Click here to read a technical explanation about Adaptive AutoBias written by Marcel Croese, the engineer who designed Adaptive AutoBias.

All PrimaLuna amplifiers come equipped with either EL-34 or KT88 power tubes. However, you can substitute in any 6550, KT66, 6L6GC, 7581, KT90, EL37, or even a 6V6GT into any amplifier.

The ProLogue One, Four, Six, and DiaLogue One amplifiers can use 6550 and KT88 tube types without any issues . The tubes will be running slightly cooler, but many customers have been using these higher dissipation tubes with great success.

Each tube will have a different effect on the sound. Adaptive AutoBias will adjust itself to the new tube type, making experimenting with different power tubes very easy. In fact, the Adaptive AutoBias circuitry is so advanced you could even plug in one 6550, one EL34, one 6L6GC, one 6V6GT, and Adaptive AutoBias would recognize the differences, make the appropriate adjustments, and the amp would function perfectly. Now... it may not sound very good, but it's just nice to know you could .

Yes, that is normal for power tubes. That blue glow is just stray electrons bouncing off the glass. Some tubes will have a more noticeable glow than others, even amongst a matched set of tubes. Sometimes the glow will burn off, that is also normal. What is NOT normal is a bright blue or purple glow or flash coming from inside the plate structure of the power tube. If you see a bright blue or purple glow coming from inside the plates, or if you ever notice a bright flash from a power tube, turn your amp off immediately and replace the tube.

You may have a bad power tube that blew the plate fuse. Read your owner's manual for detailed instructions on how to check the plate fuse. You can also download the owner's manual from this site.

You may have blown the mains fuse. Many different factors could cause this, including a power surge or spike. Replace the fuse and turn the amp back on. Read your owner's manual for detailed instructions on how to check the mains fuse and to find the appropriate value. You can also download the owner's manual from this site.

All PrimaLuna equipment comes with a two year warranty that covers parts and labor. Tubes are guaranteed for six months. This warranty is for the original purchaser only and is not transferable to subsequent owners under any circumstances.

The Home Theater input on the DiaLogue Series is a direct-line pass-thru circuit. If you plug in a component that does not have its own volume control, you may seriously damage your speakers. It is very important to make sure you only plug a home theater processor or receiver into that input! PrimaLuna, your distributor and it's Partners are not liable for any damage caused by plugging an inappropriate component into the Home Theater input. If you are unsure of what can and cannot be used, consult your PrimaLuna Partner or contact your distributor directly.

With so many people having home theater systems, they are used to preamps that have a subwoofer out. In a regular stereo amp that has no surround processing, if you see something marked subwoofer out it typically means it is a preamp out. In essence nothing more than voltage signal coming from the preamp, fed to the woofer's amp that is then amplified.

So what happens if you don't have a preamp out? Most every subwoofer made in history is designed to handle that. They have a high-level-in that is hooked up to the speaker taps of your amp. Works the same way. It takes the voltage from the amp as the signal and amplifies it.

This does not cause a power draw on the amp you hook up to. It is using the signal, not the power of the amp to make sound. So there is no "draw" or sapping of power. No negative effect to the sound of the main speakers.

In fact, the most prestigious subwoofers in the industry are made by REL of England. They are the "Gold Standard" of the industry and priced accordingly, topping out at $9,000! Though they can be installed either with line level or speaker level, most REL woofers are hooked to systems with speaker leads of amps.

One snippet of information: Often times subwoofers will allow you to hook them up to the speaker taps of the amp and to cross-over the main speakers, restricting how much low information they get. Don't assume this is a benefit. It may allow the mains to play louder as they are not having to move as much air, but the downside is you can lose some clarity. Experiment as different products work different ways.