Yes, but what is going to supply this valve with the ~75mA of current its grid wants to eat? And do you want to build a new high voltage power supply?
I would have thopught that if the 4p1l can swing 170v p-p, then you'd want to pitch the 300b bias at about -90v ish or just over and then adjust the power supply to suit.
I'd suggest Andy has a play with some loadline software programmes first.
kind regards
Marek
I would have thopught that if the 4p1l can swing 170v p-p, then you'd want to pitch the 300b bias at about -90v ish or just over and then adjust the power supply to suit.
I'd suggest Andy has a play with some loadline software programmes first.
kind regards
Marek
Evan, but you are aware that higher power means higher current means lower rp means lower OPT primary impedance means lower turn ratii and finally a louder speaker.... which leads to the effect that you need less gain upfront... obviously only if you can adpobt the turns ratio of the opt.
The higher negative grid voltage protects Ou from running into positive grid, nasty distortions and damage of the 300b. I design this always that the digital 0db level still will be within the envelope of minus Ug. Maybe some kf your recording which are recoeded with lesser levels have than, well lesser level. But thats fine for me.
The higher negative grid voltage protects Ou from running into positive grid, nasty distortions and damage of the 300b. I design this always that the digital 0db level still will be within the envelope of minus Ug. Maybe some kf your recording which are recoeded with lesser levels have than, well lesser level. But thats fine for me.
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Looking at loadlines is certainly something I should get into, and if there's software for the Mac I'd be interested to know.
I can see you guys like the 300b hot!
I can see you guys like the 300b hot!
Triode / Pentode Loadline Simulator v.1.0 (20161216 [url]www.trioda.com)[/url]
As it is html it should work with your Mac as well...
If you want an ultra transparent and dynamic 300B version with finest resolution and blackest backround but without the vintage sound...Kron 842...has easily surpassed the Eml300B Mesh or the old Scetlana 300B in my system...not sure I really want to try any psvane or elrog etc as this Kron 842 is really very impressive.
..I will test and compare the 300B with other DHT in the future, all with the same PsU (but correct voltages and bias and OPtT), same driver, so that it is really the tube you evaluate and not the setting you changed around...candidates are (all in house already): 813, 814, 828, 845, PSE 801a, 211, gm70, eml52b.
I need max 16W for my speaker...than you will bleed from your ears...
Once that I understood my favorite Output tube, I will contiue to play with driver tubes again...currently 801A, but a Kron 242 or a Telefunken Rs242 is high on the list.
As it is html it should work with your Mac as well...
If you want an ultra transparent and dynamic 300B version with finest resolution and blackest backround but without the vintage sound...Kron 842...has easily surpassed the Eml300B Mesh or the old Scetlana 300B in my system...not sure I really want to try any psvane or elrog etc as this Kron 842 is really very impressive.
..I will test and compare the 300B with other DHT in the future, all with the same PsU (but correct voltages and bias and OPtT), same driver, so that it is really the tube you evaluate and not the setting you changed around...candidates are (all in house already): 813, 814, 828, 845, PSE 801a, 211, gm70, eml52b.
I need max 16W for my speaker...than you will bleed from your ears...
Once that I understood my favorite Output tube, I will contiue to play with driver tubes again...currently 801A, but a Kron 242 or a Telefunken Rs242 is high on the list.
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So far I didn't know ... and my tubes too ... and my 10W A2 capable 300B amp living now since more than a decade. 🙂
And yes, I outwear two pairs ... each time one in pair has heater break... over about 5 years (at least 5*365*4-5 hour) working. I think it's close to the "normal" worn out.
And yes, most of 300B tubes (especially mesh anode ones) unsuitable working with grid current, but robust metal anode ones (I like using such way gold grid EH300B) perform well.
It's -my- practice for decades.
Sooner with cathode follower, later with FET source follower (better, more defined lower region).
Up to +20...30V the appropriate (for example EH) 300B tubes capable 10W output power at not so hot operating point (385-400V, 70mA) with 5k OPT.
Attached the 105V RMS gate swing FFT (0.38% THD) and 10W output FFT (THD 1.65%).
John Broskie also tried this:
Class-A2 & Evermore Single-Ended Amplifiers
Bela,
you are satisfied with sound of EH300B.
I haven't tried them, I'm just asking you.
Thanks
you are satisfied with sound of EH300B.
I haven't tried them, I'm just asking you.
Thanks
Well, I sort of use a2 as I can generate a Vpp of 200V currently with full output of my DAC at 0db sinus...and the 842 has -90V, so +10V in theory...well...my impression is that most recording dont go all of the time that loud...I use an IT and a 801A running at 20mA to satisfy potential current pulses....but nevertheless i like the amp better when it soes not have to play that loud.
