Metropoulos Forum

Hi guys. I just bought some mules and bugles for my 1987x was just wondering if they are real ( probably should have asked before I bought them lol) and any thoughts about the tubes I bought? Basically did I do good?

http://www.ebay.co.uk/itm/2-x-EL34-PAIR ... b#viTabs_0

http://www.ebay.com/itm/2-Matched-NOS-A ... 1648171933

http://www.ebay.co.uk/itm/M8162-12AT7WA ... 4836deba91

The EL34's appear to be real XF2 Mullards. Just be sure that the codes that he listed for the tubes are actually printed on the glass down near the base. Japanese made Matsushita's look very similar to Mullards but do not have the "B" code on the glass. I didn't see any test numbers listed so I can't say whether they are a strong pair or not. They do appear to be in nice condition with plenty of flashing left at the top. The main thing is that they are a close match in current draw. Most sellers do not test for this and if they are too far apart they may not perform properly. Be sure to bias the amp properly and check current draw after installing them.

The Bugle Boys also look good. Again, be sure that they have the proper codes printed on the glass. The delta symbol looks like a backwards triangle, followed by a 3 digit code. they appear to test strong and if they are free from microphonics then they should sound great!

The 12at7 also appears legit. Overall it looks like a nice set of tubes in my opinion...enjoy!

Thank you very much for your reply. Yeah that is my only concern that they aren't matched, I didn't think about that.
I contacted the seller and am waiting for a reply hopefully they are close enough.

[quote="danman"][/quote]

Any opinions on the 12AT7 Mullard in the PI Position? I posted in another forum and there were alot of guys that didn't like that idea but I had heard good things about it so I'm not sure.

Well changing tubes in that fashion mean only one thing, that they work. That's it... The operating point of the tubes are different, gains, frequency response, internal resistance that forms a voltage divider with a load, if the gain is changed, than a presence control reacts differently because of the feedback that he relies on is changed. You can try to take all that stuff in to account and to mod the amp for this tube Well fenders do use those in that way... It's not uncommon to see 12at7 as drivers in Hi-Fi amps too... More current, less plate resistance.

Haze13 wrote:Well changing tubes in that fashion mean only one thing, that they work. That's it... The operating point of the tubes are different, gains, frequency response, internal resistance that forms a voltage divider with a load, if the gain is changed, than a presence control reacts differently because of the feedback that he relies on is changed. You can try to take all that stuff in to account and to mod the amp for this tube Well fenders do use those in that way... It's not uncommon to see 12at7 as drivers in Hi-Fi amps too... More current, less plate resistance.

I bought a nice I61 mullard NIB. I really went all out on this. If my amp sounds 10% better I'll be happy.

I read the responses that the fellows over on TGP gave yesterday about the 12AT7 and most of them were spot on. You probably won't enjoy that tube in a Marshall style amp but it could work great in a more Fenderish circuit. I hope that the seller helps you out with the power tubes in the event that he didn't test them for current draw. Most Ebay sellers do not test for this unfortunately, so it can be a crapshoot when buying power tubes. I like to look for old Mullard EL34 singles on Ebay myself. You can usually get them cheaper this way and if you manage to collect enough singles, you can match them up into pairs that are close in current draw. I have been able to put together about four matched pairs of XF2's by doing it this way.

He actually did test them for "anodic current" and he said they were close so I guess I lucked out.

I would still be weary until you have the chance to bias them yourself. I believe that he is simply giving you the anode current reading from his particular tester. What you need to know is the idle current draw at a voltage close to what your amp produces. Only a couple of newer testers will actually give you this reading, one of them being the "Maximatcher". It will test tubes at real amp voltages and allow you to check the current draw in a fixed or adjustable bias mode. Unfortunately, these testers are very expensive and very few Ebay sellers are using one. Hopefully when you get your tubes, you or your tech will check the bias and you may find that the set is a fairly close match.