ECC88 substitutes - Which will be better to use ?

[kagliostro]

I've a project where the use of an ECC88 tube is planned

I'm not sure at 100% but I think I've no one of those tubes (years ago I had some, used in good shape, with gold pin, but I was thinking it was only HiFi stuff and gived it to a friend as a present), what I'm sure about is I've some 6CG7, 6N6P and 6N23P

Till few time ago I recognized the 6N23P as a substitute (as per the indication find around on the web) but recently I've read also that 6CG7 and 6N6P are good substitutes fot the ECC88

As I'm not a good datasheet reader, please, can you say which is for you the order of the substitutes from the better till the last one ?

Here the datasheet of the tubes

Many Thanks

Franco

[Merlin]

6N23P is a good substitute for the ECC88.

[kagliostro]

Thanks Merlin

Someone can say something about the other two tubes ?

Thanks

Franco

[Merlin]

They're all approximately similar, what exactly do you want to know? The 6N6P needs a lot of heater current, it is really a small power valve.

[HotBluePlates]

Someone can say something about the other two tubes ?

The 6CG7 is basically a "12AU7 that can dissipate more power."  I wouldn't think of it as an ECC88 substitute. 

But do you plan on using the ECC88 in a cascode gain stage?  That was the whole reason that type was created, so if you're not using a cascode gain stage you might as well use a more common tube type.

Even saying that, 6DJ8/ECC88 is readily available in new production and old production versions for about the same cost as a new-production 12AX7.

[kagliostro]

Many thanks for the reply

The plan of wich I was talking is to use a GU-50 tube in SE configuration

The preamp is the Dumble HMR preamp borrowed from an SE amp with EL84 power tube developed at Amp Garage (if I remember correctly)

As the GU-50 is a low sensitivity tube it was necessary to add a driver between the preamp and the power tube

Some idea were put on the paper and we arrived to one that uses an ECC88 tube

See the attached schematics

My friend Domenico was testing on a breadboard (OK, it isn't a real breadboard, he build a chassis dedicated to test) this part of the circuit with ECC88 tube and had problems, he fried 2 x ECC88 tubes that were payed 30€ each because by mistake he feeded the heaters at 12.6V instead of 6.3V, so, to save money, I gived him the council to try the way cheaper 6n23p and he did with perfect result

This last days I was at an Ham Fest and an Hungarian radio amateur that is my friend gived me some 6n6p tubes (tubes that I was trying to have because I've a few projects that uses it as power tubes)

Reading around about this tubes I readed that some people told they are similar to the ECC88 tube (thing that till now I reserved to the 6n23p), reading around I find also someone that talked about the 6cg7 as a possible substitute for the ECC88

And so is explained the reason I opened this thread and which use will be done of the ECC88 or substitutes

I've also other interest on knowing more this tubes because the 6cg7 (is not easily available) was also used in Davoli Power amps as substitute of the very expensive ELL80 (double pentode triode connected) that was used there as PI to drive EL500 & EL504 tubes and to me will be interesting to know if the 6n6p can be swapped in place of the 6cg7 for that use

Franco

[DummyLoad]

https://www.jj-electronic.com/en/ecc99

Seems like ECC99 are available in EU and are affordable - Maybe substitute for 6FQ7/6CG7? ECC99 has a steeper slope than the 6FQ7, so you'll need to rework bias.. Another option would be a 6SN7 (J&J mfg. them) instead of the 6FQ7, if it's new build, just a socket change; they are the same electrically.


--Pete

[kagliostro]

Ciao Pete

Thanks

I was asking for the tube I named because of the price, unfortunately my friend disctraction fried a pair of ecc88 @ 30€ each, ecc99 price is around 25/30€ so the price are at the same level, way higher than the tubes I named (and I've both 6N6P and 6N23P)


Franco