18watt turned ac30 ef86 channel only

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Gradysmusic
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18watt turned ac30 ef86 channel only

Post by Gradysmusic »

Hello All, I just want to thank everybody for all the invaluable information.

I had an 18w
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that was my second amp i ever built that got modded and modded until it was a basketcase and i played through a couple of Dr.Z prescription + amps that i worked on. I really got turned onto the ef86. So i scrapped the 18watt and reused transformers and chassis i made and built a mix between some of the ef86 amps on the download page and a vox ac30. the results are so silky sweet. not sure if the undersized transformers have anything to do with it i assume they do. i will post more pics and schematic/layouts as soon as i take some.
20210525_183241.jpg
20210525_183244 (2).jpg

If this is not in an appropriate area or unwanted on the forum feel free to dump it. I really just wanted to thank zaphod_phil and JMPguitars for their posts and hard work, and others too in the past have helped me quickly diagnose or remedy amp issues. Great Community with very little misinformation which I'm sure everybody notices on other forums.

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Re: 18watt turned ac30 ef86 channel only

Post by JMPGuitars »

Cool! What transformers and power tubes are you using? Where's the demo? ;)
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Re: 18watt turned ac30 ef86 channel only

Post by zaphod_phil »

Keep in mind that Marshall tone controls work quite differently to the F***er tone controls that you're used to. To understand the differences visually, I recommend using Duncan's Tone Stack Calculator - http://www.duncanamps.com/tsc/
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Re: 18watt turned ac30 ef86 channel only

Post by zaphod_phil »

JMPGuitars wrote:
Mon 01/03/22 3:06 pm
Cool! What transformers and power tubes are you using? Where's the demo? ;)
And where's the schematic, so we can see the details of what you've really done? :)
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Re: 18watt turned ac30 ef86 channel only

Post by zaphod_phil »

Your amp is totally within the guidelines of this site :) Are there any similarities with the Vajra 18W by Mark Durham RIP(ignoring the Bias switch and PP/SE control)? https://mhuss.com/18watt/schematics/Vajra18Scheme.jpg
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Re: 18watt turned ac30 ef86 channel only

Post by zaphod_phil »

Here's the EF86 preamp stage I would recommend:
"Valve Wizard" Merlin Blencowe has a web page where he shows a theoretical way to design a pentode preamp stage. However, not everyone who has tried his approach has had good results - just ask Josh :wink: You might also like to look at some of Josh's EF86 preamp designs for something that works well :)
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Re: 18watt turned ac30 ef86 channel only

Post by JMPGuitars »

zaphod_phil wrote:
Mon 01/10/22 1:42 pm
Here's the EF86 preamp stage I would recommend:
"Valve Wizard" Merlin Blencowe has a web page where he shows a theoretical way to design a pentode preamp stage. However, not everyone who has tried his approach has had good results - just ask Josh :wink: You might also like to look at some of Josh's EF86 preamp designs for something that works well :)
Ha, that's true!

The EF86 in my EF86 Xtra circuit is by far my favorite use of an EF86. Less microphonic IME too. files/JMPGuitars_18_Watt_EF86_Xtra_Schematic.pdf

Thanks,
Josh
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Re: 18watt turned ac30 ef86 channel only

Post by zaphod_phil »

That looks great, Josh! There's nothing like a tried, tested and tweaked design :)
How would you rate the difference between your EF86 Modern Classic and EF86 Xtra TMB preamps, apart from the obvious difference in overall gain? The Modern Classic looks much more traditional Vox-like to me.
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Re: 18watt turned ac30 ef86 channel only

Post by JMPGuitars »

zaphod_phil wrote:
Mon 01/10/22 4:29 pm
That looks great, Josh! There's nothing like a tried, tested and tweaked design :)
How would you rate the difference between your EF86 Modern Classic and EF86 Xtra TMB preamps, apart from the obvious difference in overall gain? The Modern Classic looks much more traditional Vox-like to me.
Thanks! You're absolutely right about the Modern Classic being more traditional Voxish. It's certainly a good sound, but the changes I made to the EF86 preamp in the EF86 Xtra, to me, sound a lot better. Better sounding dirt, and less microphonic. I think I should make an EF86 Lite 2P with those changes. We'll see if I'm too lazy or not. ;)

Thanks,
Josh
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