Background:
I have started working on this tube pre-amp project, and things are going well:
See schematics below.
…however, I have hit a barrier with the AC trafos.
The PSU needs two inputs:
If I measure the transformers (unloaded 230V input) the first one reads 11.6VAC and the second one 29.5VAC. The first one is OK as it is within the 9-12 range, but the second one is too high.
I have read that transformers will give a higher output until a load comes on, but I doubt that 60 mA will get it under 24VAC. Also I have just returned from my local electronics store with a 21VAC, but this one reads 32.2VAC??! (unloaded). This is a jungle for me :-/
Question:
So the question is; how can I calculate or figure out which transformer to get if they all have a higher output than their specs – or said in another way, how much can I expect the voltage to drop under load? Or can you actually get ones which will not have a higher output than what’s written on them?
Help!
PSU:

Pre-amp:

I have started working on this tube pre-amp project, and things are going well:
See schematics below.
…however, I have hit a barrier with the AC trafos.
The PSU needs two inputs:
- 9 - 12 VAC – for this I have bought this trafo.
- 21 – 24 VAC – for this I have bought this trafo.
If I measure the transformers (unloaded 230V input) the first one reads 11.6VAC and the second one 29.5VAC. The first one is OK as it is within the 9-12 range, but the second one is too high.
I have read that transformers will give a higher output until a load comes on, but I doubt that 60 mA will get it under 24VAC. Also I have just returned from my local electronics store with a 21VAC, but this one reads 32.2VAC??! (unloaded). This is a jungle for me :-/
Question:
So the question is; how can I calculate or figure out which transformer to get if they all have a higher output than their specs – or said in another way, how much can I expect the voltage to drop under load? Or can you actually get ones which will not have a higher output than what’s written on them?
Help!
PSU:

Pre-amp:
