EL34 Baby Huey
I was so happy with the two versions of the Baby Huey that I have built that I wanted to try a third version. I started to work on a quad EL84 with auto bias version but I have been busy with others activities and I put it on hold...
However when I read the previous post, I was thinking that a new version with octal output tube should be quite straightforward from the previous version. However instead of using a 6V6 I decided to use a EL34 to have more power !
I look at the EL34 Music Angel modifications from Ian and I use the front end stage of my previous EL84 version. For the output stage I am planning to use either an Hammond UL transformer or an Amplimo 3A524 non UL transformer.
I am not sure that the current source for the MOSFET is supplying enough current, may be I should reduce R33 and R38 ? Any recommendation ? If the schematic is OK, I will design a PCB
Cheers,
Marc
I was so happy with the two versions of the Baby Huey that I have built that I wanted to try a third version. I started to work on a quad EL84 with auto bias version but I have been busy with others activities and I put it on hold...
However when I read the previous post, I was thinking that a new version with octal output tube should be quite straightforward from the previous version. However instead of using a 6V6 I decided to use a EL34 to have more power !
I look at the EL34 Music Angel modifications from Ian and I use the front end stage of my previous EL84 version. For the output stage I am planning to use either an Hammond UL transformer or an Amplimo 3A524 non UL transformer.
I am not sure that the current source for the MOSFET is supplying enough current, may be I should reduce R33 and R38 ? Any recommendation ? If the schematic is OK, I will design a PCB
Cheers,
Marc
Please
Very nice the pcb, congratulations!
I could ask it with thanks the gerber data?
With thanks:
appme
Dear Rootz!Thanks Ian,
I hope you can help me with the next step. My dad requested a PCB design for this amp, so I made him one. He never worked with PTP and at his age learning that is too much of a challenge. Could you check the design with/for me?
Some resistors are on the tube socket side, mostly the ones that are hard to cool because there are tracks under the resistors. The ground return paths for the CCS's of the power tubes are a bit long, but do not cross low current ones from the ECC83 and its CCS. The CCS of the ECC83 gets its own transformer.
Etching will be done in the kitchen sink, hence everything is single sided. Clearances in B+ are 100mill, around the ECC83 is 50 mil, the rest is 32 mil.
There are some wire pads to get the B+ for the ECC83 from the plates or the screens of the power tubes.
Very nice the pcb, congratulations!
I could ask it with thanks the gerber data?
With thanks:
appme
I was so happy with the two versions of the Baby Huey that I have built that I wanted to try a third version. I started to work on a quad EL84 with auto bias version but I have been busy with others activities and I put it on hold...
However when I read the previous post, I was thinking that a new version with octal output tube should be quite straightforward from the previous version. However instead of using a 6V6 I decided to use a EL34 to have more power !
I look at the EL34 Music Angel modifications from Ian and I use the front end stage of my previous EL84 version. For the output stage I am planning to use either an Hammond UL transformer or an Amplimo 3A524 non UL transformer.
I am not sure that the current source for the MOSFET is supplying enough current, may be I should reduce R33 and R38 ? Any recommendation ? If the schematic is OK, I will design a PCB
Cheers,
Marc
Hi Marc.
The heater on the lower input tube seems to be missing...
Regards
Marc,
I don't see any errors in the EL34 BH schematic above.
Some component values may need to change.
The R7,R8,R9,R10 may be better at the 47K+220K values in which case the front end diffamp current would need to be reduced (R18).
For best balance you do not want teh 12AX7 triodes straying into significant grid current, so you need to keep anode voltage high (say 180 to 200V) and that means lowish current (say 700 - 800 uA per side).
Cheers,
Ian
I don't see any errors in the EL34 BH schematic above.
Some component values may need to change.
The R7,R8,R9,R10 may be better at the 47K+220K values in which case the front end diffamp current would need to be reduced (R18).
For best balance you do not want teh 12AX7 triodes straying into significant grid current, so you need to keep anode voltage high (say 180 to 200V) and that means lowish current (say 700 - 800 uA per side).
Cheers,
Ian
EL34 Baby Huey
Hi Ian,
Thank for your feedback.
For the input triode I have seen that you were using 2.5 mA on the Music Angel with the 6SL7, that's why I had a compromise value with about 1.2 mA for the 12AX7 ?
