Tube Rolling w/Crack

[12AU7-6SN7]

Hi again,

I just got a Tung Sol 5998 output tube from eBay. The weird thing is that when the volume is all the way to minimum, a loud buzzing comes from the headphones. It works if I turn it up, but this seems rather concerning that something is wrong with the tube. Is this something that happens occasionally with old tubes? My pop is an old radio tech and he had never heard of one doing something like this. No other tubes do this. Should I return the tube?

I do have a 6sn7 in the input tube socket with an adapter, but it was fine with the Cetron 7236 I was using before the 5998.

Edit: It doesn't make the noise with a 12au7 in the 9pin socket. Is using a 6sn7 adapter and a 5998 output tube a mismatch for some reason?

Thanks for any advice

 

[serpent68]

Hi again,

I just got a Tung Sol 5998 output tube from eBay. The weird thing is that when the volume is all the way to minimum, a loud buzzing comes from the headphones. It works if I turn it up, but this seems rather concerning that something is wrong with the tube. Is this something that happens occasionally with old tubes? My pop is an old radio tech and he had never heard of one doing something like this. No other tubes do this. Should I return the tube?

I do have a 6sn7 in the input tube socket with an adapter, but it was fine with the Cetron 7236 I was using before the 5998.

Edit: It doesn't make the noise with a 12au7 in the 9pin socket. Is using a 6sn7 adapter and a 5998 output tube a mismatch for some reason?

Thanks for any advice

I have the exact same issue as you, but unfortunately never figured out the reason why.  It happens only at volume 0, and only when a 5998 is paired with a E80CC / 6SN7 / 12BH7.  I believe a few others have experienced this phenomenon too.

What I do is to avoid volume 0.  Everything works perfectly, and the sound improvement from switching to e80CC (from 12au7) is more than worth it.

 

[12AU7-6SN7]

I have the exact same issue as you, but unfortunately never figured out the reason why.  It happens only at volume 0, and only when a 5998 is paired with a E80CC / 6SN7 / 12BH7.  I believe a few others have experienced this phenomenon too.

What I do is to avoid volume 0.  Everything works perfectly, and the sound improvement from switching to e80CC (from 12au7) is more than worth it.

Thanks for the confirmation of the issue on other amps. It does sound good with the 6sn7, but I like the 12au7 too.

 

[mcandmar]

More Gold Aero goodness on ebay, this time some E80CC tubes http://www.ebay.co.uk/itm/272312847324

I received the Gold Aero 5998A yesterday and from the brief listen its a very clean and detailed sounding tube, and tested with perfectly matched sections.  Need to spend some more time with it to form an opinion, but so far it seems to do a lot right, and not a long wrong.

 

[attmci]

More Gold Aero goodness on ebay, this time some E80CC tubes http://www.ebay.co.uk/itm/272312847324

I received the Gold Aero 5998A yesterday and from the brief listen its a very clean and detailed sounding tube, and tested with perfectly matched sections.  Need to spend some more time with it to form an opinion, but so far it seems to do a lot right, and not a long wrong.

The guy got a neg. feedback, and changed his user name on ebay.

He also labeled  Russian 6H13C tube as Mullard "6as7g" :

Link: http://www.ebay.com/itm/6AS7G-Mullard-NOS-3-Tubes-421A-5998-7236-6080-Little-Bear-P8-Upgrade-Component-/172264901551?rmvSB=true&nma=true&si=F73E1xNo0JlESKzU5H4ZSD1dweA%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

 

[mcandmar]

Its the same seller, he just setup a second account.  Those modern Mullards are manufactured by Sovtek as i believe they now own the brand name.

 

[attmci]

Its the same seller, he just setup a second account.  Those modern Mullards are manufactured by Sovtek as i believe they now own the brand name.

In the picture, it says "Made in England". Obviously fake tubes.

 

[jaysbob]

I've got some nice NIB RCA cleartop 6fq7/6cg7 tubes knocking around and I've seen mentions in this thread of people using them but I'm unsure of what rewiring (if any) is required to get these to work? Am I totally off base with this? I have speedball installed.

I love the way these sound in my Lyr and I'd be interested to see how they sound in Crack.

