Electro-Harmonix Tubes

[sr1200]

Just wondering if anyone had a bead on these. I put an EH into a mic i built and it's sounded great for about 2 years with VERY light use (Probably less than 100 hours of use). The other day, i started getting that old fireplace rumble out of it. Swapped the tube and it went away. I don't think I've ever had a tube go bad that quick out of any brand (even the cheapo Chinese ones). Just a fluke or are these tubes just not very good?

I've had tubes in certain gear for decades now and they still seem fine, and have served for way more time being used. Certain tube retailers are looking for up to hundreds of dollars for NOS tube of the same type (6072). Not sure it's really worth shelling out that kind of dough... maybe thats just me being cheap. The EH and JJ tubes are around $30/ea. Tung-Sol going for around $80 and RCA/Raytheon/GE anywhere from $140-over $200.

Anyone have any suggestions for a middle of the road 6072, or places to shop that aren't charging as much?

 

[ruffrecords]

I use EH tubes all the time and have found them to be consistently good. I have had tube failures with JJ but not EH or Sovtek. However, I don't use 6072 tubes so maybe they are an exception.

Cheers

Ian

 

[drtechno]

Just wondering if anyone had a bead on these. I put an EH into a mic i built and it's sounded great for about 2 years with VERY light use (Probably less than 100 hours of use). The other day, i started getting that old fireplace rumble out of it. Swapped the tube and it went away. I don't think I've ever had a tube go bad that quick out of any brand (even the cheapo Chinese ones). Just a fluke or are these tubes just not very good?

I've had tubes in certain gear for decades now and they still seem fine, and have served for way more time being used. Certain tube retailers are looking for up to hundreds of dollars for NOS tube of the same type (6072). Not sure it's really worth shelling out that kind of dough... maybe thats just me being cheap. The EH and JJ tubes are around $30/ea. Tung-Sol going for around $80 and RCA/Raytheon/GE anywhere from $140-over $200.

Anyone have any suggestions for a middle of the road 6072, or places to shop that aren't charging as much?

So is the mic made for the 6072?
The reason why I say that is people have put in a 6072 in a 12ax7 circuit and it craps out on them.

 

[Gus]

What was the measured heater voltage at the tube?
What value is the grid to ground resistor?
What are the operating points of the tube?

 

[sr1200]

The tube is for one of matadors ELA-M clones. I dont have the schematic in front of me but i can look it up when i get a few min. 6072 was the suggested tube for the project.

 

[drtechno]

The tube is for one of matadors ELA-M clones. I dont have the schematic in front of me but i can look it up when i get a few min. 6072 was the suggested tube for the project.

What is the size of the cathode resistor?

You see, this one and the C12 is another badly designed microphone that doesn't need to be perpetuated. A lot of these old mics are totally garbage.
You have a starved biased tube circuit. You con either try a bigger cathode resistor or force bias the grid with -1 V, how ever you want to do that.

 

[RuudNL]

I always had good results with EH tubes in genaral, but the latest batch (50 pcs.) of EF86's was pretty disappointing.
About 25% was not 'microphone grade'. (In the past the percentage 'usable' tubes was much higher.)
JJ tubes are even worse! They work for a short time but then they develop all kinds of problems, noise, crackling etc.

 

[Gus]

drtechno
The C12 is a nice design
Note the loading of the power supply by the pattern control and other parts
This helps make a series power supply act more like a shunt supply
IIRC Ricardo made a post years ago explaining the cleverness with the cathode/fixed type biasing used.
I am not a fan of the DIY clone power supplies on the web IMO they miss an important part of the design
I would also adjust a few things to make it "better"

The 250/251 is a standard cathode biased triode out circuit
The mix of parts used matters
The one part I am not of fan of is the pattern control there is IMO a better way to do this if you want switch the patterns at the microphone.

I have made a solid state circuit(s) to replace the tube in an 250/251 type circuit it combines the good of solid state and tube for use in microphones

 

[Tubetec]

I got away from using JJ tubes also , many small signal tubes were microphonic to begin with ,
power tubes were problematic too .

I ordered in a bunch of Sovtek years ago , ecc83's and 5881's , I didnt get a single failure or customer returning with a problem .

 

[My3gger]

I always had good results with EH tubes in genaral, but the latest batch (50 pcs.) of EF86's was pretty disappointing.
About 25% was not 'microphone grade'. (In the past the percentage 'usable' tubes was much higher.)
JJ tubes are even worse! They work for a short time but then they develop all kinds of problems, noise, crackling etc.

Not long ago we got a few EH EF86 (from 2011) for preamp retubing, all of them had similar inferior mechanical construction and pretty high noise. Jakob wrote about new and nos EF86s in mics..

