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 Post subject: Bogen DB-130 Mono Amplifer
PostPosted: Mar Sun 20, 2011 9:31 pm 
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Hi, I picked up one of these today for $15. :D It uses 6AV5s in push pull. The guy I bought it from said it had 500V on the plate and regulated 150V on the screen. Anybody have any idea what the output power is on this?

Doug


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PostPosted: Mar Sun 20, 2011 9:51 pm 
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i was bidding on one of those on ebay but let it go. its a cool little amp as it uses an odd and cheap tube. that tube was intended for tv use.

you're looking at about 10w for a pair of them. the screen supply is very important on that amp from what i read when i was researching.

if you end up not doing anything with it drop me a line. id like to tinker with one and see what it sounds like.


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PostPosted: Mar Sun 20, 2011 11:15 pm 
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Bogen rated it at 30 watts - I've measured a DB-230, which is the stereo version, and it DID make 30 watts per channel. Schematic is online here: http://www.pacifictv.ca/wanted.htm


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PostPosted: Mar Sun 20, 2011 11:31 pm 
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If it needs a regulated screen supply (like the 6146 for example), that supply is something that absolutely has to be up to spec, or those output tubes will go berserk.

Congratulations on your new acquisition, Doug, and good luck with it.

:wink:

Larry

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PostPosted: Mar Mon 21, 2011 12:10 am 
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I have one of them too. But I have had problems getting it to be stable and just moved on to another project. So, I agree that they must be rather touchy! I will be out of town for about six weeks. We could compare notes later?

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PostPosted: Mar Mon 21, 2011 9:58 pm 
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With the output transformers those have, you could probably convert them over to 807/5933 output tubes, without a whole lot of fuss. Would negate the need for the regulated screen supply (the screens could run at up to 300v, on a simple dropping resistor from main B+). Would have to change the bias settings and such, naturally. Or, you could just re-set the voltage regulator to give around 300v...

Regards,
Gordon.

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PostPosted: Mar Mon 21, 2011 11:12 pm 
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I'd stick with the 6AV5GA's, if only because all the usual suspects haven't "discovered them" and driven the price up through the stratosphere into never-never land.

It's nice to know about some viable (even if touchy) output tube that is still only a few cents more expensive than dirt :wink:.

Best regards and good luck with your project :),

Larry

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PostPosted: Mar Tue 22, 2011 12:41 am 
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I have a Bogen DB130A amp that I've owned for at least 25 years. It's a good sounding amp after being rebuilt. Mine has the 6AV5's in it and I haven't had any problems with them. Harry


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PostPosted: Mar Tue 22, 2011 2:18 am 
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Thanks for the schematic link Tom. This thing is supposed to have 605VDC on the plate. :shock: I can see some time invested in this project just for safety.

Doug


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PostPosted: Mar Tue 22, 2011 3:40 pm 
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605VDC on the plate!

that makes for pricey filter caps! seems like there's a substantial price increase once you hit 500v rated caps.


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PostPosted: Mar Tue 22, 2011 4:48 pm 
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The filter caps are 30uf 400V rated wired in series with 1meg equalizing resistors.

Doug


Last edited by hergi on Mar Thu 24, 2011 11:22 pm, edited 1 time in total.

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PostPosted: Mar Thu 24, 2011 6:39 am 
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I have two of these DB130, and a Bogen LX60 public-address amp that uses four 6AV5 tubes. For the best results, use 6FW5 output tubes which have a higher voltage and power rating, they will be completely stable and no circuit changes needed. Vacuumtubes.net lists them for $4.00 each, I am not related to them but have ordered in the past.
Don


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PostPosted: Mar Thu 24, 2011 2:16 pm 
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6FW5 has 18W plate dissipation vs 11 for the 6AV5. I might have to try that once I get this thing going.

Doug


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PostPosted: Mar Thu 24, 2011 6:26 pm 
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Doug, The 6AV5 is only rated for 550 plate volts, while the 6FW5 is rated for 700 volts. That makes a big difference in these Bogen DB130s with 605 volt supplies that go higher with today's line voltage. Luckily my LX-60 has a 125 volt tap on the power transformer.
These sweep tubes are very linear and have huge cathodes and peak currents, so the amplifiers sound much louder than their ratings and seem to have lots of headroom, especially as a public-address amplifier in a large room or outdoors. I tried the LX-60 with 4 6FW5 tubes and a Scott 240 using two 6CA7 tubes driving separate PA speakers outdoors. The Scott was struggling, distorting and clipping while the Bogen just blasted away, great sound you could hear a block away.
Don


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 Post subject:
PostPosted: Mar Thu 24, 2011 8:44 pm 
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Thanks for the info Don. I checked a couple of places on line and the 6FW5s are a dollar cheaper than the 6AV5s. $3 vs $4. Wow, audio tubes for a couple of bucks. :shock: Higher line voltage isn't a problem with a bucking transformer.

Doug


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 Post subject:
PostPosted: Mar Thu 24, 2011 9:42 pm 
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If all the usual suspects discover these tubes, you won't see those prices for long.

:mrgreen:

Larry

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 Post subject:
PostPosted: Mar Thu 24, 2011 11:04 pm 
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BigBandsMan wrote:
If all the usual suspects discover these tubes, you won't see those prices for long.

:mrgreen:

Larry


Yeah, but if there's a demand for TV sweep tubes they won't be thown out. How many tubes are just trashed because TV tubes aren't worth much? Some are hard just to give away. :shock:

Doug


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 Post subject:
PostPosted: Mar Fri 25, 2011 3:14 am 
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Vacuum Tube Valley magazine had a Dumpster Tube article praising the 6AV5 in issue 10, fall 1998 and it did not cause a run on these tubes by the audiophools. It did not mention the superior 6FW5. These tubes do not use plate caps, a safety feature.
Don


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 Post subject:
PostPosted: Mar Fri 25, 2011 8:03 pm 
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I have another question, what is the impedance load of the output transformer to the tubes? I'm curious.

Doug


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 Post subject:
PostPosted: Mar Fri 25, 2011 9:40 pm 
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BikenSwim wrote:
Vacuum Tube Valley magazine had a Dumpster Tube article praising the 6AV5 in issue 10, fall 1998 and it did not cause a run on these tubes by the audiophools. It did not mention the superior 6FW5. These tubes do not use plate caps, a safety feature.
Don


Be all that as it may, a few things have changed over the last 13 years, including availability and prices of the "standard" output tubes.

As far as I'm concerned, VTV mox nix, but if they were to reprint that article now, there would assuredly be rather more notice of it than there was in 1998.

Bet on it.

:wink:

Larry

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