a bit more bass?

[yosh]

hello

I have just finished my first scratch built amp,it sound great but i have a question.I hear people say that tubes just ar not good for making bass.is this true or is it that most tubes just don't put out the needed wattage to move big driver.
a little more bass would be better.
I guess my first question is ,what is the problem?(or is this just my amp)
followed by,
what do most people do to correct it?
Oh,what i am listening to is basicaly a 2a3 design that used to be posted on angelas site(nothing fancy),driving a set of fostex 206e back loaded horns.
thank you,
yosh

[bobhayes]

I think that tubes are very capable of producing plenty of bass. In your case the two main reasons why they can sound a bit weak here are the losses in the output transformer (eddy currents, hysteresis loss and air gap inefficiency in SE designs.) and tube rectification of the HT.
The HT voltage drops significantly as a large (bass) signal is reproduced, due to the voltage loss over the choke becoming a more significant proportion of the circuit resistance.
Diode rectification and big smoothing caps should improve the bass output, but that won't reduce the OPT factor. These are my impressions.

[yosh]

a good answer,i will play with that as a start.
does anyone ever run self powered sub(i heard mention but never asked)?

[yosh]

could i feed some kind of small ss amp,sub box with my 2a3? i like classical music,but the big kettle drums are weak.in searching threads i have noticed this option for home theater.i am afraid i know so little that a starting point is beyond me.

[astouffer]

Losses from the power supply only happen with amps running class AB or B. Class A draws the same amount of current no matter what. As far as more bass goes I built a simple tone control using a 12B4A as a line stage. However after doing some reading I discovered tone control is best used in the feedback loop of a gain stage.

A good group design would be a dual triode with enough feedback so the gain is around 1. Most peoples' sources seem to have enough drive voltage anyhow.

[Wodgy]

Yosh, many people use powered subwoofers with tube amps. It's a nice combination. You can either feed the subwoofer from your preamp or from the output of your 2A3 amp in parallel with your speakers. Some subwoofers also have a high pass feature; you feed the output of your 2A3 amp to the sub then connect the high pass from the sub to your speakers. This last approach tends not to appeal to purists.

[martinab2]

If you are brave enough, and can be bothered with all the additional hassle.. Mercury rectifiers have a low and fairly constant voltage drop so should be ideal for improving bass output. An 83 might do nicely in your application but if you are unfamiliar with these things you should search the forum first (safety issues, they need pre-heating etc)

[mcs]

What output transformer do you use?

If you use one of the small Hammonds, you shouldn't expect great bass. I think the lower cutoff is specified as 50Hz?

To get good bass with an SE amp, you will need a BIG output transformer. The tube rectifier is not a big problem, as the current doesn't change as much as in a class B amp. The current is not always the same in a class A amp BTW - if the current didn't change there would be no output...

Best regards,

Mikkel C. Simonsen

[Yvesm]

Hi

What output transformer do you use?

I've build 6BQ5, 6V6 and 6B4 SE amps and never noticed lack of basses.

All used DIY trannies about 1Kg weight and measured within the dB down to 25Hz.

May be looked as a rule of thumb for a 3 watter

Yves.

[mcs]

I have no bass problems either with my amp. The transformer is from a TV - you can see it here (on the left): http://stiftsbogtrykkeriet.dk/~mcs/2A3/2A3-amp-new.jpg

But some people want a very solid, precise bass - I like the more soft bass you get from a not big enough transformer and no feedback...

Best regards,

Mikkel C. Simonsen