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Another Maggy Thread

jaymanaa

jaymanaa

RIP 1961-2018
One more of these great amps will be spared the indignity of the landfill.:banana: This one is a 9304-20, which looks to have a hair bigger iron than some of the other 6BQ5 Maggy amps. It will get my tweeked version of the 175 circuit, which is pretty much all I use on these guys now. The wood base is Chestnut, but has no oil on it yet. I'm going to try to build a metal box on the back of this one to conceal the 3 transformers. They are in a nice clean row, so it should be fairly straight forward. I may end up putting some darker wood gussets in the corners too, since there isn't any way to put them inside.
 
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I have a matched set of EL84M tubes that I am anxious to use, but no amp to use them in. Maybe a 9304 would be the ticket!
 
Any chance you have another one of those Maggie emblems? I'd like one for the amp you did for me.

I'll post up some pics of that amp here soon.
 
yea no kidding I've been looking for one of theose emblems for my 175 for a while too. Nice looking amp !
 
Jay, wtf do you do with all of those amps?

I had a MINT logo just like that. A few weeks back I was in a cleaning frenzy and next thing you know I had stepped on it. Now it just says "Mag". :(
 
Those emblems seem hard to come by. I got this one off a console TV/stereo thing. It weighed about 20 metric tons and I hauled it home thinking it was tubes.:no:

Someday I'm going to figure out what to do with all these amps. A lot of them are for other people, but I do have way to many myself.
 
Great save. Definitely ain't landfill material!

I love how these small Maggy amps allow a lot of people to get a taste of quality tube amplification at a small price....:thmbsp:
 
what is the 175 circuit ?

Jay,

Was just wondering what the 175 circuit is :scratch2:

I don't have a Maggie amp (yet) but have a Fisher 481A that I am recapping and an old Viking 6BQ5 single ended excellent sounding tuner / amp.

These old guys really rock my Altec 19's, jazz music is especially spectacular !

Seems all I have are 6BQ5 amps, even my wife's old Blaupunkt uses them (EL84 same thing).

Your woodwork looks great and I love the idea of a metal cover over the transfomers, that should look excellent :thmbsp:
 
I too am building up a 175

Hi,

I asked in another thread on the 175, but I guess I will ask here also for more info on good ways to wire a 175 circuit.

I am building up a 175xx - but, I don't actually have one . . I have a 142x and a 128x (mono units) I am using for parts! Those amps are 6v6gt qty=4 5y3gt qty=2 12ax7 qty=1

From studying the 175 schematic I have some obvious questions. . . and probably missed many things that are important.

Here is a stock 175 schematic and the dual 5y3gt psu


http://www.audiokarma.org/forums/attachment.php?attachmentid=118337&d=1226896665


So I have questions Jay, Special, Clydeselsor, cademan, (or anyone else of course):

So did you go with the 2.2k / .001uf feedback or the 5.6k 470pf? Something inbetween?

And if you eliminated the balance did ya just go 470k on both channels?

Can I cave man some 1m pots on the input for volume controls? input -> 0--/\/\/\-- (Ya, that looks like a resister on the input!)

I have the mono preamp, don't want to get too crazy with the PT before I know how warm it runs since I don't have hard data on it. But I suppose I could just stereo up whatever it is doing.

Do you think I should change the PSU to the single 5U4B? I hooked 121Vac from the wall to my PT and read 380-0-380
(That seems high enough to handle the 5y3gt pair and get 295 ?)




I picked up components to go either way and stuff to tweak it with also later . . . . but if yours works then I am interested!




I could not generate much interest at friends of magnavox on the topic of 175 builds. (This is probably so last decade to them)

But, I am really enjoying my foray into a magnavox stereo instead of simply re-wiring my 142 and 128 into more guitar amps. - And the Magnavox group's love of maggies is what inspired me to try to save this old iron and aluminum - but as stereo.

I can't wait to see how my caveman 175CC turns out with the bigger outputs from 142/128 type magnavoxes. 5400 : 8 is the ratio.

PS. if no one has a schematic of a successful upgrade, what is a good / free or cheap program I could start a schematic with so I can help visualize what we are talking about.
 

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  • Magnavox 175x original schematic.png
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Definitely go with the 2200R and 1000mmf feedback, and use a polyester film or silver mica for the cap. Get rid of the .01 ceramic cap at the input, but if you have any devices you use upfront that might pass some DC, use a .033 film, or better yet PIO. Get rid of the single 125R 10 watt cathode resistor and use one for each channel (to improve crosstalk) of 250R, bypassed with a 500uf or better by 25v cap. If your power supply doesn't use a choke, get one and dump the big resistor after the first cap (using the choke in it's place). AES sells a Hammond that works fine for around 20 skins, I think it's 2 hy with around 50ohm R. Keep the 5U4 so you can keep the first cap 40uf (the 5Y3 won't like it). For the second cap, I like 80uf minimum. For the .047 coupling caps, use at least orange drop 716Ps, but PIO will really bring out the upper mids and top end. If I think of more later I'll post it up, but that's most of it I think. Oh, if you "really" want it to sound good, use 6BQ5s with this circuit, but you have to account for the pinout, sockets, and cathode resistor. Lots of folks like the 6V6 too though, so it's a matter of taste.:thmbsp:
 
Tiny Cad Rocks! Audiophile 175xx schematic

Ok, I downloaded Tiny Cad, and I was able to knock out an original to replace the one I posted earlier. (see above post)

And I tried to implement the changes recommended.

Any more changes let me know, this is the audiophile maggie 175 build. . . . LoL

Ok, well, it is as audiophile as it gets at knife's cave.

Feel free to pick it apart, or add!
 

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  • Magnavox 175x audiophile schematic.png
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