I read above about running the heaters with AC or DC.
I had thought of that, ac might be more noisy right? I know dc requiers rectification instead of just a resistor to drop the voltage, but if it gets rid of some noise I'd think it would be better. I know in the radios that I work with sometimes you can put your ear up to one or more of the tubes and hear the vibration of the filiment due to AC, when I apply DC to them they don't do that.
oh by the way, a little off topic here, but does anyone know where I can find the schematic for a 12at7 preamped 50c5 or 35c5 amp setup?
(besides the one from dogstar online)
I just really want a simple hookup diagram for the 50c5 and a 12at7.
I have an old radio with a 12AT7 in it I can use, and I have a 50c5 laying around. I ran my guitar through the clean channel on my amp and ran the line out into the radio's amp, it has a very nice overdrive at low volumes so its perfect for practicing at night. On top of that, it can still get pretty dang loud for only 2 watts (through the original 6 inch speaker it has on it)
I tried it with my 8 inch and its louder, but the tone absolutly stinks..
I had thought of that, ac might be more noisy right? I know dc requiers rectification instead of just a resistor to drop the voltage, but if it gets rid of some noise I'd think it would be better. I know in the radios that I work with sometimes you can put your ear up to one or more of the tubes and hear the vibration of the filiment due to AC, when I apply DC to them they don't do that.
oh by the way, a little off topic here, but does anyone know where I can find the schematic for a 12at7 preamped 50c5 or 35c5 amp setup?
(besides the one from dogstar online)
I just really want a simple hookup diagram for the 50c5 and a 12at7.
I have an old radio with a 12AT7 in it I can use, and I have a 50c5 laying around. I ran my guitar through the clean channel on my amp and ran the line out into the radio's amp, it has a very nice overdrive at low volumes so its perfect for practicing at night. On top of that, it can still get pretty dang loud for only 2 watts (through the original 6 inch speaker it has on it)
I tried it with my 8 inch and its louder, but the tone absolutly stinks..
Looks like you're gonna have to roll your own. The only ones that I know of are from dogstar, and an old Lafayette Radio design that used the 12AX7A. No reason that a 12AT7A couldn't work as a driver for a 50C5.
One suggestion: Run the 50C5 with a Vpp= 150Vdc, and a Vsgsg= 90Vdc. Getting the screen voltage down improves the linearity of the 50C5 tremendously.
Hi ThSpeakerDude88,
It sounds like you are going to use a series heater string. Therefore AC heaters. You could work in DC heaters but I don't see the point. Some of the hum comes from the amp being class A, no cancellation. So beef up the filter section to reduce that.
I find AC heaters with a positive DC bias works very well in a parallel setup. DC heaters have their own set of problems, you may need to use a regulator to get rid of the nasties. Then your filter cap may have a finite life. Lot's of heat doing this.
Now if you used a 6AQ5 or 6BQ5, you would not be using the AC line for your heaters. Now you're into a transformer for your B+ and heaters (much, much safer!). This would be much better as a first project. From the sounds of it, you want a small practice amp?
You are going to have to set a budget. Using an old piece of gear near to what you want and rebuilding / modifying would be less expensive.
-Chris
It sounds like you are going to use a series heater string. Therefore AC heaters. You could work in DC heaters but I don't see the point. Some of the hum comes from the amp being class A, no cancellation. So beef up the filter section to reduce that.
I find AC heaters with a positive DC bias works very well in a parallel setup. DC heaters have their own set of problems, you may need to use a regulator to get rid of the nasties. Then your filter cap may have a finite life. Lot's of heat doing this.
Now if you used a 6AQ5 or 6BQ5, you would not be using the AC line for your heaters. Now you're into a transformer for your B+ and heaters (much, much safer!). This would be much better as a first project. From the sounds of it, you want a small practice amp?
You are going to have to set a budget. Using an old piece of gear near to what you want and rebuilding / modifying would be less expensive.
-Chris
hi, thankyou for the replies!
Miles Power: wow that sounds good! The 50c5 seems to sound a lot better than the 35c5,even though it only has marginally more output power.
Anatech: Well i have a small practice amp (peavey transtube rage 158) But I really want something small, tube powered, and easily overdriveable without annoying everyone with. I found the 'ol radio has a sweet distortion when I run my clean channel into it with the radio at 3/4 volume. I think it was designed funny, the other radio I had had some sort of a capacitor on the tube side of the opt to cut off the bass frequencies because of the dinky speaker it used and the low power output. This radio does not have that. While it has full range sound, it has too much bass for the 1 watt output tube to handel at any volume without distorting
It does have a tone controll circuit, I believe it lowers the high/mid freq.s and leaves the bass turned up, and it doesnt sound very good to me.
