Interesting Reverb, and a question

[DiademRoyale]

Bob-I the sam issue here as on the thread on the ECL -86 reverb amp (the Royale -reverb) Most of the ECL series of tubes are triode/pentode combined (I haven't researched the entire series,so cannot vouch that all are). The main differences between them are: 1) Pin-out , 2) Gain , 3) Interstage capacitive coupling-affected mainly by frequency responce chosen for operating range. There are other minor variations, but all of the series were designed to operate in roughly the same frequency range, just different stages due to differences in gain. Most designs using these tubes usually seperated their functions further than we want when using the as driver/ power amp, or driver/recovery as in a reverb unit. Especially one like the ECL-84 (6DX-8).Years ago I used them in a stereo pre-amp/power amp combo for a bookshelf sized Hi-Fi which worked out very nicely. That design used the 6BM-8 version. I have a feeling that because of the ECL designator, some are assuming same pin-outs and this will get you into rouble with an otherwise good design. Some designs, however, are ok with the wiring mis-match- although they would work much finer if pin-out wired correctly.
If you are operating any of this series in the hotter side of the gain structure for the triode side, you will encounter more problems with the pentode amp, plus weird phase cancellation problems with output that are very hard to pin down. They just don't sound "quite right". As long as you stayfairly conservative with triode gain, the pentode likes plenty of running room.If the triode is run too hot you will almost never be satisfied with the final product. I REALLYlike this series of tube for the versatility available, and tried to convince the boys at Fender that they should use one or more of them in designs to no avail. Now that they are becoming semi-scarce, people are starting to wake up to them again. Lets get JJ or
E.H. to start mfg them again-ECL-82,ECL-83,ECL-84,ECL-86... they are all great . Don't let the pin-out variations discourage you at all. In the right application, with the correct decoupling and biasing, these tubes ROCK.. A lot of words but wiull it really help-- I hope it helps someone. Martin ........................... DiademRoyale