Design calls for 310 volts. IIRC the K1 runs at 325 volts, can be done with 10 watts dissipation per LTSpice (love your adjustable bias resistor, makes it super easy to adjust).
Why are valve rectifiers loathed?
Even if had great internet and a short thread, be more then glad to provide documents, after all, doing a huge favor.
As for a power supply, even the original article provided none. So, it reminds me need to come up with one, oops. Kept feeling like forgetting something, ha. As so far found none supplying 310 volts, 300 and 325 volts seem to be standard?
OK, basically you need to design your power supply, including rectifier etc, before you buy a power transformer. You need around 310~330V B+ (typical EL84 range), and with the transformer you mentioned (640V AC) the resulting B+ will be too high. There is a software called PSUD, which can help a lot to design your power supply, then you can buy the appropriated components for it.
It will depend on the rectifier selected, and, if using a choke, then adding an additional resistor to drop the voltage. Calpe ended with around 360V B+ using a 5AR4 and a choke, his transformer HV was around 614V AC.
All I'm saying is do the simulation/calculation before spending any money.
All I'm saying is do the simulation/calculation before spending any money.
Serious question, where did you or Richard provide these parameters when saying to buy used? Hopefully it is suitable for the ECL86 PCB amp (asked for the schematic after purchase, heard nothing, has not shipped out, so might need to file a claim and then the build be ended).
Additionally, now both times ask for feedback on used and have not heard back, so gave up. Now that purchase... Oh well. Just had an idea, maybe need to do a separate post for each one? 🤔
Thank you. 🙂 I know, tried it on this Macintosh and was lackluster, very limited on types. Have yet to load it onto the Windows 7 desktop and see if has more options, that read about. If does, great, if not, there is @Merlinb 's book and LTSpice (bought the book for future use, though things change).
So this be a better option? https://www.tme.com/us/en-us/details/tsta250_001/toroidal-transformers/toroidy/tsta-250-001/
After I said I had spent money. 😆
Clearly need to quit feeling pressured, step back, and be sure everything is sorted before end up faffing about. 🙂
I inherited from my maternal Grandmother her Mother's M100 organ (same one Matthew Fisher used) about five years ago. The sound isn't quiet right especially the vibrato, best can come up with is an asthmatic mouse trying to sing. After a wonderful private message discussion with a forum member, realized how easily could mess up the amps, so purchased an inexpensive L100 amp to have a go. Can either re-sell it to a guitar player or better, double amp the M100 (heard the video on YouTube and sounds amazing). If ever get the BIB speaker cabinets built (How many months and still no reply?), could then feed the organ into those. Buahaha.
Well, looks fine, but seems like an overkill, quite powerful. Could be used in the future for a bigger amp.
Some comments:
- Secondary not center-tapped, you will need a bridge for rectification, either with solid state or hybrid (tube+solid state).
- they quote a range for the HV voltage, but I could not find the wiring diagram for that particular transformer.
Also, have you installed PSDU II software? Quite useful for power supply simulations.
The choke used in the thread you are referring to did not have a resistance of 150R, like the Triad C14X that was recommended in the build instructions.
I think the voltage will be ok, but maybe a bit underpowered for a PP amp unless it is lower powered?
Basics of Amplifiers - Source and Load Resistance
What frustrates me about both of @Merlinb 's books is does not specify source or load resistance or how to calculate; have not found elsewhere. So can someone please point me to a resource?
One such instance where needed is the power transformer. I have looked at the specifications of actual units and find nothing on this. Figure once have the actual unit can be measured, however, this does not allow designing a power supply and then selecting a transformer based on the design obtained.
What frustrates me about both of @Merlinb 's books is does not specify source or load resistance or how to calculate; have not found elsewhere. So can someone please point me to a resource?
One such instance where needed is the power transformer. I have looked at the specifications of actual units and find nothing on this. Figure once have the actual unit can be measured, however, this does not allow designing a power supply and then selecting a transformer based on the design obtained.
I spent a few hours yesterday and read through most of Designing Power Supplies for Tube Amplifiers, enough to understand the disadvantages of valve power supply, the most concerning being a change in tone, per the specifications I provided, this does not comply. Additionally, no singular rectifier valve can supply the 200ma minimum required by a EL84 PP amp; please correct me if the requirement value is incorrect.
