Super T amp on 12V batt

[Sarchi]

Well, last weekend I pulled a 12V AC Delco car battery I had sitting in the garage, and connected it to my Super T. These are my impressions:

- the noise floor dropped, noticeable immediately. I use fairly sensitive speakers- Omega 3's, and I had a bit of a buzz (at 60Hz I believe), well apparently it was from the stock Super T's PS! On battery power - it's gone. Nothing but very faint static at high volume, a bit more static with my phono preamp turned on,
but still faint. (Bugle phono is running on 2x12V SLA's)
- the bass sounds tighter, and deeper. Actually the whole fr seems a bit 'smoother'. What I heard, I initially liked
- overall, after a week, I'm not 100% sure about the change. It definitely sounds better superficially, but I haven't done any back to back tests. But there seems to be a slight 'artificial' quality to the sound now- something inherent to the chip, but it seems to be more pronounced. I think the AC supply may sound a bit more organic.

Thoughts?

[Sarchi]

First chance I have I'm gonna do a three part A/B test:
Tone delicacy: Miles Davis (All Blues) on Mosaic
Balance/coherence: Mahler 4 (1st mvmt) on EMI/Testament
Power: Pink Floyd (Time) from DSOTM, early UK Harvest pressing

I might be able to do them today, but I need an empty house for #3.

[Pano]

The power supply that comes with the Super-T is pretty quiet, I'm surprised you got any noise at all, especially 60Hz. There is decent filtering after the supply, on the Super-T board. It is an L-C filter that should kill about all the 60kHz noise from the PSU switching. Of course, It will also kill a lot of noise from a battery too!

Let us know how your tests go. Be honest with us and with yourself, take your time. The differences may not be where you expect them to be.

Meanwhile you can have a look at the S/N graph of the stock PSU. PSU graph

[Sarchi]

I waited 'til my Rega upgrades were in, so I'd have a better front end source to do the comparisons.

So I've done the back to back tests as I'd planned, and they were interesting - but my sub (the woofer) fried out a few days after I started the PS experiments. Overall the sound wasn't staggeringly different, and for me there was more to like about the sound quality on battery.

One thing for sure: my sub moved more air with the 12V battery, at least if rattling doorknobs on DSOTM are any indication.

Right now in my setup I prefer the battery. And I haven't gone back to the smps for any real length of time. Main reasons:
- lower noise floor, as I mentioned above
- deeper bass with more impact
- cleaner sound overall, without drawbacks that I can perceive

[johnthedoctor]

Is it worth adding caps close to the 12v input?

Going to be trying out a car battery soon and was wondering what value caps to try.

[Puffin]

I have found it worth adding caps close to the 12v input. I have a stiffener cap on board and I have added a further 6,800uf cap and 0.01by-pass cap off board, after the power supply and just before it goes to the board. seems to open things up a bit and make the bass tighter. I did this originally as I had made a battery power supply and wanted to help it along as much as possible. However I still think the 3A 13.8 regulated supply gives the best results. I find the battery makes it sound a bit synthetic.

[Puffin]

Mmm, may have changed my mind. I have given the battery a longer listen and I think it may reveal more low-level detail. Can anyone give an opinion of switch-mode power supplies and how the S.I performs as against a battery/normal power supply.

[Sarchi]

I don't know about the UK, but over here the Super T comes with a cheap/generic smps, so my comparisons were with that.