| Author |
Message |
    
Kattracker
| | Posted on Sunday, September 21, 2003 - 8:58 pm: | 
|
I have contacted several sources seeking information (Mainly input wattage capability) on the Texas Star DX-500 amp.
I have spoken with some of the Copper reps and feel their info is credible, but I thought I would ask some more people in hopes of finding several people with the same info to determine fact from speculation.
My main concern is what can the Texas Star DX-500 handle in wattage input. I have got several answers ranging from 6 to 50 watts drive and up to 100 watts swing.
I am told the 500 is the same as the 667 with the exception of the 500 not having a 2SC2290 for
a driver. Both the 500 and 667 use four 2SC2879's
The 2SC2290 pill in the 667 is good for about 80
watts.
Therefore the 2SC2290 is about 80 watts driving four 2SC2879's in the 667. So it seems logical, assuming the 500 and 667 are the same except for the 500 not having the 2SC2290, you could drive the 500 with up to 80 (swing) watts input.
I am told by one distributor that both 500's that Texas Star makes are both high drive even though the variable model is the only one advertised as high drive. If anyone does not know, they make one with a variable knob and the other is without the variable, and you change output by the buttons.
It seems that if the two are truly the same except for the driver (2sc2290) not being in the 500, and if you tried to drive the 500 with a mere 4watts, the output performance would be very low to say the least.
Does anyone have one and how do you drive it, and what is the output?
Anybody with any info please reply.
Thanks,
Kattracker  |
Kattracker
| | Posted on Monday, September 22, 2003 - 7:06 pm: |
|
Anybody? I know somebody out there has one...
Kattracker |
Bigbob
| | Posted on Monday, September 22, 2003 - 7:43 pm: |
|
I do not have a dx500 but I went to rfparts spec.sheet on the 2sc2879 max P in watts is 7,so that being said,I believe the driver in the 667 is padded at the output to prevent overloading the mains inputs.And to get 80 watts out of the 2sc2290 you put 4 in,now you will get less with less drive. |
ss8541
| | Posted on Monday, September 22, 2003 - 10:57 pm: |
|
hey bigbob, nice job. the only thing i see wrong with your post is that the 667 is not padded at the output but padded at the input. the 667 only needs about 1-1.5w of carrier and 6-9w of modulation to hit full power.
the 500 also has its 'padding'/swamping network on the input. the resistors in this input are 2watt resistors, so modulating 80w into these means that they will not last very long. the 500 is really designed to work with a 4w carrier and 16-25w of modulated power(keeping in the linear range). i guess you could say it is one of the only amps designed to actually work with a cb radio. 40w of modulation will give you close to 600wpep. |
RCI 2990
| | Posted on Tuesday, September 23, 2003 - 2:40 am: |
|
I had a 500 once and ran it with my DX 2527 I used to own on the base off of a 75 amp power supplier. They like to be runned run with just a small 3 to 4 watt carrier and swing to about 30 watts PEP from the radio.. I will not devulge the wattage rating i saw on my meter on here because im fairly certain i will get some remarks to my findings on my meter.. I will say this though, the amp really talked with that 2527 driving it and the reading i had on my Dosy was pretty wild!!! :-D |
307
| | Posted on Tuesday, September 23, 2003 - 12:09 pm: |
|
TX-500 is 5 watts A.M. to 12 watts SSB. A TX-500HDV is up to 35 watts both A.M. and SSB.
The Variable Power in MOST cases (not all) is deactivated when the AM button is pressed. Either way we can make it the way you want it.
307 |
Bigbob
| | Posted on Tuesday, September 23, 2003 - 6:10 pm: |
|
Now there's the man who knows from experience AND technical skills,307! |
Kattracker
| | Posted on Tuesday, September 23, 2003 - 9:49 pm: |
|
What confused me was MANY distributors advertised the Texas Star DX-500 HDV and the option of being driven with a Texas Star Mod-V. The Mod-V uses a 2SC2290.
Two distributors told me that BOTH models of the Texas Star DX-500 are actually high drive even though only one model is advertised as high drive.
Don't misunderstand me, I am not trying to be argumentive with anybody, and I am not saying I beleive the distributors, I do think it is interesting to lay it all out on the table and hash it over.
Kattracker |
RCI 2990
| | Posted on Wednesday, September 24, 2003 - 1:44 am: |
|
I should clarify myself.. I had the 500 HDV that i ran with the 2527.. Great amp i say!!! If you can get a 500 HDV get it you will not be dissapointed!!! Its a talker!!!! |
Kattracker
| | Posted on Wednesday, September 24, 2003 - 8:00 pm: |
|
This is a copy of an e-mail I got today from a reputable Rf parts supplier. Just for kicks lets consider what he says and if you have any comments I would like to hear them. I had inquired about driving 4 2SC2879 transistors.
"Sorry for the delay, I was out yesterday. I find the best driving power is about 4-5 watts max carrier, with 15 watts peak per transistor. This
should assure a clean signal with good modulation.
Best Regards"
Again, this is from a reputable retailer that mainly just sells parts, kits. But they do sell amps as well.