 

[terry setter]

I had good luck with EH 6072 tubes in the 2000's. Maybe quality has slipped, but MAN, were they quiet! That is to say, the quiet ones were really quiet. I once measured 250 of them. The best 10 were VERY, VERY quiet and had VERY, VERY low microphonics. The worst 10 or so went straight into the trash. That is to say, it was pretty much a bell-shaped curve on whether they were good for my purposes or not. But the curve definitely leaned toward quietness. I've never tested an NOS 6072 that was as quiet as the 6 best EH 6072s that were in the box of 250. I'm not saying that such NOS tubes don't exist, but I haven't found one. I have a small stash of "selected" GE 6072, some 5-star, some no, and none of them is as quiet as the best EH 6072s. I mentioned this to David Bock once and he said "Ya, they're quiet alright. But I've never heard one that made the hairs on the back of my neck stand up the way the NOS tubes can."

I'm not trying to start a flame war here, and I still use EH 6072s in my designs and repairs, but, FWIW, all my "personal" mics have selected NOS tubes in them. Maybe I'm a bit superstitions, too...

 

[sr1200]

Cathode mark on the board has a 1.8k resistor connected to it. I thought i had the schematic printed up somewhere around here but cant find it.

 

[Delta Sigma]

Cathode mark on the board has a 1.8k resistor connected to it. I thought i had the schematic printed up somewhere around here but cant find it.

https://groupdiy.com/threads/ela-m251-inspired-microphone-build-thread.67515/

 

[CJ]

EHX did a boycott on Russia due to the war with Ukraine, this was a while back, do not know what is going on now.

Prices doubled overnight, maybe they are using seconds to fulfil orders.

Can't beat a 5 star GE.

 

[Electrobumps]

Prices doubled overnight, maybe they are using seconds to fulfil orders.

That wouldn’t be a smart business move from EHX. Not something you can get away without damaging your brand.

 

[TLRT]

You can try to clean the cathode,run the tube near max specs(I remember 330v anode max near 1.5watt dissipation)
If it is an isolation resistance between the sections then cannot be recovered.

 

[My3gger]

EHX did a boycott on Russia due to the war with Ukraine, this was a while back, do not know what is going on now.

Prices doubled overnight, maybe they are using seconds to fulfil orders.

Can't beat a 5 star GE.

The seller who sent me noisy tubes is closing his shop, other customers have also received unusually bad EH specimens from him. Local guitar amp repairman with the AT1000 tester has no problems with the latest EH series bought from Tube Amp Doctor, or what the customers brought from other shops...

 

[Tubetec]

As was said previously , a tube tester doesnt check for microphonics or noise ,so what might show as a good tube might not perform well in a particular circuit .

 

[amplexus]

EHX did a boycott on Russia due to the war with Ukraine, this was a while back, do not know what is going on now.

Prices doubled overnight, maybe they are using seconds to fulfil orders.

Can't beat a 5 star GE.

EHX Didn’t do a boycott on Russia. Mike Matthews (EHX/New Sensor) OWNS the Xpo-Pul factory in Russia and has for two decades.

Sanctions meant that Mike couldn’t get his product out of Russia for a time. Somehow a workaround was found. Those of us with dealer/OEM relationships with New Sensor got an email initially that stated they were not going to be able to take new orders, ship existing orders, or fulfill backorders “until further notice”. Some time (i believe it was a couple weeks later) a followup said that they had found a “temporary solution” and the tubes would start flowing as it were.

I didn’t get any further communication on the subject but i have a suspicion that some intermediary was found that could get tubes out of Russia and deliver to the US without violating the sanctions.

Given that New Sensor/EHX/Xpo-pul OEM tubes for basically everyone under the sun including Fender/GrooveTubes (usually as the Sovtek brand) I imagine finding a workaround was causing a lot of sleepless nights for EHX/New Sensor staff.

 

[amplexus]

I personally have pivoted more and more to EHX tubes. I love the 6072 and I have never found a NOS version (these days) that was quieter or sounded as consistent.

The EHX branded 6V6 is one of the nicer sounding around right now. The only time i use anything else is when I need a tube that will take a real shit kicking and then I’ll throw in the JJ 6V6 (or i should say 6L6 in a small bottle) but it doesn’t have the classic 6V6 sound like the EHX variant does.

2 years in a light-duty use like a tube mic is definitely a little oremature imo, and probably a fluke. But in a higher demand position like the front end (or reverb driver) of a Fender that would be about what i’d expect. Most modern tubes won’t have the same lifespan of the best of the OG NOS types.

Sadly these days NOS tubes have been so picked over, not to mention shipped around, shuffled on shelves etc for decades… that buying NOS even from a reputable seller is a crap shoot. In the last year i’ve had exactly zero failures from a current production tube, but i would say at least 50% of the NOS tubes i’ve ordered were noisy or microphonic out of the box and I sent them back. One or two weirder tubes died on first powerup. The only time I’ll buy NOS now is when a customer insists, or when the tube type simply isnt made today. The “glory days” of the NOS tube are gone imo.