Interested in building together a 300B tube amp?

[wsjoe]

Hi,
I am trying to see if there are enough people in this forum to design and build a single ended tube power amp with 300B tubes.

The whole point is to buy parts and bulk including the machining process for the chassis. I would like to know if there are enough people to start this. I think if we have about 20 people, we can definitely save some money for each other. I have 5 people I know that are interested so if we can gather another 15, we can definitely do something like this.

The idea is to build a decent amp that's definitely better than doing absolutely DIY with cheapest components. The quality of components can be chosen as a group but fixing the design with a specific power transformer, and output transformers are a must.

The transformer I am thinking are Sowter and Hashimoto and maybe even Partridtge. Another good choice is Jack's Electra Print based in Las Vegas. If those interested want to go for lower cost, we can go for Hammonds, but as many of you experienced, why not build something good that will match and/or outperform commercial products that are 2-3 times the cost. I am thinking something like Cary Audio and Antique Sound Labs.

Anybody interested?

[Richard Ellis]

Trying to get fifteen individuals on this forum to agree on one set of OPTs, or a single B+ TX....let alone a singular circuit design...is like trying to herd cats!

__________________________________________________ _____Rick.....

[BudP]

Agreement among 15?

Maybe 3, unless the attached tube curve PDF gets everyone's attention. I am about to build 3 pairs of SE OPT's centered at 4.545 Kz ohms primary impedance. Three separate secondary schemes and all are our level one or two, with level three being more complex with Litz wire secondaries and ridiculously costly. Primary DCR will be under 80 ohms for all and they are pretty substantial in size at 1.5" X 2.25" E/I core center dimension. One of the level one's will be for my amplifier.

I do think that the overwhelming choice for linearity is the above value and while harmonic distortion does drop a bit lower for higher values of impedance the linearity is no where near as good. I can offer a group deal, with some variation in primary impedance, secondary impedance (s) and even levels one or two, but the core size and bobbin must remain stable.

I will also place the relevant 300 A data sheet pages up in a bit, because it shows the distortion curves for both A and B series tubes, in detail.

Bud

[BudP]

Here are the relevant graphs for a 300 A tube. Looking at the much less detailed graph for the 300 B, these look like they will suffice in place of that graph.

Bud

[BudP]

For those of you adverse to Franks Tube Data, the numbers in the 300 A distortion curves are determined by the following chart.

Filament Voltage = 5.0 VAC
Plate voltage = 350 VDC
input in peak volts = Grid Bias
Curve Plate current Grid Bias
1 30 -81
2 40 -78
3 60 -74
4 80 -71
These come from the power plot and that plot is too big in PDF to load here and nearly unviewable in jpg format.

Bud

[Yvesm]

Originally Posted by Richard Ellis

Trying to get fifteen individuals on this forum to agree on one set of OPTs, or a single B+ TX....let alone a singular circuit design...is like trying to herd cats!

__________________________________________________ _____Rick.....

Indeed

Sometimes, I even disagree with myself

Index of ../SE_300B/KISS/

Yves.