EF86 Alternate for clean

[guiltless]

So I know the ef86 alternative discussions have been going for a bit, but they all talk about what will work in the socket rather than talking about which ones work well for different applications (at least the ones I have found)

I am getting everything together to build an 18watt TMB ef86. I want the voxy chime of the ef86 channel, but I am seriously questioning the viability of an ef86 in a gigging amp. What I build will spend most of it's time in the trunk of my suped up old vw gti which is less than a soft ride. I am fearful that the combination of a combo and the rough ride will pretty much kill an ef86.

So what I am looking for is a more durable alternative to the ef86 pentode that will still give me that voxy chime. The channel will be used primarily as the clean side to the amp and will only see dirt if I hit it with a boost pedal.

Any thoughts/suggestions?

[insanecopilot]

I like the 6sj7. It is cheap, sounds great, but needs a 8 pin octal socket.

[dotfret]

If you want the EF86 sound without compromise, use an EF806S - that is the robust answer.

If you want to get a closely similar sound, use a cascode circuit with a pair of double triodes. You can use the ones with vibration proofing for insurance purposes - there are a couple of WE / Raytheon designs, and some Russian valves, that are specially resistant to vibration.

Or you can get an old 50W Session and a Yamaha SG to inhabit your boot for spontaneous purposes. That's what I do ...

[guiltless]

If you want the EF86 sound without compromise, use an EF806S - that is the robust answer.

this seems interesting. Anyone with any experience with them? The only ones I have found are the standard JJ and Tung Sol. I am leaning toward the Tung Sol since the only other option I can find so far is the $200 Telefunken.

[kleuck]

You can try a cascode with a double-triode, 12AT7 or 12AY7, and get same gain, same sound, but much more reliable.

[guiltless]

You can try a cascode with a double-triode, 12AT7 or 12AY7, and get same gain, same sound, but much more reliable.

So I can get the same hi-fi, voxy chime with a cascoded 12at7 or 12ay7?

[LooseChange]

You can try a cascode with a double-triode, 12AT7 or 12AY7, and get same gain, same sound, but much more reliable.

I'd like to see that circuit. Thanks!

[krx]

You'd be better off using an ECC88 (aka 6DJ8) if you want to do a cascode circuit. It was actually designed for that and NOS ones are still cheap. I think the cascode is your best option if you want to build in a combo. The 6SJ7 is a good tube and also very cheap, but it's octal and has quite a bit less gain than an EF86. I like the JJ EF806 in heads but I don't think I would trust it in a combo, and I don't think I'd pay $200 for an NOS 806 unless you got some kind of warranty with it.

[StarGeezers]

Quote: "The 6SJ7 is a good tube and also very cheap, but it's octal and has quite a bit less gain than an EF86." That was the point , CLEAN eh ? The 6SJ7 is also a remarkable Tone-full tube with rich TONE and complex chime... many gain stages have been successfully tried in front of it , still a remarkable tube , and for 5 bucks ... or do like I do and get the 5693 (the red one ) which is good for 10K hours... sounds SUPER , NO microphonics

[57chevy]

5879 is also a good alternative. Go to the Hoffman Amp forum and search for 5879. Several guys have had very good results using this tube.

6AK5 or 5654 also has a lot of possibilities.

[zaphod_phil]

I am seriously questioning the viability of an ef86 in a gigging amp.

Plenty of hard-gigging amps are built with EF86s inside, including Matchless, Gabtone, 65 Amps, Trinity, etc. Just pick a good brand of tubes and possibly use shock mounting. Trinity, for example, uses Amperex Bugle Boy EF86s with no shock mounting, but that's in a head amp. So for a combo, some shock mounting may still be a good idea. Dan Boul of 65 Amps also recommends conditioning the EF86s when you first start using them. The EF83 and 6BR7 are also low-microphony alternatives to the EF86. There are some more info and tips in this thread - http://www.18watt.com/modules.php?name= ... 8&start=20

BTW I also noticed you mentioned "clean". EF86s have a lot of gain when used in a typical gain stage, and they overdrive an 18W amp in a beautifully dirty yet chimey way.

[guiltless]

That 6sj7 option sounds super nice... What would need to be done to make that work? Would I start from an ef86 circuit or a 12ax7? Is it as stable as a cascode?

This will definitely be a clean channel. I don't want tons of dirt. Just that voxy chime.

[zaphod_phil]

If you want clean then you will need to attenuate the signal quite a lot, after the preamp. Alternatively, you can use component values that give lower preamp stage gain, but some folks complain that approach gives less chime. Also in an typical 18W most of the distortion is coming from the overdriven power tubes, so you may want to decrease the drive level by reducing the EL84s' grid reference resistors from 470k to a more Vox-like 220k.

You can use a 6SJ7 pretty much with the same circuit values as EF86s. However, they draw quite a lot of grid current, so you need a 0.1uF isolation cap between the two grid resistors and the input jack, so you don't get scratchy guitar volume pot problems. Also be aware that 6SJ7s can be microphonic too, possibly just as much as EF86s.

[rjgtr]

Another idea might be to implement a Vox style 'Top Boost' channel, using the Vox values for the tone stack. Since you'll likely need to implement it with one 12ax7, just leave off the cathode follower and feed the tone stack from the plate of the second triode.

With the Vox tone stack values you get a very bright chimey tone. You can even get it to fit in the Normal channel of a standard 18watt chassis, by having only one input and puting the Volume in the other input hole with the Treble and Bass controls in the remaining control holes.

[guiltless]

I thought about a straight up TB option. Still not sure tho. So far it seems like a toss between the 6sj7 and a cascode option. The TB might be too much work.

Anyone else have experience with the 5693?

[zaphod_phil]

I'm still not so sure a 6SJ7 is what you're looking for, although it's a real nice sounding tube IMO. 6SJ7s are also often microphonic, just like EF86s, Also their tone is a little darker than an EF86's, which is something I happen to like, but may not be what you want.....

There are several other options for low microphony which have already been mentioned by various people.

[guiltless]

Sweet. Just the sort if feedback I have been looking for. So it sounds like the 6sj7 may not be a good option for me. I definitely love the dark sound but I am looking for that vox tone from this specific amp.

So here is the next question. How difficult is it to switch from an ef86 style circuit to a cascoded style?

I may just start simple with a well shock mounted Tung Sol ef806s, then try the 5693 or 5879 if that doesn't hold up well, and then ultimately move to the cascoded style circuit if those don't seem to hold up.

[kleuck]

You can try a cascode with a double-triode, 12AT7 or 12AY7, and get same gain, same sound, but much more reliable.

I'd like to see that circuit. Thanks!

http://www.freewebs.com/valvewizard/cascode.html

[StarGeezers]

We built an Absolute Minimum 18 watt ... 6SJ7 preamp , 5751 PI an two 6V6s... Sounds "Killer" , No microphonics or troubles at all , been gigged with a lot now ... 6SJ7 shown in the schematic http://www.18watt.com/modules.php?name= ... ic&t=20043
http://www.18watt.com/files/mini-min18w_142.jpg

[dotfret]

I have a particular liking for amps with EF86 front end, and I have a lot of them. I find the old Tesla EF806S superior to anything for robustness, closely followed by Philips E80F, which give a slightly more open sound.

If you're going with the cascode route there is one valve that is superior in this application, the ECC8100. Yes, it is a rocking horse dropping, purpose designed by Telefunken - but if you can find a pair ...