What means the letters PL

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This KT88 are the ultimate quality KT88 available today from new production.  Failure rate is virtually zero, and the matching is done with the double burn in "PL"method.   Sextets and Octets cost no extra, but we must have them available. 

For manufacturers we also can supply a 100pcs bulk pack at OEM Prices.

KT90-EH-PL

What means the letters PL

The KT90 can replace the KT88, but it is a different construction tube. The KT90 is made from elements of the big PL519 horizontal sweep tube for color TV's. The PL519 is in fact a tube with very high cathode emission, and it is a really good idea to make a HiFi tube from this. Grids and the plate were modified to make it compatible with the KT88.

What means the letter G <== Click there. Must read!

Another great tube from the Russian military, at it's highest point of development. This is a frame grid tube, meaning the grid wires are so extreme thin, you can not see them with the eye or handle a finished (non-frame) grid. For making a grid like this, first a frame is made of hard metal. Around this frame, the grid is wound, and then frame and grid together go inside the tube. Like this, very precise tubes of high gain can be constructed. Characteristic for frame grid tubes is the nice uniformity of transconductance. The 6C45 has a gain of 50x and it has enough plate dissipation to build a small SE output stage with it. Originally this tube was not made for SE stages, but it's a secret tip and it works very nice. This tube is ideal for use with Lundahl LL1660 driver transformers. You can wire the transformer for instance in a 4.5 : 1 step down scheme. This will still leave you with a total gain of 50/4.5= 11x which is a good number. The good part is now, the output impedance of this tube is reduced with a factor (4.5)² = 20. So the original Ri of the tube, of apr. 1100 Ohms will appear as 55 Ohms (!) at the output of the LL1660. This 55 Ohms is very nice for head phone amplifiers, or pre-amp outputs.

So a line output stage with this tube, using the LL1660/25 would have these specifications:

Design example for line output stage:

Transformer LL1660/25 with connection scheme: Alt Q (see this website for Lundahl transformers)

• Stage Gain = 11x
• Output impedance 55 Ohms
• Frequency range 10Hz...35kHz at 1db

Note, when designing with LL1660: First let's say here the normal LL1660/25 works very nice. For superior noise isolation with line driver amps, or for user increased safety with head-phone applications, the "S" version (shielded) can be used. The shield is in between primary and secondary and must be grounded. Both the standard or the "S" version are available with amorphous core.

Datasheet of LL1660

6H30Pi-EH-G

This tube is also from the best times of Russian military tube making. Actually is was forbidden to export it from Russia, I believe until 1995. It has a very large getter for longest lifetime, and you can best see of this tube as a higher voltage, higher power version of the ECC88. The pin out is the same, also the data are comparable, but is it not fullly equivalent. WIth some minor changes ( sometimes without changes) you can adapt most ECC88 circuits for the 6H30.

6H30 is widely used today as driver tube in very high ended audio equipement. Pictured is the Sovtek tube here, the EHX looks the same but has gold pins, and gold metal printing which can never wipe off or burn. The balanced version has the two systems inside one bulb matched to each other.

What means the letter G <== Click there. Must read!

What means the letters PL

For manufacturers we also can supply a 100pcs bulk pack at OEM Prices.

What means the letter G <== Click there. Must read!

This tube maintains a linear response while being able to accept a full voltage. Vintage amp users and audiophiles will be thrilled to find that a superior quality, ultra low noise replacement finally exists.  GOLDPIN version!

What means the letter G <== Click there. Must read!

This is the GB - Gold-Balanced version. This tube is simply the FINEST 6SN7 available today from new production. It maintains a linear response while being able to accept a full voltage. Vintage amp users and audiophiles will be thrilled to find that a superior quality, ultra low noise replacement finally exists.  GOLDPIN version!

With cylinder glass shape. 

Semi Long Plate version, with superior dissipation over the originals. Perfect for reverb circuits and drivers. 
This tube has RHODIUM pins, for better contacts quality.

What means the letter G <== Click there. Must read!
Semi Long Plate version, with superior dissipation over the originals. Perfect for reverb circuits and drivers. 

12AT7-EH-GB. Balance Single tube.
(Equivalent to: ECC801S)

Semi Long Plate version, with superior dissipation over the originals. Perfect for reverb circuits and drivers. 

Semi Long Plate version, with superior dissipation over the originals.
This tube has RHODIUM pins, for better contacts quality.

Semi Long Plate version, with superior dissipation over the originals. This tube has RHODIUM pins, for better contacts quality.

Balanced means, both triodes within one tube are identical.  Only like this both tube halves will produce the same sound.  We do this matching both for plate current, and Transconductance, using official Telefunken operating points. The system balancing was an official part of the original Telefunken ECC803S datasheet.  (Balancing delta by official TFK Datasheet = Max 0,15mA).  We use a difference (delta) of maximum 0,1mA, which is even better than original Telefunken. This is extremely tight for this tube. All measured data is on the tube box, and this is guaranteed data. So before a tube can be called balanced, first both halves  must first have the same plate current, and after that have the same Transconductance, and by this prove to have the same gain. It must pass both tests in sequence. Because this a high gain tube,  not many tubes will pass.  

This tube has RHODIUM pins, for better contacts quality.  This is a shiny  white metal.

