This may have been posted before but when I was building the baby huey, I went through the same challenge of finding a good price for performance option.
Doug put together a decent rundown of transformers a few years ago.
https://www.diyaudio.com/community/...uey-el84-p-p-output-iron.138512/#post-1744055
I chose to use Electraprint's transformers (no longer in production) which sound great.
.. dB
Doug put together a decent rundown of transformers a few years ago.
https://www.diyaudio.com/community/...uey-el84-p-p-output-iron.138512/#post-1744055
I chose to use Electraprint's transformers (no longer in production) which sound great.
.. dB
👍
😵 I hadn't even thought of that. I think that's more than I am looking for though.
I think the Primary Windings transformers will be fine if they fit. Chassis is in Hong Kong still waiting at the airport and the power transformer is in the mail. When they both get here I will do precise measurements to confirm fit before ordering OPTs.
I'm using 6P14P-ER instead. Nice to know in case I ever consider a true EL84. The Chinese manufacturer puts EL84 on the schematic, but it's actually 6P14. Specs attached. 6P14P-ER is the 10,000 hour life version with slightly higher heater current. The rest is the same.
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Vacuum Tube ratings are real tricky things . . .
6P14P ratings:
Higher Voltage plate?
Lets check that . . .
With less than 8 Watts plate dissipation (< 8 Watts), the maximum plate volts is 400V.
OK. Higher than an EL84.
(8 Watts / 400V = 20mA maximum to get the 400V plate voltage rating
But with more than 8 Watts plate dissipation (> 8 Watts), the 6P14P maximum plate volts is 300V.
The same as for an EL84.
At 6P14P's 14 Watts max plate dissipation and 300V, that is 46.7mA
At EL84's 12 Watts max plate dissipation and 300V, that is 40mA.
One seller on the web says the 6P14P-EV military version is a 7189.
The 7189 is the tube I mentioned earlier, but could not remember its part number/name
7189:
Plate dissipation 12W max.
Plate voltage 400V max (30mA) pentode mode; Plate voltage 375V max Ultra linear mode.
Screen voltage 300V max.
7189A:
Plate dissipation 13.2W max.
Plate voltage 440V max (30mA) pentode mode.
Screen voltage 400V max; 415V max Ultra linear mode.
Nothing simple here, those tube specifications are complex.
Just like they usually are.
6P14P ratings:
Higher Voltage plate?
Lets check that . . .
With less than 8 Watts plate dissipation (< 8 Watts), the maximum plate volts is 400V.
OK. Higher than an EL84.
(8 Watts / 400V = 20mA maximum to get the 400V plate voltage rating
But with more than 8 Watts plate dissipation (> 8 Watts), the 6P14P maximum plate volts is 300V.
The same as for an EL84.
At 6P14P's 14 Watts max plate dissipation and 300V, that is 46.7mA
At EL84's 12 Watts max plate dissipation and 300V, that is 40mA.
One seller on the web says the 6P14P-EV military version is a 7189.
The 7189 is the tube I mentioned earlier, but could not remember its part number/name
7189:
Plate dissipation 12W max.
Plate voltage 400V max (30mA) pentode mode; Plate voltage 375V max Ultra linear mode.
Screen voltage 300V max.
7189A:
Plate dissipation 13.2W max.
Plate voltage 440V max (30mA) pentode mode.
Screen voltage 400V max; 415V max Ultra linear mode.
Nothing simple here, those tube specifications are complex.
Just like they usually are.
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I "cheat" and use a calculator online. (When we started calculating circuits in physics in college I almost failed!) It calculates 10 watts for EL84 12W tubes at ~336 volts at the #7 pin, assuming I filled out the form correctly with my measured values. The higher the dissipation, the lower the maximum voltage? I assume one of the curves shows that? I didn't notice the note specifying <=8W on the spec sheet. I see it now.
https://robrobinette.com/Tube_Bias_Calculator.htm
Is this helpful? I had hoped to put items like this in a build thread, but I'm not there yet. I'll just have to refer to here later. If the chassis would move from the Hong Kong airport where it has been stuck I could move forward with OPTs.
https://robrobinette.com/Tube_Bias_Calculator.htm
Is this helpful? I had hoped to put items like this in a build thread, but I'm not there yet. I'll just have to refer to here later. If the chassis would move from the Hong Kong airport where it has been stuck I could move forward with OPTs.
