Hey Guys,
Getting close to getting all my parts together. My Edcor OPT and PWRT have been shipped. Yeah!
A few more questions, I need to now order my tubes and a little overwhelmed so many choice. I want to use the KT88 because I've read nothing but good things from them. I was thinking of the Sovtek KT88 because they are $56/pair. Now I am thinking that I should first start up the amp with some cheeprs tube just to make sure I don't blow anything out.
So, what would be the cheapest tubes I can buy for stut up?
What about tube part numbers, is a 6L6 the same as a 6L6GC? A 5881WXT the same as just a 5881?
On the Tubelab site, under the Simple SE tube section, there is a table that list different tubes at different impedence/power. How does one read the table? The power numbers are what I should be referencing?
Also, I believe that I don't have to add the 5k pot for the volume if I plan on adding a pre-amp later?
Well that is probably enough questions. I am going to order the Auricaps .22uf 400v and tubes from AES, I hope those are the correct onec for the coupling caps.
Thanks for the input.
skipper
Edcor XSE25-8-5K OPT.
Edcor xpwr059
375-0-375 , 175 mA 50V .05A 6.3V CT 6A 5V CT 3A
Getting close to getting all my parts together. My Edcor OPT and PWRT have been shipped. Yeah!
A few more questions, I need to now order my tubes and a little overwhelmed so many choice. I want to use the KT88 because I've read nothing but good things from them. I was thinking of the Sovtek KT88 because they are $56/pair. Now I am thinking that I should first start up the amp with some cheeprs tube just to make sure I don't blow anything out.
So, what would be the cheapest tubes I can buy for stut up?
What about tube part numbers, is a 6L6 the same as a 6L6GC? A 5881WXT the same as just a 5881?
On the Tubelab site, under the Simple SE tube section, there is a table that list different tubes at different impedence/power. How does one read the table? The power numbers are what I should be referencing?
Also, I believe that I don't have to add the 5k pot for the volume if I plan on adding a pre-amp later?
Well that is probably enough questions. I am going to order the Auricaps .22uf 400v and tubes from AES, I hope those are the correct onec for the coupling caps.
Thanks for the input.
skipper
Edcor XSE25-8-5K OPT.
Edcor xpwr059
375-0-375 , 175 mA 50V .05A 6.3V CT 6A 5V CT 3A
skipper said:
Chinese EL34s were the cheapest i could find at the time. They are "Valve Art", but they are made by Shuguang. However if you are using a cathode resistor tuned for a KT88, you will probably kill an EL34 in short order. A cheap 6L6GC might do the trick (I can bias my JJ 6L6GCs with the "hottest" setting on my Simple SE and they can take it). The other alternative is to just get a second set of cathode resistors or to make a switchable setup.
No and not really, respectively. The 6L6 traditionally has a ST-shaped ("coke bottle") envelope and more conservative ratings than the 6L6GC. The latter is usually in a straight-sided "GT" envelope and has higher anode dissipation and voltage ratings. The 5881 is sort of a lighter-duty 6L6.
The tables are broken down by tube type, then by B+ voltage, then by OPT primary impedance. Then you select a cathode resistance based on how hard you want to run the tube. You can lookup the maximum plate dissipations yourself on the web, but red numbers seem to mean that you are at or over the max, orange means you are pushing them hard but are within the limits. On the far right you can see the estimated power output and the distortion characteristics of each scenario. Of course this is all a simulation, but it gives you an idea of what the trade-offs are and how they affect things.
Looks like your B+ will be in the 475V range and your OPT primary impedance is 5000 ohms.
Correct.
They say that those caps should be rated for the full B+ voltage since they may see it at powerup before the tubes are completely warmed up. Once operating, the voltage across them is considerably less. Maybe George has an inkling if 400V is OK, but I put 600V rated ones in mine. AES doesn't carry them, but tubedepot.com does. I've been giving TubeDepot more of my business lately since they carry a wide selection of tubes and parts and their prices are generally lower than TheTubeStore and many other vendors. AES is sometimes slightly cheaper on certain things...you just have to shop around and compare each item if you want to save the most.
Hi Russ,
Thanks for the response. I've read and followed your build pretty closely. You built a very nice looking SE.
Currently I am just using the cathode resistor that is called out in the part list 560 ohm. I see that on your build you built a selector to switch the resistor path. Do you have a part number for that selector switch?
I think I will get a pair of the cheeper 6l6GC to get the amp running and then later change to the bigger KT88. I will take a look at the SE power table to see what a 560 ohm resistor gets me for the different tubes.
