Mullard Tubes For Testing Please

[precd]

I recently purchased 4 Mullard tubes for the Quickie, still wrapped in their packing and NOS. However I am not having good luck with them. there is a hum when using the tubes. I have switched them around in every possible position but still no luck.

Would one of you seasoned veterans let me send the tubes to you for testing in your system please? No offence but No newbies. I am one of those and need to eliminate that common denominator.

[Natural Sound]

Do the stock tubes that came with your quickie work OK? Do you have fresh batteries installed?

I have a B&K 707 tube checker that checks 3S4 tubes. I could probably do it for you but I cannot promise a fast turnaround. I have a lot of stuff going on right now. Are you in the U.S. or somewhere else?

[mcandmar]

Out of interest where did you buy them from?   I got four in the post today from that eBay seller in Cyprus, will test them later and report back.   

[precd]

Out of interest where did you buy them from?   I got four in the post today from that eBay seller in Cyprus, will test them later and report back.

Same seller. I was excited about receiving them. The tubes sound good but have a nice audible hum. Other tubes sound fine in the preamp. Let me know what you find.

[precd]

Do the stock tubes that came with your quickie work OK? Do you have fresh batteries installed?

I have a B&K 707 tube checker that checks 3S4 tubes. I could probably do it for you but I cannot promise a fast turnaround. I have a lot of stuff going on right now. Are you in the U.S. or somewhere else?

Thank you. I may shoot you a pm later and send them to you. I am in the good old U.S. of A. I have fresh batteries and the tubes i had in there before worked fine. Those are some RCA tubes from '45. Put them back in and wholla! Works fine.

[galyons]

The RCA's are VERY hard to beat.  I am a Mullard fan and have some, (from the Cypress) guy.  They just haven't made it into the Quickie yet.  I also had good luck with some Sylvania VT-174/3S4 from 1944.  They are a bit more detailed than the RCA's, but that is a trade-off for some warmth.

I have tried other brands, but found too many to be too microphonic.

Cheers,
Geary

[mcandmar]

I installed the Mullards and they are working fine for me.

I would try physically moving your quickie to see if they are picking up mains hum from something around it. It does seem odd that they would be noisier than other tubes but you never know.

We really need to start a dedicated tube thread to keep everyones findings in one place, i've tried a LOT of different brands at this stage with mixed results, some more microphonic than others, some sound smoother than others etc. I would be interesting to see if we all had the same findings with various brands.

[Paul Joppa]

The Quickie, by itself, cannot create hum. If you hear hum, it is coming in from outside, either an electric, magnetic, or electromagnetic (radio) field.

This suggests that the Mullard design is not as immune to whatever the source is, compared to the RCAs. So it's probably not a matter of a good vs. bad tube, it will be the internal geometry of the tube's components.

The most common sources of external hum and noise are things like cell phones, light dimmers, nearby power supplies in other gear, computers, etc.

[mcandmar]

I did read a thread recently that suggested they are Beam Tetrodes rather than Pentodes which may explain any difference. Interestingly the Brimar 3S4 datasheet is the only one to call them Tetrodes, all the others say Pentodes.

[precd]

The Quickie, by itself, cannot create hum. If you hear hum, it is coming in from outside, either an electric, magnetic, or electromagnetic (radio) field.

This suggests that the Mullard design is not as immune to whatever the source is, compared to the RCAs. So it's probably not a matter of a good vs. bad tube, it will be the internal geometry of the tube's components.

The most common sources of external hum and noise are things like cell phones, light dimmers, nearby power supplies in other gear, computers, etc.

I wonder if the hum is being generated from my power amplifier.  I noticed that when I turn if off the hum drops down considerably. The amps filter capacitors will run the show for around 8 seconds or so until they dissipate. The caps are 25 years old so I wonder if they have lost their ability to filter DC well. I have toyed with the idea that this could be the problem. But then I ask why do the RCA tubes not hum? I have touched a ground to the bus of the Quickie with no results. I did ground the aluminum box that houses the pre awhile back. I don't know.....I wish I did!

[galyons]

That pretty much narrows it down. Sounds like the power amp is humming along to the music!  Move and/or re-orient the Quickie away from the power amp.  Try listening to it in different locations & positions for the lowest hum.  As usual, PJ nails it.  The different internal construction of same tubes/different manufacturer will show up in this utilization, when, perhaps, not in others.

Cheers,
Geary