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ElectroHarmonix 6CA7 big bottle tetrode - precision matched

ElectroHarmonix 6CA7 / EL34 - precision matched
Manufacturer: electro harmonix

The ElectroHarmonix 6CA7EH is the budget sleeper tube of the new production EL34/6CA7/KT77 family. EL34 tube types are rated for 25w of plate dissipation, but our testing has shown that most new production types start to red plate (visibly overheat) around 22-23w. Not the EH6CA7. It hangs in there until nearly 30w. It is this overacheiving characteristic that causes us to recommend this tube in any amp that runs these tubes hard. We can also recommend it as the tube we expect to have the longest service life. 

Prior to carrying the 6CA7EH tubes, we advised customers with amps like Music Man and Dynaco ST-70s* to dial the bias back so the power tubes were in a safer range. If you use the 6CA7EH tubes, you can disregard this advice. Crank it up and enjoy. They can take the heat and more. 

*At today's higher line voltages many ST-70s run about 435v at the plate (sometimes higher with a solid state rectifier). The stock bias point calls for 50mA per tube which translates to 21.75 watts of dissipation. This puts most new production tubes right at--or over--the edge of redplating. For this reason, tube sellers (including often recommend a lower bias point than the stock settings in many vintage amps using EL34/6CA7/KT77 tubes. The idea is to get the tubes down closer to the ideal 65-70% range of maximum plate dissipation (25w x 65% = 16.25w). Since the EH6CA7 is capable of dissipating more like 30w it is safe to run them at factory settings even in vintage amps that will run them hard.

ElectroHarmonix 6CA7

A quick glance at the EH6CA7 (center) compared to an SED Winged C EL34 (left) and a Gold Lion KT77 (right) shows why this tube dissipates more heat. The the 6CA7EH's extra cooling fins and greater surface area and mass give it a more robust structure than other EL34 / KT77 tube types. 


These tubes have been burned in and tested at typical operating voltages on a laboratory grade Amplitrex AT1000 (manual setting, fixed bias mode). They are precisely matched for both current draw (mA) and transconductance (Gm). Learn more about our burn-in and testing process here


Price is for a single tube and includes burn-in and standard matching service. Tubes ship in ElectroHarmonix retail boxes.

Precision Power Tube Matching

Our power tubes are burned in and then tested on a laboratory grade Amplitrex AT1000 tube tester. We match tubes for both current draw (mA) and transconductance (Gm) at typical operating conditions (plate: 500V, screen: 450V, grid bias: -41.5V).

After burn in and testing, we hand select and custom match every power tube order we receive. To do this, each power tube set is also run on a custom, fully variable test fixture that can match the operating conditions of your amplifier based on the information you provide below. This enables us to do a final check of the power tube set's performance and matching under load. Why this matters
1. What is the manufacturer and model of your amplifier?
2. How is your amp biased?   Why we ask
3. Matching notes   Why we ask
If you know the plate, screen, and grid bias voltages your amplifier uses, please note them in the comments section when you check out and we will use this information when we select and match your power tube set. (If you don't know, don't worry--we can make an educated guess based on your amp's make and model, if we don't already know the voltages it uses.) If you are a guitarist, you can also specify if you prefer early or late breakup. Thanks!


Price per single tube: $25.00

Enter total number of tubes needed for your matched set
TC Tubes specializes in precision testing and matching of vintage and new production vacuum tubes for guitar & bass players, audiophiles, and DIY tube audio enthusiasts. Our website features secure payment options and fast, convenient shipping around the world.

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