New production 6SL7 and 6SN7

[kees52]

Thanks Chris.

I did mean the anode material, not the mechanical part, it seems that the cathode material bariumoxide was different in the past, I have try a lot of tubes and sometimes the new ones are better, special the high gm triodes with gyrator loading like the 6C4N-EB like I have now tryed, the old telefunkes are sweeter and that is relaxing listening, so What precise is the way to make good tubes the bariumoxide, the 6H9C from russia is to hars, I have try it in a lot of possibilities srpp, mu, to lean to hars, maybe the ebay source was no good I don,t now, the 6H8C in a srpp sound oke, 0n 10 ma idle. Do now I make only hybrides

regards

[SY]

Originally Posted by anatech

From my own direct experiences comparing real NOS tubes to some new ones, well designed new tubes are superior.

Ditto (and thanks for your other thoughts on this). I haven't tried new power tubes, but the best of the small signal tubes I've tried all seem to be new manufacture. For example, I love the CV1988 and 5692s that adorn my amps and preamps, but the Electroharmonix 6SN7s I tried had better linearity and consistency.

[Salas]

Also 12AY7 EH was better to American JAN NOS in my amp at least. 6V6GT new Tungsol was excellent also and lowest in microphony, as good as RCA NOS.

[kees52]

6C4N-EB high transcondutance triode loaded on a mosfet gyrator its fast, and sounds very nice, a lot detail.
afcourse a lot is gone with the compression of youtube but a idea I hope is left over.

this sound is from a hybrid mosfet tube amp, 6C4 then 6N6P who is dc coupled to mosfet powerstage, it is here on
this forum so look, I will redrawn it with the new tube.

6H8C and 6H9C are hars and to lean, special the 6H9C has no balls, the telefunken ECC83 is a lot better, a whole lot.

6C4N-EB gyrator loaded plate follower - YouTube

[anatech]

Hi SY,

I haven't tried new power tubes, but the best of the small signal tubes I've tried all seem to be new manufacture.

Well, 6L6EH (6L6GC) work very well in Fender Twin guitar amplifiers. For those who know, 'nough said right there! By direct physical comparison, the 6L6EH has about the same size plate structure as every NOS 7581A I have. The glass is heavier, most people report the heavy glass used in Russian manufactured tubes. Anyway, the 7581A has the same plate characteristics of 6L6GC tubes of old, except that the plate dissipation is rated at 35 watts, not 30 like the GC models. I'm going to strike down another myth while I'm on the topic.

All,
The 5881A is an improved substitute for the 6L6 and 6L6GA. The 6L6GC has a 30 watt plate (as mentioned above) while the 5881A is rated for a full 25 watts. Hmmm, someone or some many are reporting with incomplete information.

Back on topic. Original EL34 tubes are real pentode tubes and rated for a pretty high plate voltage (800 VDC I think). Their plate power rating is a lowish 25 watts. Normally found as a skinny tube. My beef is that they overheat too easily, and they suck about 1.5 amperes of heater current. Ahh, what's wrong with this picture folks? A 6L6 requires about 0.9 amperes of heater current while having a higher plate power rating. The 7581A also requires only 0.9 amperes too. The extra heater power is of course converted into heat, something the little EL34 can ill afford. Long story short, I use a 6CA7A, which is properly a beam power tube, that is very happy in freshly vacated EL34 sockets. Oddly enough, my ears are happier as well when the EL34 goes away. 6CA7 tubes last longer as well. Keep in mind they are a little bit wider, so there are amps designed without enough room between tubes to accommodate them. The thing is, those are also not spaced widely enough for EL34 tubes either. Just an unhappy design all around.

In case I forgot to mention this, there is zero wrong with good brands of newly manufactured power tubes. In fact, late 60's power tubes of good lineage fail in the Fender Twin amplifier. I'm using the Fender Twin as an example because it exceeds the maximum plate voltage ratings for the 6L6GC, which this amp was designed to use. The normal plate voltage in these amplifiers runs around 475 VDC while the tube is rated for 450 VDC. NOS tubes often hum and get hot, or simply turn cherry red while humming loudly. These are not a good sign in a tube amp.

-Chris

[anatech]

Hi kees52,

6H8C and 6H9C are hars and to lean, special the 6H9C has no balls, the telefunken ECC83 is a lot better, a whole lot.

I respect were you are coming from. I would like to mention that any sounds tubes make are from defects. Crackles, hissing, thumps and bangs. Not to forget the lovely ring you can get from cheap tubes.

