Okay, now for the dreaded and inevitable newb question.
Why exactly did you increase the value of that cap from 120 to 220? I'm sure you had a good reason it's just that it isn't obvious to me and I think I smell a learning opportunity. Thanks for all the help thus far Russ.
Rick
Don't go crazy bidding on Mullards on eBay. If you're patient, eventually you'll get lucky. I grabbed a Realistic labeled 5AR4 off eBay for less than $20. From the photos, I could tell it was a Mullard. Just keep watching and waiting, and eventually it will happen.
Even with a pair of KT88 in the Simple SE, it should be drawing less than 175mA through the rectifier. This is a reasonable load for most 5AR4, even the cheap ones. I've run Ruby branded Chinese 5AR4, Sovteks, Mullards, and Japanese (probably Matsushita) GZ34. They've all worked just fine. I've also run a couple 5U4GB as well.
I'd suggest you keep the first cap no larger than the specified 47uF. In fact, you might want to consider downsizing it a little. The datasheets for the 5U4 state 40uF max for the first cap. Some other "interesting" rectifiers, such as the 5R4, indicate the first cap should be no bigger than 4uF!
The Mullard and other NOS rectifiers command silly prices. I do have a pair of Mullard GZ34's in a preamp. They replaced some Chinese 5AR4's (one of which is now in my SSE). However, I could never hear a difference. Others may disagree, but I don't think rectifiers have the impact on sound quality, that say, small signal tubes do.
What I like about the NOS rectifiers is their reliability. Some reports of these tubes going for 20 years or more. I also have a few pairs of the Japanese Matsushita GZ34. They have a good reputation for longevity as well, and somewhat less money than a Mullard.
The advice about using a "cheap" rectifier is golden. It would make you very sad to lose an expensive tube on a new build that had a wiring mistake.
What I like about the NOS rectifiers is their reliability. Some reports of these tubes going for 20 years or more. I also have a few pairs of the Japanese Matsushita GZ34. They have a good reputation for longevity as well, and somewhat less money than a Mullard.
The advice about using a "cheap" rectifier is golden. It would make you very sad to lose an expensive tube on a new build that had a wiring mistake.
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The SSE and TSE are easy enough loads the 5AR4. I have two JJs and one would sometimes arc over on startup on my ST70 due to higher load there. They are known to have quality issues but they work perfectly fine in these amps.
On the Chinese 5AR4...I have to say that the two I have are pretty tough. One I use as a test tube and it's been arced over many times over the years and it's still strong!
On the Chinese 5AR4...I have to say that the two I have are pretty tough. One I use as a test tube and it's been arced over many times over the years and it's still strong!
Hey ho! Damn, today was better than Christmas.
First the Spud amp (Jerry's at Hawthorne) I bought showed up via USPS truck, then our regular mail guy delivered my Eyuda run cap and my TubeLab PCB's!
So then being inspired by all the fun stuff I got to rummaging around in the closet I keep audio type stuff in and ran across the old Peavey guitar amp I've had for 30 years. Anyway I couldn't remember what it had for tubes so I checked it out and low and behold it had a pair of 6L6GC's, Lindal branded, June 78 date, made in USA. I believe these were made by GE and I intend on trying them out in the SSE. To top it all off I also purchased a Mullard GZ34 tube for the SSE. Just don't ask what I paid for it.
Rick
First the Spud amp (Jerry's at Hawthorne) I bought showed up via USPS truck, then our regular mail guy delivered my Eyuda run cap and my TubeLab PCB's!
So then being inspired by all the fun stuff I got to rummaging around in the closet I keep audio type stuff in and ran across the old Peavey guitar amp I've had for 30 years. Anyway I couldn't remember what it had for tubes so I checked it out and low and behold it had a pair of 6L6GC's, Lindal branded, June 78 date, made in USA. I believe these were made by GE and I intend on trying them out in the SSE. To top it all off I also purchased a Mullard GZ34 tube for the SSE. Just don't ask what I paid for it.
Rick
Yeah these Lindal's were certainly a cheap tube in their day, but probably a better tube than most current production. As I understand it Lindal was a mail order house that sold inexpensive tubes for guitar amps. They actually made nothing, just rebranded stuff from companies like GE, ect.
Russ, I don't think I've ever seen a Hitachi tube, but my instincts tell me that they're more than likely a pretty good tube knowing how the Japanese usually do things. I'd guess it's rebranded (?) but not from a junk source.
What do you think of the 6L6 in the SSE? If I just put in the resistor value best suited to the KT88 that shouldn't cause any issues with the 6L6 during the trial stage would it?
Thanks & Happy Easter!
Rick
A GE is a GE, so it is probably a good tube.
I don't think so. They are marked "Made in Japan". Japan didn't have as good a reputation back in those days as the did later on. However many of the factories were setup by Western companies such as RCA and Mullard, as I understand it.
The 6L6 is a compromise between the sound of the EL34 and the KT88. Using a small resistor value meant for the KT88 with a 6L6 will make the 6L6 run very hot. Take a look at that table on George's site that I mentioned before.
A GE is a GE, so it is probably a good tube.
We'll find out. The tubes can't have many hours on them at least. I got this thing sometime in 1980 and the tubes are dated 1978. It hasn't played an hour since I got it.
I don't think so. They are marked "Made in Japan". Japan didn't have as good a reputation back in those days as the did later on. However many of the factories were setup by Western companies such as RCA and Mullard, as I understand it.
Interesting, I didn't realize they built many of their own tubes.
The 6L6 is a compromise between the sound of the EL34 and the KT88. Using a small resistor value meant for the KT88 with a 6L6 will make the 6L6 run very hot. Take a look at that table on George's site that I mentioned before.
Geeze, I'm really going to have to figure out the switching mechanism. Russ, what did you use for a switch with yours?
In mine I used a Lorlin rotary switch. I built a selectable switch very similar to what Russ has.
MOUSER LINK
MOUSER LINK
Thanks Nic, but, erm uh, could you perhaps explain the difference to the ignorant?
Also, what size resistor did you put on the board itself?
Rick
Shorting makes a connection before breaking. Non shorting breaks the connection before making one. If you go with a resistor on the board either would work just fine. If you are not having a resistor on the board you want the shorting switch.
On one of my SSEs I have a 1k ohm resistor on the board and then a few different ones on the switch to get various bias points. At first I just used a simple DPDT toggle switch to give me three different resistor values. It worked really well.
On one of my SSEs I have a 1k ohm resistor on the board and then a few different ones on the switch to get various bias points. At first I just used a simple DPDT toggle switch to give me three different resistor values. It worked really well.
Thank you Sir.
I really like this idea as implemented by Russ and yourself. It certainly affords a ton of flexibility! On the one hand I can grasp the concept of simply using different resistors to change the bias point for the output tubes. It's just that I'm a little (ok a lot) shaky on the mechanical implementation of the idea.
Nic, do you by chance have a photo of this particular portion of your SSE? Often times, especially with me, a picture can be worth a thousand words.
Rick
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