What's to chat about?

Anything not covered elsewhere.
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Rich4349
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Re: What's to chat about?

#1126 Post by Rich4349 »

Oh, I meant online. The past couple years Black Friday and Cyber Monday have basically schmeared into one long spend-a-palooza.
2 DR250s, 2 27" Lab15 T-60s, 2 30" Neo Titan 39s, 1 Autotuba...and looking for more!

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Seth
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Re: What's to chat about?

#1127 Post by Seth »

Failed attempt at a little humor. I know whatcha meant Rich. In all honesty, I didn't even look for any deals. Maybe I'll poke my nose in Amazon today and see if I can just get it all done in a day.
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Bryan Cox
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Re: What's to chat about?

#1128 Post by Bryan Cox »

Made a sweet purchase today. I got some NOS tubes and Sprague caps (and a bunch of other stuff I won't use). But the 12AX7 and 12AT7 tubes made it all worth it.
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Titan 39 x 4 (3012LF) 20" wide

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Seth
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Re: What's to chat about?

#1129 Post by Seth »

I have no/little idea what sprague caps and NOS tubes are, just assuming they're for tube amplifiers. What do you intend to do with them?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Bryan Cox
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Re: What's to chat about?

#1130 Post by Bryan Cox »

Absolutely right, Seth. Some tube amp enthusiasts and audiophiles spend time sniffing corks while demanding that these original Sprague caps and NOS tubes are the only things that sound good. I have no idea about the caps, but I do know that NOS preamp tubes will last decades if they're in good shape. And these are the military versions so they're a bit more rugged than their civilian counterparts.

I shelled out a bit of coin for a NOS tube set up for one of my amps since it was designed around them. The hum issue I had went away immediately. If I found these before I bought the others I'd have saved $300.
Otop 12 x 4 (Delta Pro 12-450a) 2x melded, 2x straight
Titan 39 x 4 (3012LF) 20" wide

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Bryan Cox
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Re: What's to chat about?

#1131 Post by Bryan Cox »

Seth wrote: Mon Dec 06, 2021 10:15 pm I have no/little idea what sprague caps and NOS tubes are, just assuming they're for tube amplifiers. What do you intend to do with them?
Should've answered your question better...

NOS (new old stock) tubes are ones from before the transistor took over (GE, Sylvania, Shughuang, Mullard, Amperex, Telefunken, etc...). Circa 1950's - late 70's or so. Everything went to transistors almost overnight and tube factories shut down. But for the last 10 years, give or take, the tube is making a fierce comeback. Factories have been opened back up and tube production is well underway, but there is a definitive change in the quality of the tubes. New tubes are a little more fragile, cannot handle the same voltages, the vacuum doesn't seem to be quite as strong, and the sound is sometimes weaker. From my experience, many of the new tubes are too compressed (squished, even) when pushed and the tone is a little less present (to my ears, in my amps)

Production differences have no impact on amps designed around those capabilities. Some of them sound damn good. But many of the older amps, designed around the capabilities of NOS tubes, suffer when retubed with newer stuff. And this is a relatively large issue for the amp cloning community because that means they either have to pay out the nose for NOS, live with a noisy amp, or change the design to lower plate voltage and compensate for new tubes (which kind of defeats the purpose of a clone).

The old-ass Sprague caps will drive cork sniffing audiophiles crazy. So I plan to stoke the fire a little. Makes me chuckle.
Otop 12 x 4 (Delta Pro 12-450a) 2x melded, 2x straight
Titan 39 x 4 (3012LF) 20" wide

Bruce Weldy
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Re: What's to chat about?

#1132 Post by Bruce Weldy »

Bryan Cox wrote: Tue Dec 07, 2021 6:05 am
NOS (new old stock) tubes are ones from before the transistor took over (GE, Sylvania, Shughuang, Mullard, Amperex, Telefunken, etc...
And to make it even simpler..... NOS stands for New Old Stock. In other words, it was built a long time ago, but hasn't been used.




Sorta' like my brain.....

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


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Seth
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Re: What's to chat about?

