There are five tubes of two types used in an ED amp - 12AX7 (ECC83) in positions V1 and V2 and 6BM8 (ECL82) in positions V3, V4 and V5. 12AX7's are easy to find and can be purchased at most music stores. The 6BM8 tube will most likely not be found at a music store as it is a more unique tube.
12AX7WA/7025 Sovtek standard gain, low microphonics
12AX7WB/7025 Sovtek 6% more gain, low microponics
ECC83/12AX7 JJ Electronic highest gain, low heater noise
6BM8[6BM8] Svetlana long lasting, reliable
ECL-82/6BM8 Ei more power, reduced life,
run hotter, good for V3 position in ED & HED amp
TUBE SET 2x12AX7 & 3x6BM8 for ED or HED amp
*Prices are in USD. Shipping charges not included.
If there is no dealer in your area, Edward Amplification has tubes available for purchase with comparable pricing. All tubes are new, currently manufactured in European factories except for the Svetlana 6BM8. All tubes are amplifier tested for proper operation and low noise. 35 day warranty on all tubes starting from date of purchase. To make a purchase, simply call us at 289-237-5691 or emailwith your name, address and telephone number and choice of product. Prices are subject to change without notice.
The 6BM8 (ECL82) is a pentode/triode combination that looks like an EL84. The 7 Watt pentode section is actually a tetrode like a 6V6 and exhibits plate characteristics that are more similar to a 6V6 than an EL84. The triode section has gain characteristics somewhere between the 12AT7 and 12AX7 and very good drive capability.
There are several different makes of 6BM8/ECL82 tubes available from various distributors and sellers you will find online as well as many available from online auction sellers. The Russian made version is desgnated as 6F3P. All these different makes have varying levels of quality so I will attempt to clarify the most important features you need to know in order to have your ED amp working at its best.
When considering 6BM8 tubes the three most important parameters for the ED amp are: cathode current, heater (filament) to cathode insulation and microphonics. Each parameter will be explained in more detail.
Cathode current is the amount of current the cathode is emitting while the amplifier is operating. As a very general rule, most Russian made 6BM8 tubes will have lower cathode current than most any NOS tube by any other make. Your ED amp was designed with the Russian made, Svetlana 6BM8 tube. Higher cathode current will provide slightly higher output and more distortion however, these tubes will operate at a higher temperature and the tubes will wear out faster. You just can't get something for nothing.
Heater insulation is not something mentioned often but is an important consideration for the ED amp. Most guitar amplifiers, such as the ED, operate tube heaters with an AC voltage. Tubes with poor heater to cathode insulation will actually have some of the AC current on the heater impressed on the cathode which will show up in the audio signal. You may have noticed that after replacing a tube in your amp there is more humming noise from the amp. Some amplifiers come equipped with a "Hum Adjust" to cancel out any heater-cathode imbalance. The ED amp was not designed with a Hum Adjust feature. The tube in position V4 of the ED amp is the most sensitive to poor heater-cathode insulation because this tube provides the gain required for output stage. Careful selection of the V4 tube is required. The V3 and V5 position tubes are not nearly as critical.
Microphonics. One of the design characteristics of the 6BM8 tube is the structure of the triode section. The triode section has a long plate structure and makes it much more susceptible to picking up surrounding vibrations. As the tube ages and parts begin to loosen up, you may even hear a "jingling" sound while you play at low levels. All 6BM8 tubes will wear down over time and produce varying amounts of microphonic related noise. This is also known to occur in other types of tubes that have been extensively used/worn.
For your ED amp, Svetlana tubes are perhaps the best all around tube because they have a good life span, good heater-cathode insulation and low microphonics. However, not all Svetlana tubes are created equal - look for Svetlana tubes made in Russia or the USSR (CCCP) labelled in Russian as 6?3? with the winged "C" logo, made after 1972. NOS Svetlana tubes made prior to 1972 will have a very high heater noise making them in-appropriate to use in the ED amp. New manufacture Electro-Harmonix 6BM8 tubes are somewhat comparable to Svetlana made tubes but, as we have discovered, have a very inconsistent heater-cathode insulation which makes it difficult to find a useful tube. The Electro-Harmonix 6BM8 tends to become noisy as well, therefore, Electro-Harmonix 6BM8 tubes are not recommended at this time. Nearly all NOS 6BM8 or ECL82 tubes from other manufacturers will work very well with low heater noise and low microphonics but with a higher cathode current that will wear out the tubes faster. NOS tubes are great for recording. Yugoslavian made ECL82's will run hotter and are more prone to glowing red on the plates and slightly higher microphonics. Japanese made 6BM8 tubes are very good and have very low microphonics. The very best tube we have tried in the ED amp is the very rare, Hungarian made, 6BM8/ECL82 by National Electronics. If you have this tube, use it only when absolutely necessary!
Most music retail stores that deal with tube equipment will have 12AX7 tubes available. Edward Amplification dealers are able to obtain the 6BM8 tubes at a nominal cost. 6BM8/ECL82 type tubes are available from many online ordering services such as the ones listed here. Check with your dealer first. Matched pairs are not required.
Antique Electronic Supply 800-706-6789 or 602-820-5411
New Sensor 800-633-5477 or 212-529-0486
Radio Electric Supply 352-475-1950
RF Parts Company 800-737-2787 or 760-744-0700
Tube Man 954-724-0443
SND Tube Sales 314-770-0119
N9TEW TUBE SALES 219-924-0945
Not familiar with the 6BM8 tube? Download the PDF file.
To find more suppliers of the 6BM8 tube, simply look up 6BM8 or ECL82 with a search engine. One thing you should keep in mind is that many suppliers of 6BM8 tubes only have New Old Stock (NOS) tubes available. NOS tubes are new unused tubes that are no longer in production by their respective brand names. NOS tubes tend to run hotter and produce slightly more power than currently produced types. Higher idle currents will show some glowing on the plates of the tube. While higher idle currents are not seriously detrimental to proper operation, the tube will not last as long as a properly selected tube. It is best to shop around before you buy, not just to get the best deal but to know what you are buying.
NOTE: Any brand 6BM8/ECL82 tube available is suitable for the V3 position in the ED and HED amps. The V3 tube is operating at only 30% of its rated power and will outlast the V4 and V5 position tubes.
...no problems, and it sounded great through the in-ears! Actually the first time my guitar has ever sounded really good in the in-ears! And the sound guys were floored, the band was floored and because they loved the tone so much they worked some extra solos in for me! That's the first time that's ever happened!
My amp arrived today. I just gave it a test run and was blown away. You have just given me the final piece of the puzzle in what has been a 25 year quest for me, the quest for the ultimate harmonica tone.