Lafayette PA conversion...

[billc]

This had old Coke bottle 6L6's in it when I bought it but only a 5Y3 rectifer, so I decided to convert it to 6V6 and used some NOS RCA 6EY6's I had on hand. Changed the PI from a 6SC7 to a 6SL7 and that tube works fine in that position, no hum problems like they often have as V1, all 4 of mine sound good and are quiet. Wired two preamp channels, one like a Gibson GA-20 with a 6SJ7 and the other like a 5B6 Bassman with a 6SC7, was inspired by a suggestion on another thread here...wired the twin triodes in parallel on that one like a Matchless. Added one terminal strip and used the original octal phono socket as another. The two channels have distinctive sounds and both are plenty loud enough. Have not wired a tone control yet, will eventually but like the sound fine as is, both channels are not too bright or dark into a 15" Big Ben. Anyway, a very satisfying project now that it is mostly done and good practice on PTP wiring in a roomy chassis...looks like this and I do have the enclosure too. The voltages are a bit high running on 120 service and I'm using a variac for now but will add a bucking transformer, plenty of room in the cavernous chassis

[img864]https://lh4.googleusercontent.com/-tkOR ... 184707.jpg[/img]

[img864]https://lh3.googleusercontent.com/-9O1X ... 174840.jpg[/img]

[Regan]

Lol, unbelievable!!!
I just searched for anything on one of these, feeling inspired after visiting David Root the other day and eyed up the lafayette on my shelf!
I'm not sure what I'm going to build in mine, thinking maybe an early pro circuit.

[billc]

Lol, unbelievable!!!
I just searched for anything on one of these, feeling inspired after visiting David Root the other day and eyed up the lafayette on my shelf!
I'm not sure what I'm going to build in mine, thinking maybe an early pro circuit.

Good to know there is another one out there. I just looked up the xfmr codes and if they are EIA the amp was probably actually made by Masco in 1949 or so. I thought about building a Fender Pro channel myself (FWIW had an old Tweed Pro a LONG time ago and paid $8 for it) but decided to go with a Bassman circuit due to the reputation and since it is cathode biased rather than grid leak like the Pro. Anyway, since there are two preamp channels I'm very glad I did something different with each, originally planned to do both like a GA-20.
Found a Masco out on the web that looks very similar...

[img:600:434]http://www.megatoneamps.com/images/17n_web.jpg[/img]

[Regan]

Sounds like a really cool amp, might just copy you, lol!!
I didn't think it was that old,, would have put it late 50's going by asthetics.
I'll probably stay with 6l6, I haven't had a full octal amp before and excited to try.
I like the idea of the pentode channel too, sounds like it would be a tasty amp!

[Regan]

Just saw the pic of the Masco,, thats a cute amp! I'm not positive but I think Lafayette built their own amps at that time... wouldn't put money on being correct on that though.

[billc]

Sounds like a really cool amp, might just copy you, lol!!
I didn't think it was that old,, would have put it late 50's going by asthetics.
I'll probably stay with 6l6, I haven't had a full octal amp before and excited to try.
I like the idea of the pentode channel too, sounds like it would be a tasty amp!

It does look more like late 50's to me too but the tube lineup is definitely late 40's/early '50's, especially the 6SJ7 and 6SC7...but that is a plus to me as amps from that era have the sound I like and I have an irrational preference for octal tubes anyway. I probably will experiment with 6L6 tubes and maybe some new 5881's since they are more like the 6L6G's the amp came with, and perhaps wire a cathode resistor switch so either can be used...also possibly a 5V4 rectifier as it will deliver more current than the original 5Y3 but does not pull any more from the 5V winding (this could bump the B+ up too high for 6V6's to sound good though)
Anyway, looking forward to seeing your build, these amps are a great platform for guitar/harp amp conversions and well worth the trouble...if I can help with any info or details let me know.

[Regan]

Thanks Bill,
I'm putting a gameplan together and hope to start it pretty quick!
Lucky I have all the tubes needed,,,, as long as they test good!
Regan

[billc]

Thanks Bill,
I'm putting a gameplan together and hope to start it pretty quick!
Lucky I have all the tubes needed,,,, as long as they test good!
Regan

Sounds good...BTW I was perusing schematics yesterday and saw that the stock Lafayette circuit is pretty similar to a Gibson GA-50, never did find a schematic for the Lafayette
(also the Gibson used a 5V4 rectifier, so if I do go back to 6L6's will do the same)

[Regan]

I was just looking through schematics too and the Valco Aztec is something that might work well in there too, and room to add a second channel.
http://www.ampix.org/albums/bargainbin/valco_aztec.pdf

Regan

[Regan]

Hmmmm, wonder how the Dumble overdrive circuit would work in a 5b6 circuit in this amp,,,,,,
Regan

[billc]

Hmmmm, wonder how the Dumble overdrive circuit would work in a 5b6 circuit in this amp,,,,,,
Regan

Not familiar with that one so I can't say, I built mine with a '50's jazz/blues tone in mind...but between the six tube sockets and huge chassis there are many possibilities. Use mine daily and like it a lot, have some 5881 tubes on the way and am going to wire a switch and two cathode resistors so 6V6 or 6L6 type tubes can be used, also same deal on the PI tube so 6SL7 or 6SN7 can be run.

[billc]

I was just looking through schematics too and the Valco Aztec is something that might work well in there too, and room to add a second channel.
http://www.ampix.org/albums/bargainbin/valco_aztec.pdf

Regan

That would work fine. FWIW I changed mine to a similar Gibson GA-50 design yesterday and that works better as the B+ and filament voltages were running high with the light load of the 6V6's, also changed the 5Y3 out for a 5V4 to match the Gibson and used a 6SN7 for the PI tube. The 6SN7 pulls double the filament current of a 6SC7 or 6SL7 but only raises the total filament load by about 10% so I'm comfortable with it. FWIW the 6SN7 and 6SL7 have the same pinout so they are swappable with the right plate and cathode resistors, am going to experiment with that as I'm using 100K and 2.2 K....the 6SC7 is NOT wired the same due to the shared cathode.

[img744]http://elektrotanya.com/PREVIEWS/634632 ... .pdf_1.png[/img]