What means the letter G <== Click there. Must read!
Very  thick GOLD  plated pins.

What means the letter G <== Click there. Must read!
5751-EH-G is a low noise, long life version of the ECC83, with gold plated pins.  The tube specifications has very small differences compared to ECC83, but this tube is used to replace an ECC83 in all circuits, where you want best reduction of noise an hum. 

Very  thick GOLD  plated pins.

6922-EH-GB
GB = Gold-pin, Balanced tube.

What means the letter G <== Click there. Must read!
The 6922 is a long life  version (10.000 hours minimum), of the ECC88 (6DJ7).
When additional this tube gets gold plated pins,  it was called E88CC. 
The G-Version has very  thick GOLD  plated pins.

Balanced means, both triodes within one tube are identical within a pre-defined limit.  Only like this both tube halves will produce the same sound.  We do this matching both for plate current, and Transconductance, using official Telefunken operating points. The system balancing was an official part of the Telefunken tubes like ECC802S  etc.  However, for 6922 this officially was never done by manufacturers.  Still we offer it for this tube, because specially with this tube it is more important than with any other audio tube! This is the number one tube where people report sound differences quickly. We use: Balancing delta = Max 1,5mA for the plate current (Static parameter) and 10% maximum difference for the transconductance (dynamic parameter).

So before a tube can be called balanced, first both halves  must first have the same plate current, and after that have the same Transconductance  It must pass both tests in sequence. This  tube is a high gain (50x) AND a low voltage (100V) tube type at the same time.  These two requirements are very hard to meet AT THE SAME TIME. So this makes it very difficult for the manufacturer to produce those tubes. The question is what will they do with the tubes that are not so good. Good NOS E88CC is almost impossible to buy now.  It  is normal that within one glass, you can have two quite different tubes, also with NOS.  So very few tubes pass the balancing test.  

Special ECC88/6922 note for technicians: I think we can say, this is one of the most difficult tubes, if you need a good replacement. If any discussion comes up about about too much noise, or bad sound, it is with this tube. Where does this come from? There are many amplifiers using this tube in so called SRPP circuits. As you know, with a circuit like this, both halves of one tube are put in series, so must draw the same plate current per definition. Problems will come with an unselected tube, where both tube halves by itself actually would have liked to draw a different current. The result of such an unbalanced tube in an SRPP circuit is, both tube halves are in a "battle" about what current they can draw. One of the two halves will try to dominate, and determine the final current for the circuit. The voltages in the circuit are now not correct any more. Also the actual current drawn can be too high or too low, depending if the "higher" or "lower" current tube is the winner. If a stronger mis-balance occurs, the circuit will produce more noise than normal and add too much distortion. Also tube wear out can be the result of this, and an acceptable result in the beginning will soon be less good, and the complaints starts from the beginning. To prevent any problems like this, for an SRPP circuit ONLY balanced tubes should be used.

Balancing a "GB" single tube means: only like this, both halves are guaranteed to have the same plate Transconductance, the same bias and same gain and by this produce the same sound.   This is done on a calibrated tube tester, which measures the tube data with a 1600 Hz test tone. (So not one of those Hickock testers, and nobody knows what the tester is really testing)

6922-EH-GB Balanced Matched Pair

Balancing a "GB" pair means: A single tube contains two triodes inside. A balanced pair means you receive two tubes containing actually four identical triodes.

Balanced tubes offer uniformity and stability in characteristics, and by this low operating costs.

What means the letters PL

The 6550EH is the finest current production tube for any amp using 6550 or KT88. The 6550EH offers the maximum power of any 6550 with the linearity guitar and bass players want. With 42 watts of plate dissipation in tetrode operation and 44 watts in triode, the 6550EH offers an improvement in power over even the most desirable vintage types including the Tung-Sol 6550 and Genelex KT88. This extra headroom in a 6550EH equipped amp means bass players can finally realize the full dynamic range of the instrument and the sweetest tone available. 

The extra ruggedness of the 6550EH was engineered with the punishing abuse of guitar amps in mind. The nickel steel side rod mica supports ensure that the 6550EH will hold up in even the most punishing environment of high powered bass amps like the Ampeg SVT and combos where the tube is only inches from the speaker and still deliver the sweetest tone of any 6550 or KT88. The 6550EH will greatly improve the performance of any amp using 6550’s but can also replace the KT88 in any application.

 For manufacturers we also can supply a 100pcs bulk pack at OEM Prices.

What means the letters PL

Vacuum Tube Valley journal says, "... the new Electro-Harmonix tube comes very close to the sonics of a Mullard EL34,   and is balanced throughout the entire music spectrum. Bass goes deep and is tight, mids are sweet and well defined and highs are detailed and extended." Sextets and Octets cost no extra, but we must have them available. 

For manufacturers we also can supply a 100pcs bulk pack at OEM Prices.

What means the letters PL

The new EL84-EH faithfully recreates the classic Mullard design. Triple laminated plate material and selected screen wire increase thermal dissipation. The EL84-EH is a remarkable reproduction of a vintage tube that is capable of maintaining its sweet and musical tone under any voltage conditions. 

 For manufacturers we also can supply a 100pcs bulk pack at OEM Prices.