soma
That is very clear.
But I will read your link also.
Thank You
http://www.tpub.com/neets/book7/27f.htm
B+ Volts
Moderators: pompeiisneaks, Colossal
Re: B+ Volts
If the voltage from the choke input filter is too low, you can add a small cap before the choke to adjust the output.
I generally end up with something in the 2-5uF range when dropping voltage like I did in a little SE stereo amp.
I had 335V and wanted to drop it to 280 so I used two 2.2uF film caps at the output of the rectifier, followed by a Hammond 1.5H inductor and then a 220uF filter cap.
I generally end up with something in the 2-5uF range when dropping voltage like I did in a little SE stereo amp.
I had 335V and wanted to drop it to 280 so I used two 2.2uF film caps at the output of the rectifier, followed by a Hammond 1.5H inductor and then a 220uF filter cap.
Re: B+ Volts
Thanks, I will keep that in mind. When ordering a choke, is it the plate current that I need to add up for all the tubes, not the MAX plate current? I think the book refers to it as Zero Load or something like that...TheGimp wrote:If the voltage from the choke input filter is too low, you can add a small cap before the choke to adjust the output.
I generally end up with something in the 2-5uF range when dropping voltage like I did in a little SE stereo amp.
I had 335V and wanted to drop it to 280 so I used two 2.2uF film caps at the output of the rectifier, followed by a Hammond 1.5H inductor and then a 220uF filter cap.
Re: B+ Volts
Yep, that is where a pi filter comes in.
Not to be confused with phase inverter.
It's called a pi filter because it resembles the Greek symbol for pi, Π.
You have a cap input then a choke then a cap.
Not to be confused with phase inverter.
It's called a pi filter because it resembles the Greek symbol for pi, Π.
You have a cap input then a choke then a cap.
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: B+ Volts
For choke input filters, not only should they be rated for higher than the peak overall current and voltage of the PT, but the iron in them should ideally be gapped (like an SE OT) to avoid saturation, and have low DC resistance to get better load regulation. So this generally means a bigger, more-expensive choke than if you are using a CLC filter. On the other hand, zenering down the B+ is relatively inexpensive, and the end result is effectively the same in terms of geetar amp quality.
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Super_Reverb
- Posts: 188
- Joined: Tue Dec 21, 2010 6:28 am
- Location: Indianapolis, USA
Re: B+ Volts
A choke with current rating you need is going to be 25 or 30 USD.
I think TheGimp has the best and most cost-effective idea.
A pi filter with a 3.3-22uF filter cap with a ~300 Ohm series resistor, followed by a largish filter cap 33-100uF feeding point 'A' on your schem (PT c/t) will give you a voltage drop you want plus a quieter plate voltage supply for the 6V6s.
This setup will affect your envelope (sag). In p/s design:
o Larger filter caps / smaller series resistors give you a stiffer P/S (less sag)
o Smaller filter caps / larger series resistors will give you more sag.
Sag in vintage amps is a result of the series resistance of the rectifier tube and the capacitance of the filter cap(s).
There is no correct amount of sag for an amp: it's your personal preference and you can experiment with it to dial in your needs.
Briefly in guitar amp (unregulated) p/s design, filter capacitors, connected between B+ and gnd work with either series inductors or resistors to filter out 120 Hz ripple from rectifiers. Much like frequency filtering in the signal path (tone control), they create filters based on R/C or L/C values. Time domain view of filtering is: capacitors store energy as electronic charge and resist changes in voltage: inductors store energy in a magnetic field and resist changes in current.
If I were doing an C/R/C pi filter to drop voltage, here's how I'd do it.
1) choose pi filter input cap 3.3-22uF.
2) choose series resistor value based in desired voltage drop/use power resistor of appropriate wattage.
3) choose output filter cap. (22-100uF) based on desired sound and feel of amp.
You should be able to do this for $10-15
cheers,
rob
I think TheGimp has the best and most cost-effective idea.
A pi filter with a 3.3-22uF filter cap with a ~300 Ohm series resistor, followed by a largish filter cap 33-100uF feeding point 'A' on your schem (PT c/t) will give you a voltage drop you want plus a quieter plate voltage supply for the 6V6s.
This setup will affect your envelope (sag). In p/s design:
o Larger filter caps / smaller series resistors give you a stiffer P/S (less sag)
o Smaller filter caps / larger series resistors will give you more sag.
Sag in vintage amps is a result of the series resistance of the rectifier tube and the capacitance of the filter cap(s).
There is no correct amount of sag for an amp: it's your personal preference and you can experiment with it to dial in your needs.
Briefly in guitar amp (unregulated) p/s design, filter capacitors, connected between B+ and gnd work with either series inductors or resistors to filter out 120 Hz ripple from rectifiers. Much like frequency filtering in the signal path (tone control), they create filters based on R/C or L/C values. Time domain view of filtering is: capacitors store energy as electronic charge and resist changes in voltage: inductors store energy in a magnetic field and resist changes in current.
If I were doing an C/R/C pi filter to drop voltage, here's how I'd do it.
1) choose pi filter input cap 3.3-22uF.
2) choose series resistor value based in desired voltage drop/use power resistor of appropriate wattage.
3) choose output filter cap. (22-100uF) based on desired sound and feel of amp.
You should be able to do this for $10-15
cheers,
rob
-
Super_Reverb
- Posts: 188
- Joined: Tue Dec 21, 2010 6:28 am
- Location: Indianapolis, USA
Re: B+ Volts
A choke with current rating you need is going to be 25 or 30 USD.
I think TheGimp has the best and most cost-effective idea.