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I typed that wrong. I actually put in 14 watts for 6P14P tubes, not 12 watts, to get those numbers from the calculator. Advice back when I built it was to increase the bias resistor, which was 150 Ohm on the schematic. I used 160 Ohm.
I found this, but I don't know how to calculate it:
Most tube data sheets will indicate MAX Class A voltage....
Which really means the valve can really handle twice that voltage +20% .... SO iF your max Class A plate voltage is 400V DC... The valve should normally be able to AC swing to 800V with arc-over breakdown at roughly 1000V or so .....
It is really the sum of the DC idle voltage plus the AC swing that dictate where you can go with a valve.... This means that you need to watch the plate load swing if your running higher B+...
Many Push-Pull circuits run higher than data sheet voltage and can do so safely in Class AB... SInce each valve usually doesn't go higher than the rail then goes into cut-off, which is still lower than the full AC swig it would experience in Class A ....
https://www.diyaudio.com/community/threads/max-plate-voltage-rating-in-tube-datasheet.88979/
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Never Get Old,
I appreciate your persistance!
In college, I took engineering physics; it required Calculus. I studied Calculus at the same time (a no no idea); I asked my Calculus instructor about a line integral, she had never heard of it. As a Veteran over 21, I stayed in a graduate dorm. The graduate math major who was 4 hours short of a physics degree; and a graduate TA, a native from Czechoslovakia got me through the physics (All B's, not to bad). The TA was using Stanford's Linear Accelerator to do graduate research, U of Washingtons computer to calculate and collate the data, and Oregon State as his Teaching Assistance job. Funny thing, he had to sign the papers that the US could Draft him into the US Army if they wanted to (what a waste it would have been, carry a rifle).
Some US men were defecting to Canada. That was 1968, remember Viet Nam; and especially the Russian invasion of Prague?
Over 30 years later, I found myself using vector math, root raised cosine filtering, looking at vector diagram symbol points over time, including various forms of fading including that from a moving vehicle. I can not do any of that now, too much hidden in the memory banks. Concepts yes, calculations etc. No.
I appreciate your persistance!
In college, I took engineering physics; it required Calculus. I studied Calculus at the same time (a no no idea); I asked my Calculus instructor about a line integral, she had never heard of it. As a Veteran over 21, I stayed in a graduate dorm. The graduate math major who was 4 hours short of a physics degree; and a graduate TA, a native from Czechoslovakia got me through the physics (All B's, not to bad). The TA was using Stanford's Linear Accelerator to do graduate research, U of Washingtons computer to calculate and collate the data, and Oregon State as his Teaching Assistance job. Funny thing, he had to sign the papers that the US could Draft him into the US Army if they wanted to (what a waste it would have been, carry a rifle).
Some US men were defecting to Canada. That was 1968, remember Viet Nam; and especially the Russian invasion of Prague?
Over 30 years later, I found myself using vector math, root raised cosine filtering, looking at vector diagram symbol points over time, including various forms of fading including that from a moving vehicle. I can not do any of that now, too much hidden in the memory banks. Concepts yes, calculations etc. No.
Way too much for me. I hired a tutor twice per week, and I survived two semesters of non-calculus (I did take calculus though and got A's) college physics with a B+ and an A-. I learned about mysterious things like gravity and orbit, magnetism, and simple electronic circuits with resistors, capacitors, transformers, inductors, AC and DC, etc. I always said, "That doesn't make sense" which is why it was hard for me. To others it makes perfect sense. Why in the world are two objects gravitationally drawn to one another? It makes no sense to me. The "right hand rule" for magnetic fields? Makes no sense to me. Nothing can go over the speed of light? Makes no sense to me. I had to go look up the bit I posted earlier about the direction of the magnetic fields in relation to the winding and laminations for transformers. Fortunately I found illustrations in a reference book when I built the amp.
