Hi Guys,
Im looking at a catalog from a well known componet source and am very curious about selecting a transformer for a single ended amp using 6V6GT, 5Y3,& 12AX7, Basically fender champish.
So, My question is more about the MA requirements. My OPT is rated for 40ma (Transformer is rated 100 Hz to 20 KHz -2 dB at 5 watts with 40 ma (maximum recommended) primary current)
The power transformer I am wonder about has the following specs.
650CT 40ma (after rectification)
5V 2A
6.3CT 2A
Is the PT 40ma rating to low?
Also With The 5V-2A rateing, The 5Y3GT requires 2A heater current, Is this also to close?
Or does anyone know a sutible source for a PT that meets the tube requirements listed abouve for $25.00us or under?
Gene
Im looking at a catalog from a well known componet source and am very curious about selecting a transformer for a single ended amp using 6V6GT, 5Y3,& 12AX7, Basically fender champish.
So, My question is more about the MA requirements. My OPT is rated for 40ma (Transformer is rated 100 Hz to 20 KHz -2 dB at 5 watts with 40 ma (maximum recommended) primary current)
The power transformer I am wonder about has the following specs.
650CT 40ma (after rectification)
5V 2A
6.3CT 2A
Is the PT 40ma rating to low?
Also With The 5V-2A rateing, The 5Y3GT requires 2A heater current, Is this also to close?
Or does anyone know a sutible source for a PT that meets the tube requirements listed abouve for $25.00us or under?
Gene
Gene,
Assuming that 40 mA. of DC is with a cap. I/P filter, a pretty conservative estimate for the AC RMS current capability of the rectifier winding is 60 mA. You can get at all 60 mA. if you use a choke I/P filter. In order to get a decent B+ rail voltage, you'll have to SS rectify. UF4007s are pretty quiet to begin with and they can be snubbed, if necessary. A small cap. (< 1 muF.) in front of the inductor allows you to tweak the O/P voltage of the PSU. It's quite safe to use the fudge factor cap. to make the O/P voltage = AC RMS voltage. A 325 V. B+ rail is not unreasonable for use with a 6V6. Tieing off the 5 V. winding puts 10 VA back into the "pool" that just might be useful. Your PSU filter is LCLC (ignoring the fudge factor cap.).
For a 325 V. PSU using a 10 H. 1st inductor, Icrit is approx. 33 mA. The 40 mA. idle current of the 6V6 easily takes care of that requirement.
Be sure to use a standby switch in the line from the rectifier winding's CT to ground. Let the tubes get good and hot before throwing the standby switch.
Assuming that 40 mA. of DC is with a cap. I/P filter, a pretty conservative estimate for the AC RMS current capability of the rectifier winding is 60 mA. You can get at all 60 mA. if you use a choke I/P filter. In order to get a decent B+ rail voltage, you'll have to SS rectify. UF4007s are pretty quiet to begin with and they can be snubbed, if necessary. A small cap. (< 1 muF.) in front of the inductor allows you to tweak the O/P voltage of the PSU. It's quite safe to use the fudge factor cap. to make the O/P voltage = AC RMS voltage. A 325 V. B+ rail is not unreasonable for use with a 6V6. Tieing off the 5 V. winding puts 10 VA back into the "pool" that just might be useful. Your PSU filter is LCLC (ignoring the fudge factor cap.).
For a 325 V. PSU using a 10 H. 1st inductor, Icrit is approx. 33 mA. The 40 mA. idle current of the 6V6 easily takes care of that requirement.
Be sure to use a standby switch in the line from the rectifier winding's CT to ground. Let the tubes get good and hot before throwing the standby switch.
Gene,
Are you willing to try something a little different? How about a tube rectified voltage doubler supply somewhat in excess of 300 V.?
Mouser stock # 553-N51X is a 35 VA isolation trafo that costs $12 each. Use that trafo to feed a "full wave" doubler made from 2X 6AU4 damper diodes. The doubler stack consists of 2X 250 WVDC 68 muF. 'lytics. Follow the doubler with a LC section.
