Tube Rolling w/Crack

[Noskipallwd]

Brad, I have two Phillips Miniwatt SQ E80CC, they can be expensive as heck. I traded tubes and cash with a friend. Not sure where he bought them but the tubes and the origiinal boxes look like they came off the assembly line yesterday. I also put one in my Hagerman CornetII phonostage and it made a significant difference in this amp as well. Finished my eros a couple of days ago though, and after listening for quite a few hours I don't think I will be listening to the Hagerman much anymore. I saw you posted you like the CBS Hytron, it is a great tube in thee Crack, plus as a side benefit it actually glows. It was my favorite driver to date but I think the E80CC might have supplanted it.

Cheers,
Shawn

[Laudanum]

Thanks. He said on the listing that no refunds were accepted...soooo, I asked if he would consider a partial refund and he said he could. It did become clear that he was not going to suggest anything as for amount, so I kicked it off by asking if he could do a 50$ refund, which he accepted once I sent it back (posted today). He did let me keep the original Tung-Sol box though! So, I got a box for 50$...more than u paid for your tube...sad. But hey, win-some-lose-some. He could have just blown me off though, then I'd have to give him a fairly low rating.

Let me know if you find more at that price!!

50 bucks is better than nothing.  Ebay definitely can getcha.  In recent memory, had a very weak 6AS7 that was supposed to be strong, a dead 12BH7 and a 6SN7 that went dead within a few minutes.  They were all dirt cheap but it's still money down the drain.  But many more good finds than lemons so I keep rolling the dice.  I was a bit bummed on the 6SN7 because it was a relabeled Sylvania VT-231 for dirt cheap.  Win some, lose some.  

Will do on the 5998's.  

[nick-seattle]

Hello eveybody, I'm now on Crack like a lot of you

I tried many tubes in the amp, but unfortunately it only works well with 12au7 family and 6sn7. Also 12bh7 and 6gu7 appear to be working well. Now to the question, I want to try 12ax7 in the amp - I have a lot of them - Telefunken, Mazda and other European brands - US brands that sound just phenomenal. What should I do to make the rolling of the tubes adjustable - I'm planning to roll a lot of them

[Paul Joppa]

In a word, you can't.

Well, nothing is impossible, but to do so you must operate at extremely low plate current and at a bias uncomfortably close to Class A2. The low current means marginal drive at high frequencies (distortion and anemic treble) and the low bias means potential distortion as the grid current loads the volume control with a nonlinear impedance.

Starting point - replace the LED in the cathode with a silicon diode, to give around 0.7v bias. Use a small signal diode, not a rectifier diode. Then increase the plate load resistor from 22K to 220K - but experiment with that value to get ~70v on the plate. If you have the speedball, increase R1 to 1700 ohms to get 0.5mA current.

[nick-seattle]

Thank, Paul. I will stay away from this kind of mod for now - need to roll all the 12au7, 6gu7 and 6sn7 tubes first

BTW, I'm posting results of rolling on www.tubemaze.info

First couple of 6as7 tubes for Crack:
http://tubemaze.info/svetlana-6as7-6%D0%BD13%D1%81/
http://tubemaze.info/raytheon-jan-6080/

Will also post review of Raytheon 5814 Windmill getter today - hope it sounds as good as advertised

[Laudanum]

There is some discussion of the Russian 6H13C's here.  I have a pair or the 70's Svetlanas.  Not as enthusiastic about them as you are.  The bass is very good as you point out but I find the treble to be gritty for lack of a better word.  Not my cup of tea.  If you are up for tube rolling, try the RCA 6AS7.   You can find them, with some persistence and patience, below $15 on epay.  Actually, I found that they were easy to find on the cheap last summer.  Looking lately, not as easy.   
If you can find a 5998 for a fair price, you might even like those better still.   They may trade some bass impact for control with improvement everywhere else.  A bit higher gain as well (or less loss as I think Doc B. pointed out).   Not cheap, commonly going upwards of $100 and beyond lately, when you can find them.   Really nice sounding tube but as always, YMMV.   

[nick-seattle]

Thanks, Laudanum. I have a few RCA & Raytheon 6as7, but didn't find them to be as transparent as the other two tubes. I was able to score them for $20 for 11!!! the dude who was selling them couldn't check the tubes - on my tube tester only one came weak the rest test great! I found that tube rolling with Crack is not as exciting as I hoped It appears that since voltage amplification is not needed in the amp and the 12au7 is used as driver with 6as7 used as cathode follower, it limits the effects that tubes can have on the sound - so in general everything sounds quite good. I even put in dreaded GE short gray plates, which I have to test various systems. Even they sounded quite decent in Crack compared to my McIntosh or SET 300B based amps. I even put 12at7 into the amp and DARN! it didn't squeal 6sn7, which usually produces much bigger sound in other systems sounded the same as 12au7s. There is a very small variation in the sound coming from different tubes, but it could be completely psychological. The same issue is with tube rolling for Driver & Cathode follower in McIntosh - there is really no point in spending large amount of money on Telefunkens for these stages - the majority of other tubes produce the same transparency and sound-stage. The two stages that affect the sound significantly are phase inverter and preamp (voltage amplifier), there you can have a lot of fun , but with Crack both stages are absent.

[Beefy]

It appears that since voltage amplification is not needed in the amp and the 12au7 is used as driver......

Errrrr, the 12AU7 is indeed a voltage amplifier in this amp.

[nick-seattle]

Errrrr, the 12AU7 is indeed a voltage amplifier in this amp.

