SE is with the load (output transformer generally) in series with the tube plate. Parafeed is with a choke supplying DC to the tube, and the load coupled to the tube with a capacitor.
The mutual advantages/disadvantages are:
- The SE transformer needs to be built to carry DC current; keeping audio quality while doing this is not cheap.
- Parafeed throws in an extra choke which is heavy, bulky and needs to have much more inductance than an equivalent SE circuit.
- Parafeed directs the DC current through a choke rather than the transformer, simplying the design of the magnetic parts. The OPT doesn't have to carry DC current, allowing for higher inductance and smaller size. (This is more than offset by the choke, of course.)
Since most audiophoo\\ile chokes cost upwards of $100, it is very cost-prohibitive.
Tim
The mutual advantages/disadvantages are:
- The SE transformer needs to be built to carry DC current; keeping audio quality while doing this is not cheap.
- Parafeed throws in an extra choke which is heavy, bulky and needs to have much more inductance than an equivalent SE circuit.
- Parafeed directs the DC current through a choke rather than the transformer, simplying the design of the magnetic parts. The OPT doesn't have to carry DC current, allowing for higher inductance and smaller size. (This is more than offset by the choke, of course.)
Since most audiophoo\\ile chokes cost upwards of $100, it is very cost-prohibitive.
Tim
Rp of 280 ohms
Hello ,
I noticed in a post above it is mentioned that 6080 have Rp of 280 ohms . At 100V this may be the case but at 200V ? Check the curves , more like double this at 200V
316a
Hello ,
I noticed in a post above it is mentioned that 6080 have Rp of 280 ohms . At 100V this may be the case but at 200V ? Check the curves , more like double this at 200V
316a
Sch3mat1c said:
At the risk of starting another "cheap chokes" war, I have to disagree. Why anyone would ever buy an "audiophile" choke is beyond me. Interwinding capacitance, etc, cause rolloff above the hundreds of kHz. Who cares?
So, once we free ourselves of the price stigma and silly notions, we can get something like a 10H@150mA choke for $35.
Thomas - "parafeed" ("parallel feed"), is a voltage amplifier topology used for output duties.
316a - who said anything about 200V? I was thinking of the 135V Va, 125mA Ia, -35V Vg operating point.
TYPICAL OP.
Hi,
Joel,
Short of telling you something you probably already know:
The 6080 like to have a slow start, so a tube rectifier (an hybrid one seems quite appropriate here) would be recommend.
Cheers,😉
Hi,
Joel,
Short of telling you something you probably already know:
The 6080 like to have a slow start, so a tube rectifier (an hybrid one seems quite appropriate here) would be recommend.
Cheers,😉
Re: TYPICAL OP.
Thanks Frank, I had thought about that too. How about two 5U4GB's for the PSU - one on each leg of the high voltage secondary, both diodes wired in parallel?
fdegrove said:
Thanks Frank, I had thought about that too. How about two 5U4GB's for the PSU - one on each leg of the high voltage secondary, both diodes wired in parallel?
ADDENDUM.
Hi,
Just out of curiosity, any idea how you're going to "attack" the 6080?
From experience, it likes to be driven with ample current reserve from a low impedance source.
Sidebar:
FWIW, I quite like Robert Morins' approach using an SRPP as an output stage, I find it quite elegant.
I do have some hypothical reservations about the driver stage but since I haven't built it I will keep quiet.
Too bad that thread died in rigor mortis.
Anyway I'd love to see Robert reviving it or starting a thread of its' own since it's a nice low power design with ample possibilities to adapt it for various other similar tubes such as 6C19P, 6C33C and other voltage reg. tubes.
Adorned with a stiff PSU these have all the guts to kick *** in the low bass department, maybe even a wet dream for tubelovers subwoofer drive.
Cheers,😉
Hi,
Just out of curiosity, any idea how you're going to "attack" the 6080?
From experience, it likes to be driven with ample current reserve from a low impedance source.
Sidebar:
FWIW, I quite like Robert Morins' approach using an SRPP as an output stage, I find it quite elegant.
I do have some hypothical reservations about the driver stage but since I haven't built it I will keep quiet.
Too bad that thread died in rigor mortis.
Anyway I'd love to see Robert reviving it or starting a thread of its' own since it's a nice low power design with ample possibilities to adapt it for various other similar tubes such as 6C19P, 6C33C and other voltage reg. tubes.
Adorned with a stiff PSU these have all the guts to kick *** in the low bass department, maybe even a wet dream for tubelovers subwoofer drive.
