HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

Stupidly just checked board photo again and seen what looks likes LM317 I think. So try again - is it worth replacing these with a better spec reg ?

There are no regulators on NVA amp boards or in NVA power amps for that matter.

Great thanks for that. My understanding of electronic circuitry is pretty much nil as I have just proven. The boards in my TSS are identical but driven by 4 x 500va transformers ( unfortunately all in one seriously heavy box ). I understand the A100's are just a split TSS minus the bling with easier to manage boxes.

NVA power amps must be pretty unique in the hifi world by not using any regs.

Actually most amps don't have regulators. Naim regulated the Nap 250 and 135's. Avondale regulate the front end only on some of their amps leaving the driver and output stage unregulated. Some other manufacturers regulate front ends too but i cant remember what they are.

Output stages generally (on amps i am familiar with) have good psrr (power supply rejection ratio) and so don't really need regulating. In fact they sound much more dynamic without. The front end of the amp is a different matter. I have messed about with regulators and capacitance multipliers for front ends . I even have some on my nva boards at present.

29mile wrote: ↑Tue Jul 16, 2019 6:22 pm
NVA power amps must be pretty unique in the hifi world by not using any regs.

They are definitely unique. No output inductor and parallel damping resistor, no output zobel, no input coupling cap, input stage designed for passive preamps.

Rather than use regulators and filters Richard thought they were the devils work(messes with phase) and instead preferred to give as stiff a power supply as possible. As most designers were throwing more and more electric components and filters in to the mix, Richard was removing them. Cheaper to have fewer components but also better in the right situation.

Yes I stumbled across Richard's interview on the NVA website again and he had not changed his views since !

https://www.nvahifi.co.uk/richard-dunn-interview

karatestu wrote: ↑Tue Jul 16, 2019 6:57 pm

29mile wrote: ↑Tue Jul 16, 2019 6:22 pm
NVA power amps must be pretty unique in the hifi world by not using any regs.

They are definitely unique. No output inductor and parallel damping resistor, no output zobel, no input coupling cap, input stage designed for passive preamps.

Rather than use regulators and filters Richard thought they were the devils work(messes with phase) and instead preferred to give as stiff a power supply as possible. As most designers were throwing more and more electric components and filters in to the mix, Richard was removing them. Cheaper to have fewer components but also better in the right situation.

S.B.O. as we said as students (Spot Bollock On)

Have just put the A60 clone and “modified-for-3-inputs” P20 back in the system. I hadn’t heard it in the system since I modified the Fane speaker grilles for a more neutral sound.

The A60 clone is good with the ‘engineered grille’ Fanes; wonderful in fact. So unlike a lot of transistor amps, this one works spot on with well engineered single driver speakers. The bloody thing has gone and upended everything again. BAH!

Although my Fanes are 100dB/W efficient, it’s interesting how the A60 clone pairs with them. Suffice it to say that the dynamics are positively frightening! There is less ‘space’ than with the OTL but this is more than made up for by the sense of scale and drama the clone produces, with big classical works in particular.

When the Fanes had the uptilted frequency response, the clone (even the kosher A20 for that matter) was, at times too much; it was like going back to an ‘eighties flat earth system. However, now the FR of the speakers has been sorted, the clone is singing nicely, and when the going gets complex and powerful, you are no longer pinned to the wall cringing, à la the Linn/Naim of old.

Whilst the OTL is undoubtedly possessed with a heavenly sonic beauty, the like of which you only get with OTLs, 1W will only get you so far, even with 100dB speakers. The OTL really needs high efficiency 16 Ohm drivers to give of its best. So...for now the OTL is retired until I can build something with a bit more power. That means a push-pull valve amp with output transformers and multiple power supplies, producing at least 15Wpc. I have a few ideas, but I’m in no rush.

But it will no longer be an OTL Steve.