Kattracker |
Bigbob
| | Posted on Thursday, September 25, 2003 - 11:22 pm: |
|
ss8541,I was meaning between the driver and the mains,so you could apply 1.5-2 watts at the input of the driver and roll off some of the excess energy at it's out put and still drive the mains to full power with out distortion. |
ss8541
| | Posted on Friday, September 26, 2003 - 9:24 am: |
|
yes bigbob, i understood what you meant. in my reply 'output' was implied to be the output of the driver since that was what you were talking about in your post. but i can see how that because i did not actually say that clearly it could be misunderstood to mean the output of the amp itself.
in any event, and to clear all confusion, the output of the driver is not padded. the only padding/swamping takes place before the input of the driver. |
Bigbob
| | Posted on Tuesday, September 30, 2003 - 12:15 am: |
|
Ok. |
fancypants
| | Posted on Saturday, October 04, 2003 - 3:33 am: |
|
Kc0gxz: the spec's presented by Texas are relatively conservative to say the least. I know exactly what they use for wattmeters as they contacted me with questions as to what they should replace them with. I don't know if they have done anything about that yet, but we suggested looking at some of the HP power measuring devices.
Other than that, if you bring the voltage up, have plenty of current available and have clean drive going into them, these amps will do WAY more power than what their faceplates say. They are one of the few amps on the market that EASILY meet their power rating ( yes, it is a power rating on these, not just a model number ). You have to be careful though as these amps will typically melt their fuseholders if you start pushing them. This is one area that they need to work on. Other than that, they are far more stable and much cleaner than the majority of other "cb amps" out there. The only amps that i see worth owning ( for CB use ) outside of the Texas Star's are Dave Made ( for AM use ) or their "clones" aka X-Force. The remainder of amps on the market are typically much poorer in every respect. Yes, this includes all of those mass produced Palomar's ( who's producing "Palomar's" this week ??? ), TnT / Comet, Cobra's, Galaxy's, etc... and all the "competition amps" like Foxie's, Skullcracka's, No Name's, Dominators, etc... Most of the "competition amps" are REAL pieces of junk.
ss8451: your figures for the 500 are pretty reasonable and in the ballpark. It is not hard to "squeeze" a few more watts out of this amp though with some very simple and common sense mods to them. With a steady 14.5 volt power supply, heavy wiring and a STRONG radio feeding a modified DX 500, one can see 700 - 750 peak on a Bird 43P while still retaining good linearity. Driving them harder with something like a Texas V+ will get you even more, but you better have a darn good antenna system and forced fan cooling. Don't take the voltage over about 15.5 either as "bad things" will start to happen due to the unregulated bias circuit.
As to the 667, it is basically a 500 with a VERY anemic / highly detuned V+ built into it. Not only is the input heavily padded on the driver section, the amp suffers from even greater current starvation due to having to feed yet another pill on power cables / fuseholders that are too scrawny for just the 400 / 500 series. One can play games with the signal attenuation taking place within the 667, but that will only further compound the current starvation problem. As such, you have to do this in a balanced manner and provide greater current to the amp AND modify the input if you really want to see some results. Even with all of that, a V+ driving a 500 will typically STOMP all over a fully modified 667 in equivalent installations.
In my book, the Texas 350 and 500's are the best bang for the buck that one can get on the current market. Personally, i would avoid the models with variables ( other than the 667 possibly ) and go with the four stage units. The variables always burn out due to people trying to use these amps as if they were "high drives". Texas does NOT make a "high drive" unit as most of their amps work best with reasonably low carrier levels (2 - 5 watts ) and a lot of modulated peak power. Obviously, the 1200, 1600, 2400 and 3200 need more than the smaller two and four pills to get them to go. While you might get an "oddball" that requires more drive due to having lower gain, those are more the exception than the rule.
For sake of clarity, i'm making these statements based on my experience with these amps after playing with them on my bench for many years. As far as equipment goes, I use a Tek 465 scope ( -3 dB at 125 mhz ), Bird 43P with the "new & improved" ( meaning "it is now accurate" ) peak detector, Wavetek SG-1146U audio generator, HP 141T Spectrum Analyzer mainframe with 8552A and 8553B plug-ins, HP 8640 RF generator ( mil-spec version ) and an HP 3465A bench-top DMM. All of this equipment is calibrated annually by a local metrology lab. My "big" dummy load is something that you guys have probably never seen. It is a commercially built mil-spec unit that weighs over 50 lbs and will take the full brunt of a "Bluegill" or "Ghostrider" AC box i.e. "mega-kilowatts". The 6 resistors in it are as big and long as your forearm and the fan that pressurizes them will flap your pant-legs at five feet. In the winter, you can use it like a "torpedo" heater if you've got enough RF feeding it as it surely moves enough air for that purpose : )
|
chickenlady
| | Posted on Saturday, October 11, 2003 - 9:47 am: |
|
where would you set your radio to run,2-2290 driving 4-2879? |
Bigbob
| | Posted on Saturday, October 11, 2003 - 7:38 pm: |
|
Chickenlady,1 to 1 1/2 watts dead key,this low mainly to stop your amp from driving your gauges nutso.Bigbob. |
|
