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In Reply to: RE: 'Overlord' 12AX7 posted by Al Noakes on September 25, 2015 at 07:34:51
A couple a months ago I brought this same tube to inmates attention. At the time it was called 12AX7 HDS. With pretty much the same hype. I guess all the tongue in cheek comments made by us and the inquiries to the seller resulted in the reiteration of the tube as the "Overlord 12ax7".
To be fair to the seller, the tube is USA made and since the WE 5755 was gold pinned unlike the Raytheon version I would have to believe his claim to that. My main complaint is that if this tube is just a WE 5755 with a fancy headdress and a repined base so that it can be plugged into a 12ax7 circuit why not just call it that? It seems a disservice to tube users to apply all this snake oil on what is an excellent WE 5755 tube. By itself that tube can stand on its own merits. Cheers, Dak
Follow Ups:
I reckon it's a Raytheon , look at the shape of the stubby exhaust tip . WE tubes typically have pointy-looking exhaust tips . The pins are chopped off and the tube is soldered to a PCB so it may have gold pins but the original pins , PCB tracks and solder are all added to the signal path . Look at the pictures and you will see a 'crystal jewel' on the base . Apparently this lengthens the life to 50,000 hours !!!
Also : try fitting one of those inside a screening can intended for a 12AX7 . That bling nonsense on top that looks like Janet Jackson's nipple during that 'wardrobe malfunction' will more than likely come a cropper
The seller informs me he has sold nearly 400 pairs in China and Europe in the last month but I can't find a single review online . I don't think anyone is being fooled . Better off buying a $7 Raytheon 5755 and a $5 adapter on Ebay . The result will be the same
Al
I've tried this tube (with adapter) in a tweed era Fender Champ (6V6GT SE) and a blackface Vibrolux (6L6GC push-pull). Both in input stage's OEM 12AX7 position. I thought the tone was quite flat. Poor harmonics, sterile.
Maybe the setup wasn't optimal for the 5755. Or I was expecting it to sound close to the Holy Raytheon 5751. Not even close. It could need more break-in, but I did not like the tone and pulled the tube after one month.
Just my 2¢ worth...
With 180V on the plate, the 5755 is a zero-bias triode. It would be starved for current in a circuit designed for a 12AX7.
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Buy Chinese. Bury freedom.
You're right ! It has double the Ra of a 12AX7 . Operating points will differ significantly
Al
Quick question for you sir (sorry couldn't email you via the forum) . I'm about to build a Champ clone using a Celestion 8" driver . I'm not sure which variant to build but it looks like the 5E1 (choked) or 5F1 (unchoked) are the ones to go for . Just wondering what the B+/G2 voltages are for the 6V6 (the rest I can work out)
Thanks !
Al
Sorry, didn't see this post, until now. 5F1 is the classic everyone does a DIY version. Plate voltage should be in 325 to 350VDC range. 5Y3GT will work fine for the rectifier. Don't use too big iron, esp for the OPT. Or you'll lose the famous "saturation tone" these Champs are noted for...
Good luck! Keep use posted.
Thanks ! I have a suitable 8K output transformer with limited primary inductance that is diminutive in size , the rest of the iron will be modern . I will be using a 8H choke in the HT so it will be a cross between the two variants . Will now be building as a combo , amp will be built in brass . I have a Celestion Eight15 driver on order , all I need to do now is brush up on my chords and bash the chassis into shape !Al
Edits: 10/02/15 10/02/15
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