Getting Parts for Ike

[ashok]

I have been using a JJ/Tesla 5AR4 that I bought from Angela, in my ST35,
and it seems to work quite well. The rectifier tube drops about 50V, so that should figure into your calculations. In my ST35, I was using the 270HX.
After fitting the tube rectifier, I left the 270HX in place, but jumpered one of the 3.3K resistors. That resulted in a B+ of about 335V, (30V less than stock). The power tubes are biased at 31mA. Hope this helps.

Ashok

[Shannon Parks]

Hey Guys, Ive been procuring parts for a pair of ikes that one day I will eventually begin to build, hopefully soon. But before I start i have a couple questions. First off I want to rectify the ikes with 5ar4's and I was wondering what I need to do to impement this. Do I need to change the Power Transformer or will the 274bx handle the chores? I know alot has been covered on the ST35 board, and I have been using that as a guide, but I also want to get it right when I build them.

Hi Brent,

I would stick with the 274BX. I get 490V B+ all the time, and being at 465V wouldn't be a problem unless you plan to run the Ike over 60W. The voltage loss is more critical in the ST35.

The Sovtek 5AR4s are cheap and have worked well for me.

Shannon

[Shannon Parks]

I have been using a JJ/Tesla 5AR4 that I bought from Angela, in my ST35,
and it seems to work quite well. The rectifier tube drops about 50V, so that should figure into your calculations. In my ST35, I was using the 270HX.
After fitting the tube rectifier, I left the 270HX in place, but jumpered one of the 3.3K resistors. That resulted in a B+ of about 335V, (30V less than stock). The power tubes are biased at 31mA. Hope this helps.

Ashok

Hi Ashok,

I plan to do a post about your amp this weekend. I jumpered the 100 ohm resistors as well as the IRCL, so you are up around 350V. Plus I upped the bias to the max position (34mA).

To be honest, it is the best ST35 clone I have heard! Maybe those Auricaps and tube rectifier make a difference? Full details coming including how to tweak the diy ST35 for low noise as well as the Eiclone.

Shannon

[Jim McShane]

I have been using a JJ/Tesla 5AR4 that I bought from Angela, in my ST35, and it seems to work quite well. The rectifier tube drops about 50V, so that should figure into your calculations. In my ST35, I was using the 270HX.
After fitting the tube rectifier, I left the 270HX in place, but jumpered one of the 3.3K resistors. That resulted in a B+ of about 335V, (30V less than stock). The power tubes are biased at 31mA. Hope this helps.

If I may, the 50 volt drop sounds a bit high. You should know that a number of early JJ 5AR4s were misbuilt, with the result that some drop much more voltage than a typical 5AR4. The tubes worked, but not to 5AR4 typical performance levels. If you ever change rectifiers (even to another JJ) be careful. You may see a big increase in B+ as a result if you get a proper tube. I dumped all my misbuilt JJs in the trash (ouch, big $$) but some vendors didn't - or didn't even know they were misbuilt. So excercise caution...

Also, FWIW, the Chinese 5AR4 built in the last few years is an excellent tube. Earlier ones were firecrackers, but the current stuff is very good. I have had ZERO failures of the Chinese tubes.

I'm sorry I haven't registered here long ago, but I'll be happy to help anyone I can now that I'm here. Thanks for the hospitality Shannon!

[Shannon Parks]

Thanks for dropping by, Jim! Everyone should have figured out by now that the center of Tubedom is located in the great state of Illinois. Maybe because we have some of the best ears in the world (insert corn joke). Yellow_Light_Colorz_PDT_06

If I may, the 50 volt drop sounds a bit high.

I see a nominal B+ of 370V with UF4007s in a diy ST35 using a 270HX. Taking into consideration the extra drop Ashok had in the filter stage, it was more like a 25V drop. Sorry I didn't mention this earlier.

Shannon

[Jim McShane]

I see a nominal B+ of 370V with UF4007s in a diy ST35 using a 270HX. Taking into consideration the extra drop Ashok had in the filter stage, it was more like a 25V drop. Sorry I didn't mention this earlier.

Oh, okay, so the 50 volt drop wasn't just the rectifier. I haven't seen the schematic of his supply, thanks for the update.

But do be careful on the JJs regardless!

[ashok]

With the stock ST-35 and the Hammond 270HX, the B+ was 370VDC. I changed to a tube-rectified version with the 5AR4, followed by a 40uF capacitor at the tube socket, the Hammond 156R choke which then fed into the standard ST35 filtering scheme.

This dropped the B+ to just under 330V. So, the overall drop in B+ was around 40V, (drop in rectifier + drop in choke + drop in the 50ohm resistor).

So, my earlier statement about a 50V drop in just the rectifier was wrong. My apologies for the confusion.

Shannon has since tweaked my amplifier to jumper the 50 ohm resistor, as also the inrush limiter in the ac input to gain some more volts at the B+.

Regards,

Ashok

[Jim McShane]

With the stock ST-35 and the Hammond 270HX, the B+ was 370VDC. I changed to a tube-rectified version with the 5AR4, followed by a 40uF capacitor at the tube socket, the Hammond 156R choke which then fed into the standard ST35 filtering scheme.

This dropped the B+ to just under 330V. So, the overall drop in B+ was around 40V, (drop in rectifier + drop in choke + drop in the 50ohm resistor).

So, my earlier statement about a 50V drop in just the rectifier was wrong. My apologies for the confusion.

Shannon has since tweaked my amplifier to jumper the 50 ohm resistor, as also the inrush limiter in the ac input to gain some more volts at the B+.

Ahh, okay, I understand completely now. Thanks for the clarification, it all makes sense. No apology needed, but thanks for the courtesy! Yellow_Light_Colorz_PDT_15