I am planning to build a Tubelab SE amp that is fine-tuned for the 45 tubes. I have no plans to use other tubes on this one since my main goal is to get the best clarity even if it comes at low power.
For the power transformer, I am planning to use Edcor X131s. Thanks to rknize for customizing it with Edcor! With its 260-0-260v HV winding, I think it is a good choice for 45s.
I will go with Electra Print OPTs since I have read only very good things about their quality. I have a question about the OPT specs for my "45-only" TubelabSE:
Based on tubelab's website, I am planning to run the 45s biased at 30mA on 280V. To have the OPT gapping close to this, I am thinking about getting the ElectraPrint OPTs with 40mA rating, rather than the typical 50mA listed on EP website for 45 tubes. Since I am pretty new to tube amps, I am not sure if I would be better off with a 50mA OPT since most builders use the 60/65mA version for the universal Tubelab SE amp.
I would appreciate any feedback, especially if you have tried 45 tubes on the Tubelab SE.
Thanks!
For the power transformer, I am planning to use Edcor X131s. Thanks to rknize for customizing it with Edcor! With its 260-0-260v HV winding, I think it is a good choice for 45s.
I will go with Electra Print OPTs since I have read only very good things about their quality. I have a question about the OPT specs for my "45-only" TubelabSE:
Based on tubelab's website, I am planning to run the 45s biased at 30mA on 280V. To have the OPT gapping close to this, I am thinking about getting the ElectraPrint OPTs with 40mA rating, rather than the typical 50mA listed on EP website for 45 tubes. Since I am pretty new to tube amps, I am not sure if I would be better off with a 50mA OPT since most builders use the 60/65mA version for the universal Tubelab SE amp.
I would appreciate any feedback, especially if you have tried 45 tubes on the Tubelab SE.
Thanks!
You should know that this transformer comes in a little "hot" when used with 45s. The secondary winding was designed for 175mA, so the 260-0-260 come in higher because I forgot to take into account the lower plate current of the 45s. Also, the load on the 6.3V winding is about half as with 300Bs, so the primary and the core have lees load. The result is that you get about 265-0-265 from that winding.
This yields about 320V B+ when the amp is in "45 mode" (I'm using a choke with 82-ohm DCR). All of my 45s (about 20 or so now) work fine at this voltage, but it is technically exceeding the plate voltage spec of a 45. I believe George has done the same, though he has those NX-483s in there now.
If you are planning to use some ultra-rare NOS blue glass globe Acturus tubes, you might want to consider lowering B+ a bit. One option is to ask Edcor to tweak my design slightly and move the 260-0-260 taps to 240-0-240. That should yield 280-300V B+, depending on what choke you use.
This yields about 320V B+ when the amp is in "45 mode" (I'm using a choke with 82-ohm DCR). All of my 45s (about 20 or so now) work fine at this voltage, but it is technically exceeding the plate voltage spec of a 45. I believe George has done the same, though he has those NX-483s in there now.
If you are planning to use some ultra-rare NOS blue glass globe Acturus tubes, you might want to consider lowering B+ a bit. One option is to ask Edcor to tweak my design slightly and move the 260-0-260 taps to 240-0-240. That should yield 280-300V B+, depending on what choke you use.
I have about 15 or so 45 tubes, all very used and in varying condition from excellent to "3 for $12 on Ebay". They all work fine at 325 volts, and I think they sound better at 325 volts than they do at 275, but maybe it is just the extra 1/2 watt. I have not tried any globe 45's because all of mine were purchased for less than $20 each and you don't get globes for that price.
I was at a flea market in the middle of nowhere a few years ago when I found the chassis of an old Sparton radio lying in the dirt. It had 7 globe tubes in it with a tag that said "all tubes replaced in 11/1929." I bought it for $20. It contained a pair of NX-483 output tubes which turned out to be a 45 with a 5 volt filament. These tubes are now 80 years old and still work great, even at 320 volts.
It is alive!
After a few months of collecting all the parts and eBay bidding for a bunch of tubes, I managed to (sort of) complete my TubelabSE project. It still needs to be put into a nice enclosure before I can call it complete but it is alive and currently burning in with Miss Sarah Vaughan.
Since I am planning to have everything except the tubes, transformers and the motor-run cap under the hood, I installed the caps to the other side of the PCB.
The power transformer is an Edcor XPWR131 and the OPTs are Electra-Print. Jack was nice to provide a 3K tap on the OPTs (in addition to 5K) in case I need to use them with 300Bs in the future.
