EL34 Baby Huey Amplifier

[ckwong99]

Hi BandoI83, do u think where the BH EL34 parts need to be changed ? When my UL output transformer is 5K impedence and all DC supply voltage will follow the original design requirement.

 

[bandol83]

Hi ckwong99,

I don't think you need to change part value with your 5k TANGO output transformer, I have build my EL34 Baby Huey with a 4.3k Hammond 1650N output transformer and a TOROIDY TSTA 250/001 power transformer (using the 275 VAC output) with the recommended values without any problem

I know also that some builders have used the TOROIDY EL34PP (6.6k) and the KT88PP (4k) output transformers and the actual BOM with good results too...

Marc

 

[ckwong99]

Good news for me Thx Sir

 

[calipilot227]

Hey guys,


Apologies if this has been asked before, but I would like to build the Baby Huey to accept the KT88 tubes. If I use the Hammond 1650N, will I need to change anything else in the circuit, or will it work with both the EL34 and KT88?

 

[bandol83]

It work with both when using Hammond 1650N, see pictures

Marc

 

[jcastellano]

Some photos

Hi,

Here are some photos from the "old" pcb and the new one. The old is installed and working wonderfully.

I will follow-up with some more info when I install the new boards.

Regards,

Jorge

 

[Vunce]

Hi Jorge,

What’s the model number of Hammond chokes your using? You have a real nice premium build right there

 

[jcastellano]

Hammond Chokes

Hi Jorge,

What’s the model number of Hammond chokes your using? You have a real nice premium build right there

Hi...

The Hammond Chokes are model 159V. I installed them because in my experience, the resistor in the PSU is noisier than a choke. I did have some humming noise and after changing the resistors and also installing bigger caps in the PSU, the noise went away. I feel that (IMHO) the 400v caps are not suitable for a 275v AC secondary. Until the amp stabilizes, the PSU voltage goes higher than the rated 400v so, for a minute more or less, the caps are pushed real hard....

https://www.mouser.es/ProductDetail...2pyFadug0NW%2bxa%2b/D4gsNxOlk1YbjkgBu8ERAfhg=

Thanks for your kind words....

Regards,

Jorge

 

[Vunce]

Thanks for the recommendation Jorge.
I will also utilize a choke in the psu.

 

[ckwong99]

Hi Bondo. Do u think i can use AC 315V then the CRC ,the R replaced with the choke (200ma 6H DC 100 ohm) . i am not sure this final voltage ,still well in driving the main circuit ?

 

[883bkong]

Hi, Bando

For output transformer can I use Hammond 1650R instead of 1650N.

Thank You

 

[bandol83]

hi 883bkong & ckwong99,

Yes, you can use 1650R but it is a big 100 W transformer expensive and generally used with quad output tubes, not necessary in the EL34 Baby Huey !

With 315 VAC you MUST use 500 V electrolytic capacitors and 630 V film capacitors !!! And yes, you can put a self instead of the power resistor or even use an external DC power supply like Jorge

Marc (not Bondo or Bando )

 

[bandol83]

Hi Jorge,

I have seen that you are using the 10 A switching power supply for the 6.3 V, it is a much simpler solution than your first build, I hope you like it

You can use 400 VDC capacitors with 275 VAC secondary of the power transformer because without load the max DC voltage will be VDC = (275 x 1.4) - 2 V = 383 V In addition, in my amplifier I am using two CL60 NTC on the primary of the transformer to reduce the power up stress : Amphenol Advanced Sensors - CL-60 - Thermistor; ICL; NTC; Res 10 Ohms; Tol 25%; Radial; Disc; Cur-Rtg 5 A; Dia-Max 0.77 In - Allied Electronics & Automation ...

I am happy that you like this amplifier, I want to remind that the merit goes to Ian (gingertube) who started the EL84 Baby Huey thread, I have only designed PCB to make it easier to build for many semiconductors audio fans who are not using point to point wiring commonly found in tubes amplifier...

Cheers,
Marc

 

[Bfpca]

Just got a parcel from Poland for BH builds. 2 each of the el34 and EL84 PP output transformers and 2 120vct 30va transformers to use for bias voltage. I have the HV and filament power covered with EI transformers. The service from Toroidy was excellent, the transformers look well made and were double packaged for shipment. Now all I need is the boards which are on their way and the time to build. I may start with the EL84 version which means I don’t need the boards as I will build it on a tube amp perf board or point to point.

 

[ckwong99]

Thanks Marc :>

 

[jcastellano]

In theory yes...but

You can use 400 VDC capacitors with 275 VAC secondary of the power transformer because without load the max DC voltage will be VDC = (275 x 1.4) - 2 V = 383 V In addition, in my amplifier I am using two CL60 NTC on the primary of the transformer to reduce the power up stress : Amphenol Advanced Sensors - CL-60 - Thermistor; ICL; NTC; Res 10 Ohms; Tol 25%; Radial; Disc; Cur-Rtg 5 A; Dia-Max 0.77 In - Allied Electronics & Automation ...

I agree with you that with 275V AC should be ok 400V electrolytics but in my case, for the very beginning from starting up the amp, the dc volts reached more than 400volts, after a 30 secs wait more or less, the B+ stabilize at around 380 volts. So I installed the 500v caps. They were installed outboard because in the first time I ordered the same capacitance as per the 400v and they did not fit in the pcb. Now with the new board, I ordered the ones you stated as 509v but with less capacity and then smaller package that fit in the PCB.

Regarding the CL60, you installed one in series with each line in the ac input, one in the live line a another in the neutral one? Any photo?

Regards
Jorge

 

[bandol83]

Yes, one in series with each line in the ac input, one in the live line a another in the neutral one

I have redraw the wiring schema in better quality...

Regards,
Marc

 

[tomlang]

I'd like to solicit comments on running 7591A output tubes on this board. Obviously the pinout is different and certainly the board should drive these tubes if it can drive EL34's.

However, I want to use toroidy cathode feedback output transformers, in particular the TTG-CFB6600PP.

TTG-CFB6600PP - Tube output CFB transformer [6,6kOhm] Cathode Feedback Push-pull - Shop Toroidy.pl

Cathode feedback will require more drive, but the 7591A requires less drive. Time to experiment.

 

[Bfpca]

Interesting setup going with cathode feedback. Let us know what you find out about gain and drive levels etc. I just purchased conventional output transformers from toroidy. Very good company to deal with IME. I’m looking forward to getting busy on the BH build but I need to finish our kitchen reno first. Probably won’t get at it until the new year.

 

[potepuh]

I need a pre for my almost finished BH, which of this would be the best Aikido Line-Stage Amplifiers