Unfortunatly, I don't have the money for a used peice of equipment to modify or I'd have one. Would really like an old bogen to use.
All I have for now is the tubes and parts from this radio to use, as well as a few other peices parts and tubes from the other one.
I do have a ton of caps, resistors, pots, etc etc ... you should see my desk
so that stuff shouldn't be a prob
Miles Power: wow that sounds good! The 50c5 seems to sound a lot better than the 35c5,even though it only has marginally more output power.
Anatech: Well i have a small practice amp (peavey transtube rage 158) But I really want something small, tube powered, and easily overdriveable without annoying everyone with. I found the 'ol radio has a sweet distortion when I run my clean channel into it with the radio at 3/4 volume. I think it was designed funny, the other radio I had had some sort of a capacitor on the tube side of the opt to cut off the bass frequencies because of the dinky speaker it used and the low power output. This radio does not have that. While it has full range sound, it has too much bass for the 1 watt output tube to handel at any volume without distorting
It does have a tone controll circuit, I believe it lowers the high/mid freq.s and leaves the bass turned up, and it doesnt sound very good to me.
Unfortunatly, I don't have the money for a used peice of equipment to modify or I'd have one. Would really like an old bogen to use.
All I have for now is the tubes and parts from this radio to use, as well as a few other peices parts and tubes from the other one.
I do have a ton of caps, resistors, pots, etc etc ... you should see my desk
so that stuff shouldn't be a prob
Hi ThSpeakerDude88,
LOL, betcha my desk is worst looking - don't take me up on it.
The tone control just cuts the highs, it's a pot in series with a capacitor across the output transformer.
I am concerned that you will end up with an amp with no isolation from the AC line. Your life isn't worth a few bucks. Please use a power transformer.
-Chris
LOL, betcha my desk is worst looking - don't take me up on it.
The tone control just cuts the highs, it's a pot in series with a capacitor across the output transformer.
I am concerned that you will end up with an amp with no isolation from the AC line. Your life isn't worth a few bucks. Please use a power transformer.
-Chris
oh, duh! forgot to mention my plans on that part
Yes I am planning on using a transformer for it to be safe, I don't like the idea of 15 amp 120v running around that thing all the time for me to accidentally touch. I have already found out which is the "polarized" plug on the cord (tryed the plug both ways in the wall, which ever way didn't give me a buzz when I touched anything ground was the right way and I marked the negative lead in black)
hmmm... I don't see a cap across the trafo.. Come to think of it I think the primary's are pcb mount on the board and the only wires coming from it are on the secondaries.
Yes I am planning on using a transformer for it to be safe, I don't like the idea of 15 amp 120v running around that thing all the time for me to accidentally touch. I have already found out which is the "polarized" plug on the cord (tryed the plug both ways in the wall, which ever way didn't give me a buzz when I touched anything ground was the right way and I marked the negative lead in black)
hmmm... I don't see a cap across the trafo.. Come to think of it I think the primary's are pcb mount on the board and the only wires coming from it are on the secondaries.
Any time that I touch one of those old series string guitar amps I ALWAYS add an isolation transformer and a 3 wire cord. They hum less, and don't shock the #%!* out of you when you touch the guitar and a mic at the same time. I recently resurrected an old Electrolab amp that used a 50C5 output tube. It sounded pretty good since I had BOTH watts working overtime when fed from the ADA preamp!
I usually use a Triad N-68X (Chinese) ($11.20USD from Mouser) or an Allied 6K140HF (Canadian) for about $15 (alliedelec.com)
Need a power transformer for a bigger tube amp, check out "Allied's own tube transformers", Hammond quality for less money.
6K56VG for 10 to 20 watt amps, and 6K7VG for the 50 watt amps.
I usually use a Triad N-68X (Chinese) ($11.20USD from Mouser) or an Allied 6K140HF (Canadian) for about $15 (alliedelec.com)
Need a power transformer for a bigger tube amp, check out "Allied's own tube transformers", Hammond quality for less money.
6K56VG for 10 to 20 watt amps, and 6K7VG for the 50 watt amps.
Allied, an electronics distributor that is older than I am, almost dissapeared after being bought up by Tandy in the 80's. I don't know who owns them now but their new 5 pound catalog says "Allied Electronics, An Electrocomponents Company"
I have ordered many of their transformers, they come from a warehouse in Texas. The transformers are "Made in Canada" and look an awful lot like Hammonds. I have been using them for about three years. The only one that ever failed was the one that got seriously wet durring hurricane Francis last year.