Thanks to all who have posted about their TubelabSE experiences in the past. Reading through various posts helped me a lot with this pretty smooth build.
Here are a few pictures:
After a few months of collecting all the parts and eBay bidding for a bunch of tubes, I managed to (sort of) complete my TubelabSE project. It still needs to be put into a nice enclosure before I can call it complete but it is alive and currently burning in with Miss Sarah Vaughan.
Since I am planning to have everything except the tubes, transformers and the motor-run cap under the hood, I installed the caps to the other side of the PCB.
The power transformer is an Edcor XPWR131 and the OPTs are Electra-Print. Jack was nice to provide a 3K tap on the OPTs (in addition to 5K) in case I need to use them with 300Bs in the future.
Thanks to all who have posted about their TubelabSE experiences in the past. Reading through various posts helped me a lot with this pretty smooth build.
Here are a few pictures:
Attachments
Thank you Russ! Your posts in the other threads helped me a lot. I must admit that the pictures on your blog inspired me with the side hanging silicons. Installing the capacitors on the back side of the PCB was straightforward but the regulator, mosfets and diodes were getting me concerned. It eventually came together pretty well.
the XPWR224 is close, but I would look for a bit more current on the 6.3 volt winding. The conversion from AC to DC and the regulator both waste some power so that the actual current drawn from the transformer is a bit more that what the tubes alone draw.
That said I use these:
Hammond Manufacturing - 6K56VG - TRANSFORMER; PRI:110-120V; 50/60HZ; 540VCT @120DCMA; 5V @3A; 6.3V @3.5A; LEADS - Allied Electronics & Automation
Which are rated for 3.5 amps and seem to do OK. I did have one of these die, but it died because of rust. A window leaked during a hurricane and the transformer got doused in a lot of water. I didn't realize this at first, and the amp worked so I used it. Then one day I saw "smoke" coming out of the transformer. I realized that the smoke was really steam, so I took the transformer apart. It was really wet inside, so I baked it in the oven for a while to dry it out. It recovered but died a few months later. Autopsy revealed some internal rust and it was still wet inside. The replacement is still in the amp and working well 11 years later.
The Xpwr131 was specifically designed for the TSE, and can be used for either 45's or 300B's. It is another option.
That said I use these:
Hammond Manufacturing - 6K56VG - TRANSFORMER; PRI:110-120V; 50/60HZ; 540VCT @120DCMA; 5V @3A; 6.3V @3.5A; LEADS - Allied Electronics & Automation
Which are rated for 3.5 amps and seem to do OK. I did have one of these die, but it died because of rust. A window leaked during a hurricane and the transformer got doused in a lot of water. I didn't realize this at first, and the amp worked so I used it. Then one day I saw "smoke" coming out of the transformer. I realized that the smoke was really steam, so I took the transformer apart. It was really wet inside, so I baked it in the oven for a while to dry it out. It recovered but died a few months later. Autopsy revealed some internal rust and it was still wet inside. The replacement is still in the amp and working well 11 years later.
The Xpwr131 was specifically designed for the TSE, and can be used for either 45's or 300B's. It is another option.
Hi all, just built TSE 45. want to add auxiliary capacitor [80uf/370v motor run]. My question is how do I wire it to C5? is it direct wire-in into C5 pads or some other way?
Also did the check out and I get these number; are they ok or should I try to lower B+ some? I'm using XPWR131, Triad CX14 choke, JJ GZ34 rectifier; rest of filtering components are as spec'd by George.
310V B+
175 B-
302V Plate voltage on 45 tubes
2.1V filament supply, kind of low? should be closer to 2.5, correct?
5842 plate at 175V
45 tubes biased at 27mA
Also just read that TSE boards will no longer be made due to the difficulty in acquiring certain parts. I hope mine works long enough to be enjoyed. Looking forward to new design from George.
Also did the check out and I get these number; are they ok or should I try to lower B+ some? I'm using XPWR131, Triad CX14 choke, JJ GZ34 rectifier; rest of filtering components are as spec'd by George.
310V B+
175 B-
302V Plate voltage on 45 tubes
2.1V filament supply, kind of low? should be closer to 2.5, correct?
5842 plate at 175V
45 tubes biased at 27mA
Also just read that TSE boards will no longer be made due to the difficulty in acquiring certain parts. I hope mine works long enough to be enjoyed. Looking forward to new design from George.
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