Hi Dieter,
I have never made a group buy, therefor I don't know if I can make one and if there should be enough interest for that ? May be I will be able to sell some spare PCB if the amplifier is good enough
Cheers,
Marc
Hi Ian,
Thank for your feedback.
For the input triode I have seen that you were using 2.5 mA on the Music Angel with the 6SL7, that's why I had a compromise value with about 1.2 mA for the 12AX7 ?
Hi Dieter,
I have never made a group buy, therefor I don't know if I can make one and if there should be enough interest for that ? May be I will be able to sell some spare PCB if the amplifier is good enough
Cheers,
Marc
Hi Rootz!
Baby Huey pcb very nice, congratulation!
Gerber data receive please...?
A little late, but I hope it still helps you. Please note that there are two jumpers to be placed and it offers two variations in that respect. Either you use the output plates to feed the preamp tube or you use the output screens to do that. Adjust the 47k resistors accordingly. Should land at about 15k when using the screens as voltage source for the pre tube.
Needless to say this amp works great. Good bass, but what really surprised me is the big forward (lower) midrange. Could be due to my speakers, but this thing sounds incredibly detailed. I used some older Telefunken power transformers I got off eBay for 40 Euros and some opt's I got at a shop in Holland for about the same money, so really cheap. Add to the package some Hammond chokes (10H 100mA) and the cost of the iron alone is just barely over 100 Euros. Around the same amount of money for the other parts. Stereo is doable for 200 Euros. I guess the fact that I made mono blocks contributes to the wide stereo and big space this amp gives. Compared it to a Menguye mini that I recently serviced and is in the same price range. It's not even close to the BH. Sounds rather lifeless, smeared and small in comparison. Both were tested trough rather low sensitivity (approx. 87dB/W) Scanspeak 3-way speakers. Driving the speakers with a 1V RMS music signal made a conversation in the same room pretty undoable. So much for my need of big power amps.
The amp is currently in my fathers house and he enjoys it everyday stating that everything, wether it's vinyl or digital, sounds better than ever before. A big thanks to Ian and other contributors for this design and the support!
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Hi!
I prepare soon diy transformers going out. Roger US Edcor Steel M6 and German (Waasner) laminated irons. I read much beautiful one Baby Huey and I will have more time, sets about sounding in this year for me.much thanks!
http://http://kepkuldes.com/images/f532aa6f461562b2881cbc160947102e.jpg
An externally hosted image should be here but it was not working when we last tested it.
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The link doesn't work. I'm curious: where did you get the Edcor transformers? I know just one supplier in Europe and they are much more expensive than in the US.
Thanks! Winding your own transformers, I wish I had the knowledge and equipment to do that! Looks great!
I was not able to put pictures up well...
Az US my friend brought the iron into Europe, on an airplane. The US there cheap, transport exorbitant. My friend brought it from a favour, 4 transformers will be from him. Ca. 10 cm2 his piece. I bought a reel body there since the measure is coll.
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May be I will be able to sell some spare PCB if the amplifier is good enough
Cheers,
Marc
Hello Marc, I'm on standby ;-)
PCL86 Baby Huey
Hi Nick,
The PCL86 Baby Huey that I have built last year is doing very well with UL output transformer and no global feedback, therefore the feedback input (without the filter components) can be use for a differential input...
The schematic is attached and you can find more information on threads 1670 & 1673 on pages 167 & 168.
Best regards,
Marc
Hi Nick,
The PCL86 Baby Huey that I have built last year is doing very well with UL output transformer and no global feedback, therefore the feedback input (without the filter components) can be use for a differential input...
The schematic is attached and you can find more information on threads 1670 & 1673 on pages 167 & 168.
Best regards,
Marc
Thanks Marc, that's perfect.
I was thinking of using these toroidal output transformers:
I was thinking of using these toroidal output transformers:
- Typenumber: VDV-8010-PPE
- Power rating : 10 Watt (20 Watt for f >= 66 Hz)
- Primary Raa : 8000Ω with UL-taps @ 33%
- Secondary : 0 - 4Ω - 8Ω - 16 . But would the 150ohm screen resistors values need changing for the 33% rather than 40% taps?