Interesting idea to use one zener reference for all 3 CCS`s. I`ll stick to the gingertube tried and proven design for my pcb for now, he spent years trying different things with listening tests so its a safe way to go... I attached a "normal" schematic of your idea so its human readable
Ciao xcicc,
the EL84 has the PSU onboard (as some EL34 versions), and you have the specs on the board itself, showing where to connect heaters, etc...
One suggestion I have, compared to the standard PSU, is to elevate the heaters-winding central-tap around 40V with a 1 MOhm - 150 kOhm voltage divider from B+ to ground, with a 10uF 63V capacitor in parallel to the 150 kOhm resistor. Connect the central tap of the heater winding to the central point of the voltage divider.
the EL84 has the PSU onboard (as some EL34 versions), and you have the specs on the board itself, showing where to connect heaters, etc...
One suggestion I have, compared to the standard PSU, is to elevate the heaters-winding central-tap around 40V with a 1 MOhm - 150 kOhm voltage divider from B+ to ground, with a 10uF 63V capacitor in parallel to the 150 kOhm resistor. Connect the central tap of the heater winding to the central point of the voltage divider.
I built the second iteration of the Baby Huey, using Yves schematic but a slightly different CCS on the driver/splitter ...
Dissident Audio PCL86
Sounds great using a pair of OPTs from Ask Jan First that cost less than £80 between them.
Dissident Audio PCL86
Sounds great using a pair of OPTs from Ask Jan First that cost less than £80 between them.
Even better, for a simpler BOM, to use 12V zener as single reference for all CCSs. Same as to protect the Power Drive mosfet.
I agree with you and I'd do the same if I were you. You can always try different things in future.
Thanks, I'd add base stoppers to the each of the three BJTs (around 220 Ohm like for the PD mosfet, again for a simpler BOM).I attached a "normal" schematic of your idea so its human readable
Hi @tubekiddo , in attachment you can find the LTSpice file.Nice work!
Any chance you can share the LTSpice file and the two includes (12AX7 and EL84). Saves me some work…
Just note that I'm not on the same PC I used yesterday, so here I have my own version of the Baby Huey with EL34 (higher currents for the PowerDrive, higher plate loads for the 12AX7, higher B+, 6k6Raa with 23% UL taps, and I have omitted some other parts). You can just adapt the voltages and parameters as per previous image posted here: https://www.diyaudio.com/community/threads/el84-amp-baby-huey.72536/post-7254266
On the same file you can see the simulated DF, THD @ 1 Wrms and max power @ 5% THD.
I've never measured the real one, but I'm happy as it sounds good. Working on optimizing the feedback (switchable).
Anyone in the US or Canada have any ideas on where I can find transformers? I see that Edcor has OPT’s with the 23% tap I am looking for. Any thoughts on how good those would be ?https://edcorusa.com/products/cxpp25-8k-23-25w-8k-ohms-push-pull-tube-output-transformer
Antek has a transformer with 230-230 and 6.3-6.3 secondaries https://www.antekinc.com/as-1t230-100va-230v-transformer/
I am running into a wall looking for a 50 volt transformer. Any suggestions?
Antek has a transformer with 230-230 and 6.3-6.3 secondaries https://www.antekinc.com/as-1t230-100va-230v-transformer/
I am running into a wall looking for a 50 volt transformer. Any suggestions?
Hello Jazzman:
All I have to say is: Edcor, Hammond, Antec,
These all seem like reasonable choices to me, there are many others in North America or Asia, or Europe.
This thread is long enough to glean lots of information about transformer options. The reading will also answer other questions you have about Tubes, Capacitors, Resistors, Etc. You may need to read a bit more to find what you need. It is worth the effort.
I hope this helps
All I have to say is: Edcor, Hammond, Antec,
These all seem like reasonable choices to me, there are many others in North America or Asia, or Europe.
This thread is long enough to glean lots of information about transformer options. The reading will also answer other questions you have about Tubes, Capacitors, Resistors, Etc. You may need to read a bit more to find what you need. It is worth the effort.
I hope this helps
Toroidy. They have standard 40% UL taps, but apparently they will custom wind Ul23% at relatively low additional cost. Check here:
https://www.diyaudio.com/community/threads/easy-diy-tube-amp.384618/page-4#post-6993896
Thank you for your suggestions. Francois, I have heard good things about Toroidy. Unfortunately, the US distributor would only quote me on the standard model. They told me they could not get a custom version from the manufacturer.
I was able to find this Hammond for the 50 volt transformer. https://www.digikey.com/en/products/detail/hammond-manufacturing/166F50/455094
However, it is center tapped. My pcb has a connection for ac (hot and neutral only). If I used this transformer, what would I do with the center tap?