#1133 Post by Seth »

Nice! Great explanation guys. I'm familiar with the new old stock term. Guess it didn't click in my mind. I just assumed the acronym had to do with something about the tubes themselves and didn't give it anymore thought. Do you have a current use or plan for them, or are they just good parts to have on hand for you?
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Bryan Cox
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Re: What's to chat about?

#1134 Post by Bryan Cox »

For now they're extras. Both my JMP 50 and Express are outfitted with NOS glass so I'll save them. Tube amp enthusiasts (such as myself) are kind of particular about the tubes they use. If one goes microphonic or dies, I have some on hand.

I also have a healthy supply of newer tubes. I kind of mix and match depending on the tone I'm after. For example, if I'm in a blues band I'll use something with great mids, high end sparkle and low compression. If I'm playing hard rock I want something with tight lows and sort of sterile. If a tube goes bad I have some on hand.
Otop 12 x 4 (Delta Pro 12-450a) 2x melded, 2x straight
Titan 39 x 4 (3012LF) 20" wide

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Seth
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Re: What's to chat about?

#1135 Post by Seth »

Another thread had some talk about a compression driver. Out of curiosity I pulled up the data sheet, just to give it a look-see and saw something I'd never seen before. I doon't shop for compression drivers, so maybe it's a common spec. I'm curious what some of you guys think. I wonder why that's so? Seems odd. I'd definitely enjoy a little enlightenment.

What do you guys make of this?

Screenshot (163).png
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

Bruce Weldy
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Re: What's to chat about?

#1136 Post by Bruce Weldy »

I'd assume that the passive rating is how much power the whole cab can take before it reaches the crossover. You notice that the lower crossover point also lowers the power rating. It always comes down to excursion. The lower the frequency, the more excursion - thus you can't hit it as hard.

With a steeper crossover slope, you could give it more power.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Bill Fitzmaurice
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Re: What's to chat about?

#1137 Post by Bill Fitzmaurice »

That's showing actual power to the HF driver, which isn't the same as the power to the speaker as a whole, which is how HF drivers are typically rated. On average 75% of broadband signal power is below 500Hz, 95% is below 5kHz.

Bruce Weldy
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Re: What's to chat about?

#1138 Post by Bruce Weldy »

Bill Fitzmaurice wrote: Sat Jan 22, 2022 4:25 pm That's showing actual power to the HF driver, which isn't the same as the power to the speaker as a whole, which is how HF drivers are typically rated. On average 75% of broadband signal power is below 500Hz, 95% is below 5kHz.
Then why the two different ratings? One says passive, which to me means running through a crossover. The other rating says active, which makes me think the power coming direct from an amp when bi-amping.

What am I missing?

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Bill Fitzmaurice
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Re: What's to chat about?

#1139 Post by Bill Fitzmaurice »

If it's passive you can't separately limit the power to the HF driver, so that's the system power. The active shows the actual power for the purposes of limiting.

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Seth
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Re: What's to chat about?

#1140 Post by Seth »

Thanks for the responses guys :thumbsup:

I'm still a foggy on it. I'll just talk it out a little and see if I can make it more clear for myself.

If system power is 160w (35.7v @ 8Ω nominal) and I run a 2K sine wave at 35.7v through a passive crossover, does it come out of the crossover at 35.7v?

Depending on the crossover design, it actually starts rolling off prior to the cutoff frequency. A 2k Linkwitz-Riley filter is down 6dB at it's cutoff frequency and actually starts rolling off at around 10k. Bessel is down 5dB and start rolling off around 6-7k. Butterworth is down 3dB and starts rolling off 4-5k.

For a 2K highpass filter, power would be down 3-6dB at 2K depending on the filter type. With 160w system power (35.7v) into the crossover, that would be 40-80w (17.8-25.3v) out of the crossover at 2k. I think that's right. No?

That's roughly the stated "active crossover limit" of 54 watts program. I wonder if there's other losses involved when going through a passive crossover.

Seems a little more clear, I suppose. Is this along the right lines of thought? Make sense to any of you other guys? (insert much needed "stroking my chin" or "scratching my head" smilie/emoji) :mrgreen:
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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