"Rat Shack" cat. # 273-1511 is a 3 A./12.6 VAC CT filament trafo. that costs $10.49 each. 6AU4 heater draw is 1.8 A. Wire the 6AU4 heaters in series and connect the junction to the trafo's CT. Use a 12V6 for the "final". Same guts as a 6V6, but costs less. 12V6 heater draw is 225 mA. 12AX7 heater draw is 150 mA. The total heater draw is well within the filament trafo's rating. $22.50 plus shipping buys the power "iron". As this is a "12" V. heater setup, you can use an $8 GE 7058 instead of an 'X7.
Are you willing to try something a little different? How about a tube rectified voltage doubler supply somewhat in excess of 300 V.?
Mouser stock # 553-N51X is a 35 VA isolation trafo that costs $12 each. Use that trafo to feed a "full wave" doubler made from 2X 6AU4 damper diodes. The doubler stack consists of 2X 250 WVDC 68 muF. 'lytics. Follow the doubler with a LC section.
"Rat Shack" cat. # 273-1511 is a 3 A./12.6 VAC CT filament trafo. that costs $10.49 each. 6AU4 heater draw is 1.8 A. Wire the 6AU4 heaters in series and connect the junction to the trafo's CT. Use a 12V6 for the "final". Same guts as a 6V6, but costs less. 12V6 heater draw is 225 mA. 12AX7 heater draw is 150 mA. The total heater draw is well within the filament trafo's rating. $22.50 plus shipping buys the power "iron". As this is a "12" V. heater setup, you can use an $8 GE 7058 instead of an 'X7.
Honestly,
I think I'll just end up biting the bullet and getting a couple from Triode or Hammond. I was hoping to pop a couple of cheap champs together for some buddies. I would really prefer to stay as close to the normal schematic as possible given my 70/30 success rate LOL
Maybe I can dig something up on evilbay.
Gene
I think I'll just end up biting the bullet and getting a couple from Triode or Hammond. I was hoping to pop a couple of cheap champs together for some buddies. I would really prefer to stay as close to the normal schematic as possible given my 70/30 success rate LOL
Maybe I can dig something up on evilbay.
Gene
I assume you are looking in the Allied Electronics catalog, since the 6K3VG transformer meets the specs that you list. I think that this one is a bit undersized. The DC voltage will drop a bit when the amp is pushed into clipping, which gives a unique sound, but this is might be too close. I have tested the Triode OPT and it will work up to 60mA so you may want more headroom. At $23 it might be worth a try if you are looking to build low cost amps.
I have been using Allied transformers in my amps for about 4 years. The only one that failed is the one that got wet during a hurricane last year, and it lasted 3 months after that. Autopsy revealed all sorts of green growth due to water. I routinely run these at or slightly above the maximum ratings. They do get hot, but don't fry.
In my SE (45, 2A3 etc) audio amps I use the 6K56VG transformer with a 5AR4 rectifier tube. This gives 320 volts with 90 mA load. You will get less voltage with a 5Y3 and more if you use SS diodes. This one costs $38 though.
For more voltage I use the 6K7VG. It gives 350 volts with a choke input filter at 130 Ma load (300B amp), and over 400 volts with a cap input. This might be too much voltage for your application. It's $43 also. I used these when I built my "turbo champs" a few years ago. Dual rectifier, switchable filter, capable of melting a 6V6 if turned up full. User education required. The schematic will be on my web site with the next update, I found a paper copy and scanned it.
If using a Hammond, try T272X. Around $40, you will get about 350 to 375 volts.
I have been using Allied transformers in my amps for about 4 years. The only one that failed is the one that got wet during a hurricane last year, and it lasted 3 months after that. Autopsy revealed all sorts of green growth due to water. I routinely run these at or slightly above the maximum ratings. They do get hot, but don't fry.
In my SE (45, 2A3 etc) audio amps I use the 6K56VG transformer with a 5AR4 rectifier tube. This gives 320 volts with 90 mA load. You will get less voltage with a 5Y3 and more if you use SS diodes. This one costs $38 though.
