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Tubelab SimpleSE: Edcor XSE15-8-5K or XSE25-16-7.6K?

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while I wait for the OPTs I simulated the SimpleSE PSU on PSUDII and see amp draw at turn on rises up to about 0.8A while the 5AR4 is rated for 0.75.

50mA doesn't seem to be much of an issue, but having read about those blown rectifiers (theoretically due to the standby switch and FRED diodes) would using a CL-90 in series with the power transformer primary help here?

Will a CL-90 be fine for 220V mains? (less than 1A current draw). I think I recall George mentioning he used another one at the HV center tap also, is this advisable too?
 
I'd like to jump onto this thread if I could since the topic was Edcor OPTs and a Simple SE.

I'm building a Simple SE of my own and have the pcb, tubes and a hammond 274BX PT so far. Tubes are JJ 5AR4, JJ 12AT7, and Shuguang 6L6GC.

I'm looking at getting a pair of the Edcor GXSE-15-8-5K OPTs but I wonder what is the best for 6 ohm speakers 4 ohm or 8 ohm taps? I will be using the amp with a pair of 92db efficient Infinity SL-30 speakers which are 6ohm.
 
Coreyk78 said:
I'm looking at getting a pair of the Edcor GXSE-15-8-5K OPTs but I wonder what is the best for 6 ohm speakers 4 ohm or 8 ohm taps? I will be using the amp with a pair of 92db efficient Infinity SL-30 speakers which are 6ohm.

For an output transformer with a specified 5K primary impedance, I would put 6 ohm speakers on an 8 ohm tap. That way your actual reflected impedance will be 6/8 * 5K, or about 3750. Keep in mind the "ideal" primary impedance is probably somewhere between 3K (more power) and 5K (lower distortion).

If you put your 6 ohm speakers on a 4 ohm tap, your reflected impedance will be 6/4 * 5K, or 7500 ohms. That's a bit high for the kinds of output tubes you'll be using in the Simple SE, and may excessively limit your power output.
 
Ty_Bower said:


For an output transformer with a specified 5K primary impedance, I would put 6 ohm speakers on an 8 ohm tap. That way your actual reflected impedance will be 6/8 * 5K, or about 3750. Keep in mind the "ideal" primary impedance is probably somewhere between 3K (more power) and 5K (lower distortion).

If you put your 6 ohm speakers on a 4 ohm tap, your reflected impedance will be 6/4 * 5K, or 7500 ohms. That's a bit high for the kinds of output tubes you'll be using in the Simple SE, and may excessively limit your power output.

Thank you for the detailed explanation, I didn't know the math behind it to make the decision. I'll be ordering the 8 ohm version then. Thanks again! :D
 
>Tubelab SimpleSE

hi there can some one post a detailed picture of the back so i can print it on copper or is this double sided soldering i have got most of the compounds but no PCB as i have tried to get one from tube lab but there is no response from them and now i don't know want to do.or is there some where i can my one apart from tube-lab
 
Tubelab does a lot of great work supporting his products and the DIY community in general. He supplies the schematic for his Simple SE on his web site. He provides the circuit boards for his amps. I would not support anyone giving out the details of the the boards as they are the one form of income he gets for all of this great support (besides, it is a double sided board).

Tubelab has had a lot of personal and work pressures for quite some time. If he is not responding, do not worry, he will when he can. It is worth waiting for the boards. A great product worth every penny asked for for the circuit boards.

Chris
 
If you've been waiting for more than a few days, try again. Also, as someone who has a website that generates a fair amount of email, I can tell you that it is important to put a meaningful subject header on the email. Even with spam filters, too much junk gets through and I don't even open email that have generic subject headers.

Tubelab's product are worth the effort and his efforts are patronized by buying the PCB. Everything you need to build the amp is right there without the need to buy one, but having the whole design handed over on a silver platter is worth the money.

Russ
 
i there thanks for the email he has just sent me the info's for paying so i am happy thanks again.

I must apologize for getting behind on email again. I can't answer Tubelab email from work, and I have been there until 8 PM for the last two weeks. Last weekend I was out of town to visit my mom which let the email monster get the best of me again. I do get considerable email , and I did see a few emails from Carl asking how to purchase a board. I thought this was explained fairly well on the web site, but he wanted a Paypal invoice. Paypal is blocked from work, and I was there most of yeaterday stuffing IC chips into test fixtures. I sent the invoice this morning, prompt payment was recieved and the board will go out tomorrow morning.

In the future, the quickest way to order a board is to just send payment via Paypal and include mention of which board you want in the subject or text box on the Paypal form. The board will go out the next day for domestic orders, and twice a week for international orders. It may take me a few days to acknowledge the order, since it requires an email, but I send the boards out quickly.
 
wrechclone wrote:
"I haven't done much critical listening with the amp, as it also has an RF oscillation issue, but I'll report back once that is straightened out."

Have you resolved the RF oscillation? I use a 100 Ohm 1 watt resistor in series from B+ to the plate cap. This stops oscillation on the 1625 and sweep tubes. Also with some the G2 voltage needs to be lowered with a voltage drop resistor to stop oscillation.
 
I'm auditioning a sand-state amp right now. I have vanquished the oscillation problem (fingers crossed) by using a larger stopper resistor (2k) at the gate of the input jfets. The jfets were fast to begin with, and cascoding them with triodes made them extra slippery. The 2k appears to have shut them up. I already had grid and plate stoppers on the 1625s - they were just doing what they were told to do. I'll move the amp back into the living room when I get a chance.
 
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