18Watt.com

Hi all
Having built and continually tweaking my 18 watt builds, I am thinking about building a 36 watter.
Apart from more volume, are there any other benefits - more headroom, punch ( expense ) ?
Also, I am in the UK and Ampmaker did have a kit but they have downsized. Primary Windings, who were making their transformers may be able to help I expect.
Tube Town in Germany sell some but not sure If anyone has good or bad things to say about them.
Hammond may have some too and they did have a distributor here in the UK.
As always, look forward to any feedback and advice.
Jim

Hi..
I'm from Belgium and I purchase a lot from Tube-Town. I actually have a 36W tremolo TMB which contains the Inmadout transformers Tube-Town sells as their house brand.
The 36w is not punchier, just more headroom. I like the 18W better.. but that's my opinion. The 36W is still a great amp
When those EL34 start roaring...wow!

For me the difference is what tubes I get to play with. EL34 are my favorites, so that's why I build 36/40 versions.

Thanks,
Josh

Bieworm wrote: ↑

Fri 02/04/22 1:18 pm

Hi..
I'm from Belgium

We all have our personal problems but don't worry, you're among friends

zaphod_phil wrote: ↑

Wed 02/09/22 10:27 pm

Bieworm wrote: ↑

Fri 02/04/22 1:18 pm

Hi..
I'm from Belgium

We all have our personal problems but don't worry, you're among friends

Thanks for the kind words ZP! I know I'm well surrounded

I have similar issues here in Australia the easiest and cheapest transformers to buy here are Hammond transformers as they have either local distribution, or free shipping from the likes of Mouser or Digikey.
The Hammond set is for the Vox AC30 rather than the 36 watt I have only just started looking into it but it seems like they will work. The Vox/Hammond 1750T output transformer has 4,000 primary ohms 8,16 output Push-Pull 30 watts
The Hammond power transformer specs are 30watts 550VCT @ 230mA 5VCT @ 3A 6.3VCT@6A​
Which is 30 volts lower on the Heyboer HTS-7042 bumped up to 290-0-290
Will this make much of a difference

If you go solid state rectifier you will keep some more B+ voltage. Maybe it’s enough?

What determines the wattage of an output transformer?
The Vox AC 30 output transformer and the tubetown 36 watt transformers both have the same primary impedance of 4000 Ohm / CT
Does this mean that I could substitute the Vox output transformer for the 36 watt one or are there other factors here?
Shipping costs on one power transformer would definitely be cheaper than importing both.

Also Given that an AC 30 Power transformer puts out 550VCT whilst the Tube Town 36 Watt is 600 CT and the Heyboer is 290VCT
And an AC 30 PT drives el84 tubes just fine even at a lower voltage, would there be a problem using the AC 30 power transformer for a 36 watt build?
I know there probably would have to be some component value changes.
Am I way off here ? I have yet to compare schematics to see how different the 2 amps actually are and I am only just learning this aspect of amp building.

Tim,

The AC 30 Power transformer puts out 550VCT = 275/0/275;
the Tube Town 36 Watt is 600VCT = 300/0/300;
the Heyboer is 580VCT = 290/0/290.

These are all very similar and all should work in a 4xEL84 build
("36 Watt" and "30 Watt").

Also, the Output transformers for these, with 4k primary to 4/8/16 secondary, should also be interchangeable.

Best,

Craig

OK I have got just about everything I need to start melting some solder {or sodder as the Americans call it} on my 36 watt build.
I will be using a Hammond 290MAX Power transformer and a 1750TB output transformer
I know the best way to locate the best position for the output transformer is with headphones and moving it around until you find the position with the least hum.
But I do not want to build then pull apart my build to mount the output transformer, so apart from orientating the laminations at 90 degrees to each other, and giving some space between the 2 transformers, is there anything else that I should consider?
Looking at an AC30 I noticed that the Transformers are actually oriented the same as each other just at the extreme ends of the amp.
Apart from placing them, so the cabinet/head is balanced to pick up, is the only other thing that I can think of

Tim

Hi to All
I'm a new in this community and i'm happy to have found you!!

I'm building 36Watt tmb but i want to be sure to do thins right. I have an Hammond 1750V as output transformer that have 30Watt as output power. This Transformer is good for this amp or could I have problems since the output power is 36Watt?

No harm in using that transformer. You’re only getting a bit less output, that ‘s all. The 1750V is a replacement for an AC30, which is still a loud amp.
What’s bad for OT’s is:
- speaker load out of spec/severe impedance mismatch
- playing full throttle all the time way too long
- bad tubes
- too hot bias

Thanks so much Bieworm
considering that I will never use the amp at maximum power I can consider myself out of danger