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Old 8th December 2005, 01:09 AM   #11
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If you haven't melted anything, you are not trying hard enough.

I have two thoughts on the stereo guitar amp idea:

My daughter won a Brownsville stereo 150 (SS) guitar amp. She left it behind when she moved out because she preferred the sound (and size) of one of my champ clones. This amp runs two identical channels through two identical 12 inch speakers mounted together in the same box. The amp is very loud, but not particularly inspiring. It sits unused in my warehouse.

On the other hand I bought a Guild Ultraflex tube amp at a flea market for $35 about 10 years ago. This amp has a single preamp with a knob labeled Ultraflex Balance that feeds the signal to two seperate power amps. The amps use 7591's and seem to put out about 30 watts each. The unique part, one channel feeds a 15 inch speaker, the other channel feeds an 8 inch speaker. Turn the knob to the left, all the sound comes from the 15, clean, little breakup, great for chords, and a hollow body sound. To the right, a screaming 8 inch Champ on roids sound, good with the Strat. In the middle, the best blues sound that I have ever heard, best fed with a Les Paul. This is like two amps in one box with a fader control.

This is the only commercial amp that I use, and right now it is the only working amp in my house. It is that good. It still has all of original 1961 tubes in it. I have never been able to find a schematic for it, or even any information about it.
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Old 8th December 2005, 01:50 AM   #12
Trout is offline Trout  United States
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Quote:
Originally posted by tubelab.com

On the other hand I bought a Guild Ultraflex tube amp at a flea market for $35 about 10 years ago. This amp has a single preamp with a knob labeled Ultraflex Balance that feeds the signal to two seperate power amps. The amps use 7591's and seem to put out about 30 watts each. The unique part, one channel feeds a 15 inch speaker, the other channel feeds an 8 inch speaker. Turn the knob to the left, all the sound comes from the 15, clean, little breakup, great for chords, and a hollow body sound. To the right, a screaming 8 inch Champ on roids sound, good with the Strat. In the middle, the best blues sound that I have ever heard, best fed with a Les Paul. This is like two amps in one box with a fader control.

This is the only commercial amp that I use, and right now it is the only working amp in my house. It is that good. It still has all of original 1961 tubes in it. I have never been able to find a schematic for it, or even any information about it.
That wouldnt be the same setup as the magnatone with ultraflex would it? Like The Panaramic

They had a couple models with that type of setup.

I dug around in the ole garage a bit, Everything out there has ugly OPT's on them. Eww brown paper. I found 3 opts that were for 6L6's, all in workable condition, But I have no data on primary impedance , The Other PT's I have are huge from organs and more of those console models.

I look into those other ones at triode I guess, I have 2 of the champ TF103-48 and three of the TF110-48-UL sitting here. Hopefully I will find some proper PT's at a fair price someplace.

Im SOoooo bored now lol I was really in the mood to melt some solder.
Gene
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Old 8th December 2005, 01:43 PM   #13
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It is the same amp. The link that you provided states that the amp was made by the Audio GUILD Corporation. Mine says the same thing, and looks the same but the faceplate is silver.

If you have a set of transformers that are all from the same amp. Then it would be a safe bet to assume that you can use them to build a similar sized amp using the same tubes. Amps from organs usually have good frequency response and power capabilities. I have used the transformers from them with good success. If you have a good "brown paper" transformer, you can often transplant the end bells from a similar sized transformer onto them, even an old power transformer.

If you have 3 transformers that are from 6L6 amps, you can obviously use them with 6L6's. The impedance is likely from 5000 to 7000 ohms, probably 6600. It does not make that much difference in a guitar amp. I have found that to drastically change the tone, you must change the impedance by at least a factor of two. You do this by purposefully connecting an 8 ohm load to the 4 or 16 ohm taps. Don't try this on an amp that is already pushed to its limits.

