Single Ended vs Push Pull

[charlyg]

Is there a place online, where I can hear the difference between a single ended amp and a push pull one? I am building a 5e3 (push pull) and also own a BH-112(single ended). There is a mod available to make the BH 13 watts by adding a 2nd output tube in parallel. If I then did the mod to the BH and finish my 5e3, I would have the same basic parts, including high end transformers, except one would be single ended parallel and the other push pull. I hear they would sound completely different.......

Any experts around?

[sharkboy]

Not an expert. I have some general ideas.

Push-pull involves an additional splitter circuit. The design of which will determine in a large way the way the amp will sound. Every splitter circuit (phase inverter) is a little different, which is part of how a Vox sounds so much different from a Marshall or a Fender p-p amp. A P-P amp may have less even harmonics (this isn't absolute- this would only happen in the strange occurrence of an actual balance between the two sides. It may have a slightly "tighter" sound. Some fanatics will call it "meatier", "ballsier", etc., than a single-ended.

The most common splitter is the long tailed pair and all of the major makers use it, but do so very differently. You can use a transformer to divide the signal, or you can use a divider network on the output tubes, making them "self-split". There are also other means of using one or two tube sections to do the division of the signal, which have different characteristics.

Hanging out on ax84.com, I get to hear a lot of clips of single-ended and push-pull amps. I've had both. While I'm sure that the same amp with two different outputs would certainly sound different under the same settings, I'm not entirely convinced that you can't get them pretty close sounding if you mess around with them. Some people have done recordings with little amps having a 12au7 (normally used in preamps) as a 2W triode wired as a "self-split" push-pull amp that sound like enormous power amps driven by large pentodes.

I'm sorry I'm not more help, but my current view is close to the Count Basie rule: "if it sounds good, it is good." And I'll keep messing around with my circuits until they meet the first criterion.

[charlyg]

Thanks for the info. I 'll check out that site. I'm sure there aren't too many audiences that say, "If only he would have used a pushpull"!!

[sir_andrew_of_left_coast]

Is there a place online, where I can hear the difference between a single ended amp and a push pull one?

This site has sound samples of their single-ended, parallel single-ended, and push-pull amps... combined with 6SL7, EF86, and 12ax7 preamp tubes and different tone stacks, too. All sorts of permutations.


http://www.electrosonicamplifiers.com/

Click "Standards" after putting your cursor over "Amplifiers."

[scott_s]

The Fender Champ is a good example of a single-ended amplifier. They clip asymmetrically, so you end up with a lot of second-order harmonics in the tone. The Count Basie rule definitely applies here.

- Scott