New SE 807 Stereo

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Those 807s really rock! They sound good in both triode and UL mode.

[Sal Brisindi]

Looking real nice. I have a bunch of 807's that I want to try one day.

Sal

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Thanks, Sal. You really should try building something with your stash of 807s. I bet they would make a great substitute for EL34s in the ST-70.

[Gingertube]

Nice,
I guess I could just about reverse engineer it from your pics but I'm feeling lazy - schematic? pretty please.

I brougght home a carton of 12 Amperex 807 NIB from the local tube supplier - 4 of them are going to run into a 100W Marshall Guitar Amp Output Tranny I have on the shelf, that leaves me with 8 more to play with.
Cheers,
Ian

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I am sure you can, Ian. But I will make it easy for you. The amp is based on the JE Labs Hi Fi EL34 SE Stereo (viewtopic.php?t=5662) but I used the 807 instead of the EL34. Please note that I split-railed the PS after the first filter cap for a choke followed by a 47 mfd/450vdc cap. The DPDT toggle switches the 807's vg2 (pin 2) between 100 ohms strapped to plate (for triode mode) and the screen grid tap of the JS6112 (UL mode). I was half expecting to fiddle with NFB for UL mode, but I was very pleased without it (and I felt lazy). Don't forget to parallel both sections of the 6SL7.

I almost went with Sun Audio circuit instead of the JE Labs since I love the 6SN7, but I am pretty pleased with how things turned out overall. You can't really go wrong with JE Labs circuits. I am now wiring up a Sun Audio SV-2A3 and later try the VT25 version, so the KT88/EL34/807 version will have to wait for now.

Hope this helps,

Min

[Shannon Parks]

Bravo, Min! I love the 807s and 1625s in SE amps. They look as good as they sound.

Shannon

[EWBrown]

JE Labs EL34 Schematic:

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Thanks, Shannon! Yes, those tubes are pretty reasonably priced too (for now).

[thehoj]

I drew up the schematic with what I believe are the changes you talked about.

http://s27.postimg.org/iy5y09r6r/UL807_Amp.jpg

Does this look correct?

What is the primary impedance of the OT's? (2.5K?)

Also, are these voltages okay? Does the UL tap have a low enough voltage for the screens?

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Looks good except you don't have to have two coupling caps, two 100K resistors, and two cathode bypasses per 6SL7. Just parallel the two sections of each 6SL7 then use only one set of these passive components. Also, you don't need two bleeder resistors in the PS. Just use one in either channel. I know that I used a split rail PS for my build, but there is no need to do it this way. Just one 20 mfd, one choke, one 100 mfd, and two 47 mfd (one per channel) and you will be fine. I typically use 3.5K but 5K can be used for improved linearity in the expense of little loss in power.

Hope this helps.

Min