• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

RM-10 (musical reference) schematic wanted

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#21
I’m currently going through the interesting and thought provoking conference videos of Roger available as resources on ramlabs’ website and YT where he explains a few things including how to implement a much smaller output transformer and get, nonetheless, a broad frequency response.
 
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#22
And in case someone is Interested in another unusual set up aimed at getting the most out of a pp of el84, with 400v or so on the plates, here is an interesting discussion on a Dutch forum concerning the cr developments Kalypso from the 1990s
https://zelfbouwaudio.nl/forum/viewtopic.php?t=20959 The owner / fixer of the amp has posted a schematic.

The Kalypso is currently my all times favorite amp in my set up (with a large diy horn system for mid/high and 2x15” in the bass).

The above discussion points to some controversial options adopted by the original designer. It seems electronicians are like politicians: they need to disagree on choices made by others…🫢😅 (leaving aside questionable improvements made by apprentice tweakers)

Would love to hear from a rm-10 owner how s/he feels about his amp. No hearsay please.
 
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#24
I had an RM-10MKII (not the high power - 35w version) and tried to draw up the schematic...but remember this version being nothing really different from what you would expect... sold it as I liked the Quads powered by NCore amps (I always feel compelled to watch tube amps for red-plating / runaway)

Anyway, I now have another RM-10MKII well, minus the base, but the "guts"....the circuit is a bit different than my previous MKII...This one only has 8 ohm taps only (supposedly designed for the Quad ESLs), and has a choke, and it also has individual bias pots for each tube (Fixed Bias) - my previous one had the LEDs and the Cathode resistor (Cathode Bias)...

I have not put power on it yet as it has some loose components... more later...
 
#32
The secondary has just the 8 ohm tap...I will look again, but think that is it, no other windings...

I agree someone has modified the unit for Octals....a couple components (mainly one large cap) is detatch and dangling...need to figure out wher it goes...the heater winding is AC and tubes wired series-parallel, and I beleive the bias circuit is also off this voltage...

But I cannot figure out the Doubler circuit (if it is a doubler circuit) on the power supply...
 
#35
Its not too special- a 12AX7 voltage amplifier and concertina, to a pair of EL84 with fixed bias. The real secret sauce is high plate voltage and higher impedance than usual output transformers.

Did you take a look at this review on the very sinilar MKII? There's a shot from underneath showing all the wiring and components, this should be enough for a start to start tracing things by eye-
hero_open.jpg

Some more pics here- https://6moons.com/audioreviews/musicreference/rm10_2.html


There's also the web archive to look at his design philosophy for the original RM-10-
https://web.archive.org/web/20200727222903/http://www.ramlabs-musicreference.com/rm10design.html

From when I last worked on an RM-10 years ago I remember the center tap of the voltage doubler being used for the screen supply to the EL84s, I can't find anything else and my notes are long gone.
 
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