Tweed Overdrive Special - EF86

[adamG]

Hi Guys,

Is it possible to replace V3 - 5879 with EF86?
If so, then what elements within OD stage circuit or whole amp schematic need to be changed?
The main thing is that 5879 are not easly available in Europe and they're expensive...

Thank in advance.

Regards,

Adam

[John]

I believe the tubes are electrically similar, which means you probably won't have to change many values. You will need to re-wire the socket pin though. On this side of the pond the EF86's are expensive and the 5879's are cheap, so we use those instead. :)

[jazbo8]

I believe the tubes are electrically similar,

Not really, unless you want to change the gain & the tone, the component values need to be adjusted. Below is a comparison of the transfer charactersitics between the two tubes, EF86 is shown in brown with the screen voltage markings, the other set is the 5879.




 

[adamG]

Thank you jazbo.
So, what am I to change?!
I'm not an electronic man. I just can manufacture, but advanced electronics is still a kind of mistery for me.
Any thoughts would be very appreciated...

Adam

[adamG]

On this side of the pond the EF86's are expensive and the 5879's are cheap, so we use those instead. :)

;) I really admire that kind of humour;)
We should do that ,but there's something more...US export fees.
In States such technical purchase is fundamentally cheaper.
Guys on customs clearance are very sensitive;)

Regards,

Adam

[jazbo8]

Thank you jazbo.
So, what am I to change?!
I'm not an electronic man. I just can manufacture, but advanced electronics is still a kind of mistery for me.
Any thoughts would be very appreciated...

Adam

Ah, that's a more difficult question, I can't recall now, but I believe there were some discussion on using the EF86 in the original TOS thread, perhaps tubenit will pop in to give you some advise, as he worked on the design with Geezer back in the day. I'll be on a road trip for the next few days, when I get back next week, I will take a closer look at the design to see what needs to be changed...

[tubenit]

I've never personally used an EF86 since I have heard so many negative things about them about microphonics etc...

Mat (on The Amp Garage)  has experimented some with EF86 in D-style inspired amp circuits.  He has had some success with that.  However, he also PM'd me at one point stating the 5879 was a more useable and musically sweet tone.

Regarding the TOS and the 5879.....................    Other options are also the 6AU6 and the 5654 (Sluckey gave me one to try and I really liked it a lot).   So if you can find those at a good cost or the European tube equivalent, those might work.   I did use a 6AU6 alone and a 5654 alone in place of the 5879 in one amp design and liked both of them.  I liked the 5879 best, then the 5654 (needs a little lower voltage then the 5879) and then the 6AU6.

Hope some of those thoughts might be useful to you as you try this.

With regards, Tubenit

[jazbo8]

+1, try to avoid the EF86 if you can. Another alternative is the 6J7, an octal tube, Brimar made them, so they should be readily available in the EU. Its characterisitc is pretty close to the 5879. It does need a plate cap though...

[John]

Not really, unless you want to change the gain & the tone, the component values need to be adjusted.

Just goes to show, can't believe everything you read.... 'specially on other forums. ;)

[adamG]

...Other options are also the 6AU6 and the 5654 (Sluckey gave me one to try and I really liked it a lot).   So if you can find those at a good cost or the European tube equivalent, those might work.   I did use a 6AU6 alone and a 5654 alone in place of the 5879 in one amp design and liked both of them.  I liked the 5879 best, then the 5654 (needs a little lower voltage then the 5879) and then the 6AU6.

You were right.Both equivalent tubes came out very cheap in my place. I've purchased few of them;) Could you try to redesign OD stage with 5654 or 6AU6? For me it's to early to accomplish such task. I just can manufacture. Nothing more.
Kind thanks in advance.

Regards,

Adam

 

[tubenit]

Adam,

This is really simple .......................

Just use the exact same values that you see for the 5879.   Geezer and I did a "sort of HoSo56" thing yrs ago where we paralleled a 7 pin socket using either 5654 or a 6AU6 with a 5879.  This is the schematic (attached)

It worked great and had a really nice FAT sound!  It allowed us to have a 5879/6AU6, 5879/5654, 5879, 5654 or 6AU6 in the V1 position.

With the 5879 out of it's socket & a 5654 or 6AU6 alone using the 5879 component values, the amp sounded really great to me.

So try the 5879 values and then tweak to taste. 

With respect, Tubenit