OT for 183 build

[Oddvar R]

Hi. I was wondering what would be essential to a OT for a OD 183 build, that is, what to look for and if anyone could advise on the best value for money/sound?

[martin manning]

Where are you located? Local availability will be a large factor in cost since transformers are heavy.

[Oddvar R]

I am in Norway. I am aware that shipping is costly, but I bought the other transformers in the build from Digi-Keys, and the shipping was free. So I am thinking of getting the best OT, sound-wise and and value. There might not always be that expensive is better. On the layout it says Marshall Plexi 1700 ohms. There are some of those replacements, but there are also others that can run 4 EL34's. I was wondering what would be essential in this build?

[martin manning]

1k7 is typical for a 100W Plexi running 4 EL34’s. There are several options in EU for such things. Marcus has had good results using Fender spec transformers from InMadOut in Italy, They were reasonably priced, and I’m sure they can do Matshall types too. The German tube amp suppliers (TubeTown e.g.) will have them but I don’t know who is making them or if they get good reviews. Maybe some of the EU members can comment further.

[Oddvar R]

Is the 1700 ohm crucial or are there other alternatives?

[martin manning]

It goes with the output tube type, how many of them you are using, and the anode voltage. If you are building a 50W version with two EL34 output tubes and the typical 450V B+, you would want a 50W OT, which will be around 3400 (2x 1700) ohms. Like this: https://www.tube-town.net/ttstore/Trans ... 4skl7fgap5

[norburybrook]

I have had great service from Savino @InMadOut transformers, he will build you anything you want but keeps stock of the 'regular' Fender/Marshall/Vox transformers/chokes etc.

I've also used Hammond transformers too and they've been fine. They have doubled in price nearly though over the last 5 years due to the exchange rate I imagine......don't get me started on BREXIT.....


M

[Oddvar R]

I am thinking about this one from Mercury Magnetics, but the ohming isn't mentioned:
"Marshall | 100 Watt | Output Transformer
Optimized for 6L6 / KT88 / 6550 tubes — 1.5″ stack. Uses Grain-Oriented Iron"

[martin manning]

If it’s for a 100W, it’s ~1700. If you have to have Mercury, they make a 50W version that would be the right impedance for two output tubes. Don’t get me started on them not providing specs on their products. Some kind of marketing BS.

[Oddvar R]

I am building a 100watter.

[ChopSauce]

Rumour is some TT-labelled transformers are made by inMADout, for what it's worth ...

[Synchu]

It’s not a rumor

I’m happier with Savino's transformers than with Hammonds. Mains are spot on the specs and the OTs sound Very nice.

Niki

[norburybrook]

It’s not a rumor

I’m happier with Savino's transformers than with Hammonds. Mains are spot on the specs and the OTs sound Very nice.

Niki

Niki,

I couldn't agree more the first transformers I got from Savino I thought were broken as there was Zero noise coming from then when I powered up......Zero in a studio with a -80db noise floor!!!

I've been using them ever since unless I use vintage iron.



M

[ChopSauce]

Thanks for the confirmation!

[rogb]

My no. 1 choice is Classictone but the cost of shipping and taxes puts me off now, and I have spent a LOT on those transformers for various builds.
My 50w JCM800 2204 uses Classictone and sounds... like a Marshall Runs really cool too.

Hammond has always been good and I have used a few sets with great results. My first D-style used them and AFAIK was gigged hard with zero problems for years. My 35w Tweedle Dee uses Hammonds and sounds fine. That circuit runs HOT too! I don't think the price is that bad for 1750U + 290HX at £160 + VAT from Bluebell Audio minus 10% at the moment.

I have used MM in an AB763 and although they sounded good, the high price plus shipping from the USA made it a one time only experiment.

I think Marcus's choice of InMadOut has been proved to be a good one. Apart from the off the shelf pieces, you can get a custom wind too! Plus they sound great! Not sure of the prices.
Good luck with your final decision.