DIY Valve Guitar Amp Head

[Simon Barden]

Any more thoughts on making a load bank? Don’t forget that if you put them in an enclosure you’ll need to have a lot of ventilation for them as they will get pretty hot. And unless they are being screwed to a heat sink, then they will need to be mounted away from any backboard/PCB for better heat dissipation.

9 ohms won’t make a difference compared to 8 ohms. A speaker impedance will be less at some frequencies and higher at others. If you want 8 ohms, just add some more resistors in parallel.

I’d certainly have more power capacity in the resistors than you need. I don’t know how close to its limit a 5W resistor passing 5W is, but if you give it more power when setting up the amp, then you could get a succession of blown resistors and no load bank, and power tube and output transformer damage following.

Of course you don’t need to bias the amp at full power with a signal going through it at all. Just use the speaker and don’t have anything plugged in the input.

[DrNomis_44]

Any more thoughts on making a load bank? Don’t forget that if you put them in an enclosure you’ll need to have a lot of ventilation for them as they will get pretty hot. And unless they are being screwed to a heat sink, then they will need to be mounted away from any backboard/PCB for better heat dissipation.

9 ohms won’t make a difference compared to 8 ohms. A speaker impedance will be less at some frequencies and higher at others. If you want 8 ohms, just add some more resistors in parallel.

I’d certainly have more power capacity in the resistors than you need. I don’t know how close to its limit a 5W resistor passing 5W is, but if you give it more power when setting up the amp, then you could get a succession of blown resistors and no load bank, and power tube and output transformer damage following.

Of course you don’t need to bias the amp at full power with a signal going through it at all. Just use the speaker and don’t have anything plugged in the input.

Yep, I'm going to use the same type of metal enclosure as I used for my XR2206 Function Generator, it does have some good ventilation, and I'm also going to include a small 12V DC powered fan as used in some computer cases to add some extra cooling, with the help of another forum member, I came up with a suitable design for the Dummy Load that uses a total of X22 180 Ohm/5W ceramic resistors in parallel to give an 8.2 Ohm/110W Dummy Load, that should be more than enough for testing purposes.

Here's a link to the Dummy Load project thread I started:

https://www.buildyourownguitar.com.a...ad.php?t=12363


Note that the basic design I came up with can be easily modded to suit the requirements of those wanting to build one for themselves.