I am interested in the "whys" of the design of this amplifier. It sounds very nice, and I do understand the basics of the circuit now. I have no idea why it sounds good though. The kit has been for sale for many years, and other people who have built it also like it a lot. They sell a whole lot of these. Even with the smallish output transformers in the kit it sounds great. I hope bigger better OPTs from this thread will have a positive impact on the second amp. I will have two essentially identical amps with OPTs being the biggest difference so I can compare. I had hoped to put circuit analysis into a future build thread, but we seem to have veered from OPTs into the voltages used already. I don't understand if we are violating the spec sheet rules for the 6P14P tube or not, and if so by how much. If anyone knows how to figure it out given the last few posts, please do. It's above my knowledge and ability.
Regarding OPTs, two manufacturers have told me that it is better to omit the ultra-linear outputs and redesign the transformer without them rather than just not use them. Something about losses in the ouput transformer. Anybody here got any experience with that?
Even if the kit arrives next week, I won't be able to start until after the first of the year, but I can measure and buy OPTs as soon as the kit and the power xformer get here. Both should be here next week with luck. Painting will take 2-3 weeks depending on weather. I also have to order upgrade parts and a new soldering iron. It's always something. There is no end to this hobby ... unless I just stop building things! Four kit tube amplifiers, three modded DACs, DIY speaker cables, and a DIY digital coax cable in only 12 months? 🙄
I am interested in the "whys" of the design of this amplifier. It sounds very nice, and I do understand the basics of the circuit now. I have no idea why it sounds good though. The kit has been for sale for many years, and other people who have built it also like it a lot. They sell a whole lot of these. Even with the smallish output transformers in the kit it sounds great. I hope bigger better OPTs from this thread will have a positive impact on the second amp. I will have two essentially identical amps with OPTs being the biggest difference so I can compare. I had hoped to put circuit analysis into a future build thread, but we seem to have veered from OPTs into the voltages used already. I don't understand if we are violating the spec sheet rules for the 6P14P tube or not, and if so by how much. If anyone knows how to figure it out given the last few posts, please do. It's above my knowledge and ability.
Regarding OPTs, two manufacturers have told me that it is better to omit the ultra-linear outputs and redesign the transformer without them rather than just not use them. Something about losses in the ouput transformer. Anybody here got any experience with that?
Even if the kit arrives next week, I won't be able to start until after the first of the year, but I can measure and buy OPTs as soon as the kit and the power xformer get here. Both should be here next week with luck. Painting will take 2-3 weeks depending on weather. I also have to order upgrade parts and a new soldering iron. It's always something. There is no end to this hobby ... unless I just stop building things! Four kit tube amplifiers, three modded DACs, DIY speaker cables, and a DIY digital coax cable in only 12 months? 🙄
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The speed of light is the clock rate of the simulation we're living in.
All good fortune,
Neo
I am on the 45th parallel, going around in circles at 707MPH.
Pity those speedsters on the Equator, they are going 1000MPH.
The simplest conversion formula for temperature is degrees C = degrees F (at -40 degrees of course!).
I just love math!
(and I used to hate it)
Pity those speedsters on the Equator, they are going 1000MPH.
The simplest conversion formula for temperature is degrees C = degrees F (at -40 degrees of course!).
I just love math!
(and I used to hate it)
For such small sized transformers, I do not think it is really necessary to redesign the whole transformer, considering the UL as a progressive tap within the primary. To achieve a lower leakage inductance from UL windings related to the rest of the primary, one could scatter them around all primary interleave packages. For example, something like P2+UL1 - S - P4+UL2 - S - P2+UL1 to keep symmetry. However this doesn't come as a free lunch, as primary to primary capacitance is increased. In a recent SE transformer with UL, I found a good compromise to keep the UL windings in the center, something like P3-S-Px+UL+B+UL+Px-S-P3. In a PP single bobbin transformer, this comes as a default setting, so there shouldn't be a big fuzz about it.
Good information. Thanks for the clarification. So it appears that the benefit of winding without UL, if any, would be minimal. When I don't know, I always ask. 🙂
That guess-tamate is 1/24th slow. Circumference of the Earth at the Equator is ~25000 miles not 24000.
So at the 45th the speed would be ~707 (25 / 24) mph, making it seem even less likely that God would
have or could have stopped the Sun & Moon so that Joshua could win his battle.