The character of sound a tube lends to a circuit is created from the interaction of the circuit design, the passive parts and of course, the tube characteristics. Tubes do not sound warm or edgy or soft. If the circuit is designed for the "boogey" tube of a certain type, then all tubes manufactured to those characteristics should sound very similar in a well designed circuit. If there is no feedback used, then everything depends on the interplay between the tube characteristics and the circuit. Take a "hard" sounding tube from one circuit and place it in another and you may have an entirely different impression of how the tube sounds. Never mind that some tubes marked as one brand may be from a different factory that makes another brand. This makes life for people who want to quantify the sound of a tube brand kinda difficult. This is all old news though.

-Chris

[riccoryder]

It's good to hear that there are some reliable 6SN7s being made now. My previous experience was poor. I like the look of octals, but for the sake of reliability and very low cost have used the 9-pin 6GU7, a 6FQ7 replacement that was very popular as a crt driver in 60's color TV sets. Although the plate voltage rating is lower, I pulse tested a number of them and found them reliable at high voltages as is seen with similar types marketed for deflection circuit use. The total plate rating is 6 Watts, similar to the 12BH7A and 6CG7/6FQ7. The 6CG7 shares the 6SN7 curve set up to the power limits.

Originally Posted by anatech

Hi SY,

Well, 6L6EH (6L6GC) work very well in Fender Twin guitar amplifiers. For those who know, 'nough said right there! By direct physical comparison, the 6L6EH has about the same size plate structure as every NOS 7581A I have. The glass is heavier, most people report the heavy glass used in Russian manufactured tubes. Anyway, the 7581A has the same plate characteristics of 6L6GC tubes of old, except that the plate dissipation is rated at 35 watts, not 30 like the GC models. I'm going to strike down another myth while I'm on the topic.

All,
The 5881A is an improved substitute for the 6L6 and 6L6GA. The 6L6GC has a 30 watt plate (as mentioned above) while the 5881A is rated for a full 25 watts. Hmmm, someone or some many are reporting with incomplete information.

Back on topic. Original EL34 tubes are real pentode tubes and rated for a pretty high plate voltage (800 VDC I think). Their plate power rating is a lowish 25 watts. Normally found as a skinny tube. My beef is that they overheat too easily, and they suck about 1.5 amperes of heater current. Ahh, what's wrong with this picture folks? A 6L6 requires about 0.9 amperes of heater current while having a higher plate power rating. The 7581A also requires only 0.9 amperes too. The extra heater power is of course converted into heat, something the little EL34 can ill afford. Long story short, I use a 6CA7A, which is properly a beam power tube, that is very happy in freshly vacated EL34 sockets. Oddly enough, my ears are happier as well when the EL34 goes away. 6CA7 tubes last longer as well. Keep in mind they are a little bit wider, so there are amps designed without enough room between tubes to accommodate them. The thing is, those are also not spaced widely enough for EL34 tubes either. Just an unhappy design all around.

In case I forgot to mention this, there is zero wrong with good brands of newly manufactured power tubes. In fact, late 60's power tubes of good lineage fail in the Fender Twin amplifier. I'm using the Fender Twin as an example because it exceeds the maximum plate voltage ratings for the 6L6GC, which this amp was designed to use. The normal plate voltage in these amplifiers runs around 475 VDC while the tube is rated for 450 VDC. NOS tubes often hum and get hot, or simply turn cherry red while humming loudly. These are not a good sign in a tube amp.

-Chris

It is telling that there's only one pair of "5881A" on Ebay (they're Chinese), and none of my manuals or the sites I checked have a data sheet. The physical appearance is also much different than the 5881 which makes me believe they're likely remarked counterfeits of a "A" type that doesn't even exist. Ironically the listing shows the plates at 23 Watts. Renumbered tubes on Ebay should be reported as counterfeit. Sellers should use the real numbers and can still mention others as keywords. It may actually be good quality tubes that fail in the Fender Twins. The screen supply is 470V through 470 Ohms, fused at 100 mA per pair of 6L6GCs. That's very high, about 200V above the typical operating shown in the data sheets. A look at the curves shows that screen current skyrockets when the plate current is high and plate voltage gets low, which a guitar amp drivin into clipping sees a bunch of. The screens are only rated at 5 Watts. Ironically some inferior tubes that can't pull the plate voltage as low would end up protected from the problem. That Y2K Fender design, not from Fullerton, is clearly marginal. But in fairness, many other tube amps also fry the screens under some conditions.