 

[mcandmar]

They have a different pinout so not plug and play. The best option is to source an adapter like these http://www.ebay.co.uk/itm/201398493602

 

[jaysbob]

They have a different pinout so not plug and play. The best option is to source an adapter like these

thanks for the suggestion. Wired my own adapter using an old socket saver (removed pin 4 from the base and soldered a jumper from pin4 to pin 9) and and the 6cg7 is working great! sounds fantastic, voltages look nominal. Thought it wasn't working at first but it turns out headphones need to be plugged in to get sound.

edit: the RCA 6CG7 really sounds great, been listening to it all day. Nice and warm with just enough detail to fill things out. I've got a couple cheapy Sylvania 6gu7's I'm thinking of trying as well but the cleartop RCA just sounds so good I can't bring myself to turn it off.

 

[mSummers]

I have two tubes that I purchased recently that are acting strange.  One is a 12au7 that occasionally produces a loud buzzing sound in the left channel.  The other is a 6080WA that produces an intermittent crackling sound.  Both tubes test fine with no shorts or gas.  None of my other tubes have this problem.  Is this just two examples of noisy tubes?

 

[Paul Joppa]

Tubes that are both popular and out of production are a diminishing resource. So they are "picked over"; many so-called new old stock tubes have been tested and rejected by conscientious dealers who want to offer tubes they can guarantee to have low noise and other features. Those rejects don't always go to the landfill, they get sold to less scrupulous dealers. So the pool of available tubes acquires a greater proportion of defectives, and it gets worse over time.

That said, sporadic noises are often due to problems outside the tube, such as weak connections on the socket or marginal solder joints. A different tube may have slightly different pins, so some will work and others won't even if they are all good tubes.

 

[mSummers]

Paul,  thanks for the response. I suspect it's an issue with the pins. The 12au7 did seem to slide into the socket very easily. All of my other 12au7's fit very snug in the socket.

 

[hemenabergaz]

Hello,

I have a few questions. I am very new here and apologize for my lack of knowledge. It is hard to extract this all from the thousands of posts in this forum (which is certainly fun to read and very informative).

I just finished a crack with speedball, my first DIY build. I am really happy how it sounds fed by my Schiit Gungnir MB. Before building it I thought that I should buy a couple of cheaper tubes just to compare a bit and see if I can hear differences at all. In particular, I bought

Tubeampdoctor 12AU7WA / E82CC TAD Premium Selected
Philips 6080WC
6AS7G / 6N5P Shuguang

I tried different combinations of these tube with each other and with the stock tubes. It turns out that whenever one of the new tubes is in the system, the amp sounds really bad. The soundstage collapses, it sounds shouty, no air etc. It is not subtle, it really ruins the sound. The stock tubes in contrast sound excellent, despite the fact that the input tube is very sensitive to vibrations.

My questions:

Would you expect this kind of difference?
Do I need to burn the new tubes in for many hours (I used them a couple of hours only) before I can really tell?
I cannot hear any problems during music, but is the stock input tube microphonic if it maks a tapping sound when touching it?
Would you then try to replace the input tube?
Most importantly, what are the stock tubes? The labels are rubbed off and I would love to stock up on them.
How long will the original tube set last? Do the stock tubes measure NOS?
While there are many recommendations to go to Tung Sol 5998 and other tubes that are close to the price of the Crack itself, is there a recommendation for an affordable upgrade for the 6080?

I am very happy that the stock tubes are so satisfying. It shows how much bottlehead cares when they put together your parts. No parts missing either. The only problem occurred when I broke one of the tiny LEDs, but this was easily fixable.

Thank you!

 

[Paul Birkeland]

Tubeampdoctor 12AU7WA / E82CC TAD Premium Selected
Philips 6080WC
6AS7G / 6N5P Shuguang

I tried different combinations of these tube with each other and with the stock tubes. It turns out that whenever one of the new tubes is in the system, the amp sounds really bad. The soundstage collapses, it sounds shouty, no air etc. It is not subtle, it really ruins the sound. The stock tubes in contrast sound excellent, despite the fact that the input tube is very sensitive to vibrations.

