Flea-Powered SETs - Niiiiice!

[SteveTheShadow]

Now then,

To get a bit more DIY on the amplification side onto this forum, I thought I'd better introduce y'all to a nice little Single Ended amp.

This one is based on the National Union 46 dual grid power tube.
Strapped as triode, it puts out about 1 watt per channel. Now this might be seen as a laughably low power output, but with 100dB efficient open-baffles or horns there is sufficient welly to rattle the windows in a typical British living room.

It is a direct-coupled reactance drive amp based on Jack Elliano's and Jeremy Epstein's designs.

Here's a schematic:



The input/driver is a 12AT7 directly coupled to the grid of the 46.

Looking at the schematic, you can see that there are only four components in the signal path excluding the volume control and valves.
Amps dont get much simpler than this.
The reward for all this simplicity is a lovely musical sound, with gorgeous detail and that nice glow you get from valves.

Heres a pic of the amp itself:



Of course it won't work in the majority of systems, but if you are running efficient baffles or horns, it is a lovely experience.

Trouble is it might just usurp the bigger PX25 SET amp and kick it out of the system.

Steve

[SPS]

nice amp steve, i have a couple of 46's somewhere..

i gather it sounds well..

i really need more than watts though..my 2 watter is on the edge at some of the volumes i play..
the px25 takes some beating as a valve.. my amp sounds better than my 2p amp in my veiw.. when everything in the 2p amp should make it better .. except for the px25 valve

[SteveTheShadow]

nice amp steve, i have a couple of 46's somewhere..

i gather it sounds well..

i really need more than watts though..my 2 watter is on the edge at some of the volumes i play..
the px25 takes some beating as a valve.. my amp sounds better than my 2p amp in my veiw.. when everything in the 2p amp should make it better .. except for the px25 valve

Hi Steve

Your PX25s would probably sound better than the 46 amp, but then yours are proper ones, not like my TJ meshplates. Good though the TJs are, and as good as the ST shape PXs they may be, but they are certainly not up to the standard of your old globes.

Part of the reason I think the 46 amp is a success is that it meshes well with the active baffles. Also the baffles have the benefit of having a 100watt solid state plate amp built into them to drive the bass. Without that degree of support from the active baffles, the amp would probably struggle on peaks in a large room such as yours.

It does work very well though I'll have to bring the amp and baffles round some time.

Steve

[aquapiranha]

That sounds very interesting. I have a Decware Zen Select, which is just about 2 watts single ended, and it drives the Fostex's very well. I will however looking fo rsomething a little bigger for the 4 alphas I will be adding.

[Ali Tait]

Steve,what Fostexes do you have?

[aquapiranha]

Hi Ali. They are FE206's with full enable treatment and planet 10 phase plugs. They are in Sachiko cabinets designed by Scott. See the link below entitled hifi past and present for pics.

[Ali Tait]

Hi Steve,
I can't open the link as I'm using my work laptop.Just interesting what you say about yours,as the Fe167e's I have are quoted by Fostex as I think 95dB,but they are actually 91.5.Do you know how sensitive yours are?

[aquapiranha]

Hi again Ali. I think they were quoted around 95db. I have another pair of FE103E's (4 inch) and I am sure they are slightly lower. Not sure what effect the enabling and / or cabinet would have though.

[Ali Tait]

The cabinet only affects the bass frequencies.Mid and top stay the same.Also,The cabinet does not change efficiency.So Scott says anyway,and he should know! So your Fostex should be around the same as mine,i.e. not as sensitive as you thought! I asked (planet10) Dave about mine as found myself setting about the same volume level as on my B&W P5's which are 90dB.He's measured the 167's himself and found 91.5,so I wasn't far off.

[aquapiranha]

well whatever the sensitivity, I find that even with 2 watts I can't go much past 1 )'clock on the volume control or it is too loud!