I believe those who built a2 amp with a2 transmitter tubes who have pretty linear curves as well in a2 (like 8o1a, but as well others) reported they like the sound of those amps better, when they always play loud...so stay in a2. So for me (with very limited experience on a2), i understood that the huge impedance change from infinity impedance to a few kohm is not helpful for good sound, so you either better stay on the the low or the high impedance side of things and design for those conditions, but dont force the amp to move back and force...but that was only my theoretical thinking.
I believe those who built a2 amp with a2 transmitter tubes who have pretty linear curves as well in a2 (like 8o1a, but as well others) reported they like the sound of those amps better, when they always play loud...so stay in a2. So for me (with very limited experience on a2), i understood that the huge impedance change from infinity impedance to a few kohm is not helpful for good sound, so you either better stay on the the low or the high impedance side of things and design for those conditions, but dont force the amp to move back and force...but that was only my theoretical thinking.
If you use standard EH300B (black logo) at "classical" 300B structure (cathode bias, capacitor coupling, A1 region, 2k5-3k5 OPT) -for me- the sound (which is good, but there are more better amps) is -as many criticism typifies- "spheric", "tube" sound. For me it's boring.
If I try to drive with harder drive (but no DC driving 300B gate), sometimes it would be little scratched, more "HiFI" than I like (due to the increased H3 distortion at higher levels).
More than a decade I switched another driving and loading method: direct (DC) driving, higher (5k) OPT.
I did not discard driving output tube to A2 region (I always in "love" with thoriated tungsten transmitter tubes since when I heard amplifiers in Japan for decades ago, which tubes "begging" to drive it A2), so tried this method in 300B tubes.
Some of 300B endured it well (for example early metal plate chinese ones), some wilding distorted.
Finally I selected the gold grid EH300B tubes for A2 amplifiers.
It has enough good tone at moderated -not so hot- operating point, higher (5k) load, with extra hard driving (FET), and produce enough power (up to 10-11W) with acceptable distortion.
... or start engineering zero bias (A2) amplifier.
I'm afraid, that this summer taken by the devil (Covid), so I'll get to making new amplifiers. :-(
I planning convert 841, 801a PSE amplifier to zero bias ones.
Attachments
It's the original schematic (at least a decade old):
Attachments
It's a custom wound 5k:8 transformer, but any appropriate 4-5k, 70..80mA 10W transformer usable.
I made this type amplifier to my friends with Lundahl, Transcendar or Tribute transformer so.
Do any of you use this online loadline calculator? Seems useful.
Loadline calculator for power stages with reactive load - Vacuum Tube Amplifiers - DIY
Loadline calculator for power stages with reactive load - Vacuum Tube Amplifiers - DIY
I imagine most people would just load up a copy of LTSpiceIV (or maybe a newer version) and do it that way.
This gives the advantage that you can put a probe into any part of the circuit, load it up with sinewave or or other signal and then see where the current or voltage is going. You can then ramp up or reduce your voltages, swap components around and sim what the circuit does in real time or look at its frequency response.
A loadline only shows you the DC conditions at the operating point and lets you plot the safe operating area from the datasheet. The sim uses the same valve data to let you see so much more.
Another tool is Dmitry's paint tool where you use a picture of the graph and match up the parameters to make an electronic version of the datasheet graph so you can then plot your way around the graph to your heart's content. See Model Paint Tools: Trace Tube Parameters over Plate Curves, Interactively
kind regards
Marek
This gives the advantage that you can put a probe into any part of the circuit, load it up with sinewave or or other signal and then see where the current or voltage is going. You can then ramp up or reduce your voltages, swap components around and sim what the circuit does in real time or look at its frequency response.
A loadline only shows you the DC conditions at the operating point and lets you plot the safe operating area from the datasheet. The sim uses the same valve data to let you see so much more.
Another tool is Dmitry's paint tool where you use a picture of the graph and match up the parameters to make an electronic version of the datasheet graph so you can then plot your way around the graph to your heart's content. See Model Paint Tools: Trace Tube Parameters over Plate Curves, Interactively
kind regards
Marek
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This is good advise...I guess I never made the step to spice as I did not found the time to really get into it...how difficult is it to learn ?
I liked the triode load line simulator as it actually gave you the option to play with different imoedances, bias point and simulated as well the distirtion spectrum and level for the selected input sinus level. There are some bugs that you have to change the input level always a bit to get accurate distortion figures, but once you figure that out its a pretty powerful tool.
Do I read your schematic right ...1k5 primary for two 801A in PSE ? What rp do they have ? 4k, so two have 2k...no ?
I liked the triode load line simulator as it actually gave you the option to play with different imoedances, bias point and simulated as well the distirtion spectrum and level for the selected input sinus level. There are some bugs that you have to change the input level always a bit to get accurate distortion figures, but once you figure that out its a pretty powerful tool.
Do I read your schematic right ...1k5 primary for two 801A in PSE ? What rp do they have ? 4k, so two have 2k...no ?
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