Cheers,😉
SRPP
Already built a 6C33 SRPP , been using it for the last six months . Also tried 6C41 but prefer the sound of the 6C33 . Agree that these series reg triodes need a beefy driver , 6SN7 seem very marginal and sound rather dull . I'm currently using a power double triode (2C50) to drive the 6C33 but may (eventually) use a cascaded 6EM7 or 7N7/7236 cascade instead . The only real problem with these power SRPP output stages is the waste heat , chassis spacing needs to be carefully considered . I also used fixed bias for the lower stage , the loss of HT across the top SRPP cathode resistor is bad enough .
316a
Already built a 6C33 SRPP , been using it for the last six months . Also tried 6C41 but prefer the sound of the 6C33 . Agree that these series reg triodes need a beefy driver , 6SN7 seem very marginal and sound rather dull . I'm currently using a power double triode (2C50) to drive the 6C33 but may (eventually) use a cascaded 6EM7 or 7N7/7236 cascade instead . The only real problem with these power SRPP output stages is the waste heat , chassis spacing needs to be carefully considered . I also used fixed bias for the lower stage , the loss of HT across the top SRPP cathode resistor is bad enough .
316a
Reggit.
Hi,
Ever thought about using shunt regs to keep the lot in line?
Can't have it both ways ol' chap.😉
Hi,
Ever thought about using shunt regs to keep the lot in line?
Can't have it both ways ol' chap.😉
Shunt Regs ?
...are about the last thing I need in this amp . Any more heat and I'll may as well use the thing to heat the house in winter . The main reason why I used 6C33 as a top load was due to the 24x15x4cm heatsink I had not being large enough to dissipate the heat of the solid state (unsuccessful) power CCS I built . In this respect glass is king ! If it wasn't for the voltage drop (and even more heat) I'd use a meaty pentode as a load instead .
316a
...are about the last thing I need in this amp . Any more heat and I'll may as well use the thing to heat the house in winter . The main reason why I used 6C33 as a top load was due to the 24x15x4cm heatsink I had not being large enough to dissipate the heat of the solid state (unsuccessful) power CCS I built . In this respect glass is king ! If it wasn't for the voltage drop (and even more heat) I'd use a meaty pentode as a load instead .
316a
RE:Shunt Regs ?
Hi,
Ah, well , turn of the heating system and do some serious listening.
Don't listen to radiators they tend to sound too warm.🙄
LOL.
Shall I tell the tale of my 1500W OTLs?
Cheers,
/Never had a cold winter since going OTL.
EDIT:Before I forget: mine have their input stages regged and a PSU close to major Joules for the output.
Hi,
Ah, well , turn of the heating system and do some serious listening.
Don't listen to radiators they tend to sound too warm.🙄
LOL.
Shall I tell the tale of my 1500W OTLs?
Cheers,
/Never had a cold winter since going OTL.
EDIT:Before I forget: mine have their input stages regged and a PSU close to major Joules for the output.
Re: ADDENDUM.
Other than the need for a 1meg terminating resistor from the grid of the bottom half of the 6080 to ground I really don't know what else to say that has not been said. I am useing RCA 6as7g at this time. I guess a more high end OPT could be an improvement but I am very slow to shell out big cash for only a few% of improvement. Heat is not a big issue in my rev. because it is built open face on a blank of wood. As far as the drive ability of the 6av6/6111 I think the outZ of the 6111 as a CF is just enough to get the job done with a 6080. Some hi-gm tube could give extra performance but I really don't have the time to brew this sort of thing up because I am busy building EQ's to launch my company www.loungeaudio.com.
I will try the 5998 in a few days and report.
here is a lo quality pic of the unit on top of my cd player.
Robert Morin
FRANK,fdegrove said:
Other than the need for a 1meg terminating resistor from the grid of the bottom half of the 6080 to ground I really don't know what else to say that has not been said. I am useing RCA 6as7g at this time. I guess a more high end OPT could be an improvement but I am very slow to shell out big cash for only a few% of improvement. Heat is not a big issue in my rev. because it is built open face on a blank of wood. As far as the drive ability of the 6av6/6111 I think the outZ of the 6111 as a CF is just enough to get the job done with a 6080. Some hi-gm tube could give extra performance but I really don't have the time to brew this sort of thing up because I am busy building EQ's to launch my company www.loungeaudio.com.
I will try the 5998 in a few days and report.
here is a lo quality pic of the unit on top of my cd player.
Robert Morin
Attachments
Re: SRPP
I'm curious why you'd say that. They have a typical input capacitance - certainly not high - and the 35V bias point is not a particularly large signal requirement.
316a said:
I'm curious why you'd say that. They have a typical input capacitance - certainly not high - and the 35V bias point is not a particularly large signal requirement.
