Magnavox Console Amp Chassis

[wrenchone]

I scored 3 vintage Magnavox (as touted by seller) power amp chassis that obviously began life in consoles of various sorts. I got 3 different flavors - a P-P 6V6 amp, a P-P 6BQ5 amp, and a SE 6V6 amp. All 3 are stereo, and all 3 have power transformers, so I don't have to worry about "sudden death chassis syndrome". They came with no tubes, but with all iron in place. I plan to use these as platforms for experimentation, probably starting with the 6V6 SE chassis, as it is least complete underneath. The little demon familiar that sits on my shoulder and gets me into trouble is whispering "Schade" for this one. I might try using a modest sweep tube like a 6AU5 instead of the 6V6 as I have some on hand, but no 6V6. If I remember correctly, this chassis has two driver sockets available, so I might try using a triode-pentode of some sort, allowing me to hang a cathode follower in between the input and output tubes for class A2 capability. Likely suspects might be the venerable 6U8 with some decent plate current on the pentode instead of the usual starvation mode that I see in the classic circuits. Another possibility would be to change out the sockets to 10-pin and use a 6U9 or 6X9. The output transformers are relatively wimpy, so I don't want to get too ambitious.

 

[kegger]

I hear you on those chassis to experiment with, I have something like 5 of the mono
PPP variety's destined for something or another, a couple have the transformer xover
deals and some the tranny phase splitters, I think I can match a few and frankenamp.

I'll be curious what you come up with..

 

[Tubelab_com]

Got any 6JB5/6JC5/6HE5's ? They make a nice stand in for the 6V6 but you need a 12 pin socket, which usually fits the same size hole as an octal socket.

I stuffed 4 of them into Petes red board and cranked them up to 25WPC where I decided to stop. I have read on the pages of this forum that these tubes "sound better than a 6V6" I dont know if this is true, but they do sound really good.

I tested these guys in post # 248 of the red board thread. I definitely will come back to them some day. I had been saving several old Magnavox amps for years until I decided that I need the space. Saved the transformers though. The red board uses "Schade"!

 

[wrenchone]

I have a fair number of the 6JB5/6JC5s. I'm using them in my Lil' Devil amp, which is about 3/4 done. I don't want to use anything that's too lively in the SE Magnavox chassis, as the transformers are fairly small. I figure the 6AU5 in pentode mode will be just about right.

 

[Tubelab_com]

I figure the 6AU5 in pentode mode will be just about right.

I guess you could always turn things down a bit

I got about 50 watts out of a pair of 6AU5's in P-P screen drive. They weren't melting either. Never got around to trying SE though. The 6AU5 shares the pinout with the 6AV5, which works real nice in triode.

I also found another little gem for SE, the 6EZ5. It falls in between the 6V6 and the 6W6 and it used to be on the dollar menu so I got a bunch. I melted a couple of them finding the limits in triode mode. Knowing what I know now, I think pentode with a dose of Schade would be a better choice.

 

[kegger]

Recently built a cheap singled ended amp with those 6JB5's.
(power and output tranny's combo found on the bay)..

An interesting thing I discovered in the process is the 6JA5, is mismarked/labeled
in most of the online tube info including TDSL and N7JP, it's actually the same as
the 6JB5, 6JC5, 6HE5 pinout, there a 19w plate and draw a fair amount of current
compared to the 6JB5 ect, on the 6JB5 I'm running a 325v B+ with 25v on 500ohm
cathode resistor in UL, the 6JA5 blows right past that current with a same resistor.

Anywho that 6JB5 is a nice sounding tube, I don't know about the better then 6V6
stated in other threads but a nice tube none the less, driving it with a 6AQ8 there.

Gotta love nice cheap tubes though.

 

[wrenchone]

It's nice to find a 19W plate rating with no #$%!!! plate cap.

 

[Tubelab_com]

An interesting thing I discovered in the process is the 6JA5

I found two of those, but they are totally different inside. One has a much bigger plate than the other. The Sylvania is the biggest. I didn't have two the same, so I didn't try them in the red board.

The real problem with the 6JA5 is the price, $10 to $20 each! I would rather melt some Chinese 6L6GC's at least they are $4 each. The 10JA5 can be found for $5 sometimes.

It's nice to find a 19W plate rating with no #$%!!! plate cap.

6HJ5, 24 watts no cap and $4 to $5 each. I cranked them to 140 WPC in the red board. I dialed them back to 100 WPC where they aren't stressed. Sound so good that I bought a bunch.

 

[kegger]

I hear yu about the price of those 6JA5, I was kinda bummed after I found out
but hey it's also nice to have stash of funky tubes and find a few "gems" there.

Also the fact that it is the same pinout does make it rather intriguing, I'll keep my
eyes peeled for any stashes there may be hidden away, there out there somewhere.

I'm sure in your stash George there's a few more hiding..

 

[wrenchone]

I think I'll concentrate on working with the tubes I have - already too many. As for George's comment on the Magnavox SE amp - remember, it's an SE amp (and a wimpy one at that), so you can't turn it up to 20. You can't even turn it up to 11, unless you love the sound of a clipped negative excursion. P-P amps, however, are a different matter, as long as your output transformer (and your B+ supply) has the stones to go along for the ride.

 

[wrenchone]

I dragged the 6V6 SE amp out of the box last night to have a look, and it will need another socket hole to do what I plan - no big deal, as there is plenty of room on the chassis. First up for all the amps, however, is a stringent cleaning - the seller was a world-class smoker...