Maybe down the road when build a tele valve phono amp build a 6BY5 bridge.
Not only that, did a few simulations. A LC filter is no longer an option because chokes with sufficient amperage rating are no longer available, according to Merlin. Additionally, with SS the diodes don't limit the reservoir capacitor size and capacitors increase voltage.
So, a 250 volt transformer puts out about 340 volts DC ripple. Since ripple filtering is not available on PSUD2, then have to be modeled in LTSpice and see how many orders drop the voltage down to 310 volts; my concern is a drop in current.
By the way, PSUD2 for Microsoft OS is more supplied then the Macintosh OS version, glad made the switch.
Hi Adriel,
About the rectifier valve, please have a look at the 5AR4 datasheet, it has several examples of capacitor input arrangements with 250mA output current.
Regarding chokes, you can buy 200mA chokes, they are available. Personally I do not bother with chokes for push-pull amps, they are expensive, heavy, and push pull amps have a good rejection of the power supply ripple noise.
About the rectifier valve, please have a look at the 5AR4 datasheet, it has several examples of capacitor input arrangements with 250mA output current.
Regarding chokes, you can buy 200mA chokes, they are available. Personally I do not bother with chokes for push-pull amps, they are expensive, heavy, and push pull amps have a good rejection of the power supply ripple noise.
Hi José.
Yes, I misread it. Though not seeing anything about capacitors...
https://frank.pocnet.net/sheets/127/5/5R4WGA.pdf
However, the 200ma specification is not correct. Looking at the datasheets:
EF86
Anode - 4ma
Grid - 2ma
Cathode - 6ma
Total - 10ma
*SL7
Anode - 3,2ma x2 = 6,4
Grid - N/A
Cathode - N/A
Total - Guess be 10ma x 2 = 20ma
EL84
Anode - 46ma x2 = 92ma
Grid - 15ma
Cathode - 65ma
Total - Guess be 10ma x 2 = 252ma
Or EL86 (Way less cost.)
Anode - 70ma x2 = 140ma
Grid - 3,5ma
Cathode - 100ma
Total - Guess be 10ma x 2 = 347ma
So the highest demand be for both channels be: (10x2)+(20x2)+(347x2)=754ma. I am not seeing how a single 5R4 can provide this, though still afflicted with brain fog.
What then what affect does valve rectification have on tone?
Your calculations above do not take into account, for example, how a push pull works. At idle you have the quiescent current on the output tubes, around 35mA plate+screen for an EL84. Then when amp the input signal increases, the current goes up for one EL84 (the push bit) and down in the other (pull). Things reverse for the negative part of the input signal, therefore the total current is not two times the current in one tube.
You can see in Ltspice, check the average current on the power supply at full signal.
Basically, you need real current values for your circuit, not datasheet maximum values. The datasheet has no idea how are you using the tube, push pull, single ended or something else.
You can see in Ltspice, check the average current on the power supply at full signal.
Basically, you need real current values for your circuit, not datasheet maximum values. The datasheet has no idea how are you using the tube, push pull, single ended or something else.
Hi Adriel, you really need to get on and build a proven circuit, like the Tubelab SPP, and break out of this scholarly fug that you are in. Use a PCB because it is 100 times simpler. Build 1 amplifier and not two monoblocks because that is 10 times simpler. There are a million schemas out there that use a power transformer like the one you have bought, with a PP amplifier. So how can you state that such an amplifier requires a 754mA power supply? You must see that is non-sensical?
Once you have built something, measured voltages, got it running, a lot of this theoretical stuff will dissolve away, and the important stuff will be left. You will be building and modifying amplifiers for starters. One day, years down the line, you may be designing then too.
Once you have built something, measured voltages, got it running, a lot of this theoretical stuff will dissolve away, and the important stuff will be left. You will be building and modifying amplifiers for starters. One day, years down the line, you may be designing then too.
Clearly I was tired, as evidenced by values not corrected after copy and pasting. 😆
So the values in LTSpice are when the valves are driven to the maximum?
Actually, on one it does have values for PP, interestingly.
There is also the data sheets missing current values.