Re: Re: ADDENDUM.
One suggestion: you'll get a lot more meaningful hits on your site if you cut down your bandwidth demands. On a slow dial-up, it takes forever to download.
Robert Morin said:
One suggestion: you'll get a lot more meaningful hits on your site if you cut down your bandwidth demands. On a slow dial-up, it takes forever to download.
What ?
Joel ,
You may as well use a 12AX7 with your design then . Large valves require meaty drivers , period !
316a
Joel ,
You may as well use a 12AX7 with your design then . Large valves require meaty drivers , period !
316a
???
Hungry triodes need feeding , simple ! Why not work out how much gain you're going to lose in the gridleak of the next valve for a start ! Distortion is also important , you are certainly not going to get low distortion from large voltage swings in piffly valves such as the 12A*7 family . I don't see the point in arguing with someone who has clearly not experimented and is arguing for arguement's sake (...and Joel : you're almost famous for that!)
316a
Hungry triodes need feeding , simple ! Why not work out how much gain you're going to lose in the gridleak of the next valve for a start ! Distortion is also important , you are certainly not going to get low distortion from large voltage swings in piffly valves such as the 12A*7 family . I don't see the point in arguing with someone who has clearly not experimented and is arguing for arguement's sake (...and Joel : you're almost famous for that!)
316a
Re: ???
Ok... well, with a 470k resistance - not much at all.
Huh? Actually, a 12AX7, etc, are designed specifically for large voltage swings. And assuming the power supply is up to it, I'm not sure why you correlate gain with distortion.
Who's "arguing"??? I asked you what the reasoning was behind your statements. 😕
And, why do you say I have "not experimented", simply because I want to know why you say to use "meaty" triodes? This is not a very productive attitude, is it 316a?
I suspect you are defensive, and attacking me like this because you don't know why you said that. Do you know the current requirements for a 6080 driver stage? Do you know how to calculate the full input capacitance, and slew rate needs? Do you know the distortion of a class A voltage amplifier stage swinging 62V pk-pk?
So, you see there is a lot more to it than simply repeating what you read in Glass Audio. We can actually calculate all of those requirements, down to the last milliampere - and I know from experience that the drive current value required will actually be quite low - a mA or two. So, yes, one could quite easily drive this tube with a 6SL7, 12AY7, 12AT7, etc.
See, we don't need voodoo to design circuits afterall! 😎 🙄 🙂
316a said:
Ok... well, with a 470k resistance - not much at all.
Huh? Actually, a 12AX7, etc, are designed specifically for large voltage swings. And assuming the power supply is up to it, I'm not sure why you correlate gain with distortion.
Who's "arguing"??? I asked you what the reasoning was behind your statements. 😕
And, why do you say I have "not experimented", simply because I want to know why you say to use "meaty" triodes? This is not a very productive attitude, is it 316a?
I suspect you are defensive, and attacking me like this because you don't know why you said that. Do you know the current requirements for a 6080 driver stage? Do you know how to calculate the full input capacitance, and slew rate needs? Do you know the distortion of a class A voltage amplifier stage swinging 62V pk-pk?
So, you see there is a lot more to it than simply repeating what you read in Glass Audio. We can actually calculate all of those requirements, down to the last milliampere - and I know from experience that the drive current value required will actually be quite low - a mA or two. So, yes, one could quite easily drive this tube with a 6SL7, 12AY7, 12AT7, etc.
See, we don't need voodoo to design circuits afterall! 😎 🙄 🙂
6080
enjoy the possible ensuing poor sound then ! <img src='http://ga-server02.globalarray.net/user/bigdaddy/hammer.gif'>The output stage should be the limiting factor , not the driver , enough headroom with low distortion should be the order of the day . Who was talking about 'drive current' anyway ? (not me) If you think 12AX7 can linearly provide large voltage swings , with low high order harmonics and enough headroom then good luck to you . No voodoo here , both feet are firmly on the ground . <img src='http://www.diyaudio.com/forums/images/smilies/nod.gif'>
ps I've never read Glass Audio
316a
enjoy the possible ensuing poor sound then ! <img src='http://ga-server02.globalarray.net/user/bigdaddy/hammer.gif'>The output stage should be the limiting factor , not the driver , enough headroom with low distortion should be the order of the day . Who was talking about 'drive current' anyway ? (not me) If you think 12AX7 can linearly provide large voltage swings , with low high order harmonics and enough headroom then good luck to you . No voodoo here , both feet are firmly on the ground . <img src='http://www.diyaudio.com/forums/images/smilies/nod.gif'>
ps I've never read Glass Audio
316a
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