They used to have PDF's of their entire catalog on the web site, so you could find what you wanted, even if you don't know what you wanted. Now I have to look in the 4 inch thick book. They will send you one if you fill out the form on the web site. They also have 500 volt Cornell Dubilier electrolytics and other useful parts cheaper than DigiKey.
The Triads that come from Mouser are cheaper, but I like the looks of the Allied transformer better (maybe I am just paranoid), It just looks more robust. The Triads do work OK.
I have ordered many of their transformers, they come from a warehouse in Texas. The transformers are "Made in Canada" and look an awful lot like Hammonds. I have been using them for about three years. The only one that ever failed was the one that got seriously wet durring hurricane Francis last year.
They used to have PDF's of their entire catalog on the web site, so you could find what you wanted, even if you don't know what you wanted. Now I have to look in the 4 inch thick book. They will send you one if you fill out the form on the web site. They also have 500 volt Cornell Dubilier electrolytics and other useful parts cheaper than DigiKey.
The Triads that come from Mouser are cheaper, but I like the looks of the Allied transformer better (maybe I am just paranoid), It just looks more robust. The Triads do work OK.
Im running a 13.5vac 5 amp transformer through a 10:1 to step the current back up again, then rectifying that with four 1n4007 diodes, then into the radio (as it is an AC/DC radio) Seems to work great. I added a 680uf cap across the dc lines and it filters out all the hum. It now goes a little louder too. I think however, I am running it on 135v instead of 120 (13.5 x 10:1 x-fmr )
Think it will hurt it any?
By the way, silly question here: Did they still have DC mains back in the 50's in some ultra remote locations, or was the AC/DC radio circuit a cheap design to manufacture?
Think it will hurt it any?
By the way, silly question here: Did they still have DC mains back in the 50's in some ultra remote locations, or was the AC/DC radio circuit a cheap design to manufacture?
I have been using Hammond transformers for years, definitely a good transformer for the price. I will be "building the big one" soon. A 100 WPC SE amp using 1642SE transformers and 833A output tubes. In my quest to save money, I am using a surplus power transformer I got off Ebay. The seller turned out to be another forum member.
"By the way, silly question here: Did they still have DC mains back in the 50's in some ultra remote locations, or was the AC/DC radio circuit a cheap design to manufacture?"
It was just a very cheap, potentially dangerous, way to make a cheap product. Eliminate the power xfmr, and you cut costs considerably. Calling it an "AC/DC" radio sounds better than the truth.
It was just a very cheap, potentially dangerous, way to make a cheap product. Eliminate the power xfmr, and you cut costs considerably. Calling it an "AC/DC" radio sounds better than the truth.
Hi ThSpeakerDude88,
I don't know. Compared to the typical speaker used, they may be right. It is shown as a triode, directly heated. The RCA data sheet shows plate curves from which you may be able to figure out what the "book" THD figures are. The Cunningham data sheet provides the same info.
-Chris
I don't know. Compared to the typical speaker used, they may be right. It is shown as a triode, directly heated. The RCA data sheet shows plate curves from which you may be able to figure out what the "book" THD figures are. The Cunningham data sheet provides the same info.
-Chris
So now that I have my 50c5 project working, I'd like to try it with my 42 I have.
Do I set it up basically the same as the 50c5?
I know the pinout will be different , Its a bit confusing.
How would I set up the 42? It would help to have a schematic, just to know where is the input, and the grids.
Also, it seems than all Class AB is is having a driver tube in front of it. Can I use a 50c5 to drive it to slightly more power?
Do I set it up basically the same as the 50c5?
I know the pinout will be different , Its a bit confusing.
How would I set up the 42? It would help to have a schematic, just to know where is the input, and the grids.
Also, it seems than all Class AB is is having a driver tube in front of it. Can I use a 50c5 to drive it to slightly more power?
Hi ThSpeakerDude88,
The '42 has different parameters, but is used in the same way. I haven't looked, but the output transformer may have a different primary impedance.
Class AB implies push pull, two outputs tubes with some way of providing differential drive. It was done with transformers but it can be done with tube(s) in a phase splitter.
Go ahead and play.
-Chris
The '42 has different parameters, but is used in the same way. I haven't looked, but the output transformer may have a different primary impedance.
Class AB implies push pull, two outputs tubes with some way of providing differential drive. It was done with transformers but it can be done with tube(s) in a phase splitter.
Go ahead and play.
-Chris
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