Heavy Watter parallel triode output stage question

[frequencycentral]

I'm exploring different amp topologies and came across the Heavy Watter, which has two parallel triodes forming the output stage. Whats with that then? In what way does it differ from using just one triode as an output stage? I'm hoping the answer is more power.

http://www.prowessamplifiers.com/schematics/misc/ThunderTweak_HeavyWatter-Thunder_Tweak_Heavy_Watter.html

[slacker]

I used parallel output triodes for my Rascal low voltage amp. In that it increased the volume noticeably compared to just using one triode in the normal Class A way.

[frequencycentral]

I used parallel output triodes for my Rascal low voltage amp. In that it increased the volume noticeably compared to just using one triode in the normal Class A way.

Hi Ian - so you did. I knew I had seen it somewhere before. I'll give it a go. Thanks! You should try MAX1044 for your plates! It's fun - I'm now thinking of using different (lower) voltages from the MAX for each preamp stage to keep it clean.

[slacker]

Yeah a MAX1044 is something I keep meaning to try, but haven't got round to it yet. I want to try doing a push pull output stage as well at some point.

The parallel output stage with the Fender reverb transformer should hopefully work well, because that's how Fender drive it in their amps.

[frequencycentral]

Yeah a MAX1044 is something I keep meaning to try, but haven't got round to it yet. I want to try doing a push pull output stage as well at some point.

The parallel output stage with the Fender reverb transformer should hopefully work well, because that's how Fender drive it in their amps.

Yeah - I still can't quite believe the MAX does work - but it does. I'll try the parallel output stage tomorrow. It also occured to me that maybe two cascaded parallel stages might make for a killer overdrive/boost pedal.

[frequencycentral]

Actually I'm hearing hardly any difference - if at all. Very very very subtle - I was expecting more. Hmm - do I need to change the ohmage of the speaker from 8ohm? FYI I'm using 6111 tubes at 60 volts from the MAX.

[slacker]

Not really sure. Thinking about it the reason it worked well for me might have been because the transformer I used had a low resistance on the primary side so one tube couldn't drive it very well, but a pair could. As you've actually got a proper valve output tube perhaps there's no advantage to be had with a pair.

[frequencycentral]

Could it be anything to do with the MAX do you think? Maybe two tubes in parallel are starving for juice from the puny ma the MAX gives? I'm going to try feeding the preamp stages with lower voltage taps from the PS to se if that makes any difference.

Also, it obviously worked for the Heavy Watter! The schematic I linked to says:

- fender reverb transformer
- 25K @ 4 ohm load / 3.5 watts
- #125A20B & #022921 Models

.....which is the same OT I have (22921), which I am given to understand is 25K:8.

[sean k]

If you double the tubes then you wanna halve the resistance on the valve side of the tranformer and you can either put a 8ohm speaker on the 16ohm load or a 4ohm speaker on the 8ohm load.

[sean k]

Just to clarify. so what you've got with a 4 ohm speaker on the 8ohm load of the 25k/8ohm transformer turns the output transformer into a 12.5k/4ohms transformer.