For more voltage I use the 6K7VG. It gives 350 volts with a choke input filter at 130 Ma load (300B amp), and over 400 volts with a cap input. This might be too much voltage for your application. It's $43 also. I used these when I built my "turbo champs" a few years ago. Dual rectifier, switchable filter, capable of melting a 6V6 if turned up full. User education required. The schematic will be on my web site with the next update, I found a paper copy and scanned it.
If using a Hammond, try T272X. Around $40, you will get about 350 to 375 volts.
tubelab.com said:
Yep,, Thats the unit. I have a discontinued unit from them in a Marshall clone that is very impressive but I was a $5.00 special at a estate sale 6K6 model. I sure wish they still offered that model!
On the SAME topic, But Different project. I have 3 matching PT's in perfect working order from some salvaged consoles. Looking at the schematic and the tube compliment, I am thinking a couple 18W clone projects.
Transformer Specs on Schematic
I am guessing that it is safe to assume I can run 2-EL84's and 4-5 12AX7's on the filament winding, And 210MA on the HV seems pretty close to safe, or borderline to much?
Once again, Triodes OPT rated at 80ma per side in PP 25 watts,Primary 6600 ohm CT .
I am already going winter crazy here LOL it was the big "ZERO" degrees this morning and not expected to get above the single digits for overnites till maybe saturday BRRrrrRRRrrrrrr
Good time to tinker by the glow of a few warm tubes
Gene
The power supply schematic that you provided shows that it provides 360 Volts with a 210 mA load. 210 Ma is about right for 4 6BQ5's and 2 12ax7's. If you use this to power an amp that uses 2 6BQ5's and 3 12AX7's (about 110 mA) you will get 375 to 400 volts of B+ voltage. This is on the edge of meltdown for garden variety 6BQ5's and EL-84's. If you have 7189's or 7189A's this is not a problem. The other possibility is to use a tube that can live with the higher voltages like the 6L6 and it's relatives.
Since you have a transformer that was made to power 4 6BQ5's and 2 12AX7's, you could build an amp that uses this tube line-up. An AC-30 clone maybe. You will need a larger output transformer, like the Triode 22848ULT which costs more.
An extra 12AX7 would not likely be a problem if you needed it. it could be connected to the extra 6.3 volt winding. By the way a 12AX7 draws .3 amps when run from 6.3 volts.
Since you have a transformer that was made to power 4 6BQ5's and 2 12AX7's, you could build an amp that uses this tube line-up. An AC-30 clone maybe. You will need a larger output transformer, like the Triode 22848ULT which costs more.
An extra 12AX7 would not likely be a problem if you needed it. it could be connected to the extra 6.3 volt winding. By the way a 12AX7 draws .3 amps when run from 6.3 volts.
Lets not forget the transformer also powered the tuner filaments so figure at least 5 more 6.3V tubes. The Pilot windings are basically not needed.
Looks like everything I have is either to big( PT's) or to small (OPTS)
Maybe I should just build a stereo guitar amp haha, Hey that might sound pretty nice with the stereo chorus unit I have.
I so hate looking in the garage for more stuff to salvage, But It looks like thats this evenings entertainment.
I have more junk out there than a resale shop.
Gene
Hmm thinking maybe I have a PT & OPT for 6L6's in an old pacemaker pa amp.
I know I have a OPT & PT that drove an old wurlitzer organ with 6L6's also, But no specs on the transformers.
But hey, I haven't melted anything yet this week
gene
Looks like everything I have is either to big( PT's) or to small (OPTS)
Maybe I should just build a stereo guitar amp haha, Hey that might sound pretty nice with the stereo chorus unit I have.
I so hate looking in the garage for more stuff to salvage, But It looks like thats this evenings entertainment.
I have more junk out there than a resale shop.
Gene
Hmm thinking maybe I have a PT & OPT for 6L6's in an old pacemaker pa amp.
I know I have a OPT & PT that drove an old wurlitzer organ with 6L6's also, But no specs on the transformers.
But hey, I haven't melted anything yet this week
gene
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.
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.
tubelab.com said:
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
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.
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.
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
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
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.
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
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
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.
Now,....cheez and nearly new junk. Guitars, too.
Reddy KW said: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
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.
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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