Merlin's Ultra High Gain preamp

[M Fowler]

From Merlin Belencowe's book I plan to build his Ultra High Gain preamp with 50w Marshall JCM800 output section and add presence and deep (Resonance) pots.

Board layout could certainly be improved if you want.

This will fit into a standard Marshall style JTM45 chassis or JCM800 2204 stock chassis since there are only 3 preamp tubes on this design.

Stay tuned.

Mark

Designing Valve Preamps for Guitar and Bass, Second Edition

Page 260, Fig. 14:7 Practical Ultra High Gain

Each design has a different name, there is only one schematic titled Ultra High Gain.

Mark

Ultra High Gain amp Merlin B.gif

[dorrisant]

I'm very interested in how this compares to the other high gain stuff you've been building. Your ears are surely tuned to critique it if anyone is.

Eyes peeled.

[M Fowler]

Added some 220pf and 100pf SM caps from V1 & V2 tube sockets to ground as short as possible.

I can't post the copy right schematic from his book so I thought I better add in some of the small stuff.

Mark

Ultra High Gain amp Merlin B.gif

[sluckey]

Just so we can follow along, which book? What page?

[pompeiisneaks]

yeah I think he has multiple different guitar schematics in the book, maybe even 2 high gain variants?

~Phil

[M Fowler]

Designing Valve Preamps for Guitar and Bass.

Fig. 14:7 Practical Ultra High Gain

Each design has a different name, there is only one schematic titled Ultra High Gain.

Mark

[martin manning]

Designing Valve Preamps for Guitar and Bass, Second Edition

Page 260, Fig. 14:7 Practical Ultra High Gain

Each design has a different name, there is only one schematic titled Ultra High Gain.

Mark

Clarification added ;^)

[M Fowler]

Thanks Martin, nice knowing you got me covered so I didn't have to scrounge for my book.

Mark

[sluckey]

I see three 1k8 resistor labels but the resistors are color coded as 1k5.

Oh, and the 220pfs on the socket should be between pins 2,3 and 7,8, rather than connected to ground. You could probably also connect the 100pF for the first triode directly between grid and cathode for a cleaner look.

[M Fowler]

Thanks Steve we need one of your cool circuit pages on this.

Changed layout to reflect discussion.

Remember guys I am terrible at Visio as you can see.
I took the color bands off the ones I don't have in my library rather then change the colors I got to get going so maybe later I can add back in color bands.

Mark

EDIT: In fig. 14.7 on page 260, the cathode bias resistor of the fourth stage should be 820 ohms not 1.8k. The anode voltage shoud be approximately 140V not 192V.

Ultra High Gain amp Merlin B V3.gif

[sluckey]

I took the color bands off the ones I don't have in my library rather then change the colors I got to get going so maybe later I can add back in color bands.

You had to select the color bands to delete them. While you had the green band selected you could simply change the fill color to gray. Then deselect the gray color band. Now select the 1.8K resistor. Right click on the title of your resistor stencil and select edit. Now hold down the Ctrl key and drag the new 1.8K resistor to the stencil. Place it between your 1.5K and 2.2K and rename it 1.8K. Save the stencil and take it out of edit mode. It'll take less time to do it than to read this post. You can do this to fill in any missing values in your stencil. Just drag the closest value to your work page, change the fill color of the particular color band then drag the modified resistor onto the stencil as above.

Or, you could use my resistor stencils. I have full size for 1/2, 1, and 2w CCs and 1/2w MF, and popular power resistors, 3w MO, 5 and 10w cement resistors. I even have a RN65 stencil but I have never used that.

[M Fowler]

Or I could just build the amp and move on.

Ultra High Gain amp.jpg

[sluckey]

Haha. That works. Forgot how fast you are.

[sluckey]

Any progress? I'm really curious about this circuit.

[Littlewyan]

Yeah I'm dying to find out how this sounds