36 Watt Superlite TMB EL34 with Reverb

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JMPGuitars
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36 Watt Superlite TMB EL34 with Reverb

Postby JMPGuitars » Tue 09/04/18 3:32 pm

EL84s sound great in the 18 Watt circuits, but I missed the sound of EL34 tubes. With a little help from Zaphod_Phil, I modified his Superlite TMB circuit for EL34s and reverb.

I may decide to share my schematic and layout drawings I made at some point for this, but not yet. They'll be in the downloads section if/when I do. ;)

Anyway, here's a few photos:
Image

Image

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More photos and details in the Gallery album: galleries/thumbnails.php?album=13

I'll post a demo in the Hear It! section soon after I, you know, record a demo. ;)

Thanks,
Josh
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geoff 1965
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Re: 36 Watt Superlite TMB EL34 with Reverb

Postby geoff 1965 » Tue 09/04/18 4:52 pm

Cool Josh!
i like this one,looks like you've used the latest superlite preamp and phase inverter,V1 biasing 2K7/.68uf - 680r/.68uf?
note you have 290-290 GZ34 rectified,what B+ does that give you?
looking forward to hearing the demo.
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Re: 36 Watt Superlite TMB EL34 with Reverb

Postby JMPGuitars » Wed 09/05/18 6:18 am

geoff 1965 wrote:
Tue 09/04/18 4:52 pm
Cool Josh!
i like this one,looks like you've used the latest superlite preamp and phase inverter,V1 biasing 2K7/.68uf - 680r/.68uf?
note you have 290-290 GZ34 rectified,what B+ does that give you?
looking forward to hearing the demo.
Look at you trying to reverse engineer already. ;)

j/k - V1 is at 1.5k / .68μF & 680R / .68μF.

The voltages coming to the caps/board are what you would normally see. One of the reasons I chose the GZ34 was for its voltage drop specs. Obviously there are changes on the board to cater to the power tubes besides that.
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Re: 36 Watt Superlite TMB EL34 with Reverb

Postby geoff 1965 » Wed 09/05/18 10:43 am

thank's Josh,
so if your B+ is pretty much the same i presume the gz34 is better suited to the higher current draw of the el34's to give you the "sag/compression" you want?
i learned this from curtiss when i was calculating what sag resistance i needed to simulate on my bridge rectified amp.
i.e. the more voltage drop = the more sag/compression, and the voltage drop is determined by the current draw of the tubes.
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Re: 36 Watt Superlite TMB EL34 with Reverb

Postby JMPGuitars » Wed 09/05/18 11:04 am

GZ34/5AR4 is a very popular rectifier for a reason. The typical voltage drop is 30. There's some rectifier tube charts out there if you want to compare different rectifiers. You can see their specs and get an idea of what kind of sag they might have in a circuit.

Thanks,
Josh
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Re: 36 Watt Superlite TMB EL34 with Reverb

Postby geoff 1965 » Wed 09/05/18 12:31 pm

will do Josh, although i'm not quite at that level yet but slowly getting there!
one thing i have found very useful in learning about the workings of guitar amps is being able to study the schematic & layout of a particular amp! hint! hint!
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