I don’t think the Zobel does anything for the bass reflex peaks at the low end of the frequency range, does it? Wouldn’t you need a notch filter for that? My woofers (Western Electric 2080a) have a rather high inductance (2mH) and the Zobel is there to stop the impedance from rising at higher frequencies, especially since i am using a first order crossover.
This explains it, using the appropriate formulas:
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Right, but the relevant thing here is to realize that damping factors under 20 influence basic loudspeaker behaviour like frequency and impulse response.
Too often it is overlooked that SE tube amplifiers and loudspeakers must work well as a combo.
Otherwise either the amplifier or the loudspeaker (and likely both) will not give their best.
Too often it is overlooked that SE tube amplifiers and loudspeakers must work well as a combo.
Otherwise either the amplifier or the loudspeaker (and likely both) will not give their best.
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boli46,
You are right in your Post # 433.
I could not find any 8 Ohm Western Electric loudspeakers.
I have to admit I was wrong.
So, the other poster needs to get a pair of another manufacturer's 8 Ohm speakers,
and either wire in series to get 16 Ohms, or in parallel to get 4 Ohms.
I see many Western Electric 8 inch drivers that are for sale for more than $1,000.
The poster who has a Western Electric speaker, should sell it quickly for $500,
and then he can purchase a pair of 8 Ohm speakers.
Just another silly solution of mine.
You are right in your Post # 433.
I could not find any 8 Ohm Western Electric loudspeakers.
I have to admit I was wrong.
So, the other poster needs to get a pair of another manufacturer's 8 Ohm speakers,
and either wire in series to get 16 Ohms, or in parallel to get 4 Ohms.
I see many Western Electric 8 inch drivers that are for sale for more than $1,000.
The poster who has a Western Electric speaker, should sell it quickly for $500,
and then he can purchase a pair of 8 Ohm speakers.
Just another silly solution of mine.
For low frequencies, another influence on the impulse response of a woofer is the inductance of the output transformer secondary.
I used a Vector Network Analyzer to measure the impedance versus frequency of a single ended amplifier, with the output tube removed, and the amplifier turned off.
That varying impedance of the output transformer secondary is in parallel with the load.
That has an effect on damping factor of the amplifier when the output tube is in place, and the amp is turned on.
The impedance of a bare bones single ended output transformer secondary is interesting.
There is the secondary inductance influence on impedance at low frequencies,
And the primary winding's distributed capacitative impedance at high frequencies, which is impedance transformed downward (it reflects to a lower impedance on the secondary winding).
I used a Vector Network Analyzer to measure the impedance versus frequency of a single ended amplifier, with the output tube removed, and the amplifier turned off.
That varying impedance of the output transformer secondary is in parallel with the load.
That has an effect on damping factor of the amplifier when the output tube is in place, and the amp is turned on.
The impedance of a bare bones single ended output transformer secondary is interesting.
There is the secondary inductance influence on impedance at low frequencies,
And the primary winding's distributed capacitative impedance at high frequencies, which is impedance transformed downward (it reflects to a lower impedance on the secondary winding).
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I've previously been rather dismissive of Lundahl's LL1664 as a SE OPT for the 300b, preferring the LL1682. This is still the case - to me ears a higher primary impedance cleans up the midrange from some of the 300b's euphonic sound.
But I'm now using the LL1664 with a pair of 6C4C outputs and the result is excellent. The 6C4C is a Soviet copy of early US biplate 2a3s and I rate it very highly - usual Svetlana quality build. So my 300bs are going back on the shelf and I'm converting my amps to 6C4C. Good to know that the LL1664 is a good option for this - it's not overpriced.
But I'm now using the LL1664 with a pair of 6C4C outputs and the result is excellent. The 6C4C is a Soviet copy of early US biplate 2a3s and I rate it very highly - usual Svetlana quality build. So my 300bs are going back on the shelf and I'm converting my amps to 6C4C. Good to know that the LL1664 is a good option for this - it's not overpriced.
The 6C4C seems to be a dual anode plate tube, like a 2A3.
Without knowing this tube in detail, I've always preferred single plate tubes like an AD1/RE604 over double plates. The price seems reasonable, but I paid not much more for my stash of F2A Siemens, a 10K hour pentode with the same output rating like a 300B.
Don't know if the soviet tube is able for such long distances, but they have produced excellent military equipment.
In the end, a well engineered tube amp design to MIL standards and heavily oversized will sound good with nearly any output tube, doesn't matter if its a 300B.
Without knowing this tube in detail, I've always preferred single plate tubes like an AD1/RE604 over double plates. The price seems reasonable, but I paid not much more for my stash of F2A Siemens, a 10K hour pentode with the same output rating like a 300B.
Don't know if the soviet tube is able for such long distances, but they have produced excellent military equipment.
In the end, a well engineered tube amp design to MIL standards and heavily oversized will sound good with nearly any output tube, doesn't matter if its a 300B.
do you have a schematic for your F2A amp? I have a pair and I haven't used them yet.
How long ago did you buy your F2a. Ebay today F2a 500$ a pair vs 6C4C 80$ a pair.
But if the the F2a in triode, is a linear as the schematic suggest. I might understand the price. Especially when you look at how easy it is to drive.
Here you go. But this is one is hyper sensitive at the input...just saying.
Bought F2A five years ago, price was reasonable
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I was just offering up Bud Purvine's opinions as a very experienced transformer winder. By all means try with and without if you want to test the hypothesis.
