need quick help with A10.3 info !

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In my case it has been chosen because a) it can drive a 2A3 directly coupled, b) it provides high sensitivity, c) operates at low current allowing pure resistor plate load, d) it is a tube in current production, e) there are many vintage variants for tube rolling, f) it has been used by others like this with good reports of it's performance.
 
Well we're getting off topic here. But remember the 2A3 is a low gain tube so miller capacitance is low. C grid-plate is 16.5pF, with mu=4.2 we get C input of roughly 70pF. The 2A3 runs typically +/-45V on the grid. So at 20kHz we can estimate the current needed for maximum slew rate i = C x 45V x 2 x Pi x 20kHz = 0.42mA. Yes, more is better but we're in the right ball park for a 12AX7. And we can also include g) low noise, h) low microphonics, i) low heater hum (especially the LPS version).

This is not to say the 6SL7 isn't a good choice.
 
let's see how long we can extend the OT tango ? if already committed to noval drivers for the 2A3, howzabout something like WE417 / 5842, ECC99, 5687or triode wired EF86?

I'm sure there are others, but probably anything could kick the shi touta 12AX7 for this application
 
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I'd say the ECC99 is a nice choice. The WE417, isn't that the ultra-high transconductance tube that oscillates by itself in the box ? - the Russian 6C45Pi is more or less the same beast. And if I wanted to kick shi touta levels I'd not be using a 2A3. I will have other experimental amps for listening to the Top 40, the TGM7 is a candidate.

So what will I be using my 2A3 for - it's aimed at a 15" driver in a 13 cu ft box, but since this is Mark's forum let's not get into that. Anyhow even though it may be aimed at an existing installation - after hearing the 10.3 I am seriously considering building another speaker to put beside it and give me more choice depending on the type of music I'm listening to. I quite like that idea.

My set up is mono - now there's a whole nother conversation.

Buit I did like the sound of the 10.3. I just don't know if the Pencil gave me the bass I would want.

I am curious about Scot's double mouthed horns - Silbury and Avebury but so few reports on this forum to gain insight from. I have WAF approval for a big speaker and I am using my existing 15" in a corner so I could probably get away with a 10.3 or 12p in a BLH. Hmmmm.....
 
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Re the above, everything. Leaving aside that you'd have a radically different loading on the drivers, the internal configuration would need to be changed, which would in turn alter the load & behaviour further since the physical shape of the FH enclosure are functional parts of the design, and you will have completely departed from that too. You would then need to consider the difference in the power-response & tuning and make alterations based on that. And then... (you get the idea).
 
If you had two drivers you could low pass one of them to provide bass extension and avoid lobing by ensuring the low pass cross-over is set appropriately - just a guess, it's a foreign concept to me.

Anyhow, I'd prefer a single driver in a pair of siamesed FH's. I'd keep the tuned lengths the same but halve the cross-sectional areas. This should be pretty close to the right alignment. What was your proposal Dave ?
 
Quite. Which is why Dave didn't recommend it. The Siamesed FH3 concept with multiple drivers has problems enough, let alone fooling around trying to combine things.

If you're using 1 driver you can't just mirror a couple of FH3 cabinets then hack the CSA & expect it to work properly. The dimensions & physical size / shape of the cabinet (as I regularly point out) are functional parts of the design. If you depart from them, you're in technical terms 'stuffed' unless you know what it is you are doing. Which basically means a new design. Is this desired? And if so, how would people prefer it to be made available?

The truth is that if you want the highest performing back-horn I can manage in design terms within reasonable size / cost / complexity constraints for the A7 / CHR / CHP, it's Maeshowe. That's why it's on the site in question (it wouldn't be on it if it wasn't), & why a small charge is made, so, like Bob with his MLTLs, Dave who hosts the site & draws the pdfs & I get to cover our costs. If something like what you are talking about is demanded, fair enough: I'll do it. I can say, because I looked at just such a cabinet about two years back, performance will take a hit compared to Maeshowe. It'll be as good as I can manage with the load in question, but by nature it won't be of quite the same level. Depends on where the priorities lie -performance or (relative) physical simplicity. Sadly, you can't acoustically speaking get something for nothing.
 
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Once I commit to sawing wood it isn't such a big deal to go a little more complex if there are real performance gains to be made. I am curious why you developed these double mouthed BLH (here we go off topic again) since I understand you don't use them yourself due to their large size, and since you don't promote your web site it isn't a money spinner ?
 
I don't have any permanent system at all. No space or money to do it.

Re the boxes on the site in question, they're not really double-mouth designs: although the expansion path bifurcates, they are ultimately single terminus speakers. Rather large single terminus I grant you (the curved back is functional).

No, the site doesn't bring much in. We cover running costs, although when you factor the time spent in design work, drawing the pdf plan-sets, creating the site itself we probably haven't broken even if you base that on a reasonable hourly rate. Since you ask, this is the position: as a rule I don't discuss my designs unless asked a specific question, & the site is not in my signature to prevent any possibility of accusations that I use the forum to sell things. I believe Bob takes a similar approach.
 
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