Question about power transformer current.

[psychepool]

Everytime I make a diy amp, my essential goal is make it as tiny and loud as possible.

Recently, I made a 6v6 pair head amp based on Fender Deluxe Reverb.
Everything is good but the output(exactly, clean headroom) is a little dissatisfied.
So I planed to make It more louder.

Currently, It has two 6v6 and four 12ax7
and Hammond 1760H for OT
http://www.hammondmfg.com/pdf/EDB1760H.pdf
and Hammond 1750A for Reverb Driver
http://www.hammondmfg.com/pdf/EDB1750A.pdf
and Hammond 194A for choke.
http://www.hammondmfg.com/pdf/EDB194A.pdf

I want to change it with
Hammond 1760J for OT
http://www.hammondmfg.com/pdf/EDB1760J.pdf
and two 5881 for output tube.

But the PT has not enough current to deal with it.
When I install 5881 tubes and rebias, there's huge voltage drop.
so I want to order new PT.
The problem occurs from here.

I can't install the larger sized PT because of my head cabinet inner space.
MY amp chassis and trarsformers are fit very tightly in my cabinet.

I want to ask the size of new PT to local electronic shop but before than I must know about the current that I needed.
But I make diy amps just for hobby. I have no knowledge about electronics. So I don't know about way to check the current need for my plan.

Can you tell me the PT secondary current for my plan?(12ax7 x 4 / 5881 x 2 / Hammond 1750J / Hammond 1750A)
I just need main B+ and heater for my PT secondary taps. No other taps are needed.


Thanks.

[bluesfendermanblues]

In order to achieve your initial goal - tiny size and loud - maybe you should look for speaker(s) with higher effiency instead of changing tubes and iron. The cost would be the same or less.

A neo magnet speaker over an alnico would be way louder.

[tubeswell]

For a quick'n;dirty rule of thumb

Each 12AX7 draws 300mA on the heater winding (when operated at 6.3VAC) and about 2mA on the HT winding (summed for both triodes on average)

Each 6V6 draws 450mA on the heater winding and between 18mA and 40mA on the HT winding at idle*, depending on the voltage and class of operation

Each 5881 draws 900mA on the heater winding and between 35 and 60mA on the HT winding depending on the voltage you're running them at at idle* and the class of operation.

*The average HT current draw increases somewhat under signal conditions. If you design for a total current draw that's slightly above the higher end of all the summed draw of all the tubes on each winding, you should be fine.

[psychepool]

In order to achieve your initial goal - tiny size and high power - maybe you should look for speaker(s) with higher effiency instead of changing tubes and iron. The cost would be the same or less.

A neo magnet speaker over an alnico would be way louder.

Thanks for advise.
But I have no personal sound room. Everytime I meet different speaker cabinet!

Of course, in my house, It is loud enough to break my room but sometimes I feel dissatisfied about my output when I go to band practice room.

Frankly, the power of my 20W OT with 6v6 is not bad. But I want more stability power.
Because I set the amp tone clean for use my pedalboard.

[psychepool]

For a quick'n;dirty rule of thumb

Each 12AX7 draws 300mA on the heater winding (when operated at 6.3VAC) and about 2mA on the HT winding (summed for both triodes on average)

Each 6V6 draws 450mA on the heater winding and between 18mA and 40mA on the HT winding at idle*, depending on the voltage and class of operation

Each 5881 draws 900mA on the heater winding and between 35 and 60mA on the HT winding depending on the voltage you're running them at at idle* and the class of operation.

*The average HT current draw increases somewhat under signal conditions. If you design for a total current draw that's slightly above the higher end of all the summed draw of all the tubes on each winding, you should be fine.

Thanks for easy answer. This type of advise is very good for the not majored in electronic persons, like me!

With note your information, I summarize the PT spces that I need.

Main B+ : 325V-0v-325V 250mA
Heater : 3.15V-0V-3.15V(6.3v-0V) 3A


I think it's almost minimum spec.
Give me advise if it seems too tight or not enought.

[tubeswell]

With note your information, I summarize the PT spces that I need.

Main B+ : 325V-0v-325V 250mA
Heater : 3.15V-0V-3.15V(6.3v-0V) 3A
.

200mA on the HT would be okay

going to 4A (or more) heater current is ok too. It doesn't hurt to have a bit more capacity than you need in the heater winding department. (and I forgot to factor in an additional 150-300mA for a 6V lamp in my last post)

[Roe]

do you use a tube rectifier?

