What if I select a power transformer that doesn't have a 5V output for the filaments?
I have looked locally, and there isn't much to save (aside shipping) for ordering from a local distributor of Hammond, even tough I am in Canada...
I am looking trough EDCOR, and the most suitable (I think) is the XPWR023-120
EDCOR Electronics Corporation. XPWR023-120
I want some extra mAmps to be on the safe side, and to power some front end display, so I am keeping away from the 200mA ones. However, the 250mA one has no 5V filament output for the GZ34 in the reference schematics I ended up deciding to reproduce:
DIY Push-Pull (PP) 6V6 / 6V6GT Tube Amplifier Schematic
Can I use an 7805 voltage regulator over the 6.3V output and expect good result? Or add a resistor?
I have looked locally, and there isn't much to save (aside shipping) for ordering from a local distributor of Hammond, even tough I am in Canada...
I am looking trough EDCOR, and the most suitable (I think) is the XPWR023-120
EDCOR Electronics Corporation. XPWR023-120
I want some extra mAmps to be on the safe side, and to power some front end display, so I am keeping away from the 200mA ones. However, the 250mA one has no 5V filament output for the GZ34 in the reference schematics I ended up deciding to reproduce:
DIY Push-Pull (PP) 6V6 / 6V6GT Tube Amplifier Schematic
Can I use an 7805 voltage regulator over the 6.3V output and expect good result? Or add a resistor?
Have you read Morgan Jones' "Valve Amplifiers"? The 4th edition came out recently, but is sold out everywhere. The 3rd edition is still well worth having, is fun to read, and is very informative. There's a nice push-pull EL84 amp in there that should be pretty easy to convert to 6V6 if you want.
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rknize, that's the point; what if there's no 5V winding, but a 6.3V instead? Is it a huge issue?
Maybe I should select another rectifier tube? lower the voltage? What's the generally accepted method for that?
Or maybe I should go to a higher voltage secondary winding? Edcor has this one at 760V instead of 600
EDCOR Electronics Corporation. XPWR132-120
I'd loose some of this power in reducing the rectified voltage out of the tube, but I understand the GZ34 could endure up to 900V
GZ 34, Tube GZ34; Röhre GZ 34 ID3410, Full-Wave Vacuum Recti
On the positive side, this method gives me a second 5V I can use to power the front-end electronics; kind of good as the previous transfo didn't offer that. I'd only have to change the first 10W resistor... if I understand well the operation charactistics of the GZ34 from there
http://www.triodeel.com/5ar4_p3.gif
the output would be proportionnal; having 2x 380 would lead to an excess of 80 more volts; my calculations might not be best, but I'd hasard to say I'd need about 400 ohm resistor instead of 100; and could follow the rest of the schematics.
(if I am being an idiot, please someone let me know)
rogon, I haven't read it, sadly. Trying to learn all of this by myself is a tedious job. I didn't know such book existed, to be honest. I wonder if it's available in bookstores around here. The schematics I am looking at is the alteration of a P-P EL84 Dynaco amp, might be similar?
Maybe I should select another rectifier tube? lower the voltage? What's the generally accepted method for that?
Or maybe I should go to a higher voltage secondary winding? Edcor has this one at 760V instead of 600
EDCOR Electronics Corporation. XPWR132-120
I'd loose some of this power in reducing the rectified voltage out of the tube, but I understand the GZ34 could endure up to 900V
GZ 34, Tube GZ34; Röhre GZ 34 ID3410, Full-Wave Vacuum Recti
On the positive side, this method gives me a second 5V I can use to power the front-end electronics; kind of good as the previous transfo didn't offer that. I'd only have to change the first 10W resistor... if I understand well the operation charactistics of the GZ34 from there
http://www.triodeel.com/5ar4_p3.gif
the output would be proportionnal; having 2x 380 would lead to an excess of 80 more volts; my calculations might not be best, but I'd hasard to say I'd need about 400 ohm resistor instead of 100; and could follow the rest of the schematics.