Hmm, that's very strange then - do you know what gain is in that phase? One explanation is that since I use the amp at a very low volume - it has enough power to drive HD650 at 25% of max, the stage doesn't have as much affect on the sound wave. I guess I will just enjoy the amp And use my Dared & McIntosh for the rolling fun.

Some of my experiences with MC rolling...
http://tubemaze.info/rolling-with-mcintosh-275/

[Paul Joppa]

The 12AU7 has a gain of 17 with the current source load; closer to 12 with the stock resistor. The 6080 cathode follower is around 2/3 - it's a very low-mu tube.

Probably what you are hearing is the small output voltage of the 12AU7 - since it's a tiny fraction of the maximum, the distortion is miniscule, and what there is is almost entirely second order. In a power amp, the driver usually has to put out nearly all the voltage it is capable of, and can dominate the distortion signature unless precautions are taken.

[Laudanum]

Thanks, Laudanum. I have a few RCA & Raytheon 6as7, but didn't find them to be as transparent as the other two tubes. I was able to score them for $20 for 11!!! the dude who was selling them couldn't check the tubes - on my tube tester only one came weak the rest test great! I found that tube rolling with Crack is not as exciting as I hoped It appears that since voltage amplification is not needed in the amp and the 12au7 is used as driver with 6as7 used as cathode follower, it limits the effects that tubes can have on the sound - so in general everything sounds quite good. I even put in dreaded GE short gray plates, which I have to test various systems. Even they sounded quite decent in Crack compared to my McIntosh or SET 300B based amps. I even put 12at7 into the amp and DARN! it didn't squeal 6sn7, which usually produces much bigger sound in other systems sounded the same as 12au7s. There is a very small variation in the sound coming from different tubes, but it could be completely psychological. The same issue is with tube rolling for Driver & Cathode follower in McIntosh - there is really no point in spending large amount of money on Telefunkens for these stages - the majority of other tubes produce the same transparency and sound-stage. The two stages that affect the sound significantly are phase inverter and preamp (voltage amplifier), there you can have a lot of fun , but with Crack both stages are absent.

In my experience with Crack, some of the 12AU7 rolling has made for fairly subtle differences, some more distinct than others.  Going to a different tube like the 12BH7 or 6SN7 for example makes for a bigger change, less subtle than some of the changes between 12AU7's.   I dont have nearly as many 6080/6AS7's as I do 12AU7's but there are pretty distinct differences between all of them with one exception.  The difference between the RCA and GE 6AS7's that I have are pretty subtle.  But rolling between those 6AS7's or the Russian 6H13C, Raytheon 6080 or the TS 5998  all make for fairly distinct differences, not hard to discern.    BTW, glad you enjoy the 6H13C.  Affordable and available is always nice.  I really enjoy the 5998 but could be perfectly happy with the 6AS7's I mentioned.

[nick-seattle]

Laudanum. Thanks for sharing your experience. Crack is very difficult to roll. It's great on one hand, but disappointing on the other. Great, because you can get great sound from many tubes. Disappointing, because some tubes provide a very unique sound. As you stated, 6sn7 produce fantastic sound. I changed my Crack to work with 6v family (6dj8, 6gu7), 12v family (12au7...), Octal Family (6sn7). and Yes I do have 3 sockets in my Crack   - in addition to the 6as7 socket.

Recently, I was able to find a tube that made Crack shine. It created a huge difference, not a small one - and it was 12au7!!! I was not expecting that. I got the tube cheap on Ebay to try it out - it was Mazda 12au7 - now I bought 8 more (more expensive, but well worth it)  

Check out my review:
http://tubemaze.info/mazda-12au7-gray-plates/

[BNAL]

Nick,

What power tube are you using with the Mazda? In my Crack I like the Mazda with the Mullard 6080 best.

After reading your review I will have to give the Mazda another listen with some of my other power tubes.

[Grainger49]

This is a man who found a way to get whatever tube he found into the Crack.  Congratulations are in order.

Laudanum. Thanks for sharing your experience. Crack is very difficult to roll. It's great on one hand, but disappointing on the other. Great, because you can get great sound from many tubes. Disappointing, because some tubes provide a very unique sound. As you stated, 6sn7 produce fantastic sound. I changed my Crack to work with 6v family (6dj8, 6gu7), 12v family (12au7...), Octal Family (6sn7). and Yes I do have 3 sockets in my Crack  - in addition to the 6as7 socket.

Recently, I was able to find a tube that made Crack shine. It created a huge difference, not a small one - and it was 12au7!!! I was not expecting that. I got the tube cheap on Ebay to try it out - it was Mazda 12au7 - now I bought 8 more (more expensive, but well worth it) 

Check out my review:
http://tubemaze.info/mazda-12au7-gray-plates/

[nick-seattle]

Nick,

What power tube are you using with the Mazda? In my Crack I like the Mazda with the Mullard 6080 best.

After reading your review I will have to give the Mazda another listen with some of my other power tubes.

I'm using Svetlanas. Really like the airiness they produce and mid base tightness, but at the same time maintain warmth. Or maybe because I'm from Russia and was born the same year they were born

I haven't tried many 6as7 tubes to be honest. Structurally the majority of them look similar, so why bother. However, WE, Mullard, Tung-sol are on my list to try. I haven't had much luck rolling power tubes - they produce practically no sonic difference, so my investment is in drivers - so many to try. If you go to tubemaze.info, you will find all my rolling experiences between 4 tube amps - about 60 tubes and counting. Submit your review of Mullard 6080 there - let's make it fun.