I will also go with the higher voltage coupling caps.
One other thing I would really like to understand is the circuit. I would like to really understand what all the voltages and currents are through all the components. A long time ago I remember using Pspice to analyze RLC circuits in lab. I will just keep reading this forum and hope to regain some of that lost knowledge
Thanks again,
skipper
Thanks for the response. I've read and followed your build pretty closely. You built a very nice looking SE.
Currently I am just using the cathode resistor that is called out in the part list 560 ohm. I see that on your build you built a selector to switch the resistor path. Do you have a part number for that selector switch?
I think I will get a pair of the cheeper 6l6GC to get the amp running and then later change to the bigger KT88. I will take a look at the SE power table to see what a 560 ohm resistor gets me for the different tubes.
I will also go with the higher voltage coupling caps.
One other thing I would really like to understand is the circuit. I would like to really understand what all the voltages and currents are through all the components. A long time ago I remember using Pspice to analyze RLC circuits in lab. I will just keep reading this forum and hope to regain some of that lost knowledge
Thanks again,
skipper
skipper said:
Thanks!
http://www.tubesandmore.com/scripts...elevclients/cemirror/ELEVATOR.FXP?item=P-H393
560 ohm should be a good middle-ground. I run my EL34s like this with 460V B+. The 6L6 I run a little hotter at 470 ohms. At least two builds recently have been able to get their 6L6s to glow with the 560 ohm. If I remember correctly, they were both Chinese 6L6s, not 6L6GCs. My JJ 6L6GCs don't start to glow until I crank them with about 340 ohms on the cathodes.
Sounds like a good plan. The resistors are fairly cheap, so it might be worth your while to pickup a pair of 680s as well, in case the cheap 6L6s don't like the 560s. KT88s will want to run hotter...470 or 430 would be a good choice.
One other thing I would really like to understand is the circuit. I would like to really understand what all the voltages and currents are through all the components. A long time ago I remember using Pspice to analyze RLC circuits in lab. I will just keep reading this forum and hope to regain some of that lost knowledge
Aside from the CCS plate load on the input/driver stage, this is a pretty classic design. Should be able to model it fairly closely in SPICE. You can use an ideal current source on those plates if you can't find a model for the CCS.
It looks like the 560ohm resistor will be OK but will run the 6L6GC really hot. I think I will look further into a selector switch. Just when I thought I was done ordering parts.
When you guy say "Crank it up" do you guys mean you change the cathode resistor which is fixed but you change the resistance on the input with the volume pot. Changing the input resistance will change the current through the cathode resistor thus "cranking it up".
skipper
When you guy say "Crank it up" do you guys mean you change the cathode resistor which is fixed but you change the resistance on the input with the volume pot. Changing the input resistance will change the current through the cathode resistor thus "cranking it up".
skipper
rknize said:
I just popped my EL34's back in last night, and I was kind of surprised when I couldn't turn the volume up past 1/2 way with out the speakers breaking up. I'm probably going to try and put in a selectable resistor setup.
I have Chinese 6L6GC's that glow - visible red plates with the lights on... they were really cheap so I'm not super worried, but thats not quite right either.
Hmm...sounds like the tube was up against one of the rails. Did you have them in UL mode? Most of my output tubes will break-up at high volume in UL mode. This is compounded when there is no CFB. In triode, they are pretty clean up to about 85% where they start going into cutout (blue glow in the tube flashes off). Pushed a little harder is when the distortion becomes audible to me.
Maybe measure the cathode-to-grid voltage at idle?
Maybe measure the cathode-to-grid voltage at idle?
I feel like I'm thread jacking!
sorry skipper - I'll continue this in my original thread (after this post
)
yes Russ it was in UL mode, no feedback. After switching in Cath feedback I can turn up the volume... I think I was just surprised that this tube (EL34) was so different.
My initial build was with transendar OPTs that don't have a UL tap, and I don't think I tried all of the various options with the '34 when I received the massive Edcor's.
back to you skipper
sorry skipper - I'll continue this in my original thread (after this post
)yes Russ it was in UL mode, no feedback. After switching in Cath feedback I can turn up the volume... I think I was just surprised that this tube (EL34) was so different.