A pi filter with a 3.3-22uF filter cap with a ~300 Ohm series resistor, followed by a largish filter cap 33-100uF feeding point 'A' on your schem (PT c/t) will give you a voltage drop you want plus a quieter plate voltage supply for the 6V6s.
This setup will affect your envelope (sag). In p/s design:
o Larger filter caps / smaller series resistors give you a stiffer P/S (less sag)
o Smaller filter caps / larger series resistors will give you more sag.
Sag in vintage amps is a result of the series resistance of the rectifier tube and the capacitance of the filter cap(s).
There is no correct amount of sag for an amp: it's your personal preference and you can experiment with it to dial in your needs.
Briefly in guitar amp (unregulated) p/s design, filter capacitors, connected between B+ and gnd work with either series inductors or resistors to filter out 120 Hz ripple from rectifiers. Much like frequency filtering in the signal path (tone control), they create filters based on R/C or L/C values. Time domain view of filtering is: capacitors store energy as electronic charge and resist changes in voltage: inductors store energy in a magnetic field and resist changes in current.
If I were doing an C/R/C pi filter to drop voltage, here's how I'd do it.
1) choose pi filter input cap 3.3-22uF.
2) choose series resistor value based in desired voltage drop/use power resistor of appropriate wattage.
3) choose output filter cap. (22-100uF) based on desired sound and feel of amp.
You should be able to do this for $10-15
cheers,
rob
I think TheGimp has the best and most cost-effective idea.
A pi filter with a 3.3-22uF filter cap with a ~300 Ohm series resistor, followed by a largish filter cap 33-100uF feeding point 'A' on your schem (PT c/t) will give you a voltage drop you want plus a quieter plate voltage supply for the 6V6s.
This setup will affect your envelope (sag). In p/s design:
o Larger filter caps / smaller series resistors give you a stiffer P/S (less sag)
o Smaller filter caps / larger series resistors will give you more sag.
Sag in vintage amps is a result of the series resistance of the rectifier tube and the capacitance of the filter cap(s).
There is no correct amount of sag for an amp: it's your personal preference and you can experiment with it to dial in your needs.
Briefly in guitar amp (unregulated) p/s design, filter capacitors, connected between B+ and gnd work with either series inductors or resistors to filter out 120 Hz ripple from rectifiers. Much like frequency filtering in the signal path (tone control), they create filters based on R/C or L/C values. Time domain view of filtering is: capacitors store energy as electronic charge and resist changes in voltage: inductors store energy in a magnetic field and resist changes in current.
If I were doing an C/R/C pi filter to drop voltage, here's how I'd do it.
1) choose pi filter input cap 3.3-22uF.
2) choose series resistor value based in desired voltage drop/use power resistor of appropriate wattage.
3) choose output filter cap. (22-100uF) based on desired sound and feel of amp.
You should be able to do this for $10-15
cheers,
rob
Re: B+ Volts
Well....I have a Hammond 159S. Looks like it is rated for 4 H, 225mA, 500 Volts, and 65 Ohms.
I will arrange the filter like you guys suggested. Then I guess I may have to adjust the other dropping resistors down the B+ line......
Thanks
I will arrange the filter like you guys suggested. Then I guess I may have to adjust the other dropping resistors down the B+ line......
Thanks
Re: B+ Volts
While filtering is always nice, why not a voltage follower using a MOSFET if all that is needed is a voltage drop. Probably wouldn't cost more than $3.
It also makes for an easier design than a filter (for me anyway). By just changing the D1 zener values (and corresponding R1 to keep the current withing the D1 parameters) you can pretty much drop whatever voltage you want......about the only thing that limits you is the 70W rating of the MOSFET (which wouldn't be pushed past 15 Watts with >150mA and 100V drop, but a proper heat sink is still a must)
It also makes for an easier design than a filter (for me anyway). By just changing the D1 zener values (and corresponding R1 to keep the current withing the D1 parameters) you can pretty much drop whatever voltage you want......about the only thing that limits you is the 70W rating of the MOSFET (which wouldn't be pushed past 15 Watts with >150mA and 100V drop, but a proper heat sink is still a must)
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Re: B+ Volts
If I decide to try a Zener, is it as simple as picking one with close to the voltage drop I desire? For example, from the list below, would I just buy a 30V Zener from that list of 50 Watt diodes?
I was figuring on the current at about 250 mA.
Thank You
http://www.nteinc.com/specs/5200to5299/pdf/nte5240a.pdf
I was figuring on the current at about 250 mA.
Thank You
http://www.nteinc.com/specs/5200to5299/pdf/nte5240a.pdf
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Philoffline
- Posts: 19
- Joined: Fri Nov 19, 2010 10:36 pm
Re: B+ Volts
It's as simple as that, but you need a reverse polarity, or "cathode to case" zener. For an NTE that would be the same number with "AK" at the end, not "A."
I just did the same thing on a recycled Hammond organ chassis and it worked like a charm. It will get hot, though.
I just did the same thing on a recycled Hammond organ chassis and it worked like a charm. It will get hot, though.
Any old tagline will do
Re: B+ Volts
OK, Thanks -
So, if I have finally located the correct diode, these things are only a few dollars cheaper than a choke. Well, maybe 10 dollars cheaper. And that is OK, if it works....."it works". But I will give the choke a try first and see how that goes.....
Thanks
http://www.mouser.com/ProductDetail/NTE ... 1kFFs3k%3d
So, if I have finally located the correct diode, these things are only a few dollars cheaper than a choke. Well, maybe 10 dollars cheaper. And that is OK, if it works....."it works". But I will give the choke a try first and see how that goes.....
Thanks
http://www.mouser.com/ProductDetail/NTE ... 1kFFs3k%3d