Solid state amps usually sound different from vacuum tube amps, most players agree that tube amps sound “warmer” and “sweeter”. Some players who want very heavy distortion actually prefer solid state gear. Tube amps generally have less odd order harmonics than their transistorized counterparts. Solid state distortion is usually less pleasing to the ear than the compression, even order harmonic enrichment and colorfull distortion that occurs in a tube circuit when it's pushed hard. Tube circuits can also be extremely clean , as well as deliver vast amounts of power to cabinets. I defy anyone to find a solid state amp( with similar power ratings) that can deliver the amount of sound that tube amps such as a HIWATT 200, a Marshall Plexi, or an Ampeg SVT will.

I do work on solid state gear.

Solid state technology and now microcircuits and digital signal modeling are great advances in amplifier production and function. They have not, at (at least in MY opinion) duplicated the sound of the original vacuum tube circuits used in older tube gear. DavesTechShop will glady service and repair all of your solid state gear!

NOS is a an acronym for New Old Stock, it means just that. Typically
these tubes have been sitting in warehouses and distribution centers since they were produced. Some of them can be well over 50 years old. It is also very common to see “MilSpec” (short for military specification) tubes included in the NOS category, these are usually very good tubes. Generally speaking most vintage tube gear was designed by engineers using specific brands of tubes during their prototyping, (RCA, GE, TungSol, Mullard, ect.). The circuits will tend to behave the way the engineers wanted them to with the same models and brands of tubes that were initially used in their designs. You don’t ALWAYS HAVE to use them and you may not even be able to FIND them. The tubes currently in production are for the most part pretty good, but be carefully when you pop and swap them. They aren’t ALWAYS electrically the same, this is ESPECIALLY true of POWER TUBES!

BEWARE OF NEW 7591 AND 7027 TUBES FROM CHINA AND RUSSIA , THEY ALMOST NEVER “FIT” WITHOUT SUBSTANTIAL CATHODE AND SCREEN CIRCUIT CHANGES.

I see quite a few amps with smoked power supplies and output stages because of this.

They're not .

Let me explain (this may piss some of you off). 99% of the tube circuits that most of us ever deal with do not require matched tubes. No Fender or Marshall does, PERIOD. If you have a tech go through your amp and “blueprint” it, (make certain that all the component values are ACTUALLY what they are supposed to be) and you get an output transformer that is accurate from side to side THEN matched tubes MAY make a noticeable difference. In the audiophile world there are some exceptions to this, but not nearly as many as the tube retailers would have you believe. Some older high powered tube gear like and SVT or big Hiwatt may be easier for your tech to bias with matched tubes but even those amps do not REQUIRE them. Often time if a tech is paying attention he/she will notice that matched tubes do not conduct the same when they are installed in a circuit, this is because the circuit for whatever reason, isn't matched very well. Sometimes and especially in amps like Marshall Plexis, the factory tolerances in the design specs and component specs were so wide that there is absolutely no way to get the output stages even close to being equal. Thus the classic sound that we all know an love, some of the best sounding amps ever made (most of them actually) are textbook examples of how NOT to design an audio amp.

Groove Tubes uses a matching system that rates a tube either H for Hard or S for Soft and then a corresponding numerical value 1-10. If you replace your power tubes with the same tube type with the same 1-10 rating, you shouldn't have to re-bias the power section of your amp. This is virtually the only matching system that I am familiar with that provides any benefit to the end user, and you pay for it.

This is one of the most misunderstood subjects that every guitar player eventually will have to learn, and it's easy so pay attention!

When you connect speakers in SERIES (+ to – all along in a row and eventually you end up with 1 positive(+) and 1 negative (-) lead which go to the amp.) the impedance simply adds up. Two Four Ohm speakers in series is 8 Ohms, three eight Ohm speakers in series 24 Ohms, two eight Ohm speakers in series is 16 Ohms.

When you connect speakers in PARELLEL (all + together and all - together) the impedance goes down, however there is a tiny little bit of math involved. To figure parallel impedance you take 1 over the impedance of the speaker and add it to 1 over the impedance of the next speaker etc. etc. , then convert your fractions and divide the whole thing into 1. ( you do remember fractions don't you)

1/8 Ohm + 1/8 Ohm + 1/8 Ohm=3/8 Ohms covert to decimal =.375. Now divide 1 by .375 and you get 2.666 Ohms.

Simple Huh!

It happens, mostly due to use, abuse, time, and normal wear and tear. Tube amps need to be serviced at reasonable intervals, if you play yours a lot and play it loud you will need more frequent servicing than someone who plays at lower volumes and not as often. When you bought your amp you made the decision to purchase based (hopefully) on the premise that you liked the sound of it or possibly you had heard another amp of the same make and model at some other time. If that amp now digusts you whenever you play, it is reasonable to assume that the amp is not performing as it once did. This could be due to tubes aging and or failing power supply components doing the same and also speakers wearing over time. It can also be due to your ears or tastes changing, are you using the same guitar and pickups as you did when you got the amp? What about effects between then and now……..Lots of variables huh! If you don't think your amp is performing as it should, it probably isn't, have it checked.

Anyone who is QUALIFIED and has EXPERIENCE working with vacuum tube circuits and who YOU TRUST. Those three requirements should weed out the vast majority of wannabe techs.

30 seconds is a great rule, 15 will work but nothing less. Most tubes designed in America back in the day were rated with a minimum warm up time of 11 seconds, this is right out of the RCA Tube manual.

Get an older version of the ARRL (Amatuer Radio Relay Leage) handbook, pre 1980. READ ALL of the first chapters on basic math and circuit functions, then read about tube theory and solid state devices. Next get on the web and get schematics for your amp, then go for it! Always remember the golden rule of life……

IF YOU DON'T KNOW WHAT IT DOES, THEN DON'T MESS WITH IT!

Remember, Tube amps have very high voltages in them, they can KILL YOU if you do not observe proper safety precautions while working on them.