My initial build was with transendar OPTs that don't have a UL tap, and I don't think I tried all of the various options with the '34 when I received the massive Edcor's.
back to you skipper
Hey Guys,
I've received 90% of my parts and I have started to assemble my board. I am still waiting for my coupling caps, I think they arrive tomorrow. I am going to get it up and running first before I start adding extra stuff like the adjustable cathode resistors. Below is a list of my build. The tubes I ordered were12AT7 and 5AR4 but I was sent the GZ34 and a CC81, are they the same.
Thanks for all the help so far.
skipper
Edcor XSE25-8-5K OPT.
Edcor xpwr059
Hammond 193H choke
Auricap coupling caps .22uf 600V
6L6GC (chineese)
GZ34 JJ
CC81 JJ
I've received 90% of my parts and I have started to assemble my board. I am still waiting for my coupling caps, I think they arrive tomorrow. I am going to get it up and running first before I start adding extra stuff like the adjustable cathode resistors. Below is a list of my build. The tubes I ordered were12AT7 and 5AR4 but I was sent the GZ34 and a CC81, are they the same.
Thanks for all the help so far.
skipper
Edcor XSE25-8-5K OPT.
Edcor xpwr059
Hammond 193H choke
Auricap coupling caps .22uf 600V
6L6GC (chineese)
GZ34 JJ
CC81 JJ
can someone compare their wiring
Hi,
The Edcor PWR transformer I am using has these values:
Edcor xpwr059
375-0-375 , 175 mA 50V .05A 6.3V CT 6A 5V CT 3A
Its wiring color is different than what is in the simple se wiring instructions. This is how I am wiring it. Can anyone who's used the XPWR059 comment on wiring this to the board.
2x brown wires 5V (2.5V each one) - T1-YEL terminals
5V CT white/brown wire not used.
2x Yellow wires 6.3V (3.15V each one) - T1-GRN terminals
6.3V CT white/yellow wire not used.
2x Red wires 750V (375V each one) - T1-RED terminals
750V CT BLK/RED wire to T1-RED-YEL
2x Grey wires 50V and Common, not used.
Per the lable that came with the Trans.
120 Volt Primary: Connect the two primary windings in parrallel.
Black adn Green connected together
Black/White and Green/White connected together.
Does that sound about right, I suppose it does not mater which wire is connect to the fuse? What is the 750V CT used for?
Thanks,
skipper
Hi,
The Edcor PWR transformer I am using has these values:
Edcor xpwr059
375-0-375 , 175 mA 50V .05A 6.3V CT 6A 5V CT 3A
Its wiring color is different than what is in the simple se wiring instructions. This is how I am wiring it. Can anyone who's used the XPWR059 comment on wiring this to the board.
2x brown wires 5V (2.5V each one) - T1-YEL terminals
5V CT white/brown wire not used.
2x Yellow wires 6.3V (3.15V each one) - T1-GRN terminals
6.3V CT white/yellow wire not used.
2x Red wires 750V (375V each one) - T1-RED terminals
750V CT BLK/RED wire to T1-RED-YEL
2x Grey wires 50V and Common, not used.
Per the lable that came with the Trans.
120 Volt Primary: Connect the two primary windings in parrallel.
Black adn Green connected together
Black/White and Green/White connected together.
Does that sound about right, I suppose it does not mater which wire is connect to the fuse? What is the 750V CT used for?
Thanks,
skipper
looks right, but I don't have that transformer.
Some people have a preference on fusing the hot side, but I don't believe that there is an electrical reason to do so. Break the loop and no current flows...
Re: grounding the 750v center tap. Thats a good question. If I had to guess I'd say that it provides the return path to the rectified B+ voltage. It's not like the heater windings where the return is obvious...
Some people have a preference on fusing the hot side, but I don't believe that there is an electrical reason to do so. Break the loop and no current flows...
Re: grounding the 750v center tap. Thats a good question. If I had to guess I'd say that it provides the return path to the rectified B+ voltage. It's not like the heater windings where the return is obvious...
Put the fuse on the hot side of the mains, it's safer. That way if the fuse blows, there is no mains power in the amp. If it's on the neutral side and blows, there is still mains power inside the amp.
For devices with CE, UL, CSA safety approval, the hot side has to be fused, and with medical devices, both sides have to be fused. That's why most IEC power entry modules have two fuses. Arguably, with two fuses you could end up with live mains inside the unit if the neutral fuse blows and the hot fuse is still intact.
For devices with CE, UL, CSA safety approval, the hot side has to be fused, and with medical devices, both sides have to be fused. That's why most IEC power entry modules have two fuses. Arguably, with two fuses you could end up with live mains inside the unit if the neutral fuse blows and the hot fuse is still intact.
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