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Author Topic: Solid State vs Tubes - Any Thoughts?  (Read 5432 times)
K7PEH
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Posts: 1124




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« Reply #15 on: March 25, 2013, 02:31:16 PM »

I read somewhere that I'll need something between my solid state radio and the tube amp I'm building.I didn't see any coments about output power of radio.Allot of the SS amps I looked at needed a low Input 

Typically, a tube amp would have the following connections between the XCVR and the AMP in addition to the COAX connection (XCVR Antenna out to AMP RF Input).

(1)  Keying relay interface.  This is where you might use a relay buffer like the ARB-704 (See Ameritron web site).  This is to protect the relay in your XCVR from over voltage damage caused by the amp.  Not all XCVR/AMP interfaces need one.  If you know that your amp cannot cause damage to your XCVR keying relay then you may get by without one.

(2)  ALC control line.  This is used with a tube amplifier to protect grid current (usually) in the amplifier from being too high by overdriving from the XCVR.  Depending on how you operate this may be important (but, your amplifier will work without it too).

Caveat -- I am not near as experienced or knowledgeable as other's on this forum with regard to ALC and other practices with tube amps so take my comments above with a grain of salt.  If someone like Tom, W8JI, or Steve, WB2WIK, comment then their comments will always trump mine with regard to amps.

73, phil, K7PEH
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N3QE
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Posts: 2204




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« Reply #16 on: March 25, 2013, 05:36:08 PM »

Allot of the SS amps I looked at needed a low Input 

Often (but not always) rated input of a few to 5 watts is a sign that it's intended for CB's.

Even more reliably... lack of a keying line is another sign that it's intended for CB's.

And most reliable of all: an "AM" power rating or "AM" selector switch is the sure sign it's intended for CB's.
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PE5T
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Posts: 35




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« Reply #17 on: March 25, 2013, 11:41:18 PM »

I made a lot of amps, from 811, 572b, 813's, QB3-750/1100, GS31b. I also owned a commercial amp with a GU84b.
Some months ago I bought an expert SPE amp. A new world. Almost not destructable, with build-in tuner, antenna switch, rig switch, low fan noise and instant power (no warm-up time). And, only two (2x) cables between my K3 and TS480 transceivers and the amp: coax for the rf and one CAT cable for auto-band-change, amp keying, amp on/off and ALC (I use the ''NC'' pins of the COM ports of my transceivers for these functions -bringing these functions from the original connectors also to the com-port).
My conclusion: once you get used to this amp you will never consider a tube amp again.
  
« Last Edit: March 26, 2013, 12:13:34 AM by PE5T » Logged
G3RZP
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Posts: 4589




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« Reply #18 on: March 26, 2013, 10:02:47 AM »

PE5T

Is that SPE amp CE marked?
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PE5T
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Posts: 35




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« Reply #19 on: March 26, 2013, 10:55:52 AM »

G3RZP,

CE marked, yes and it has a FCC number. It does not work below 28 MHz or on other ferquencies outside the ham bands.
Forgot to mention that I can operate the amp with my PC mouse.
The manual can be found on their web site,

Kees
« Last Edit: March 26, 2013, 11:06:54 AM by PE5T » Logged
G3RZP
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« Reply #20 on: March 26, 2013, 02:26:33 PM »

Thanks, Kees.

An interesting problem (!) is that the ETSI Harmonized Standard has a problem above 170 watts in that there is no  accepted international standard for measurement uncertainty above that level.
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KH2G
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Posts: 277




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« Reply #21 on: March 30, 2013, 01:03:08 PM »

The thing you may have to consider between your SS radio and a tube amp is the keying circuit. Many of the older amp keying relays draw a fairly high current and in some cases a voltage that may be anywhere from 5 VDC to 24 VDC. Ameritron makes a little ARB-704 that give the isolation needed but you could build something as cheap once you see what you need.
As far as RF input etc there should be no problem but I'd put an SWR meter between them initially to make sure the old amp input is really matched as it should be.
73
Dick
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ZENKI
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Posts: 935




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« Reply #22 on: March 31, 2013, 03:58:43 PM »

Tube amplifiers are cleaner and have better IMD performance under all load conditions.

Solid state amplifier makers dont even publish  IMD data, most use industrial not RF fets and the IMD performance.

You cant beat a clean tube amplifier that runs 3-500s, 3cx800's or a 8877.

If you short on cash a any amplifier with a pair of 3-500's. Actually if you invest  the money you spend on a solid state amplifier, you could buy a tube amplifier for every band.
Now if you come up with a switching system for the key line and the input relays can handle high power you can string all the amplifiers in series. Now you have a pretuned amplifier on every
band thats as fast as any solid state amp. A do this with modified SB220's and Drake L4BS.

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