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Magnavox Tube Console Preamp Needed

I've used my Maggies, a 9300, 8800,175 and a 8600....both with and without preamps....for my computer sound system and to play an iPod thru.

A Preamp always gives the Maggies more volume capability....and of course the tone controls...if needed.

I have not tried wiring a volume control into a Maggie yet.
Does putting a volume control into a Maggie circuit give additional volume to the standard circuit?
 
Dswankey said:
Gordon,

Sorry if this question doesn't make sense but what does this do? eliminate having to use a preamp?
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It IS a preamp. A very simple one, that can easily be added to the Magnavox stereo amp chassis, and run off the same power supply.

If you do this, you won't need an external preamp at all, except for if you use a phono (you would need a phono RIAA preamp for that).

The only issue I've run into, is that sometimes, even though this is a pretty low-gain tube, you can wind up with TOO much gain (i.e, it's too loud at too low of a volume control setting). If that's the case, try adding a 47K resistor between the coupling cap and the volume pot, on each channel. That usually does it.

Regards,
Gordon.
 
^ Thanks for the explanation Gordon as always i appreciate the knowledge you and the other tube gurus share on topics such as this.
 
Dswankey said:
Sorry if this question doesn't make sense but what does this do? eliminate having to use a preamp?
Click to expand...


It builds a preamp on the chassis, using the extra tube socket hole. If you mate it up with a selector switch for multiple inputs, you now have a handy dandy integrated amp with however many input sockets you dare to add.

Another option is to re-work it per Dave Gillespie's updated design. Input sensitivity is marked as 0.60v, which means you need about 2/3 of a volt to hit full output power.

http://audiokarma.org/forums/index....ox-the-9300-series.687735/page-4#post-9213408
 
Tubeglowpio said:
Thanks for that input and values Gordon and thanks everyone. As far as Maggies go this 9302 that I'm picking up tomorrow will be my second Maggie, first one got the full re-cap and resistors changed and has been on daily duty. How do the 6v6 maggies rival the 6bq5's?
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Dswankey said:
^ I can see it now, is that the most advantageous spot to install one?
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I just tried for the shortest wire run
 
The 6v6's seem to have a smoother midrange to me. The bottom end sounds a bit looser too. The el84s have a more controlled low end and the midrange sounds more forawrd to me. My 9303 is heading over to my sons house today. I just dont have the room for OB's right now so im setting up a system at his place. I have 5 systems set up here already so I need more room and my son has it. He has a big-0-room not being used that will be perfect.
 
Lavane said:
The 6v6's seem to have a smoother midrange to me. The bottom end sounds a bit looser too. The el84s have a more controlled low end and the midrange sounds more forawrd to me. My 9303 is heading over to my sons house today. I just dont have the room for OB's right now so im setting up a system at his place. I have 5 systems set up here already so I need more room and my son has it. He has a big-0-room not being used that will be perfect.
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That's good that you're bonding with your son over audio, I'm 26 and trying to get my dad who grew up in the 50's/60's back into music. I'm trying to make him a home made stereo with built in phono stage and build the chassis and do the wood work for the case, will post photos when done.
 
Tubeglowpio said:
That's good that you're bonding with your son over audio, I'm 26 and trying to get my dad who grew up in the 50's/60's back into music. I'm trying to make him a home made stereo with built in phono stage and build the chassis and do the wood work for the case, will post photos when done.
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Very cool. My son plays guitar so ive worked on his amps and set him up with some stage monitors and such. I gave him one of my SS Marantz systems and now trying to get him more into tubes.
 
Nice! I play guitar too, been thinking of changing resistors and caps in my fender blues deluxe reissue. For solid state I have a Marantz 2230 that sounds amazing but need to source new transistors before I recap it. I prefer working on tube stuff but this is a ss worth fixing up, warmest ss I've heard. I also have a Pioneer sx 850 that I'm thinking of selling. I don't have a huge budget currently but am trying to get more into the tube stuff. I haven't been able to hear many different tubes yet but am hoping to go to the rocky mountain audio fest next year.
 
I gave him a 1060 intgrated I recapped. Pretty much a 2230 without the tuner. It makes for a nice preamp for the 140 amp. He has a Red Bear 120 tube guitar amp head, man that thing gets loud. It drives 4 12" drivers.
 
Lavane said:
I gave him a 1060 intgrated I recapped. Pretty much a 2230 without the tuner. It makes for a nice preamp for the 140 amp. He has a Red Bear 120 tube guitar amp head, man that thing gets loud. It drives 4 12" drivers.
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Very cool, yeah my fender puts out a true 40 watts and it's too loud for my girl at 1 or 2 lol. Yeah, I'm not a huge fan of the tuner in the 2230 but love the look and the amp and phono have a sweet sound to them. Some stuff sounds so 3d when hooked up to my smaller advents. Any budget speaker idea that would go great with a single ended El84 amp, hard to find quality high db speakers for cheap?
 
Lavane said:
I havnt found really efficient speakers cheap. The most effcient I have are 93db.
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Yeah my pioneers are 92/93 db and they sound nice sometimes but bass can get flabby I want something 96 or more. Thinking of building a pair, will just take time as when I build stuff I try as many different cap/resistor types and arrangements as possible, throw in multiple driver and this will take awhile lol. I've been thinking of ways to create a third channel to send the bass freq to a separate powered woofer, would be cool to do to a Maggie.
 
Would someone be willing to sketch the schematic the Gordon discussed in his quote? I'd like to be insert this pre into a maggie console amp, but am confused about a few of the steps, and I think that the schematic would help.

GordonW said:
Single 12AU7 or 6CG7 (prefer 6CG7) for stereo channels, 0.1uf input caps, 470K grid ground resistors and 1K grid stoppers, 820 ohm 1/2w cathode resistors, 22K 2w plate resistors, .22uf 630v coupling caps. Run it on between 275-320v B+. Feed that into a 100K stereo pot, then into the existing first tube in the Magnavox amp, through a 1K grid stopper (change the existing stopper resistor, if there is one, to a 1K- or add a 1K if there isn't an existing grid stopper).

I've lost count of how many times I've done that- and it ALWAYS sounded great.

Regards,
Gordon.
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GordonW said:
Single 12AU7 or 6CG7 (prefer 6CG7) for stereo channels, 0.1uf input caps, 470K grid ground resistors and 1K grid stoppers, 820 ohm 1/2w cathode resistors, 22K 2w plate resistors, .22uf 630v coupling caps. Run it on between 275-320v B+. Feed that into a 100K stereo pot, then into the existing first tube in the Magnavox amp, through a 1K grid stopper (change the existing stopper resistor, if there is one, to a 1K- or add a 1K if there isn't an existing grid stopper).

I've lost count of how many times I've done that- and it ALWAYS sounded great.

Regards,
Gordon.
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Superb suggestion!
Mind that this single element gain stage addition inverts acoustic polarity, so reverse the polarity connection of both speakers to compensate.
 
Might play around with one of the Little Bear tube buffer amps. Not a lot of money and sure are versatile for buffering inputs to about anything. Pretty too.
 
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