Hey Francois,
I’m using one per mono, and they are supplying enough current, i can’t remember how I worked out the current requirements, I’ll have to go through my notes, I grabbed a whole lot of info which may have the bias current, but In that configuration they were sufficient.
I was just up in Sabi, damn hot, plenty of game and big sky though, not Warmbaths, but close enough to remind you of home.
I’m using one per mono, and they are supplying enough current, i can’t remember how I worked out the current requirements, I’ll have to go through my notes, I grabbed a whole lot of info which may have the bias current, but In that configuration they were sufficient.
I was just up in Sabi, damn hot, plenty of game and big sky though, not Warmbaths, but close enough to remind you of home.
Power tranny for BH EL84 in North America
With the PCBs on the way I wonder what other builders in North America consider getting/using for a power transformer for the EL84 Baby Huey. I will probably look for something manufactured/sourced in U.S or Canada.
On the Edcor website I spotted one that looks promissing at ~$94 to serve two channels. Specs are 120 ac to 500V (250-0-250) at 400mA center tapped, 60V at 50mA and 6.3V at 7A. See:
EDCOR - XPWR078
What do you experts think? Any other better candidates?
With the PCBs on the way I wonder what other builders in North America consider getting/using for a power transformer for the EL84 Baby Huey. I will probably look for something manufactured/sourced in U.S or Canada.
On the Edcor website I spotted one that looks promissing at ~$94 to serve two channels. Specs are 120 ac to 500V (250-0-250) at 400mA center tapped, 60V at 50mA and 6.3V at 7A. See:
EDCOR - XPWR078
What do you experts think? Any other better candidates?
Hi potepuh,
This is the voltmeter used to monitor the bias : YB5135D 3 1/2 DC Voltage Meter Three Wires LCD Digital Voltmeter 12V 0 2V/20V/100V/200V/300V/500V ICL7106 3.5 Volt Panel Meter dans Voltmetres de Outils sur AliExpress.com | Alibaba Group
I selected the 2V version, 400 mV indicate a bias of 40 mA, and used the 6.3 V DC to power it but I had to connect the heater GND to the GND test point since the ground is common
The following one can be also used, it has the advantage of separate power supply and input lines :
YB5135D LCD Numerique Voltmetre DC 200mV/2 v/20 v/200 v/500 v DC Tension voltmetre Panel Meter Moniteur de Tension Voltmetre Voltmetre dans Voltmetres de Outils sur AliExpress.com | Alibaba Group
Rgds,
Marc
This is the voltmeter used to monitor the bias : YB5135D 3 1/2 DC Voltage Meter Three Wires LCD Digital Voltmeter 12V 0 2V/20V/100V/200V/300V/500V ICL7106 3.5 Volt Panel Meter dans Voltmetres de Outils sur AliExpress.com | Alibaba Group
I selected the 2V version, 400 mV indicate a bias of 40 mA, and used the 6.3 V DC to power it but I had to connect the heater GND to the GND test point since the ground is common
The following one can be also used, it has the advantage of separate power supply and input lines :
YB5135D LCD Numerique Voltmetre DC 200mV/2 v/20 v/200 v/500 v DC Tension voltmetre Panel Meter Moniteur de Tension Voltmetre Voltmetre dans Voltmetres de Outils sur AliExpress.com | Alibaba Group
Rgds,
Marc
Hi Francois,
Your transformer will be OK only if you are using an external full wave rectifier, see posts 156, 158 & 164...
In my opinion, 250 V AC is a maximum for the EL84, I have been using it but you must be careful with the bias not to exceed the power limit of the tube ! An other inexpensive solution is to use a standard 115 V / 230 V transformer like this one : VPS230-570 Triad Magnetics | Mouser France available from stock easily
Of course, in this case you will need a small 48 V AC 10 W transformer for the bias and driver supply and a heater power supply which can be a switch mode ones like this one Bloc de Chauffage 6,3 V / 10 A Regule pour Ampli a Tubes AL0007 : RADIOELEC : Composants et Modules Electroniques, specialiste Audiophiles et Radioamateurs !
Rgds,
Marc
Your transformer will be OK only if you are using an external full wave rectifier, see posts 156, 158 & 164...
In my opinion, 250 V AC is a maximum for the EL84, I have been using it but you must be careful with the bias not to exceed the power limit of the tube ! An other inexpensive solution is to use a standard 115 V / 230 V transformer like this one : VPS230-570 Triad Magnetics | Mouser France available from stock easily
Of course, in this case you will need a small 48 V AC 10 W transformer for the bias and driver supply and a heater power supply which can be a switch mode ones like this one Bloc de Chauffage 6,3 V / 10 A Regule pour Ampli a Tubes AL0007 : RADIOELEC : Composants et Modules Electroniques, specialiste Audiophiles et Radioamateurs !
