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Messages - Steve Conner

#16
Ha! Ninja simulpost!

I'm spreading confusion on the intertubes and loving it. 8)

The idea comes from a Douglas Self paper where he proved that CC and CE output stages are the same, just with a different reference for the input signal.
#17
In 30 watt mode, the grounded end of the OPT gets lifted off ground and connected to the speaker output.

You can look at this in one of two ways:

The voltage gain is achieved by bootstrapping, or:

It's not an emitter follower any more, but a common emitter amp. (To visualise this, ground the speaker output and float the other end of the speaker, where it joins the power supply smoothing caps. Same circuit.)

This was a trick to allow me to use a standard valve amp OPT.
#18
Hi JM,

At 4:15 I put the neck and middle pickups both on. That gives the kind of phasey, mushy Strat sound that many people just find annoying. :) I did it because that's what Bill Perry does in his version of Little Wing that appears on "Live In NYC". :) Also the output stage is getting clipped really hard at that point, maybe too hard.

If you like a more edgy sound, you'll probably find that you start to like it again when I switch back to the bridge pickup.
#19
Hi JM!

There should be a link to an MP3 in my first post. It was recorded at the same time as the video, but using a handy recorder with a stereo condenser mic. I will do some more, the next time I can book some time in the studio at work.

As for the interstage: I realised that if I used complementary output transistors, the interstage would only need one winding, so I could use an ordinary Champ output transformer.

For my next build, I'm going to combine it with a solid-state preamp and "PI", and use a small toroidal mains transformer as the interstage. I'm aiming for a clone of a Bassman or Marshall 2203. We'll see how that sounds. :)

Tone is definitely subjective. I liked the tone of the amp, and thought it had a bit of Clapton's Beano mojo. (Not with a Strat, mind you.) But I guess plenty of people don't like the Beano tone, either.
#20
The link works for me.
I've included the schematic as an attachment, maybe that will work.

Re the sound: That was what the original amp sounded like. It is a bit ratty. No super-saturated modern gain there. :) You have to listen to the MP3 version of the soundtrack to judge it, because the camera mic is distorting too.

I was taking it apart today anyway, so I shortened some of the time constants in there to try and tighten it up a bit.

I've done the power soaking and reamping many times. It was experiments like that that persuaded me to give solid-state a try. But this is different. It's simpler and it all fits in one box, plus it gives a highish impedance drive to the speaker, like a tube amp or the Valvestate power amp.
#21
Tubes and Hybrids / My new hybrid- demo and schematic
January 29, 2011, 10:17:28 AM
Hey all

I normally hang out on the MEF, but I thought I would cross-post this here. I've been building amps for years, and the whole time have struggled with the questions: Is there really anything bad about transistors? Is it possible to make a good sounding hybrid? Well, after all those years of experimenting, here is my answer.

http://scopeboy.com/scopeblog/?page_id=96 - full story behind the project

http://www.youtube.com/v/DZigVupYve4 - demo video

http://scopeboy.com/scopeblog/wp-content/uploads/2010/12/ninja-corvette-demo-hq.mp3 - better quality version of video soundtrack

http://scopeboy.com/scopeblog/wp-content/uploads/2010/12/NinjaCorvetteHybrid.pdf - schematic

I'm working on getting rid of the remaining tubes.  :trouble

I was partly inspired by RG Keen's guide to the old Thomas Vox SS amps. If you squint at my output stage in the right light, it looks like an old Thomas Vox or Leslie, except with current limiting and a proper bias scheme. And I probably got some ideas from Teemu Kyttala's book, too.
#22
Hi all... I've been a long time contributor to the MEF, but this is my first post here, and I've been thinking about this subject a lot lately.

You can copy the transfer function of a tube as closely as you like, with circuits of ever increasing complexity, but what I'm wondering is: How close does it really need to be?

It seems to me that all a "tube simulator" needs is a gradual, soft clipping characteristic that starts with low-order harmonics, moving to higher-order as you push it harder. It shouldn't hang up from saturation effects, and it should draw "grid current" so that you can have duty cycle modulation.

I don't think any finer level of detail than that really matters. It might change the "flavour" of the tone a little, but it won't make the difference between caviar and cr@p.

Thoughts?