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Old 18th June 2011, 02:16 AM   #201
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The neck pickup has very attenuated 2'nd hatmonic. The 4'th one with fundamental gives a kind of romantic sound.
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Old 18th June 2011, 02:26 AM   #202
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This is a SS amp with a 10" speaker, $129 MSRP, and can be found used for $50 which is a good price for the box, chassis, knobs etc. Some have gutted them and built a tube amp into them:
Fender Products

Tube mod:
http://laird.vectorstar.com/music/amps/6g2princeton

Speaker is the weak link, it sounds fairly good as is with a decent speaker upgrade.
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Last edited by PB2; 18th June 2011 at 02:36 AM.
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Old 18th June 2011, 02:34 AM   #203
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Quote:
Originally Posted by PB2 View Post
This is a SS amp with a 10" speaker, $129 MSRP, and can be found used for $50 which is a good price for the box, chassis, knobs etc. Some have gutted them and built a tube amp into them:
Fender Products

Speaker is the weak link, it sounds fairly good as is with a decent speaker upgrade.
Thank you Pete!

Looks like one more great donor found, after Marshall MXL condenser microphones.
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Old 18th June 2011, 02:37 AM   #204
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"Has anyone ever played with "Flathead" transformers as OPTs?"

You can find them cheap on surplus sites:
PC MOUNT TRANSFORMER, 16VCT @ 0.35A OR 8V @ 0.70A | AllElectronics.com

I've done some measurements on one here and their problem is high leakage inductance between the split bobbins. So you may find the HF end somewhat compromised even for guitar use.
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Old 18th June 2011, 02:52 AM   #205
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So, I wonder if they would work as a cheap output transformer? with an 8 ohm load on the parallel secondaries the primaries would be around 8.5K p-p
.


I tried a bunch of low buck low power transformers like this as P-P OPT's a few years ago. They didn't work well at power above a few watts, and I was thinking HiFi amps. I still have them here, and they will be among the first things I try.

Back In high school I was making amps on zero budget. All the transformers came from the trash dump. My guitar amps used OPT's ripped out of HiFi consoles or TV sets but they were rather limited in the power department. I got this brilliant idea to use a power transformer for an OPT. You connect B+ to the HV center tap, each HV wire to a 6L6 plate, wire all heater windings in series, and all speakers in parallel, then connect them together. They rock as a guitar amp OPT and they eat more power than I could make.
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Old 18th June 2011, 04:48 AM   #206
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I used C-core power supply transformers from Soviet tube TV sets for 100W guitar amps with 6P36S outputs. They were LOUD!
The same way, I combined windings to get needed impedances.
For the current studio&practice Amp I am going to use some transformer from All-American-Five radios.
Also, I have some 12" and 15" speakers from Magnavox consoles, does anybody know how good they are for guitar amps?
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Old 18th June 2011, 05:01 AM   #207
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Anyone see any safety issue with turning around the Triad N-68X to get 230CT on the secondary?
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Old 18th June 2011, 12:18 PM   #208
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This is playing a fat 'G' bar chord on the 3rd fret with about as much bite as I can muster.
YouTube - ‪Jimi Hendrix teeth solo‬‏

I wouldn't try this...some guitars have a bad ground.
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Old 18th June 2011, 01:33 PM   #209
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Anyone see any safety issue with turning around the Triad N-68X to get 230CT on the secondary?
The N-68X is a true isolation transformer. There should be ample isolation between the primary and secondary to prevent shorts or leakage current between the windings. It even has a shield between the primary and secondary which should be connected to the ground wire on the line cord and circuit ground. Although it isn't stated in the spec sheet, the transformer I have in front of me carries the UL mark (no CSA though). It is about 5 years old.

It makes no difference which windings you use for primary of secondary as long as you use do not make any connection across the isolation boundry. I have been running the N-68X's backwards for about 5 years with good results. I do this because I need + / - 140 VDC to run my mosfet based PowerDrive circuits. You won't quite get 230 volts since the transformer isn't quite 1:1 to make up for losses.

Eli has suggested running the transformer as intended followed by a voltage doubler. This allows world wide use of the amp if your heater transformer has dual primaries. If it doesn't, run it off the output of the N-68X unless you are running out of VA capability, in whch case your amp is bigger than mine!

Quote:
YouTube - ‪Jimi Hendrix teeth solo‬‏
I wouldn't try this...some guitars have a bad ground.
I am showing my age by admitting that I saw Jimi live in concert. Most of the "use of body parts other than fingers" to play the guitar is a great stage trick. The real action happening on the guitars neck. Right hand in Jimi's case. Using an amp with excessive preamp gain like a Marshall cranked to 11, you can play one handed. (OK, Jimi can, I can't) The string will vibrate enough just by hitting the fret hard. Having the whole system on the verge of acoustic feedback helps by providing additional stimulus to the strings already set in motion.

When you are done with your amp there should be continuity between the metal parts of the guitar and the ground pin on the power cord.

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Also, I have some 12" and 15" speakers from Magnavox consoles, does anybody know how good they are for guitar amps?
I had good luck with some, some didn't sound too good, and some didn't live long. I had a pair of 12's from a Maggie that also had die cast aluminum horn tweeters. I used all 4 (2X12 and both horns) speakers and the power amp (2 X 6BQ5 SE) to make a rather nice sounding guitar amp.

That may also apply to speakers from old guitar amps too. I found an old Electrolab "shock box" guitar amp in an antique shop for $5. The circuit was derived from an AA5 radio. I replaced the tubes, caps, and a few resistors, and added an N-68X to prevent shocking moments, but did nothing to increase the power. I cranked it up and started playing. The speaker lasted about 5 minutes. The 50 year old paper cone just came apart and the voice coil seperated from the cone.
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Old 18th June 2011, 03:46 PM   #210
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Anyone see any safety issue with turning around the Triad N-68X to get 230CT on the secondary?
No but you may lose a few % of the power rating. As the coupling into the core will be a bit less.

The other trick transformer use is to use one of the flatpack variety where there are two bobbins side by side. You can use one of the primaries as a 120 V AC input and the other as an isolated 120 volt output, of course the transformer has to be derated to 1/2 power! But that way you can get a single inexpensive transformer to supply HV and filament voltage.
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