HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

Ithilstone wrote: ↑Tue Jun 30, 2020 12:50 pm
Next would be 2 transformers - one for input and another for output stages (as A60+) or one per channel (as A70). Different compromises that roughly balance each other.

.....

Currently we use only 25V, and with the A80 we use 150VA for both input and output.

Hannes-Gregor wrote: ↑Tue Jun 30, 2020 1:54 pm

Ithilstone wrote: ↑Tue Jun 30, 2020 12:50 pm
Next would be 2 transformers - one for input and another for output stages (as A60+) or one per channel (as A70). Different compromises that roughly balance each other.

.....

Currently we use only 25V, and with the A80 we use 150VA for both input and output.

So no need to reconfigure the AP70. Do you only use 25V at the moment for sonic reasons or because the reduced heat compared to 30V?

savvypaul wrote: ↑Tue Jun 30, 2020 2:26 pm
We now use 25v to give a little extra headroom to the boards. The boards were originally designed to see 230v from the mains. In the UK most people are now seeing an average of 240 plus.

29mile wrote: ↑Tue Jun 30, 2020 3:39 pm

savvypaul wrote: ↑Tue Jun 30, 2020 2:26 pm
We now use 25v to give a little extra headroom to the boards. The boards were originally designed to see 230v from the mains. In the UK most people are now seeing an average of 240 plus.

Good point. My PSU on my mains ( c 238v ) with 30v transformers gives a 46vDC offset a bit close to 50vDC. But I use an old Purepower mains regenerator set at 230v in my system giving me a bit more headroom.

savvypaul wrote: ↑Tue Jun 30, 2020 2:26 pm

Hannes-Gregor wrote: ↑Tue Jun 30, 2020 1:54 pm

Ithilstone wrote: ↑Tue Jun 30, 2020 12:50 pm
Next would be 2 transformers - one for input and another for output stages (as A60+) or one per channel (as A70). Different compromises that roughly balance each other.

.....

Currently we use only 25V, and with the A80 we use 150VA for both input and output.

So no need to reconfigure the AP70. Do you only use 25V at the moment for sonic reasons or because the reduced heat compared to 30V?

No. The configuration of the AP70 is the best for that particular design - integrated in a wide case, with the transformers that Richard used at the time. With the new Toroidy transformers you could do either, if you were starting from scratch.

We now use 25v to give a little extra headroom to the boards. The boards were originally designed to see 230v from the mains. In the UK most people are now seeing an average of 240 plus.

Hannes-Gregor wrote: ↑Tue Jun 30, 2020 6:26 pm
Thank you, but what is the reason for the agility of the ap20 compared to ap70? I always thought it was the difference in the voltage.

Ithilstone wrote: ↑Tue Jun 30, 2020 6:50 pm

Hannes-Gregor wrote: ↑Tue Jun 30, 2020 6:26 pm
Thank you, but what is the reason for the agility of the ap20 compared to ap70? I always thought it was the difference in the voltage.

Hannes there can be many reasons but first did you compare them side by side everything else equal?

So just couple ideas
Different volume pot
Different era boards old vs new
Difference in power supply (brand of transformer or caps)

Also it could be simple as your ap20 running out of puff driving your speaker = less low end and body so top end is more pronounced speakers sound slightly brighter and you perceive it as more lively also tweeters will always be faster than bass drivers so when you hear less of low end it sounds faster.

Or it might be something completely different

Daniel Quinn wrote: ↑Tue Jun 30, 2020 1:13 pm Phono 1 as a 30v transformer.

Daniel Quinn wrote: ↑Tue Jun 30, 2020 1:13 pm Phono 1 as a 30v transformer.