changing transformer on an A400

[metako]

Hi,
I am new to the forum and while I am mostly satisfied with the performance of my Pioneer A400 driving my KEF transmission lines one area I would like to improve is the bass where the amp lacks a bit of grip or drive. My idea is to replace the laminated transformer with a torroidal type as in my limited experience amps with torroidals seem to control the bass better (damping?). Does this idea have legs or am I on the wrong track? Which other components have a larger bearing on the bass control? If I do replace the transformer for a torroidal will any other components need to be replaced with it and should I replace it with one of similar spec/size or go bigger? Thanks for your replies.

[richie00boy]

I would try with another amp before you go spending money spoiling yours for possibly no benefit.

It may be the speakers themselves or their location that is the root of the problem, or maybe they are a complex load that your amp simply can't drive very well due to (preset) current limits or topology.

[metako]

some time ago I tried my speakers with a Creek amp and though the mids and highs were messy and no match for the Pioneer, the bass was terrific, powerful and authoritative which leads me to believe the amp is the limiting factor rather than the speakers.

[richie00boy]

Due to the harmonic content of music the mid and treble performance can be greatly influenced by the bass performance.

If you want to have a play then, choose a toroidal that is rated at the same or higher VA then the existing EI. Try also fitting higher capacitance PSU reservoir caps as well, but not at the expense of relocating them as the increased wire lengths will undo any good.

Beware that the amp topology itself can have a lot of influence on the sound and it may simply be that is the sonic signature that you are stuck with.

[BobEllis]

you might want to try adding capacitance to the power supply before replacing the transformer. It's probably cheaper and easier to do.

[anatech]

Pioneers do sound a bit thin on the bass. Changing the transformer is the wrong direction entirely. Try out a Luxman, Marantz or a few other well made older sets. Then there are amplifiers you can construct yourself. The info is on this board.

-Chris

[metako]

Thanks for the replies. I will probably try replacing the reservoir caps first. Sounds like there is not agreement that fitting a torroidal will improve the bass. Can anyone recommend a brand of capacitor other than Black Gates or are these the best?

[AKSA]

Metako,

Transformers have minimal sonic signature, and what they do have shows up only at high power output. You are better off to upgrade the power diodes and particularly the filter caps. This is where the sonic differences are profound.

Cheers,

Hugh

[metako]

Thanks Hugh. Should the diodes be replaced by similar spec ones only more modern designs such as the Schottky, or different spec? Sorry but I know very little about amp design/workings (but handy with a soldering iron). Also any recommendations for brand/size of capacitor?

[AKSA]

Metako,

The good diodes are indeed Schottkys and/or Ultrafast soft recovery, and good caps are just about universal these days, I use United Chemi-con with good results. Some, such as the Nichicon Muse (KG) series, are specially designed for audio, but they are hard to find in Oz. What size are they? I might be able to help you.....

The best diodes, I should add, are the very latest Silicon Carbides from CREE and others, which have zero recovery time. tns plays havoc with noise, which obscures detail in the amp. The disadvantage of the very fast diodes is fragility; exceed the PIV or current rating and they actually explode....

Cheers,

Hugh