EL34 Baby Huey Amplifier

[bandol83]

Hello EL34 Baby Huey builders,

As suggested by SCD in the following thread : EL84 Amp - Baby Huey I am starting a new thread specially dedicated to the building of Baby Huey amplifier based on my PCB which has been produced in more than 330 pieces and is still requested by many tube amplifier fans in a possible future Group Buy 4 : GB for Baby Huey PCB

I will put in this thread all the information available about the assembly of the EL34 Baby Huey amplifier and some of the auxiliary board that I have used or designed to add some features to the amplifier. I must tell you that I am not in professional amplifier business, this is just a time consuming hobby for me and, as you will see, English is not my first language and I have sometimes difficulties to explain things correctly, sorry for that but at least you will understand easily schematics, pictures, B.O.M., etc...

History

All that started about two years ago when I read the EL84 Amp - Baby Huey post from "gingertube" ! As I was interested by the shunt feedback concept that I didn't know I wanted to test it and decided to build the simplest version with two PCL86 tubes. Since I am very bad in point to point wiring, I made a small PCB. This amplifier was so good that I decided to continue my quest and, since the ECL86 or PCL86 were unfortunately no more produced, I made a second PCB for the EL84 version which needed a third tube, a 12AX7 (ECC83) for the input stage and added MOSFET with current source to drive the output tubes. This amplifier was very good and I was very satisfied by the MOSFET driver stage, but I was also a little bit frustrated by the limitation in power, about 12 W, and the fact that I could not use different power tubes...

To solve this problem, I made an identical version but with octal socket to accept many compatible tubes from the 6V6 to the KT88 and the EL34 Baby Huey was born ! Following the presentation of this solution on the diyaudio forum some members asked me if I could sell the PCB, I had never done this before but since the moderator move this discussion to the Group Buy forum I have received several request and started a GB1 with a target of 50 boards but finally closed it with 80 PCB ordered I had to send them Worldwide and to learn how to make PayPal invoice... Later others readers asked me for more board and I offered a second and "last" GB2 which finished with 120 boards ordered !!!

Later, since there was still a strong demand, I asked Prasi, to whom I have bought a CRC power supply PCB, if he would accept to manage a third GB and he kindly accepted He also suggested to make 2.4 mm boards for better rigidity. Now 120 more boards have been ordered and are in production and there is already 20 PCB's in waiting list for a possible GB4 ?

Documentation

In this first post I will enclose some of the latest documents available for building the EL34 Baby Huey and I will add more in next posts depending of your questions.

You will find the updated BOM in the GB letter, the latest schematics, some building recommendations, how to connect and to adjust the amplifier and several pictures showing the PCB assembled on top side (big components go on bottom side), a 6CA7 board fully assembled in test and finally the EL34 Baby Huey in its enclosure nearly finished (two vu-meters are still missing).

More pictures and data will come from all the people who have built this nice small amplifier. It is a very nice project for those who have never made and listen a tube amplifier, but remember there is some lethal high voltage (up to 500 V) and you should be very careful when you work on it

Have a nice time building the EL34 Baby Huey...

Best regards,
Marc

[prasi]

Hello Marc,
Its very nice of you to have started this thread. I am sure it will help lot of builders with ideas for their own build.
It is indeed a very premium looking chassis. I think you should produce more of these, many would like to own such a case for this amplifier.

regards
Prasi

[huggygood]

to see for the future.
I already have a lot of work in progress and I put myself on the waiting list for the baby huey that I intend to assemble in 6v6 gt

[Vunce]

Thanks Marc for starting a dedicated thread for the EL34 Baby Huey. I am eagerly awaiting to start this project, unfortunately I have to wait several weeks for my output transformers to arrive
We all appreciate your time put into the BH project!

Also worth noting, we are in good hands with Prasi

[bandol83]

Hi Prasi,

The chassis is made in China and was bought to a French distributor : Boitier DIY 100% Aluminium angles arrondis 380x320x90mm Noir - Audiophonics and the top panel was made by FPE...

Hi huggygood,

The 6V6 work very well with this PCB, see picture

Hi Vunce,

Thanks for your support... Which transformers are you waiting for ?

Marc

[Vunce]

Originally Posted by bandol83

Hi Vunce,

Thanks for your support... Which transformers are you waiting for ?

Marc

Marc,

I ordered a pair of Edcor OT’s, they are made to order so I must wait.

EDCOR - CXPP60-4.2K

Regards,
Vunce

[bekim]

Hi Marc,

That’s great chassis for amp you build.
I want to ask you about white letters and numbers you are using on the chassis.
Can you provide info on where you bought them and, how to search for?


Thanks a lot,
bekim

[meanie]

Subscribed

[bandol83]

Hi Bekim,

These white letters are not white in fact, it is the silver color of the aluminium after the black anodizing has been removed during the panel manufacturing !

This panel is made by Front Panel Express ( Schaeffer AG: Home in Europe), they are quite expensive, about 130 € for the top panel but the quality is superb as you can see on the pictures...

The tough jog is to make the panel drawing on their CAD software, but to help you I can supply my version, of course it should be adapted to your chassis and transformer but all the holes for the EL34 Baby Huey will be done

Best regards,
Marc

[prasi]

Hello Marc,
Wow! , the back side is as good as the front Can you share the schema of input selector? I think you have it somewhere here, but cant remember, sorry.
regards
Prasi