[psychepool]

200mA on the HT would be okay

going to 4A (or more) heater current is ok too. It doesn't hour to have a bit more capacity than you need in the heater winding department. (and I forgot to factor in an additional 150-300mA for a 6V lamp in my last post)

Thanks! I will supply the power of the indicator lamp from main power socket to economize the trans power current. (use 220vac bulb)

I also note the Hammond JTM30 or Hot rod deluxe replacement.

JTM30 : Hammond 290QX
325-0-325 270mA
6.3V 3.1A

Hot rod deluxe Hammond 290UEX
319V @ 120mA
308.5V @ 250mA
6.6V 3.75A

They has 12ax7 x 3 and 6L6/5881 x3 and 30~40W output.
It's simmlar with my amp except one more 12ax7 and reverb transformer.

And then would it be alright to sets heater current 3.5A?

[JMFahey]

One small detail: you say you have no space available for a larger transformer.
The custom built transformer will also be quite larger than the one you have now , winders don´t do magic, they have to design it following what materials can do or not, copper is still copper, iron is iron.

[dorrisant]

A toroidal PT may work... What about Antek? Are they available where you are located? It may have a wider footprint but the height is usually lower if clearance within the hardshell is an issue.

[R.G.]

Because I set the amp tone clean for use my pedalboard.

Then I have a really good deal for you.

Since you're getting your tone from your pedalboard and want your amp clean, don't use tubes at all. Go for a solid state amp, even a Class D switching amp. You can get a 200-700 watt solid state Class D amp in a box small enough to sit beside your pedalboard or even screw it onto the pedalboard. It will be clean and LOUD as well as much smaller than a tube amp anywhere close to the same power.

You're fighting a losing game by deciding the physical size, then trying to stuff everything into it. Even if you get everything into the box, it will be so crammed that it will probably have overheating issues or self-oscillation from wire routing feedback.

[psychepool]

One small detail: you say you have no space available for a larger transformer.
The custom built transformer will also be quite larger than the one you have now , winders don¢¥t do magic, they have to design it following what materials can do or not, copper is still copper, iron is iron.

Frankly, I'm skeptical of it's possibility too. But I think it's not bad to experience about the limit of transformer size.

A toroidal PT may work... What about Antek? Are they available where you are located? It may have a wider footprint but the height is usually lower if clearance within the hardshell is an issue.

Unfortunatly, I don't know the shop that make toroidal PT in my country. Is there any good shop that offers international shipping?
Transformers are the heavy product so the shipping cost always make trouble to me.

Then I have a really good deal for you.

Since you're getting your tone from your pedalboard and want your amp clean, don't use tubes at all. Go for a solid state amp, even a Class D switching amp. You can get a 200-700 watt solid state Class D amp in a box small enough to sit beside your pedalboard or even screw it onto the pedalboard. It will be clean and LOUD as well as much smaller than a tube amp anywhere close to the same power.

You're fighting a losing game by deciding the physical size, then trying to stuff everything into it. Even if you get everything into the box, it will be so crammed that it will probably have overheating issues or self-oscillation from wire routing feedback.

Thanks for your suggestion.

I know it's not a clever choice too, but it's just a hobby to me.
It looks like a stupid thing, but I feel funny about to do this work.
And I'm not use clean tone only. clean+pedalboard is just one option. I also use break up+boost/overdrive, crunch+fuzz and many other option.

If I use SS poweramp, I would waste the time to find out the preamp that taste good for me and my pedalboard.
I feel good with the characters of my diy amp. and want to expand the function of it.
Too loud output is not a matter because I have attenuator, but if the output is not loud, there's no way to get over it.

[JMFahey]

Unfortunatly, I don't know the shop that make toroidal PT in my country.

Where are you?

Is there any good shop that offers international shipping?

Where are you?

Transformers are the heavy product so the shipping cost always make trouble to me.

Where are you?

Ha ha, hope my message got through

ALWAYS say where you are from, suggestions depend heavily on that.

[psychepool]

Where are you?

I live in Korea.(South!)

There's many shop that make transformers for the audio amp but no professional shop for guitar tube amp in my country.
But I think the power transformer has no difference between audio amp and guitar amp.

The reason that I use Hammond for OT and etc is the shipping cost.
Mouser Digikey offers free international shipping if I order over about 60$ and they deals Hammond transformers.

[JMFahey]

If it´s a PT any of those suppliers can design and build what you need, all they need is each winding voltage and current.

If any, *maybe* they won´t want to design and make "just one" or they´ll charge too much.