That extra bit is what we live on without getting a hot foot. And we don't need the
Theorems of Pappus & Guldinus to help us estimate the extra volume involved. 😀
Remember that it also depends of the designer, interleaving geometry and coil design can vary a lot by manufacturer. To some extent, everyone has his/her own cookbook. The topic on iterleaving preferences can be vague. I cannot say for certain before comparing different interleaving patterns with a direct comparison.
My first transformer mentor believed you could just pick a random SE interstage transformer with center tapped coils and reconnect it as SE -PP for phase splitting duty. When we began observing HF waveforms, **** hit the fan.
Anywa, I'm confident most transformer designer will wind the UL tapped transformer the regular, progressive way. Which is good enough. So I'm pretty certain you'll get very little risk in this UL case.
For a typical A1-S-B+B+-S-A2 configuration, with anodes at inner and outer end of the bobbin, the intermediary UL taps are pretty fine. Patrick Turner demonstrated such interleaving schematics, CFB included.
Here's a rare, but possible design to really FAIL at UL tap. Wind a double-coil SE transformer with an UL tap sticking from one coil only. That will spike Leakage inductance for at least *100 times, because of attempted magnetic coupling from coil A to coil B. I know a guy who imagined he could wind a TVC transformer this way = resonant tanks in the audio 1-5kHz band with variation.
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jcalvarez,
Thanks for putting up the SV83 link.
I would expect the SV83 to be real good in Pentode mode . . .
not very good for UL, and not very good for Triode wired, except at low voltages (those modes limit the power capabilities of the tube).
At what part of the Earth is the length of daylight and length of darkness the same all year long, approximately 24 hours.
(the day is not 24 hours, there is an extra factor), try the Equator as a location.
All this information, has another factor, the fact that the earth is not round, it is pear shaped.
The bulge below the equator gets in the way of the sun, but above the equator there is not a bulge in the way.
So the length of day and night is not equal during 1/2 of the year.
Sorry, back to Transformers and such . . .
Factors get in the way of what we expect.
Our tube amplifiers may have factors that we never even thought of.
Thanks for putting up the SV83 link.
I would expect the SV83 to be real good in Pentode mode . . .
not very good for UL, and not very good for Triode wired, except at low voltages (those modes limit the power capabilities of the tube).
At what part of the Earth is the length of daylight and length of darkness the same all year long, approximately 24 hours.
(the day is not 24 hours, there is an extra factor), try the Equator as a location.
All this information, has another factor, the fact that the earth is not round, it is pear shaped.
The bulge below the equator gets in the way of the sun, but above the equator there is not a bulge in the way.
So the length of day and night is not equal during 1/2 of the year.
Sorry, back to Transformers and such . . .
Factors get in the way of what we expect.
Our tube amplifiers may have factors that we never even thought of.
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It is hard to build a bad sounding EL84 amp, period.
Personally, I think they sound best when Va-k is down around 240V to 250V and with around 40 to 45mA Ik or so.
As well as sounding good, the tubes are run well within their ratings and will thus last a long time.
EL84 and related tubes are tough little buggers and have a reputation to be able to take abuse, particularly in guitar amps, and keep working.
But that’s not a recipe for reliable long term operation. Please strong consider not abusing the crap out of your EL84s.
Also, that circuit you posted is not really great chops either tbh.
They are many very good EL84 designs out there. The Baby Huey is a wonderful sounding amp, even if Gingertube runs the B+ a bit close to the maximum for my personal liking. Morgan Jones design is very good. There are lots more good EL84 design's that have good reputations.
All I’m suggesting is don’t get too hung up on using a design that has more than a few opportunities for improvement and is clearly designed for “max power” from a pair of EL84s per channel.
My 2 cents, ymmv etc etc
My question is, by how much is this amplifier violating the specs of the 6P14P-ER tube, if it is doing so? I can post the schematic again if needed. It's somewhere above, along with the 6P14P spec sheet. It's a very rugged tube with a 10,000 life rating, and it sounds great. If the life gets reduced "a little" I'm ok with that. If it starts needed tubes every year or more often than that, well that's not so great. It only has a few months on it so far. I'd start a thread on overvoltage but certain people here would get mad. 😉 I'm also running 6P14P-ER in the ST-35 with 360-370 volts on pin #7. I think the ST-35 qualifies as tube abuse. One thing I like about this little amplifier is that it doesn't run very hot, unlike the ST-35 which everyone expects to be like a small fireplace, and it is. I found a few old threads on overvoltage, but nothing leading me to a definitive answer on how much this amplifier is abusing the tubes.
