Using JJ ECC99 in place of 5687 tubes

[mrarroyo]

Hi, my name is Miguel and I have been lurking in this forum for a while. Finally joined a couple of weeks ago and this is my first post.

I am not knowledgeable in electronics and I would appreciate your help since I would like to use the JJ ECC99 tube in a Singlepower MPX3 as an output tube. Yes I know, Mikhail has made some horrible amps and has stolen a lot of money from many. However I already own the amp (bought it from Tyrion) and w/ Dr. Gilmore's help I replaced the diodes, verified the transformer is acceptable, and installed a couple of resistors to bleed the large power caps.

I first came across the JJ ECC99 tube in a headphone amp by Dr. Lloyd of Mapletreee Audio. Recently I read the JJ ECC99 could be used in place of the 5687 provided a base is made to properly account for the difference in pin location. I would appreciate it if someone could help me by first verifying the JJ ECC99 can indeed be used in place of the 5687. Then I would like to know if could find an interested builder so I could commission two bases to adapt the JJ ECC99 to the 6SN7 bases in the Singlepower MPX3.

Thanks.

[deepak]

Welcome to Head-Case

[mrarroyo]

Thank you it is good to be here, lots of familiar names but perhaps a different forum flavor.

[luvdunhill]

I think it might work. I'm not sure I'd risk it though.

Edited September 26, 2009 by luvdunhill

[dsavitsk]

Hi Miguel,

For a given bias and current, the ecc99 runs at a higher plate voltage than the 5687 -- typically ~20% higher I'd say. This means that with a fixed plate voltage, the bias and current will run lower than on the 5687. Not knowing the circuit, I have no idea if this makes any difference, but probably not.

However, 5687's are linear, plentiful, and relatively cheap, so I don't think you are gaining anything by using the other tube. I agree with Marc that I'd leave it as is and save your pennies.

[Torpedo]

Hi Miguel, nice to read you here too

As I replied you at Auriculares.org, I don't think it's a great idea to use a 5687 --worse an ECC99 which is not direct 5687 replacement-- on a circuit designed around the 6SN7 if you cannot change plate voltage, bias current and other parameters to take the tube to its specified performance. Moreover, knowing how Mikhail worked on his amps, I'm not very sure the amp will stand working flawlessly for much time if you start swapping tube types.

In any case you may wish to try a search at Ebay, there are many tube adapters over there. At this moment no 5687 to 6SN7 available, but you might contact any of the sellers (most are chinese), eventually one could make the adapter for you. Otherwise one may appear in the future.

[mrarroyo]

Thanks for the feedback, sadly I was a fool and since I read they were compatible in a site I oredered and received them. The only one I can recall may have a copy of the circuit is Dr. Gilmore. Meanwhile with the assistace of an aussie friend ...

[Torpedo]

As you can see in the left graph, the pins layout of the ECC99 is not the same as the 5687's. So for your amp you'd need either a direct adapter from the amp's 6SN7 socket to the ECC99's pins, or using two adapters, one from 6SN7 to 5687 and a second one from 5687 to your ECC99. Sounds like a tough call to me

I'd contact JJ to see if they can direct you to some manufacturer making such adapters. Good luck.

[nikongod]

Nice to see you on the dark side. Isnt it nice to have a forum to go to where you can ask a question about an unpopular amp without being reminded how unpopular it is? I may have just reminded you. Whatever, I like the MPX3 too.

Unless Im mistaken,the ECC99 fits what singlepower called the ECC-1 adapter. Same adapter as for the 12a*7 & 12bh7

The MPX3 puts about 160V on the plate of the "bottom" triode in the WCF, which looks like a nice voltage for the ECC99 BUT! I would note that the ECC99 will draw about twice as much current as 6sn7 in an MPX3 (about 25mA vs 8-12mA depending on exactly how the amp was built) This puts you very close to the maximum plate dissipation on the ecc99. If your amp can run 6BL7/6BX7 for sure it can handle the current, but the tube will be running just short of its power limit. If your amp has the high-voltage switch DO NOT use high voltage with this tube.

[mrarroyo]

Hi Ari! I do not know if the following helps or not but the transformer in my MPX3 is ...

According to the Hammond site ( Hammond Mfg. - Universal Primary - "Classic" Power Transformers ) the specs of the 372BX are:

372BX

98

600V C.T. @ 115ma.

50

5V C.T. @ 2A

6.3V C.T. @ 3A

The inside of the amp before I replaced the diodes looks like ...

Here is a picture of the replaced diodes ...

Does this information help in any way? Thanks.

[voodoochile]

While the two tubes are relativelty compatible, I think you will find the 5687 to sound better anyway. At least that was my experience.

The JJ ECC99 is a nice tube- relative to other current production tubes, that is. I have a couple of them, and also some Svetlana versions of the same. The JJ is better than the older Svetlana tubes, but the 5687 is notably sweeter.

Looks like your former bridge was working pretty hard.

[mrarroyo]

Thanks again guys, I am going to give it a try so I ordered tube bases and will see how it comes out. I may even post pics of my newbie work.

voodoochile, you are correct. The diodes were burning up the board, I have since cleaned up my work and re-flowed the solder joints. They are much better now.

Thanks again.

[dsavitsk]

Thanks again guys, I am going to give it a try so I ordered tube bases and will see how it comes out. I may even post pics of my newbie work.

One thing -- these are high Gm tubes, and they can and will oscillate without some care. And, the long leads necessary to build an adapter can act as antennae. To that end, stoppers on all the pins (of the 9 pin socket), except the heaters, would be prudent. I'd maybe put 1K resistors on the grid pins, and 10 to 20 ohm resistors on the cathode and plate pins. The best resistors to use would be SMDs, but if that presents too much of a soldering challenge, some sort of carbon film or comps would be fine. Just get them as close to the tube pins as possible.

Also, keep in mind that oscillation is not necessarilly obvious -- sometimes it will just manifest itself as a bit of hardness, or glare, or jut lack of midrange clarity. Indeed, ECC99's have a reputation of being hard sounding, and I wouldn't be at all surprised if it isn't just a tendency to oscillate at HF.

-d

[mrarroyo]

Sorry for the newbie question, would the resistor be in series? That is between the pins on one socket and the socket base? Thanks.

[dsavitsk]

Yes

[mrarroyo]

Thank you.

[regal]

I agree with dsavitsk, the Ec99 is a hard sounding tube. I really like the 6N6P in its place.