Hot Mama tube amp attenuator assembly instructions

Thank you for purchasing the UralTone Hot Mama kit!

Read the instructions carefully and if you have any questions you can contact us by email. Always remember that safety is the priority when working with electronics. Hot Mama is a passive product, which means there are no high voltages inside, but if it is built incorrectly you can damage your tube amp so be careful!

Check all the parts

Check that all components according to the parts list are included in the package.
• Aluminum case (have to purchase separately)
• 50W aluminum profile resistors 13pcs total
• 2 * 6pole rotary switch 753-2×6 (1pc)
• 10 – 25K potentiometer
• 2W metal film resistor
• knobs
• 3pcs Mono jackets
• Jack and potentiometer washer, Place between component and chassis.
• Connecting cable
• Shrinking tube
• 3mm screws, nuts, and washers
• Rubber feet under the case

Tools you need

Tools you need to assemble this kit:

• Soldering iron, 25-35W basic soldering iron is fine but the quality soldering station is much better. You can buy one for under 100€ and it is worth the price!
• solder, please choose one with 3g silver (AG3 like: this product). Low price lead-free solders are very difficult to solder. They are meant for the industry, not for DIYers
• Plier and side cutting pliers
• drilling machine (any will do)
• drill bits
• screwdrivers, etc.

After the housing is drilled, attach 50W power resistors, potentiometers, jacks, and other parts to the housing.

Once everything is attached, check again that the correct parts are in the correct places.

Drilling tips: You should first drill all the holes with a 2-3mm drill. A small drill makes it easier to get holes in exactly marked places than a large one. Later, large holes to the desired size.

Next connect the pots, switches, etc to the chassis. Then wire and solder all the parts using layout that is included in the kit. Please note:
The shorter the connecting wires, the better.

When all components have been soldered and wiring is done, check the connection at least twice.

PLEASE NOTE: The tube amplifier may be damaged if it is turned on without a speaker load. So check the connections of the amplifier, speaker, and Hot Mama attenuator before turning on the amplifier! This is really important.

Measure hot mama with multimeters resistance meter.

• Connect speaker cable to the output of Hot Mama attenuator
• Connect speaker cable to input of the Hot Mama and measure from the other side of this cable
• Measure resistance between tip and sleeve (or + and -, hot and ground) points
• With 8 ohm Hot Mama meter should read about 8 ohms (20% tolerance). If you have 4 ohm Hot Mama, meter shows 4 ohm and 16 ohms Hot Mama 16ohm.
• Check all the switch positions – meter should show ABOUT same resistance in all steps.

Please note:
Only use 8 ohm speaker and 8 ohm output with 8ohm Hot Mama
Only use 4 ohm speaker and 4 ohm output with 4ohm Hot Mama
Only use 16 ohm speaker and 16 ohm output with 16ohm Hot Mama

Hot Mama will get hot so use heat-resistance paints (from car part shops for example).

Hot Mama Features:
• Max amp power 100W (with extra cooling you can use bigger amps), max peak power approx. 300W.
• Connections: Speaker out, Input from amp and Line out
• Speaker output attenuation:  0dB, -4dB, -7dB, -11dB, -15dB, infinite dB /  dummy load (amplifier sees 8 ohm resistive load)
• Line out output level adjustable with potentiometer.

Use the Hot Mama power attenuator / dummy load only at your own risk and only with high quality built in amplifiers that can withstand playing at high volume levels. Note that many amplifiers, especially those built in the 50s and 60s, are designed to play clean and use tiny transformers so any additional load can damage the amplifier. In the worst case, the output transformer can be damaged.

However, we have never experienced or heard of a case where the amplifier would have been damaged when using  Hot Mama powe attenuator.