FAQs

Technical Support

We are often asked for technical support however due to the nature of tube amplifiers we are limited in the help we can give.

Tube amplifiers contain lethal levels of voltages and can hurt or potentially kill you even if switched off. This is the main reason we cannot provide technical information. If you know what you are doing then you won’t need the support of anyone over email or phone. Secondly, any technician will tell you that in most cases you really need to see the amp before making recommendations.

What will we support you with regarding technical information?

• Products selection (Choosing the right product *excluding transformers)
• Understanding what tubes go with your amp
• Limited technical information e.g. questions that won’t put you in harm's way.

Here are a few of our most common questions

• Will these tubes sound good in my amp?
  • The answer is “no one knows”, the reason is that sound is personal and what you like someone else might not. In saying that I believe that I could get most tubes to work in most amps without any real issues.
  • I believe some work better than others and I personally haven’t tried every option out there.
  • I would suggest (and often do) that you look for people who have a similar amp (and you like their sound) and try those tubes as a start.
• Do the tubes I use, make a big difference?
  • Yes, they will. To be very clear though it's my opinion that there are so many factors in determining the sound of an amplifier that thinking tubes are the ultimate answer to your search for tone is probably futile
  • The biggest differences heard in an amp is through the preamp tube (different brands and types), Thats' not to say power tubes cant make a difference, just less of an impact.
• The cheapest mod you can do
  • Look to change your preamp tubes.
  • Try using a 12AU7 or 12AT7 in you first slot to tame the amp.
  • I often keep a few preamp tubes around and test them in different positions...you would be astounded at how much difference to the sound it can make.
• Should I bias my amp?
  • Well, it depends, not all valve amps need biasing (wait, what?) well an example is if an amp has a single 12ax7 in the preamp and no valves in the power section e.g. Marshall valvestate, then no. However, most will over time 
  • As for, should you? Valve amps can run very high voltages and are dangerous to work on, so qualified technicians should perform these tasks for you if required.
  • When does it need to be biased? This is a huge subject with many opinions, I have heard of people saying that you should bias them every time you change and then every two weeks for a period to ensure they are just right and yet others claim, half the mojo is in not having the tubes biased perfectly. The reality is that if valve fall outside of their manufacturers specifications then they will either sound bad or cause issues, luckily this is rare.
  • How to be safe. Simple, I advocate having your amp bench checked by qualified, reputuable technician every 2 years for a gigging musician or every 3 to 5 for someone just playing here and there. HiFi follows the same logic, (using the amp every day, then ever 2 years for a check-up) once a week then the latter. Ask for a written report, nothing special, just something as part of your receipt.

    • Remember that issues in valve amps can come from a lot of places and when a tube redplates or dies, it could be other parts of the circuit, so you may be putting new valves at risk. Things like electrolytic capacitors have a limited life span and can affect you sound, even producing weird issues, people will come in saying I have a scratchy potentiometer, only to find out it is their caps. A resistor failing in key areas of the circuit e.g. bias can cause red plating, blaming the tubes for red plating out of the box. 

  • What if I only change preamp tubes. Then no, Preamp tubes do not need biasing.
  • Do I bias my amps every time I change power tubes, No, Tubes are tested and matched prior to sale and are safe just to add in (unless you have other amp issues) and I always let them cook off for a few hours before I bias, then the phone rings, I forget and before I know it, months have gone by and I am still playing. 
  • Research, you can find people talking pros and cons about this topic, and the best place to start is to research your needs with reputable sites. Forums are not necessarily the best place to find information, sometimes there are brilliant people in there but often it is people that have spare time that tend to respond the most. Great place to read vary depending on how technical you want to become : If you would like two recommendations then try Rob Robinette's site (found here) for great information on guitar amps and The valve Wizard site (found here) for a broader view.
• Do you bias amps?
  • No sorry. Technicians are set up ready to go for this and we just don’t have space.
  • I will add that I believe trying different preamp tubes is my first love when chasing tone but Biasing an amp to my taste is the second favourite thing to do
  • Also, let your tubes run for a while before biasing them, I often find tubes a bit harsher at the start until they boil off some electrons and then settle down, after that I bias 
• Do you sell bias probes?
  • No Sorry...they just aren’t worth it...there are plenty around though
• What are the best tubes to buy?
  • There is no such thing.
  • There are definitely people's favourites or types that amps come out with but we sell all the top brands and when you blind test people most can’t tell. Yes, I know there are people reading this right now saying they can and maybe they have some superpower but I am yet to see any A/B scenario that solves this age-old question for no other reason than sound is personal. What one person likes another doesn’t.
• What reverb tank goes with my amp?
  • You need to look for the number on the side or top of your existing reverb tank, then search the website.
• What style grill cloth looks good with my amp?
  • Go black, you can never go wrong. Nah not really
  • Similar to sound, a look is personal.
  • Try looking at google images and get some ideas from there
• How do I glue tolex on and what do I use?
  • I use good old contact glue from Selleys Kwik Grip
  • Her are a few tips though
    • Lay you tolex out in the sun for a while. It will help remove any creases etc
    • Map out "on the back which is the cloth side" your amp.. each side top etc.. allowing room on the edges to wrap inside the amp
    • spread a thin layer.. well covered but thin, no pooling of glue, onto both the cloth and the timber.
    • LET THEM DRY TACKY… Sorry to yell but you can let these almost dry completely and they will stick (don’t let them dry but let them get very tacky)
    • Have the right tools ready.
      • Sharp decent scissors
      • A Stanley knife
      • A roller (to flatten the tolex)
      • Do Not stretch the tolex, it needs to be laid on then rolled flat but stretching will hurt it
      • Watch youtube… there are some great videos on the web
• Do you have testers and will you test my tubes?

Yes, we have several testers here including

• Amplitrex 1000 (perhaps the greatest of testers)
• Maximatcher testers x 2,
  • 1 x Preamp tube tester
  • 1 x Power tube tester

We can test tubes but you need to think about what you want to be tested. We simply don't test easily accessible tubes like a set of el84 JJs or EH.

We only test Expensive tubes and we charge for it, sorry but time spent testing your tubes will only be my time being removed from something else I could be doing. The price varies and we would need to discuss via email.

Warranty - What warranty exists on tubes?

All tubes ranged at Evatco are tested and measured in advance.

All tubes on the site that are advertised as matched pairs, quads or sextets have been tested and matched on IP and Gm.

The warranty period is 60 days.

If you feel you have a faulty tube for any reason you will need to send the tube back for testing prior to any refund or exchange and within this 60 day period.