Rgds,
Marc
In my opinion, 250 V AC is a maximum for the EL84, I have been using it but you must be careful with the bias not to exceed the power limit of the tube ! An other inexpensive solution is to use a standard 115 V / 230 V transformer like this one : VPS230-570 Triad Magnetics | Mouser France available from stock easily
Thanks for the Triad VPS230-570 pointer. That is a very inexpensive B+ solution. In the U.S. Mouser lists it for only only US$27.29. Would one provide sufficient current for two BH boards? It would appear so.
Could we discuss the ideal value of B+? I also would like other BH builder’s input on a “sweet spot” voltage for the EL84.
I see that Dynaco SCA35, which burned their EL84s near max values specified a B+ of 380 VDC, which translated to 370 VDC on the plate of the EL84. Since it uses automatic bias of 14 VDC it means 356VDC across the EL84.
Marc, do you feel 350+ VDC is too high for the sweet spot for EL84s? Your recommended 230 VAC source probably only provides 320 VDC, whereas the maximum of 250 VAC you mentioned should provide around 350VDC, using silicon rectifiers.
Good question. I also would like to know how much AF swing the PCB topology/implementation can provide at acceptable distortion levels. Marc or anyone else?
I have not built one yet, but based on previously reported experience, we heard that relatively low-HV EL34s (under 500V) are driven addequately by the BH board. Since the 6L6 family of tubes are less sensitive it is still an open question if 7581s could be used. (Tyman, why 7581s, out of curiosity).
Has anyone actually tested the performance of this BH incarnation? Simulated it?
I have not built one yet, but based on previously reported experience, we heard that relatively low-HV EL34s (under 500V) are driven addequately by the BH board. Since the 6L6 family of tubes are less sensitive it is still an open question if 7581s could be used. (Tyman, why 7581s, out of curiosity).
Has anyone actually tested the performance of this BH incarnation? Simulated it?
Sorry if I didn't answer before but I have been quite busy these days
Regarding the max voltage for the EL84 Baby Huey, I think you should not exceed 350 V, this is what I had on my old prototype which used a 250 V AC custom transformer ( see photos ) ! After that you have to be careful with the bias and use a value that will not generate a power dissipation higher than the maximum power dissipation indicated in the specification of the tube ( https://www.jj-electronic.com/images/stories/product/power_tubes/pdf/el84.pdf and http://www.tubeampdoctor.com/images/File/TAD-Datasheet_EL84-STR Version1.3-08.07.11.pdf ) which is about 12 W
With 300 V, max 40 mA (12 W), but with 350 V I will not use more than 35 mA (12.25 W)... You can also use 6P14P the Russian equivalent or Sovtek EL84M which is specified up to 500 V
The 7581A is an equivalent of the 6L6 and can be used with the EL34 Baby Huey PCB since it is an octal tube
For information I have tested the EL34 version with 6V6, EL34, 6CA7 (my actual version) and KT88 (see photos)...
If you want to know more about Baby Huey amplifier, you can also read the very interesting thread from "gingertube" : EL84 Amp - Baby Huey it is only 234 pages long
Rgds,
Marc
Regarding the max voltage for the EL84 Baby Huey, I think you should not exceed 350 V, this is what I had on my old prototype which used a 250 V AC custom transformer ( see photos ) ! After that you have to be careful with the bias and use a value that will not generate a power dissipation higher than the maximum power dissipation indicated in the specification of the tube ( https://www.jj-electronic.com/images/stories/product/power_tubes/pdf/el84.pdf and http://www.tubeampdoctor.com/images/File/TAD-Datasheet_EL84-STR Version1.3-08.07.11.pdf ) which is about 12 W
With 300 V, max 40 mA (12 W), but with 350 V I will not use more than 35 mA (12.25 W)... You can also use 6P14P the Russian equivalent or Sovtek EL84M which is specified up to 500 V
The 7581A is an equivalent of the 6L6 and can be used with the EL34 Baby Huey PCB since it is an octal tube
For information I have tested the EL34 version with 6V6, EL34, 6CA7 (my actual version) and KT88 (see photos)...
If you want to know more about Baby Huey amplifier, you can also read the very interesting thread from "gingertube" : EL84 Amp - Baby Huey it is only 234 pages long
Rgds,
Marc
Attachments
Hi Francois,
It is not 150 stereo set which have been sold but 250 since October 2017, this include 200 EL34 sets and 50 EL84 sets without taking in account tenths of prototypes
You can look here : EL84 Amp - Baby Huey post 1831 !
Marc
It is not 150 stereo set which have been sold but 250 since October 2017, this include 200 EL34 sets and 50 EL84 sets without taking in account tenths of prototypes
You can look here : EL84 Amp - Baby Huey post 1831 !
Marc
if you like the ray brown trio,try all the cd's of Gene HarrisHello,
The baby, equipped here in 6CA7, is really a wonderful music machine.
It was a great project to do.
Thank you
Thanks for that tip. Another one with RB is The Very Tall Band - a CD where Ray plays with Oscar Peterson and Vibe player Milt Jackson. They have all passed away for years now but their art lives on in some great recordings.