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Old 12th April 2005, 01:42 PM   #1
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Default two value tube amps for active DIY horns

(To the extent possible) Iím asking for technically based/ value opinions:

I need two (hence not too much cost each) identical amps for a DIY active hybrid horn system (105 db midbass & 100 db upper end) Iím putting together. The mid bass starts at 250 Hz, and my hearing drops off at 12 kHz, so extension is not needed.

Do any of these power or integrated amps (available in HK, most by mail order) sound promising options at all, based on their tube compliment??

(Prices are approx)

KELLY - Tube Art Pride 845
6SL7 x 2 , 6SN7 x 2, 845 x 2
NON-feedback 0 db
Class A, 22 W x 2

CATTYLINK:

Melody SP3 USD 650
Power 4 * 5881
12AX7 * 2, 12AU7 * 2, 6922 * 2
38 W x 2

Yarland Pro200SE USD 550
Power 300B
12AX7 * 2, 6SN7 * 2, 5U4G * 1 (rectifier).
Class A, 8 W x 2

LS845B USD 737
845 * 2
6J4P * 2 (rectifiers)
Class A, 22 w * 2.

Yarland FV-34C III integrated
Pre 5670 tube
4 EL84. USD 150!

Opera Cyber-500 monoblocks
300B * 2
6SL7 * 2, 5AR4 * 2

Meixing MC-84A integrated USD 350
13 w *2
EL 84 * 4
12AX7 * 1, 12 AU7 * 2.

Cayin MT12 integrated USD 350
12 w *2
OTK EL 84 * 4
12AX7 * 1, 12 AU7 * 2.

Thanks for any advice

Cheers
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Old 12th April 2005, 02:40 PM   #2
Sheldon is offline Sheldon  United States
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I don't know anything about the cited kits (I'm pretty much a beginner so, in fact, I don't know much about the respective qualities of amps period). but I do know that at 100db efficiency, you only need one watt for 100db output. So, unless you have a huge room or like your music loud to the point of hearing damage, you could get by with a couple of watts output.

I plugged in "low powered tube amps" into Yahoo and got this review: http://www.enjoythemusic.com/magazin...2/aslwave8.htm

The Antique Sound Lab amps cited in the article were US $99, in 2002. I'm sure if you looked you would find other choices in your price range. You might get more for your money by looking at low power amps.

Sheldon
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Old 12th April 2005, 09:05 PM   #3
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Hi
Yes, you only need one watt for 100 db, but for dynamic headroom 10-20 watts would be desirable.

The Antique Sound Labs monoblocks ($200 a pair) S/N Ratio: is only 70 dB! Although I donít want to spend much, that is a bit too noisy Iím afraid.
I just checked at www.divertech.com/antiquesl.html and itís been apparently replaced as their entry model with a $345 a side monoblock ($US 690) Wave AV-25 DT with S/N Ratio of 80dB with 2 * 6L6, and 1 * 12AX7s.

For eg $US 350, the Cayin MT12 has OTK EL 84 * 4, 12AX7 * 1 and 12 AU7 * 2.

Any comments based on their tube compliment on the amps listed?

Thanks

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Old 13th April 2005, 02:27 AM   #4
Sheldon is offline Sheldon  United States
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I didn't mean to imply that I endorsed the amp I cited, only to use it as an example of what you might find.

Not trying to belabor the point, so I won't beyond this. Normal listening levels are not 100db, but more like 70-80. So a couple of watts does give you significant head room, especially since each amp only has to cover a small range. More power won't hurt, but costs more, all else equal.

Sheldon
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Old 13th April 2005, 05:56 AM   #5
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Quote:
Originally posted by rick57
For eg $US 350, the Cayin MT12 has OTK EL 84 * 4, 12AX7 * 1 and 12 AU7 * 2.
It mist be an "integrated" amp... there is 1 more tube than necessary there for just a power amp. If this was point-to-point it could be the basis of a project amp (ie pre-built kit).

There are some schools that say in a 2-way speaker system like yours to use a PP amp on the bottom, and an SE amp with the same output tube on the top. I'm a big fan of EL84, so this is a candidtae... a really good SE EL84 kit is the Decware ZEN. A DIY SE EL84 is also not all thet hard, something based on the RH84 being the seeming amp of choice. DIYing you can also look for small OPTs with no bass but extended highs. An RH84 PP with a differential front-end is also possible -- have a look at this thread

Hey Planet_10 (and others)

where Gingertube talks about an ECL86 version (ECL86 can be considered to be 1/2 of a 12AX7 + an EL84 in the same bottle)

dave
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Old 13th April 2005, 10:59 AM   #6
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> It mist be an "integrated" amp... there is 1 more tube than necessary there for just a power amp.
Yes, it must be integrated.

If this was point-to-point it could be the basis of a project amp (ie pre-built kit).
Donít know, itís off a cryptic (extremely slow loading) site http://cattylink.com/


> There are some schools that say in a 2-way speaker system like yours, to use a PP amp on the bottom, and an SE amp with the same output tube on the top.

Itís actually a 4 way: < 250 Hz dipole (driven probably by Hypex), 250 Ė 1000 Hz horn midbass with tube amp 1, 1000 Ė 4000 PHL 1040 & Aurum 1: tube amp 2.

> I'm a big fan of EL84, so this is a candidtae... a really good SE EL84 kit is the Decware ZEN. A DIY SE EL84 is also not all thet hard, something based on the RH84 being the seeming amp of choice.

Iíve heard quite a few good things about EL84s. Other things being equal, Iíd probably go a triode. Iíve heard good things about the Decware ZEN ($678). But at only 2 w, it may not be enough; maybe the 8 w Zen Taboo could be.
Iíll look into the RH84.

> DIYing you can also look for small OPTs with no bass but extended highs.

For >250 & >1000 that would be fine. But would small OPTs also have reduced dynamics??

Iíll have a read of Gingertube thread a bit alter as time permits

Thanks heaps!!

Any other views?

Cheers
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Old 13th April 2005, 02:57 PM   #7
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Default How about a scratch built Ultralinear?

I just read in another thread here:

"Its faster, better pace, rhythm and attack than triode mode.
Its lower output impedance than pentode mode and therefore requires less feedback to achieve a good damping factor.
Harmonic Distortion is less than either Triode or Pentode Mode
Intermodulation Distortion is less than Triode or Pentode Mode.

These last two items tell me its more linear than Triode or Pentode mode and rule 1 for any feedback design is make it as linear as possible BEFORE applying feedback.

AND not insignificantly - it sounds lovely and is simple."

What's wrong with UL anyway ?
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Old 13th April 2005, 10:24 PM   #8
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Default Re: How about a scratch built Ultralinear?

Quote:
Originally posted by rick57
These last two items tell me its more linear than Triode or Pentode mode and rule 1 for any feedback design is make it as linear as possible BEFORE applying feedback.
In general, ultralinear is only more linear than triode operation after the application of feedback. Ultralinear operation is a form of feedback itself.
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Old 14th April 2005, 08:32 AM   #9
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Is the Ultralinear form of feedback as detrimental as the normal feedback in some (many) amps?

Has anyone heard UL and found it faster, . .

. . that its lower output impedance (or other requires) requires less feedback to achieve a good damping factor.

. . . (I wonít worry about THD)
and that measured IMD is heard distortion is less than Triode or Pentode?
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Old 14th April 2005, 08:37 AM   #10
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are you there?

I am hoping for your incisive and sometimes highly humorous comments
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