My questions:

Would you expect this kind of difference?
Do I need to burn the new tubes in for many hours (I used them a couple of hours only) before I can really tell?
I cannot hear any problems during music, but is the stock input tube microphonic if it maks a tapping sound when touching it?
Would you then try to replace the input tube?
Most importantly, what are the stock tubes? The labels are rubbed off and I would love to stock up on them.
How long will the original tube set last? Do the stock tubes measure NOS?
While there are many recommendations to go to Tung Sol 5998 and other tubes that are close to the price of the Crack itself, is there a recommendation for an affordable upgrade for the 6080?

A lot of new tubes will need 50-100 hours to settle in and sound their best.  The tubes that come with the Crack are old stock (mostly American) tubes.  They are tested for transconductance prior to shipping.  Some of these old stock tubes may be microphonic, but this isn't endemic to any particular variant of old stock 12AU7.

I would expect the 12AU7 provided to last several tens of thousands of hours.  I have less experience with running 6080's long term.  I could see reasons to argue that it may last a bit longer than the 12AU7. 

 

[jaysbob]

After messing around with the clear top RCA 6CG7 I found I enjoyed the sound (bassy and warm) but I felt like I was missing detail. I've read good things about the e80cc in this thread so I figured I'd give that a shot. First I tried the e80cc without any modifications and it sounded pretty good but the noise floor was significantly higher and while the detail was there it just didn't sound quite right.

After that I changed out the R1 resistors on the small board with 1.7k's as many users suggested. This one change made all the difference in the world. Dead quiet and clear as a bell. The e80cc is low distortion and very detailed. The difference is really impressive. Seems to be a soundstage improvement as well, but that could just be due to the improved clarity.

Anybody else running e80cc's in their crack? Anything else I should change out to make the e80cc happier?

Next I was thinking of trying a 12BH7 but I'm unsure if I would need to change out the R1 resistors again?

 

[ChrisP]

Hi I just finished building my crack+speedball. I was pretty sad that once the speedball was installed, my crack lost a bit of mellowness which was a quality I really liked. On the other hand everything became tight and involving.

Anyways are there any 12au7 tubes that brings back that "laidbackness" of stock crack? Or any other tubes you guys generally recommend for a newcomer?

Edit: My question was pretty vague. Laidbackness as in a tube that has a bit more rolloff in the treble region, isn't as tight or punchy in the bass, and a bit more airy. I don't know how to really describe the stock crack besides mellow and laidback.

 

[12AU7-6SN7]

Hi I just finished building my crack+speedball. I was pretty sad that once the speedball was installed, my crack lost a bit of mellowness which was a quality I really liked. On the other hand everything became tight and involving.

Anyways are there any 12au7 tubes that brings back that "laidbackness" of stock crack? Or any other tubes you guys generally recommend for a newcomer?

Edit: My question was pretty vague. Laidbackness as in a tube that has a bit more rolloff in the treble region, isn't as tight or punchy in the bass, and a bit more airy. I don't know how to really describe the stock crack besides mellow and laidback.

I took the speedball out since for me it ruined what I liked about the stock circuit. Vocal and instrumental echoes and reverb etc were getting over powered by the attack of the sound with the speedball and it hurt my ears to listen for a decent amount of time.

Going with a garage1217 6sn7 adapter and a nice sounding  6sn7 plus a 5998 output tube gave me a sound I really enjoy. Do be aware that this combo causes a loud buzz from the headphones if the volume is turned down all the way, which is remedied by just never turning it all the way down.

 

[ashneel]

Did you make any other modifications to use the adapter? The adapters I tried some years back were a waste. Also what are you guys using as 6sn7 tubes? (primarily with a 5998 and Bendix)
I can't use my Crack very often now, but I did get the impression I preferred the stock Crack over Speedball too

 

[12AU7-6SN7]

Did you make any other modifications to use the adapter? The adapters I tried some years back were a waste. Also what are you guys using as 6sn7 tubes? (primarily with a 5998 and Bendix)
I can't use my Crack very often now, but I did get the impression I preferred the stock Crack over Speedball too

No mods to the adapter. I got the $25 garage 1217 adapter that is noted to work with the BH Crack.

I've got a late 70s NOS RCA 6SN7GTB installed now.