Merlin's Ultra High Gain preamp

[M Fowler]

Checking voltages and then will upload my voltage chart for the Merlin Ultra High Gain circuit into JCM800 power amp.

I will also get Steve Stine to make a video of both the Fowler HRP and this Merlin amp, mean while I uploaded a video of his playing. He is a great guitar player and teacher.
https://www.youtube.com/watch?v=HM_3SGbSlME

Mark

[M Fowler]

My voltage chart for this Merlin Ultra High Gain preamp circuit into Marshall JCM800 2204 type power amp.

Merlin Ultra High Gain Voltage Chart.pdf

Mark

[M Fowler]

In it's cab now.

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[M Fowler]

Maybe it's just me but I don't hear anything when I use the noise reduction switch two diodes.

[pompeiisneaks]

You may not have much noise

~Phil

[M Fowler]

Phil, it is really a high gain sucker so I reduced v1 to 5751 and plan on tube rolling some more 12AY7 in V1 & V2 and maybe this amp would like a 12AT7 phase inverter!

[pompeiisneaks]

Very cool. I really would love to hear some samples of the amp!

~Phil

[M Fowler]

Guys like the Merlin Ultra High Gain circuit it's crazy high gain.

I like my other AFD circuit better.

I get a lot of oscillation so will be back inside the amp to try cure that. Might have to punch a new preamp tube hole further over plus gain stage grid resister.

Also, wondering if my layout is correct for that noise reduction diode circuit, I hear no difference when switching.

[ChopSauce]

Sorry for being late, but I think I remember Merlin wrote a few lines about the minimal distance between pre-amp tubes in his book. Maybe that had to do with his experiences with this pre-amp?

[M Fowler]

I knew that too, but I wanted to use a standard punched chassis readily available to all.

[Davidg]

Did u by chance get time to do any soundclips or videos of this amp? Really anxious to hear it ! Your amps always look and sound great.

[M Fowler]

No I didn't but I will in future.

Home remodeling right now, bought a cheap house for my oldest son.

[frankdrebin]

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

Ultra High Gain amp Merlin B V3.gif

the 4th stage cathode resistor is 820 ohms,there is an errata page on Merlin's site.

[M Fowler]

820R in place of the 1k8 and 10uf cathode 4th gain stage?

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 should be approximately 140V not 192V.

[M Fowler]

I finally got around to changing out the bypass resistor and removed the 10uf cap all together.

The amp still has plenty of high gain and I took it over to the local guitar shop for people to play around with along with my 50w Hot Rod Plexi.

Mark