New power supplies book out

[TransLucid]

Merlin's books

I don't have Merlin's second book yet, but I'm just about finished reading his first book through for the second time, and I'd like to share a couple of points he makes that seem important to me. [My apologies if this is the wrong place to do so...]

1. Use higher-value grid stoppers everywhere. Kevin O'Conner makes this point for screen grids in pentode output tubes, but Merlin's point is that using them in preamp stages will avoid grid conduction and the nasty distortion that causes. This can really improve the sound of overdrive preamps.

2. It makes no sense to use different plate resistors in long-tail phase inverters. Just use 100k for both (in the Fender circuit). To find out why, read Chapter 8.

What I'd like to know from others (related to Merlin's 1st book, among other things):

1. How does Merlin"s "scale" control (where the phase inverter bias is varied to limit output voltage) sound? Has anyone built one?

2. Has anyone tried cascode stages in guitar amps?

Bob

[imaradiostar]

2. Has anyone tried cascode stages in guitar amps?

I'm a fan. I think they sound pretty neat. I haven't built any with a 12au7 but I have used 12ax7's and 6DJ8's. The latter has incredible gain!

jamie

[TransLucid]

Jamie -

Which stage in the amp? I've used the 6DJ8 in cascode for an OTL headphone amp, which worked pretty well with high-impedance headphones.

Bob

[imaradiostar]

Hi Bob, I've only used them as the input stage in a "vox style" amp. I like the cascode driving a Traynor/Dr. Z style tone control directly into a long tailed phase inverter. It's not the cleanest sound you'll ever hear but it has that neat Vox AC15 kind of sound- bright and sparkly but in a pleasant rather than ear-splitting way.

I have been wanting to try a cascode as the second stage with a lowish gain triode as the first stage to allow the cascode to generate some more interesting harmonic content. This seems lilke a good place to use a lower gain dual triode like a 12au7.

jamie

[imaradiostar]

Oh...and to put things back on topic, I've asked for Merlin's new book for Christmas but if it doesn't make it my way I'll be buying it for sure!! It'll be a long time before I've tested all the ideas I got from reading the first book!

jamie

[defaced]

I've asked for Merlin's new book for Christmas but if it doesn't make it my way I'll be buying it for sure!!

Same here. There are a couple of items like that one my list. I'm just trying to be generous and give people gift ideas. Yea, that's what I'm doing...

[GregS]

I just ordered a copy - a Christmas present to myself I guess! I found the first book excellent and a big help in my first design. I'm looking forward to this one as I haven't found much information on power supplies so far.

Greg

[soundmasterg]

I got my copy of merlin's 2nd book the other day and am now done with finals so I'll be doing lots of reading in between adding power scaling (O'Connor's kit) to my Bogen project over the break. I'm also adding Merlin's shift circuit to the tone stack.....should be fun and I hope it gets rid of an oscillation that the amp has when the controls are dimed. The book looks great Merlin, thanks!

Greg

[overtone]

arrived today!

As soon as I heard that Merlin was going to publish this work I put all my builds on hold. This morning it arrived from Lulu and, dipping in to it over lunch today, I can already see that this book is a great investment, as indeed was the first one.
I really miss having a mentor to go through my ideas with. My mentor used to be my grandfather. These days by searching this forum and reading both of Merlin's books I can find most answers without having start a new thread. May I just say a very big thank you to all of you here.

...1. How does Merlin"s "scale" control (where the phase inverter bias is varied to limit output voltage) sound? Has anyone built one?
Bob

Bob, I tried the Scale Control in two different builds of the K.F. Rocket circuit (which is like a minimalist AC30). I could still get some good touch response at low volumes. I am not much good at talking sound and suggest you try a test hook up to see how it performs with respect to your expectations. You could also compare it with a test of the so called P.I.G. Control over at The Amp Garage which attenuates before the PI. Both are very easy to rig up.

...I'm also adding Merlin's shift circuit to the tone stack.....should be fun and I hope it gets rid of an oscillation that the amp has when the controls are dimed.
Greg

Greg, I really love the Shift Control on the James stack, but I am not sure if would it really help an oscillation problem when dimed? Certainly, I will be building that tone stack with shift again.

Best, tony

[trem]

My copy shipped on December 13. I wonder if it explains electron path of travel in a power tube..?

[soundmasterg]

Greg, I really love the Shift Control on the James stack, but I am not sure if would it really help an oscillation problem when dimed? Certainly, I will be building that tone stack with shift again.

Best, tony

Hi Tony,

I'm putting the shift control in with a FMV tone stack so we'll see how it works there. What I'm thinking is that by changing to a 250k pot instead of the 1M that I have in the amp right now for the treble pot, it will reduce the highs just a bit (Duncan's tone stack sim seems to confirm this), and the shift control will add some versatility to the amp, and will replace the current cut control that doesn't do much. I added a cut control to my AC100 clone project and I really like it on there, but on this amp it's always run at full treble so its going to go. The squeal only happens when the volumes and the treble control are dimed, so reducing the treble response might be just the ticket to tame this thing.

Greg

[wyomingrocks]

I just ordered my copy from Lulu today. December 21 and used code DEC21 to save an additional 15% off. It covered shipping.