6L6's and their relatives can take a lot of voltage, the power transformers that you have will likely work, including the one that you mentioned above. Use one of the "mystery output transformers" but think about how you could also mount the Triode transformer when you build the amp. That way you could put it in later if the "mystery transformer" didn't work out.
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Old 8th December 2005, 02:32 PM   #14
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Hey Trout,

You can measure the impedance of your OPT's fairly easily.

Hook the primary up to your AC line... Make sure all the others wires are taped, insulated etc...!

Measure the primary AC RMS voltage, then measure the ouptut AC RMS voltage.

Divide the Primary by the Secondary; take this number and square it; take this number and multiply it by your speaker impedance and there is your primary impedance.

Just takes a minute... and the result will be close enough.

If you are curious about power handling of an OPT... weigh it.

Most instrument amps come in at about 0.13 lbs per watt... hifi about 2 - 3 times that.

Cheers
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Old 8th December 2005, 02:37 PM   #15
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Oh,

I am not certain if the 0.13 lbs per watt applies to all output configurations... it valid for push-pull.

Tubelab would surely know...

Later
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Old 8th December 2005, 05:40 PM   #16
Trout is offline Trout  United States
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Thats Cool on the ultraflex Amp! I am betting that theres a schematic someplace on the web. The tricky part is the search hours involved.


Quote:
If you have a set of transformers that are all from the same amp. Then it would be a safe bet to assume that you can use them to build a similar sized amp using the same tubes. Amps from organs usually have good frequency response and power capabilities. I have used the transformers from them with good success. If you have a good "brown paper" transformer, you can often transplant the end bells from a similar sized transformer onto them, even an old power transformer.
I was able to transplant end bells from some old radio PT's directly onto a 6L6 PP OPT off an old wurlitzer. What was really nice was I was able to rewire the leads so I now have nice 12 inchers to start out with.

Also salvaged a second 6L6PP OPT from an old Bell Labs Pacemaker amp. Put end bells on it, New wire, And Its even got 4-8 & 16 ohm taps.

Now I am inspired to rewire a couple of Scott 99A trannies for my future (soon) Stereo project.
A-6L6PP at about 22W should serve me great. And Those OPTs are great quality.

I think I'll build the guitar amp all the way up, but not mount the OPT until I can test it on, Then I wont have any messy holes to deal with should it be a flop.

Gene
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Old 8th December 2005, 05:55 PM   #17
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SE OPTs will be heavier than PP for a given wattage.
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Old 8th December 2005, 06:01 PM   #18
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Not to hijack the thread, but, man, I miss pawn shops as they were 20+ years ago. You could find the coolest old amps. Obscure ones. Excellent ones that fetch insane prices on E-Bay now. Whutizzits, like, from outer space. Even downright scary WTF izzits?!? All kinds.

Now,....cheez and nearly new junk. Guitars, too.
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Old 8th December 2005, 07:16 PM   #19
Trout is offline Trout  United States
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Quote:
Originally posted by Reddy KW
Not to hijack the thread, but, man, I miss pawn shops as they were 20+ years ago. You could find the coolest old amps. Obscure ones. Excellent ones that fetch insane prices on E-Bay now. Whutizzits, like, from outer space. Even downright scary WTF izzits?!? All kinds.

Now,....cheez and nearly new junk. Guitars, too.
Oh Yeah, you have that right!
I remember grabbing a huge HV transformer and building a Jacobs ladder for like 5 bucks.
Used to see old fender tweeds in those places regularly, These days they are as rare as news channels without political agendas
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Old 8th December 2005, 07:44 PM   #20
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Now the pawn shops and the flea markets all look up the unusual stuff on Ebay, then ask Ebay money for it. You really have to travel far off the beaten path to find treasures any more.

The flea market where I got the Guild is now Ebay aware. I got an old "broken amplifier" there for $40. It contained 2 UTC P-P OPT's they go for $150 each on Ebay. Not any more.
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