Two PT in parallel

[GERPUD]

In the case that we want more power, instead of changing the PT for a bigger one, would it be feasible of adding a second in parallel?
Exemple, if we have a 100W PT, and we need 150W, adding a 75W PT in parallel to the 100W should give 150W (75W load on each PT).
Anyone has done it?
It's a lot cheaper to do...
In the exemple, does adding a 50W PT next to the 100W PT would give 150W?
(In all cases, I assume that the phases are correctly connected of course).

To be even more specific in my question:
I have an amp that I want to increase the PT power. The PT has only two red wires 190-0-190. I can't find the specs. The power input in the back of the amp says 80W. I'd like to get 100-120W. The only PT I can find with 190-0-190 is Hammond 339EX that is 45W. Is adding this PT in parallel would work?

Thanks!

[JMFahey]

It's next to impossible to parallel two voltage sources , which is wat a transformer is, so the short answer is no, don't even dream of doing it.

That said, there is only one case where it can be done (and is not yours): when you have 2 exact same transformers, say 2 Hammond ones bought together and obviously same model, you can trust that they have the exact same number of turns, etc. and the parallelling is safe because they won't fight each other.

Any other case, even a slight difference will be seen as a shorted turn, overheating and burning them.

In your case , even if both are Hammond and both nominally 190+190 ,they are different types and for practical reasons maybe one is 189.7V where the other is 191.2V ... no problem in building an amp but a big one if they are parallel.

[GERPUD]

Thank!

[Phil_S]

What is it that you really want to do? Are you thinking that you can increase output from 80W to 120W? I'm thinking the 80W label isn't the amplifier's power rating. Remember, the power consumption rating includes filament supply. If you have a rectifier 2A @ 5V and a typical 3 preamp 2 power tube amp that's maybe 3 or 5A @ 6.3V. So, your amp is using maybe 30-40W just to power the heaters. Your amp might be anywhere from 20W to 50W and I'm guessing with a 380V secondary, it is at the lower end of that.

Are you trying to make it louder? I assume we are discussing a tube amp. If so, there are a number of considerations. Let's guess you have a 20W amp. Twice as loud will require 200W (and that will be really, really loud.) The simple truth is that the difference between a 50W amp and a 100W amp (for example a pair of EL34 vs a quad of EL34) is only about 10% volume-wise.

To translate transformer power into amplifier power requires more than just changing the transformer (or as you supposed, adding another in parallel.) And, I'd agree, adding a second PT isn't the way to do this.

[Zippy]

The power input in the back of the amp says 80W. I'd like to get 100-120W.

The power INPUT labeling is NOT an accurate indication of output power.

What is the amp?

+1 to "Don't parallel power transformers."

[GERPUD]

Thanks for the advice. It is now clear enough that 2 PT is a bad idea.

I have a Fender Ramparte (2x12AX7+1x6L6GC SE).
What I'm trying to do: Having fun in modifying some elements to make it more unique and learning tube amp design at the same time.

I had help in an other post to fit a KT66, because I like the sound. Now, I'd like to fit maybe a KT88 to make it a bit louder (maybe 12-15W instead of 10W). This way I could play with a drum. (louder than that I don't find it "enjoyable" anyway). I'd like to put a switch to fit a 6V6 for home use (~5W).

The problem is that I can't find the PT specs. When I compare the dimensions of the PT with Hammonds PT, it shouldn't be able to push 80W, but it's doing it (I've measure it).

So I found 263CX which is 180-0-180 instead of 190-0-190. Would it work without changing every amp components?

Thanks for your replies!

[ToneMerc]

Thanks for the advice. It is now clear enough that 2 PT is a bad idea.

I have a Fender Ramparte (2x12AX7+1x6L6GC SE).
What I'm trying to do: Having fun in modifying some elements to make it more unique and learning tube amp design at the same time.

I had help in an other post to fit a KT66, because I like the sound. Now, I'd like to fit maybe a KT88 to make it a bit louder (maybe 12-15W instead of 10W). This way I could play with a drum. (louder than that I don't find it "enjoyable" anyway). I'd like to put a switch to fit a 6V6 for home use (~5W).

The problem is that I can't find the PT specs. When I compare the dimensions of the PT with Hammonds PT, it shouldn't be able to push 80W, but it's doing it (I've measure it).

So I found 263CX which is 180-0-180 instead of 190-0-190. Would it work without changing every amp components?

Thanks for your replies!

You have to look at amp design in it's entirely; you cannot just install a larger wattage tube and expect an 100% increase in audio power out when you are using the same tiny 5W output transformer.

TM

[GERPUD]

I'll change the OT as well.
It's not a big deal.

[M Fowler]

Why don't you start with larger OT first and experiment from there.

If your current PT can't handle the filament voltage required for the KT88 power tube then bolt in a new filament transformer.

[GERPUD]

Ok, I'll change the OT first, but like I said, from the size of the PT, it shouldn't work.
If it doesn't, is a PT 180-0-180 will work as a replacement for a 190-0-190? If it's not, I wont try the KT88 because I won't have any solution to power it.

[matt h]

(deleted)

[GERPUD]

Thanks again Matt H for your wises advises!
I'm definitely going to try more speakers, but I'll take a serious look at the badcat unleash.I didn't know it was existing. I've put a 120W speaker in that amp so that would be a good solution!

But I'm sad because now I need to find something else to modify!

I'll get back to you when I'll get a new idea!

[M Fowler]

BadCat unleash is currently being redesigned and new units have not been released or at least that is what I was told. I'm waiting for my unit to ship.

[matt h]

(deleted)

[JMFahey]

Thanks again
But I'm sad because now I need to find something else to modify!

Why don't you go all the way and plain build one amp ?

The "ultimate Mod" : going from a bag o' parts to a working amp!!!!

For the first one, get a kit, mainly because sourcing parts all over the place is tedious .

You will learn, of course you will enjoy it, and Modding something you know so well is easier.

Rather than a single ended amp, which is a "stiff" design, very hard to Mod for higher power; build a push pull one.

Something with 2xEL84 is fine, even better something with 2 x 6V6 because being octal sockets, they will also take 6L6, EL34, KT66, KT88, etc.
Just what you were trying to do

Only precaution is to order , just from the beginning, a power transformer with filamet windings hefty enough to feed the largest tubes, plus any preamp tubes you fancy to add later on.

You can also use a beefy separate filament transformer.

Best of both worlds.