Tim614 -
The Magnavox tube amps need minor adjustments to use as a stand alone amp. The amp was designed to be used with the tuner \ preamp included in the console. You need to wire in an on \ off switch or modify so it powers up when you plug it in. Most of the Magnavox amps also need the addition of a couple 390 ohm resistors to replace a balance circuit. It your amp has a balance pot you don't need these. If it doesn't the amp will "motor boat" or distort when you turn the volume up. It would also be a good idea to replace the power supply caps as electrolytic caps dry out over time.
There is a Yahoo Group called Friends of Magnavox that includes a lot of information on these amps. I don’t know much about electronics so I basically replaced all of the capacitors and resistors in the push pull amp (the one with the wood frame). I also replaced the rca inputs and speaker terminals. IMHO the amp sounds really good. I’m currently using a 200 watt Tripath amp because I’m driving some power hungry speakers. I do miss the tube glow. I’m traveling this week but would be happy to share more specifics on my rebuild when I get home.
Bruce
The Magnavox tube amps need minor adjustments to use as a stand alone amp. The amp was designed to be used with the tuner \ preamp included in the console. You need to wire in an on \ off switch or modify so it powers up when you plug it in. Most of the Magnavox amps also need the addition of a couple 390 ohm resistors to replace a balance circuit. It your amp has a balance pot you don't need these. If it doesn't the amp will "motor boat" or distort when you turn the volume up. It would also be a good idea to replace the power supply caps as electrolytic caps dry out over time.
There is a Yahoo Group called Friends of Magnavox that includes a lot of information on these amps. I don’t know much about electronics so I basically replaced all of the capacitors and resistors in the push pull amp (the one with the wood frame). I also replaced the rca inputs and speaker terminals. IMHO the amp sounds really good. I’m currently using a 200 watt Tripath amp because I’m driving some power hungry speakers. I do miss the tube glow. I’m traveling this week but would be happy to share more specifics on my rebuild when I get home.
Bruce
Re: very simple question and nedd very simple answer im so new at this
Three-prong cords are a VERY BAD idea on a Magnavox amplifier.
These amps use the chassis as signal ground... the RCA plugs, and all the ground returns from all the tubes are connected directly to the chassis. Using a 3-wire power cable is an almost CERTAIN GUARANTEE of a ground loop (i.e, 60 Hz HUMMMMMMMM).
In all the Magnavox amps I've restored, I've always used a 2-wire cord... and they all have been as quiet as the proverbial church mouse, as far as noise is concerned. With replacement caps installed, never one problem with any stray voltage on the chassis, either.
BTW: I now have one of the more rare variants of the SE amp, per the original poster's amp type... the 8608. Brass plated chassis! Really nice looking amp, once it's all polished up with NevrDull and 0000 steel wool!
Regards,
Gordon.
tim614 said:
Three-prong cords are a VERY BAD idea on a Magnavox amplifier.
These amps use the chassis as signal ground... the RCA plugs, and all the ground returns from all the tubes are connected directly to the chassis. Using a 3-wire power cable is an almost CERTAIN GUARANTEE of a ground loop (i.e, 60 Hz HUMMMMMMMM).
In all the Magnavox amps I've restored, I've always used a 2-wire cord... and they all have been as quiet as the proverbial church mouse, as far as noise is concerned. With replacement caps installed, never one problem with any stray voltage on the chassis, either.
BTW: I now have one of the more rare variants of the SE amp, per the original poster's amp type... the 8608. Brass plated chassis! Really nice looking amp, once it's all polished up with NevrDull and 0000 steel wool!
Regards,
Gordon.
bcrescen said:
Bruce,
Would you mind documenting your upgrades, changes and repairs/replacements to your 93xx amp. It is the very same amp as mine, which just arrived to my house yesterday.
I am going to run a dim bulb test today. I have an idea of what I would like to do, that is to say, strip it down and rebuild on a new base plate. Additionally, I want to add the basics, power switch, pilot, grounded cord, cap upgrades. If I new the changes you made it would help me plan mine. I like having a place to start from.
Regards,
Alan
Well, it's exciting to see this thread alive, as I recently scored two of these EL84 Magnavox amps! Even better, the EL84's are Magnavox branded but one set is GB (Mullard presumably) and the other German (Telefunken or Siemens?). The 6CA4 is Mullard, but sadly the getter is completely white.
One is a 196 AA and the other 8301 10.
The 196 is the SE EL84 pair driven by 12AX7, with 5U4 rectifier.
The 8301 is SE EL84 pair driven by 6EU7, with 6CA4 rectifier.
A few people I've spoken to say these amps sound really good, and one person said the stock OPTs are pretty decent for their size. I'm curious if anyone knows the primary impedance on them, and I've been wondering if a pair of XSE Edcors would really up the ante on the sound performance.
I also found an interesting Aluminum project box that isn't terribly expensive on eBay (250297136275) that I was thinking of using as a new chassis for the amps. It looks sizable enough to hold everything and it has a nice appearance too. I am gathering that all the tone control circuitry should be removed, so a bit of rewiring is in order anyway.
Curious to hear others' thoughts...
One is a 196 AA and the other 8301 10.
The 196 is the SE EL84 pair driven by 12AX7, with 5U4 rectifier.
The 8301 is SE EL84 pair driven by 6EU7, with 6CA4 rectifier.
A few people I've spoken to say these amps sound really good, and one person said the stock OPTs are pretty decent for their size. I'm curious if anyone knows the primary impedance on them, and I've been wondering if a pair of XSE Edcors would really up the ante on the sound performance.
I also found an interesting Aluminum project box that isn't terribly expensive on eBay (250297136275) that I was thinking of using as a new chassis for the amps. It looks sizable enough to hold everything and it has a nice appearance too. I am gathering that all the tone control circuitry should be removed, so a bit of rewiring is in order anyway.
Curious to hear others' thoughts...
It figures, I'm at school now so I cannot comment on the Mullards since I didn't look closely at them - however I do remember that the German tubes had a number molded in the glass inside the pins, but I don't believe they had the diamond that I have seen in Telefunken tubes in the past. I think it was a 22, if that means anything.
I'll check when I get home to see if I have Blackburn EL84s - that's an exciting prospect from what I've heard about them.
I'll check when I get home to see if I have Blackburn EL84s - that's an exciting prospect from what I've heard about them.
Before you go and strip everything out of the original chassis, try using some 0000-grade steel wool, some Nevr-Dull (metal polish) and some car wax on the chassis.
Those old Maggies can look pretty spectacular, if the original plating is still in reasonably good shape. You can get a good "nickel-plated" looking finish, with reasonable work...
Regards,
Gordon.
Those old Maggies can look pretty spectacular, if the original plating is still in reasonably good shape. You can get a good "nickel-plated" looking finish, with reasonable work...
Regards,
Gordon.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.