF86 or 5879 just by wiring the socket for the different pin configuration. At the most you may need to tweak a resistor or two.
The clubman tone circuit is quite different from the typical Fender tone stack.
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As an alternative to the EF86 as second gain stage, I looked at the ACxx schematics again and drew a layout together with a 12AU7 cathode follower (and the add ons of the merlin b book). The other half of the 12AU7 could drive the reverb. I am "giving new life" to a broken down hammond K-100 organ and want to work with as much parts of it as possible. Thats where the 7591 power amp comes from (although I changed it to ampeg reverberrocket specs). In the orgna the reverb was driven by a 6FG7, but since it also included the 12AU7 I want to use it, because replacements are better available where I live.
I am wondering where to insert the reverb circuit.. The way I have it right now (with the 3,3M and capacitor from a fender reverb circuit) I think might clash with the tone/volume controls. What do you think about it?
It is my first attempt of putting together a layout and I dont have the power supply included at the moment since it is in very early design stage (so pls be gentle^^)
I would love to work with express pcb, but I did not find tubes in the programme. Is there a library that you can add to it?
The link goes to the schematic that I created with schemeit online.
http://imgur.com/4CRn8E6 (http://imgur.com/4CRn8E6)