I was able to find this Hammond for the 50 volt transformer. https://www.digikey.com/en/products/detail/hammond-manufacturing/166F50/455094
However, it is center tapped. My pcb has a connection for ac (hot and neutral only). If I used this transformer, what would I do with the center tap?
@jazzman - you can ignore the center tap = as an FYI, I ended up reducing the bias voltage, so don't clip the lead too short in case you need to use it as a 25V transformer and not 50V
regarding edcore - they make good transformers - rock solid, nothing crazy but do an excellent job. I was set to use them but then found a deal on some electraprint and went that way instead.
regarding edcore - they make good transformers - rock solid, nothing crazy but do an excellent job. I was set to use them but then found a deal on some electraprint and went that way instead.
@jazzzman,
I assume you interacted with TME in Atlanta regarding the Toroidy OT. TME does not sell the 23% UL version, and it has to be ordered from Toroidy in Poland directly. I have not done that, but several folks here, including @zintolo, had pleasant experiences dealing with Toroidy directly and acquired the 23% UL version at small extra cost (much less than I expected, but I don’t remember the details). I know Toroidy charges more for shipping (than TME), so you better inquire if you decided to go this route.
Your bias transformer (Hammond 166F50) seems to provide 25-0-25VAC. If so, you could simply leave the CT unconnected, if you are using the Rev 1.6 9-pin PCB (schematic dated Nov 19, 2018) where the bias-2 connector is grounded to the circuit ground. I don’t recall that you mentioned which PCB you are using. Your selected transformer is probably over-kill if you plan to use EL84 power tubes. A much smaller 0-30 Vac transformer will suffice, such as: https://www.mouser.com/datasheet/2/410/FD4_36-781155.pdf
Good luck.
I assume you interacted with TME in Atlanta regarding the Toroidy OT. TME does not sell the 23% UL version, and it has to be ordered from Toroidy in Poland directly. I have not done that, but several folks here, including @zintolo, had pleasant experiences dealing with Toroidy directly and acquired the 23% UL version at small extra cost (much less than I expected, but I don’t remember the details). I know Toroidy charges more for shipping (than TME), so you better inquire if you decided to go this route.
Your bias transformer (Hammond 166F50) seems to provide 25-0-25VAC. If so, you could simply leave the CT unconnected, if you are using the Rev 1.6 9-pin PCB (schematic dated Nov 19, 2018) where the bias-2 connector is grounded to the circuit ground. I don’t recall that you mentioned which PCB you are using. Your selected transformer is probably over-kill if you plan to use EL84 power tubes. A much smaller 0-30 Vac transformer will suffice, such as: https://www.mouser.com/datasheet/2/410/FD4_36-781155.pdf
Good luck.
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The bias required for EL84 tubes typically up to ~16 Vdc. In the Baby Huey circuit (implemented in Rev 1.6) you need an “envelope“ of twice that and allow for losses, so it is good to supply 3x the required bias voltage. 36 Vac supply will yield about 48Vdc and is about as low as you want to go. I thought the 166F50 Hammond over-kill based on current capability, because the bias supply needs <50 ma. Perhaps dBel84 (others?) has experience to add.
I have the Antek 230Vac power transformer but in 200 VA version, due to only a small difference in price with the 100VA. I tell myself I get less sag in B+ under load. I wish Antek had a 240Vac transformer.
I have the Antek 230Vac power transformer but in 200 VA version, due to only a small difference in price with the 100VA. I tell myself I get less sag in B+ under load. I wish Antek had a 240Vac transformer.
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Hi,
I use generally around 3x the bias for the powerdrive, and +30V for AB1 just to stay away from the area where Ciss raises.
Something more on both negative and positive rails if I'm into AB2.
To do so I play with LTSpice and PSUD2 to determine the resistors for the PowerDrive and phase splitter.
I do not care about the ripple of the negative rail as there are three CCS with cascoded BJTs connected to it, so noise rejection is really good.
On the positive side the need of less voltage helps to keep the ripple lower (noise rejection here is worse) because there's need of an higher value dropping resistor.
I use generally around 3x the bias for the powerdrive, and +30V for AB1 just to stay away from the area where Ciss raises.
Something more on both negative and positive rails if I'm into AB2.
To do so I play with LTSpice and PSUD2 to determine the resistors for the PowerDrive and phase splitter.
I do not care about the ripple of the negative rail as there are three CCS with cascoded BJTs connected to it, so noise rejection is really good.
On the positive side the need of less voltage helps to keep the ripple lower (noise rejection here is worse) because there's need of an higher value dropping resistor.