Tube Rolling w/Crack

[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)  ;D

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)  ;D

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.

 

[nick-seattle]

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

I wish that would be the case. The only tubes I can use in the amp are all limited by gain up to 60 work fine, but anything above doesn't work, so no 12ax7 or 5751 rolling (although Sylvania JAN 5751 worked, but JHS 5751 wouldn't  )

 

[Doc B]

Are you checking the voltages with each of these different tube types? The nature of the direct coupled circuit is such that the bias on some tubes might be less than optimal unless some other changes are made.

 

[nick-seattle]

Are you checking the voltages with each of these different tube types? The nature of the direct coupled circuit is such that the bias on some tubes might be less than optimal unless some other changes are made.

Hi Doc, I'm in a monkey mode right now - I see and I do, but have no idea how to calculate things. It's been suggested to I should replace LED with Silicon Diode, but I have no idea what value that diode should be or if there are other changes I should make

 

[Doc B]

In general I think one needs to be careful when publishing tube rolling reviews where you plug a tube in that was not intended to be used in the circuit. A 12AU7 and 12AX7 are not really interchangeable. Yes, they have the same pinout - you can put Vanagon wheels on an SLK, too -  but they are designed for different jobs. I'm not saying don't try it, and in most cases no harm will be done. But I think it is important to note in the review that a given tube might not be operating at it's best without some changes to the circuit (or that it might not really be the best choice for the job at hand) and thus it might not be getting the fairest representation.

With this in mind I'll suggest that with the proper changes to the tube socket and heater voltage and current requirements a 6SN7 will typically work in place of a 12AU7. A 12BH7 will too, if one makes sure there is enough additional heater current available. As one gets further away from the 12AU7 spec, for example 12AT7s, 12AV7s, 12AZ7s and 12AX7s, one may need to alter the circuit anywhere from mildly to fairly radically. Also be careful with 6DJ8s, they aren't designed for as much plate voltage as a 12A_7 family tube and thus they may be subjected to too high a plate to cathode potential in some circuits.

 

[nick-seattle]

Understand - putting a tube that the amp is not designed for is not a fair test. Yah. I've been using my other 3 amps to do the rolling with 12at7 & 12ax7 (McIntosh 275) and 12at7 & 12au7 (300B based SET amp & my hybrid tube amp). Using Crack to roll only 12au7 family

 

[nick-seattle]

And after publicly stating that I don't use 12at7 in Crack... I just did Crack was the closes amp and I needed to try a new tube - it worked extremely well. I then double checked the results in other amps with very similar outcome.

Check it out - this one is out of this world:
http://tubemaze.info/sylvania-12at7-gray-plates-2-mica/

If you find it - buy it. If you don't, let me know and I'll buy it!

 

[Laudanum]

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.

Im really surprised that you dont hear a difference between power tubes.  I dont have a whole lot of different ones and I agree on one point that I think I mentioned ... I cant hear much between the GE 6AS7 and the RCA 6AS7.  I have 3 or 4 of the RCA's and, I think 2 of the GE's one with copper shield, one without.  All ST shape tubes.  The GE's have a smaller bottle but the internals are very similiar.  There are subtle differences that I wouldnt swear on hearing and I highly doubt that I could I pick between these two in a blind test.  But that aside,  between those 6AS7's I mention and the Raytheon 6080's that I have as well as the Svetlana 6H13C and the Tungsol 5998 there are distinct differences between most of them.  Now to be fair, the 5998 and probably the 6H13C are slightly different specs wise.  But the differences between these tubes I find to be more distinct than between most of the different 12AU7's.  Give your drivers some longer listening time and then try a different one, I would be surprised if you couldnt hear differences.  It would only be 3 tubes but I'd bet I could pick between the 6H13C, RCA 6AS7 and TS 5998 in a blind test ... and probably the Raytheon 6080 as well.  I cant say the same for most of the 12au7's I have,  those are mostly a "feel" thing.  And I absolutely dont have golden ears.  Give it a try with the power tubes.

 

[nick-seattle]

Im really surprised that you dont hear a difference between power tubes.  I dont have a whole lot of different ones and I agree on one point that I think I mentioned ... I cant hear much between the GE 6AS7 and the RCA 6AS7.  I have 3 or 4 of the RCA's and, I think 2 of the GE's one with copper shield, one without.  All ST shape tubes.  The GE's have a smaller bottle but the internals are very similiar.   There are subtle differences that I wouldnt swear on hearing and I highly doubt that I could I pick between these two in a blind test.   But that aside,  between those 6AS7's I mention and the Raytheon 6080's that I have as well as the Svetlana 6H13C and the Tungsol 5998 there are distinct differences between most of them.  Now to be fair, the 5998 and probably the 6H13C are slightly different specs wise.  But the differences between these tubes I find to be more distinct than between most of the different 12AU7's.  Give your drivers some longer listening time and then try a different one, I would be surprised if you couldnt hear differences.   It would only be 3 tubes but I'd bet I could pick between the 6H13C, RCA 6AS7 and TS 5998 in a blind test ... and probably the Raytheon 6080 as well.  I cant say the same for most of the 12au7's I have,  those are mostly a "feel" thing.  And I absolutely dont have golden ears.   Give it a try with the power tubes.

I definitely did hear a difference, but it's not as huge as input or driver tubes. they only one I didn't hear a difference are RCA & Raytheon 6as7 - I bet they were produced in the same place. Really want to get my hands on 5998, but it has to wait right now - they are going for at least $50 a tube for a low measuring tube. It looks like WE 421 & Tung-sol 5998 have the same plate structure, so I would assume that they sound the same - any comments?

 

[nick-seattle]

Dan's warning about using other tube numbers that are not 12AU7s in Crack is for listening and proper performance.  But if you want to test a tube and it has the right heater arrangement you might find out if it makes sound.  I once used a 12AX7 in place of a 6DJ8 because I didn't have a spare when my 6DJ8 went out.  It didn't sound right but did OK for background music for a few hours.

Dan is warning that you will not get the intended performance, gain, output and distortion using different tubes. 

I do understand the physics that are involved in rolling different tubes - mechanical & electrical But 12at7 does work in Crack and works fairly well especially at low volume. If I'm not mistaken there should be enough bias to allow for a small voltage swings with 12at7. However, I tested the tube at full volume and it still sounded phenomenally - so no matter what physics mighty state, my ears state that this is one of the best tubes that I've ever rolled in Crack (and I have zero interest in it, just want to share my OPINION) and I've tried over 50 tubes (different brands and models of 12au7 & 5814 & 5963 & 6189 ... ) - I'm collecting unusual tubes, so I have all sorts of crazy tubes from the family.  ;D

 

[Doc B]

Did you measure the voltages?