(if I am being an idiot, please someone let me know)
rogon, I haven't read it, sadly. Trying to learn all of this by myself is a tedious job. I didn't know such book existed, to be honest. I wonder if it's available in bookstores around here. The schematics I am looking at is the alteration of a P-P EL84 Dynaco amp, might be similar?
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No. You can't put DC on a rectifier. The 5V secondary has to "float" up to what ever B+ is.
two solutions for you (1) Buy a 5V transformer. It will take extra space but they are not super expensive. and (2) call Edcor. They will make semi custom transformers for not to much more as long as they can use their existing parts. For example maybe they have a 6.3 that could be converted to 5V. It is not hard for then as they build everything to order, unlike Hamon who keeps inventory.
Have you checked out Antek? My next project is a low power stereo and I'll use an Antek PT. They sell steel cans if you don't like the looks or need shielding.
I don't think the book would be available in most bookstores. Kind of a niche product. But it's on Amazon.com, etc.
I saw that Dyna circuit from DIYaudio. The one in the Morgan Jones book is more like the later Dyna ST35 amp (a slightly different push-pull EL84 amp that was very popular and available as a kit). But then again, it's different from that too.
Anyway, I just thought the Morgan Jones book would be helpful. I certainly learned a ton from it, and Mr. Jones' writing style makes it the easiest-reading tube hifi design primer I know of. There are lots of other circuits in there, including a couple of RIAA preamps, other power amps, and a nice overview and analysis of some classic tube amp designs.
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Might sound like silly questions, but I guess that's how we learn.
Does the 5V winding needs the center tap?
All the non-center-tapped ones I see have one lead to common/gnd, can I still use those "grounded" 5VAC in the circuit, tying it with the CT of the the secondary winding, or would that cause issues? I see the circuit calls for the CT & one side of the 5V to act as ground...
There's a lot of transformers that has 6.3 and 5V extra windings but aren't CT. I guess we don't care for the output tube heaters (isolated from the rest of the circuit) but being that the 5V winding is connected to the output of the rectifier, I am a bit lost...
but thanks a lot for the input guys, all this information slowly sinks in, and I am learning this dark art of power transformer selection. It is really appreciated!
Does the 5V winding needs the center tap?
All the non-center-tapped ones I see have one lead to common/gnd, can I still use those "grounded" 5VAC in the circuit, tying it with the CT of the the secondary winding, or would that cause issues? I see the circuit calls for the CT & one side of the 5V to act as ground...
There's a lot of transformers that has 6.3 and 5V extra windings but aren't CT. I guess we don't care for the output tube heaters (isolated from the rest of the circuit) but being that the 5V winding is connected to the output of the rectifier, I am a bit lost...
but thanks a lot for the input guys, all this information slowly sinks in, and I am learning this dark art of power transformer selection. It is really appreciated!
I'm a bit confused by your description. Are you talking about your Philco schematic? I don't see a 5V winding there that has it's center tap grounded. Looking at "section 1" of that schematic, the secondaries from top to bottom appear to be (it's very hard to read):
1) 260-0-260 for the plates
2) 5V for the rectifier heater
3) 6.3V for tube heaters ("A")
4) 6.3V for tube heaters ("B")
The "B" heater supply has a center tap that is grounded while the "A" supply is grounded on one side. The grounding at the center tap is helpful to reduce hum induced between the heater and the cathode. The circuit seems to use supply "A" for most things and uses "B" in a few key locations.
1) 260-0-260 for the plates
2) 5V for the rectifier heater
3) 6.3V for tube heaters ("A")
4) 6.3V for tube heaters ("B")
The "B" heater supply has a center tap that is grounded while the "A" supply is grounded on one side. The grounding at the center tap is helpful to reduce hum induced between the heater and the cathode. The circuit seems to use supply "A" for most things and uses "B" in a few key locations.
So the 5V rectifier heater doesn't need any center tap, and can be literally grounded. On other heaters, a center tap would help reduce hum.
Thanks a lot for this answer!
Would it be OK to connect that GND to the chassis frame?
I'll start digging again in Edcor transformers, I was avoiding all the non CT 5V windings for my rectifier heater... silly me. That's going to help a lot finding a suitable PT!
