807 E-Linear

[JandG]

Also since I have 4-8 & 16 0hm taps could i not get the ouput load to 5k in PSE with useing the 4 or 16...? ohm tap on my 8ohm speakers. The JBL L65's w' OB mids have only a coil in series on the bass driver & caps in the network on the mids & horn top end. I fear the DC on the bass driver with that cathode loop, maybe I shouldn't..? It sure would ne nice to try PSE for a possible 18w if I can get the 5 k loading. I single pair still puts me at 99db at full tilt in SE, but PSE puts me @ 102db @1w1M. These paticular speakers are at 89.5 & maybe 90db 1w1m. Sometimes I like to listen to SRV at 102...
Also I will have a 2v input of a CDP on this amp.
Joe

 

[revintage]

Hope I don´t dissapoint you, but your OPTs can only handle the current from one 807(6L6). Max is 100mA with 23H/70mA.

You´ll have to move your chair closer to the L65´s when SRV hits the fat strings on his Strat, playing Texas Flood .

 

[JandG]

Yes indeed I will have to give up on the PSE & go SE only, I listen @ 9' anyway so I can get away with alot. 99db will have to do. Here are the specs of the O'Netics IT as I read them direct from spec sheet given me from Bud P.

Input:
Primary; 0.9 to 1.8kZ ohms impedance
Leads 1* to 2: 500 ohms DCR
[90 vac rms from brown to blue]

Output:
Secondary impedance;
Leads 3* to 4: 1:1 , 460 ohms DCR
This is all I have on the IT's other than a part #

Thanks Joe

 

[revintage]

Hey Joe,
The UL version with B+ 300V will leave you with ca 4W. If you go tetrode at 450V/250V you will get something like 8-9W. This is what it could look like. R2 may be trimmed. Also 5k/7k can be tried.

 

[revintage]

If you want superior performance you should skip the triode/IT and go for a high-Gm pentode like D3a or E280F. The 6AU6´s you have won´t do as they are far to unlinear(distortion-cancellation doesn´t help) with a heavy load like this.

 

[JandG]

Superior performance ..? I am allways game for such a thing for the small $ involved of the changes. I would have to find some D3a or E280F. I have the heaters wired up in this chassis allready in series because of the 12.6v filament tranny in middle of pic but can easily change it around for a pair of 807.Main PS will be outbourd anyway. I can save my IT's for another project as I have other SE OTpairs about in closet. Main reason going 807 is I like 6l6 family tubes for sound + allready have them & trying to get away from 300B as my PP 300B amp ran away not long ago & I refuse to retube such expensive outputs. 807 still cheap for some reason. Can you expain why the D3a non IT version would out perform the 5687 IT version..? Thanks for the large amount of help indeed. Just so you know I am not just dreaming here is a pic of signal chassis .
Joe

 

[aa7qu]

I've been following this thread with great interest. Thanks especially to Revintage for his excellent simulations. May I ask Revintage: what model are you using for the 807, and are you satisfied with its accuracy?

Russ

 

[revintage]

Wow, that looks nice. Maybe you should go for 5687 anyway as the chassi already is done.

A possible explanation: D3a is more linear and the unlinearity that is left might be the same style as the 807, thereby canceling the 807s.

But it isn´t sure you like the D3a better. It´s up to you to decide.

My schematic might need some fine tuning but that is up to you.

 

[JandG]

I have almost converted this amp to PSE useing new 5-7k OT's & after listening to it in SE & found it to be wonderfull. All I need left to do is install the 4-20k trim pots into this circuit properly for individual bias on the 4-807's.
Can someone show how to install the 4- 20k trim pots into this schematic. I have a variable regulated negative supply in use.
thanks, Joe

 

[tinitus]

this deserve a bump

or did you solve your problem ?

 

[JandG]

Yep,
I just went back to SE & added a 2c22 front end & it is wonderfull. I am not to touch circuit anymore. I am running a regulated g2 via glow tubes in it's own PS CLCLC all poly. Regulated 807 bias, battery grid leak bias on the 5687, series battery grid bias on the 2c22. 807's have dedicated supply also. So deos the 5687. over kill ,.....but it's DIY & can do what I want. *s*
2c22- 100v @ 5mA
5687 220v @ 20mA max dissapation now, so might back off a little, but not much.
807-460v @ 50mA
It is the best amp I have heard
good ridance 300B..............
Joe

 

[Zekk]

Yep,
I just went back to SE & added a 2c22 front end & it is wonderfull. I am not to touch circuit anymore. I am running a regulated g2 via glow tubes in it's own PS CLCLC all poly. Regulated 807 bias, battery grid leak bias on the 5687, series battery grid bias on the 2c22. 807's have dedicated supply also. So deos the 5687. over kill ,.....but it's DIY & can do what I want. *s*
2c22- 100v @ 5mA
5687 220v @ 20mA max dissapation now, so might back off a little, but not much.
807-460v @ 50mA
It is the best amp I have heard
good ridance 300B..............
Joe

Hi Joe!

Is that a three stage amp?

Care to share your schematics!?

I've a pair of gorgeous looking Mullard QV05-25 !

Thanks.

Zekk