Why this amplifier? 1) It's a kit so ... no fabrication that I hate, I don't have to spend a bunch of time and effort ordering individual parts, and I only have to replace/upgrade any parts I choose like the OPTs, 2) It's not expensive at $300 delivered (on sale plus a promo code), 3) I know that I like the sound as I already built one, 4) The compact left-right footprint is perfect for me, 5) I already built one so little chance of me making mistakes this time. I had to build my confidence by building the first one, breaking it twice, blowing a tube, repairing it, and finally ending up with a great amp. So those all are valid reasons for me, despite the circuit not being ideal. I know there are other designs for people who really want to build their own, but I don't want to do that, at least not anytime soon. Maybe someday but not now. I am not above making modifications to this amp, and I would like to look at that next year in a build thread, but it is a PCB amp with a very crowded chassis, so modifications have to be limited. I also do not want to alter the sound in any meaningful way as I love it the way it is. It sounds "right" to me unlike many amplifiers. Curiosity killed the cat as the saying goes, but I want to try larger OPTs and see what happens. Thus, this thread was born.
Why this amplifier? 1) It's a kit so ... no fabrication that I hate, I don't have to spend a bunch of time and effort ordering individual parts, and I only have to replace/upgrade any parts I choose like the OPTs, 2) It's not expensive at $300 delivered (on sale plus a promo code), 3) I know that I like the sound as I already built one, 4) The compact left-right footprint is perfect for me, 5) I already built one so little chance of me making mistakes this time. I had to build my confidence by building the first one, breaking it twice, blowing a tube, repairing it, and finally ending up with a great amp. So those all are valid reasons for me, despite the circuit not being ideal. I know there are other designs for people who really want to build their own, but I don't want to do that, at least not anytime soon. Maybe someday but not now. I am not above making modifications to this amp, and I would like to look at that next year in a build thread, but it is a PCB amp with a very crowded chassis, so modifications have to be limited. I also do not want to alter the sound in any meaningful way as I love it the way it is. It sounds "right" to me unlike many amplifiers. Curiosity killed the cat as the saying goes, but I want to try larger OPTs and see what happens. Thus, this thread was born.
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Build the Kit Amp.
Get it up and running.
Listen a lot.
Then, only after that, should you consider any modification to the amp.
Back in 1959, I built my first Knight Kit EL84 push pull mono block amplifier, and listened on an Electro Voice 12 inch Wolverine "full" range driver.
It sounded Wonderful, . . . but what did I know back then?
I do know that my ears were better back then.
"I never heard a 2A3 amplifier that I did not like" - a quote from a "Sound Practices" magazine.
Usually, the same can be said for most push pull EL84 amplifiers; and lots of single ended ones too.
No two tubes are exactly alike, some take more abuse than others.
The 807 was famous for that.
Did any of you ever tune up a Pi network on an 807 transmitter?
Did you see the meter swing way beyond 'safe' until you got it properly tuned? How much overload for how long?
Did you try to get 2 more S units of power for the guy at the other end?
Get it up and running.
Listen a lot.
Then, only after that, should you consider any modification to the amp.
Back in 1959, I built my first Knight Kit EL84 push pull mono block amplifier, and listened on an Electro Voice 12 inch Wolverine "full" range driver.
It sounded Wonderful, . . . but what did I know back then?
I do know that my ears were better back then.
"I never heard a 2A3 amplifier that I did not like" - a quote from a "Sound Practices" magazine.
Usually, the same can be said for most push pull EL84 amplifiers; and lots of single ended ones too.
No two tubes are exactly alike, some take more abuse than others.
The 807 was famous for that.
Did any of you ever tune up a Pi network on an 807 transmitter?
Did you see the meter swing way beyond 'safe' until you got it properly tuned? How much overload for how long?
Did you try to get 2 more S units of power for the guy at the other end?
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