Did I mention I start to enjoy looking at transformer specs? a few months ago, I had no idea what to look for. You guys are being very helpful, thanks a lot.
Thanks a lot for this answer!
Would it be OK to connect that GND to the chassis frame?
I'll start digging again in Edcor transformers, I was avoiding all the non CT 5V windings for my rectifier heater... silly me. That's going to help a lot finding a suitable PT!
Did I mention I start to enjoy looking at transformer specs? a few months ago, I had no idea what to look for. You guys are being very helpful, thanks a lot.
No, the 5V winding is *not* grounded. That would short the PSU out. It is floating at the unfiltered B+ potential because the rectifier's cathode is attached to or is part of the heater. Sometimes you will see a 5V rectifier heater with a center tap and they pull B+ off of that instead of one of the other legs of the heater. This is not common though.
Where do you see the 5V winding shorted to ground?
Where do you see the 5V winding shorted to ground?
Looking trough edcor, most transformers have the 5V without center tap, and with one end grounded. Would that mean I can't use it? not good 
Or are they just calling it "ground" while it is not tied to any physical ground?
the Dynaco schematics have a grounded 5V.
Dynaco Push-Pull EL84/6BQ5 or 6V6/6AQ5 Tube Amp Schematic
I somewhat assumed it was also doable on other variants, but you are right, it is not on the other schematics for the Hammond alteration I would like to use as main reference
DIY Push-Pull (PP) 6V6 / 6V6GT Tube Amplifier Schematic
Is there a way to use those edcor transformers?
Or are they just calling it "ground" while it is not tied to any physical ground?
the Dynaco schematics have a grounded 5V.
Dynaco Push-Pull EL84/6BQ5 or 6V6/6AQ5 Tube Amp Schematic
I somewhat assumed it was also doable on other variants, but you are right, it is not on the other schematics for the Hammond alteration I would like to use as main reference
DIY Push-Pull (PP) 6V6 / 6V6GT Tube Amplifier Schematic
Is there a way to use those edcor transformers?
I decided to build up from this schematic instead of keeping the base Philco one
DIY Push-Pull (PP) 6V6 / 6V6GT Tube Amplifier Schematic
When they draw their 5V winding with one end mentionned as 5V and the other as "common" - does that mean it is grounded, or can I use it as anything else regardless?
DIY Push-Pull (PP) 6V6 / 6V6GT Tube Amplifier Schematic
When they draw their 5V winding with one end mentionned as 5V and the other as "common" - does that mean it is grounded, or can I use it as anything else regardless?
from there:
EDCOR Electronics Corporation. XPWR149-120/240
this image
It has all windings I need: a 5V for the rectifier heater, a 6.3V that I'll rectify to 5VDC for the front-end electronics, and a 6.3VCT for the other tubes' heaters.
The thing that bugs me big time is the "common" that is mentioned in both the 5V and 6.3V...
however, being that those windings have both ends with the same color, maybe its just a weird way of saying 0V.
EDCOR Electronics Corporation. XPWR149-120/240
this image
An externally hosted image should be here but it was not working when we last tested it.
It has all windings I need: a 5V for the rectifier heater, a 6.3V that I'll rectify to 5VDC for the front-end electronics, and a 6.3VCT for the other tubes' heaters.
The thing that bugs me big time is the "common" that is mentioned in both the 5V and 6.3V...
however, being that those windings have both ends with the same color, maybe its just a weird way of saying 0V.
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The "common" designation is arbitrary. Don't sweat it.
One thing to consider (and sorry for introducing complication to deal with fine points) is using separate transformers for heaters and B+. The logic behind this is that rectifier switching noise from the high voltage winding can couple very efficiently to the heater windings, where it enters the tubes as common mode noise. Depending on the circuit and the particular tubes, this may or may not be an audible issue, but it's nearly always measurable.
One thing to consider (and sorry for introducing complication to deal with fine points) is using separate transformers for heaters and B+. The logic behind this is that rectifier switching noise from the high voltage winding can couple very efficiently to the heater windings, where it enters the tubes as common mode noise. Depending on the circuit and the particular tubes, this may or may not be an audible issue, but it's nearly always measurable.
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