One of the joys of owning tube audio equipment is the fact that you can experiment with different tubes.

If you're new to tube audio,  you might want to download our primer on tubes, "Tube Rolling with the HA-2" (37kB PDF file).  It describes in detail the tubes in the HA-2, recommended substitutes and upgrades, and "tube rolling" in general.  It also has a list of resources that you might find useful,

 Tubes in the HA-2

The HA-2 uses three tubes:  A 6SN7GT dual-triode voltage amplifier, a  6080 dual-triode power follower, and a 5U4G rectifier tube.  We use Russian tubes,  as well as NOS 6080 tubes for the power output tube.  

We are also shipping the HA-2 with a premium set of tubes (for more money, or course).  The premium set includes an NOS GE side-getter 6SN7, an NOS 6528A, and an NOS GZ37/CV378 rectifier tube.  This combination results in lower noise and a slightly faster, less "tubey" sound.  It also lowers the output impedance, which helps to drive lower impedance headphones.

You can replace the tubes with any tube that has the same basic part number, or exact electrical equivalents.  Note that the letters at the end specify the glass shape only, and you do not have to use the same glass shape as we do.  For example, you can substitute a 5U4GB for a 5U4G, etc.

Svetlana is the only current manufacturer of 6AS7G and 5U4G tubes, and the Reflektor factory (whose tubes sold by Sovtek) is the only one we know of  making 6SN7's.  

You can substantially alter the sound of the HA-2 by replacing the tubes with various NOS tubes.  The output impedance and noise can be lowered as well by substituting different type output tube.  Especially if you want to use 32-ohm headphones (like Grado's), you may want to replace the 6AS7/6080 with a 7236 or 6528(A) tube.

The tubes, and some possible tube type substitutions:     

6SN7GT 6AS7G  /  6080WC 5U4G
6SN7GTB 6080 5U4GB
6SN7WGT 7236  5U4GT
6SN7WGTA 5998 - recommended GZ37/ CV378 - recommended
5692 ECC230
6528 (A) - low impedance
6336 (A)

Note that these are not all possible substitutions.  If you're not sure of yourself please consult someone knowledgeable before you try it.

A special note about the power tube, the 6AS7G or 6080.... We've found that a significant percentage of the new production Russian 6AS7G's (which all come from the same Svetlana factory, regardless of who is selling the tube), have a noise problem in the HA-2 circuit.  We reject perhaps one out of four of these tubes because they are unacceptably noisy to us.  Because of this, we currently ship standard amplifiers with NOS General Electric 6080 tubes.  The 6080 is a military version of the 6AS7G, with exactly the same characteristics.  It looks completely different, but be assured, it's the same tube inside. 

 We've had excellent success with the GE 6080's, and there is virtually a limitless supply thanks to our buddy Uncle Sam.

If you need to replace the power tube, be forewarned that you might get a tube that's noisy, especially if you use a Russian 6AS7G.  Depending on where you buy it, they may or may not let you return it to get a quieter one.  Luckily, the cost for this tube ranges from $4.00 up to $12.95, so it's not a big financial burden.  Perhaps the best thing to do is buy a couple of different replacement tubes and listen to them.  Or contact us and we can point you to our sources....

Remember, tubes need some time to break in.  The sound of your amp may change a little when you replace a tube, and may take anywhere from 20-200  hours of operation to settle down completely.



Tubes in the HA-1

The HA-1 uses three tubes, but only two different types:  An ECC82/12AU7 (we use a new production JJ/Tesla ECC83), and a pair of NOS 7044 tubes.  The 7044 is a special tube, designed for computer service, which gives the HA-1 it's low output impedance.

The tubes, and some possible substitutions:

ECC82 7044
12AU7 (A) 7119
5814 E182CC

You can experiment with any 12AU7 type if you want.  We've found that the new production JJ/Tesla  ECC82 is pretty darned good, especially compared to some of the Russian and Chinese stuff out there.

The output tube has limited possibilities for replacement, but the 7119 and E182CC types are compatible with the 7044 we use.

Tube dealers

We would like to point you to a couple of on-line tube dealers...


thetubestore is  a really slick e-commerce site that specializes in, you guessed it, tubes!  They stock the current production Sovtek tubes that we ship with the HA-2, as well as some NOS tubes.  Their prices are among the best, and they almost always have the tubes you need in stock.

Angela Instruments

Angela Instruments is a great source of NOS tubes, as well as other high-end parts of interest to the tube audio nut.  We buy some of our components from Angela.  Their site not only lists the parts, but some valuable opinions about them (like which NOS 6SN7 sounds the best).

Triode Electronics

Triode Electronics is another great source for NOS tubes and other audio parts.  They stock a variety of NOS and current production Russian tubes at great prices.