• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

EL34 Baby Huey Amplifier

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Hi

While waiting for the MKII Boards of the Baby Huey, I looked a bit around concerning output transformers and wanted to share my findings by supplying a list of manufacturers (rather Europe based) for torodial and classical output transformers.
...
Best regards
Christoph
You can add Welcome to MONOLITH MAGNETICS | MONOLITH MAGNETICS to the list. I haven't bought from they yet and am not affiliated. They just seems to be quite serious stuff.
 
Irons

Hi Ev
Thanks for the Menno Van der Veen Site. Did not know it!
Regards
Christoph

It is appreciated that you share what we have in the European market, it seems to be for all qualities, tastes and pockets :scratch:

These "Menno Van der Veen" and other toroids, will it be true that Toroidy has reached the quality of all toroids, even improved some?

Another prestigious one that seems to keep improving
Audio transformatoren

Best Regards
Fernan
 
You can add Welcome to MONOLITH MAGNETICS | MONOLITH MAGNETICS to the list. I haven't bought from they yet and am not affiliated. They just seems to be quite serious stuff.

I personally know one of the guys behind the company as he is a professor at an institute where I worked and still have certain ties to. Cool guy and certainly knows what he is doing. Personally didn't use his transformers because well... money. But I know Thomas Mayer has used them

Side note on the list of transformers: I have some indel/toroidy transformers and it hurts to spend 50% of the value on a metal box to put over them.
 
Side note on the list of transformers: I have some indel/toroidy transformers and it hurts to spend 50% of the value on a metal box to put over them.

I think the same, the two toroidy games I bought them clean, the finish I will see how to do it for little money,
........ with cans of asparagus and some paint? :D

..... and add the plastic base, for the passage of cables ........,
are things that are beyond my budget.

I respect who can, they are really pretty!
 
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Would it make sense to take the driver supply after the regulator? Or is it better to have the driver supply sag with the B+? Would 12Vdc be enough for the driver supply?

My question (two posts) up had not elicited a reply yet, but it got me thinking and searching.

Autobiasing output tubes (6L6)? post #12 argues that it is better NOT to regulate the bias supply if the B+ is not regulated. The author says if the bias supply is regulated then the B+ should also be regulated.

Just wondering how this applies to the regulated bias supply and unregulated B+ of our BH EL34 . Discussion of these questions would be appreciated.
 
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Ian,
Thanks for straightening me out on the capacitance multiplier; I did not look closely enough and somehow assumed the active component regulates supply voltage.

Now I’m puzzling over why we are multiplying the capacitance of a 2uF capacitor? Am I missing something?
 
No - It just improves filtering (reduces -ve supply ripple) without the need for huge caps.

Note also that the Mosfet source followers which drive the output tube grids have current source loads. Those current sources have huge AC impedance and the source followers have very small AC impedance looking into the source pin. These form a voltage divider for any residual -ve supply noise/ripple and that will be divided down to next nothing anyway.
So maybe an "overkill" but we don't mind "overkill" when it comes to power supply noise elimination.

Cheers,
Ian
 
If you want to use a choke you can take this one : 158T Hammond Manufacturing | Mouser France

With 300 mA max, you can run the EL34 output tubes at 400 V and 50 mA safely ( https://www.jj-electronic.com/images/stories/product/power_tubes/pdf/el34_e34l.pdf )

I have started the BOM for the Power Supply, it is not finished yet but you can have a look at it. The high voltage capacitors are for less than 450 V version, if you want to use the 330 VAC output of the power transformer (330 x 1.4 = 462 V - 2 V = 460 V !) it is a little bit marginal and I suggest to use 500 V version even if the capacity will be lower to keep the same size, I will give suggestion later...

Rgds,
Marc
 

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  • Baby Huey MK2 Power Supply BOM.pdf
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Marc,
Thank you for the PS and the BOM!

I checked the relay specified for the Mk 2 PS and it seems that it is specified to switch 125VDC max. I’m not sure how tightly the specs of relays are to be adhered to. Will this work in our application?
 
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Hi Francois,

You are right this relay is specified at 125 VDC and 250 VAC therefor it could not be used before the rectifier either and if we use it on the primary it will be OK but we will need a separate power supply for the heaters :cuss:

I am using it without problem in this power supply, may be because the two used contact are bypassed by the 10k resistor ?

If you want to be safe you have two solution :

1) replace the 10k resistor by a jumper and do not use the power on delay :eek:
2) replace the relay by a bigger one that will support the DC voltage at the power on :firefite:

Here is an updated BOM with more references :)

Rgds
Marc
 

Attachments

  • Baby Huey MK2 Power Supply BOM.pdf
    970.6 KB · Views: 215
Dear Marc

The delays use 250VAC speec relays, I don't think it's a problem possibly due to the amperage and the switched on peak includes charging the electrolytics,

if it's a bit short If this relay of the BOM is not enough, the solutions are simple (such as adapting a socket with another relay ....... small master relay with slave plus power... a small mod .... )

Thanks for all your work and patience
Regards
Fernan

P.S. revised other delays circuit, they use relays 2x10A ...1x 40A ... for a large block of capacitors PSU, I have not had problems with 2x10A
 
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Would it make sense to take the driver supply after the regulator? Or is it better to have the driver supply sag with the B+? Would 12Vdc be enough for the driver supply?

I am still trying to understand the answer(s) to this question. As gingertube confirmed, it seems better to let the power tube negative bias float with the supply voltage. But what does that mean for the +supply to the Mosfet drivers. Sorry that I don’t have the analytical knowledge to figure this out.

Also tried to find Bas Horneman’s wiki on Baby Huey, but could not find that either. Is it still somewhere?
 
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Is this thread old and tired? Over the wall?

I am still trying to understand the answer(s) to this question. As gingertube confirmed, it seems better to let the power tube negative bias float with the supply voltage. But what does that mean for the +supply to the Mosfet drivers. Sorry that I don’t have the analytical knowledge to figure this out.

Also tried to find Bas Horneman’s wiki on Baby Huey, but could not find that either. Is it still somewhere?

I have politely asked the same primary question three times and did not receive any response. Could someone reply please. To reiterate the question- does it make sense to take the +supply for the drivers AFTER the regulator? In stead of letting the regulator serve the 12v supply for the defunct relay only.
 
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