Tube Rolling For ASL Hurricanes

Any experiences in tube rolling for these amps yet? I find it hard to believe Chinese KT88s can be the best option.

I have another ASL integrated,(the MGSI 15DT)and swapped the Chinese KT88s for JJ/Tesla which are way better but I suspect there are better options like Electro-harmonix and Svetlana. has the former at $50. and the latter at $70. the matched pair.
I am still testing (listening to mine)....however, I did change the 6SN7's from the original tubes (I believe Chinese) to NOS Sylvanya and it made a marked improvement. The sound became more mellow and smoother. It also felt that there was more control over the images. I have about 60 hours the amps and I hope to report to you all soon on my overall comments.
I have had both the older version (MIT caps) moded by Israel Blume and the latest version (new grey green PIO metal can caps). I prefer the newer version, they seem a little smoother in the mid-range.

A word of advice - you must replace the stock tubes to get any where near the capablities of these amps.

I have replaced the power tubes with the new Electo-Harmonix KT-88s. The new version come with the Value Arts which are good. The EHs are vastly superior. I encourge you visit this web site:

Jason gives a great discription of the various 6550 and KT-88s.

Next, I replaced the driver tubes (the orignals are Chinese copy of the metal based Slyvania 6SN7 Ws). Here I have tried just about every NOS 6SN7 there are (notable exception the NUs)and even a set of Mullard ECC32s. Here is a list: Slyvania 6SN7W (Metal base & black base both short and tall),WGA, WGT, Tall boys , VT-231, 52s, Kenrads VT-231, dark and clear glass, Tung-sols Vt-231 grey glass, RCA VT-231 grey glass.
Hear is the best combination I have herad yet RCA VT-231 Grey Glass in position 1, Sly metal base in position 2 ,and Tung-sol Grey glass in position 3.

The sound improvement is unbelieveable. Same tonal neutrality with major improvements in resolution, imaging depth and width of sound staging, three dementionality. More extended on top, and much more extended in the bottom.

Before you judge these amps you have to hear them with at least a decent set of NOS drivers.

The addition of top gun power chords and a set of richard greys also helped overall, but no where near the NOS and Power tube upgrades.

I have had no reliablity problems. These amps have to come a long ways, it is not surprising some people have had a defective pair or two.

For the $4400 these amps cost, they are a steal. They have beaten amps priced five times as much! I can see why some people who have $20,000 amps are a little testy about some of the positive reviews these amps have recieved.

Hello Gang.I don't post very often, as I am a one fingered typer and it generally takes far too much of my time to respond.However: most veteran tubies know and understand that different tube types and brands do sound different in most audio circuits. The general consensus is that most of the nos tubes are supperior to what is currently being made today and I would agree in most cases.After manufactering reached its pinnicle in the late 50's.However....Most commercial equipment manufacturers cannot market their equipment with nos tubes for obvious reasons[cost]and therefore "voice" their designs with currently available tubes. What I found it most interesting is: that rb99 found a specific combination of driver tubes in the hurricane's that had the biggest influence on the overall performance of the amp.To qualify things here... I do not use the ASL hurricanes in my own system and have only heard them with stock tubes in a friends rig and was impressed with what I did hear.I use another ASL amp [1006 dt] that also use 3 6sn7's as drivers for the single ended 845 output tube.While I honestly believe the chineese 6sn7's are a very decent sounding "current" tube [they literally stomps on the sovtek]and in many respects better than "some" of the later nos GTA's and GTB's. HOWEVER:.....Almost all of the pre-60's versions of 6sn7GT's and WGT's are in a different league altogether and should transform "any" amp using that tube topology in the driver stage. A good analogy... would be like comparing a good siemen ecc83/12ax7 or telefunken e803cc to a currently made 12ax7 in a high resolution preamp. Anyone with a decent ear could never go back to using a sovtek in their preamp ever again!What I found most interesting about rb99's selection of drivers... was the order in which he combined them to "voice" his amps.Oddly enough...I use "exactly" the same tubes, and in "exactly" the same order in my amplifiers as well.What this combo did for my amps was simply sooooooo much better that it would just be impossible for me to go back to the stock tubes that came with the amp.I can only surmise,given that combination of driver tubes used in the Hurricanes would simply elevate them to a whole higher level altogether.The good thing is that the common RCA grey glass can be easily found for very little money with a little searching, Tungsol rounds will cost about twice the money of the rca's.Unfortunately..the Slvania wgt metals are a different story as they are quite rare and currently sell for too much money in my opinion.Try the tung sol gt's instead as they also work very well in that combination.One day I will get my buddies Hurricanes over and hear them in my rig and report back. cheers David.
Ecclectique wrote - "What I found most interesting about rb99's selection of drivers... was the order in which he combined them to "voice" his amps.Oddly enough...I use "exactly" the same tubes, and in "exactly" the same order in my amplifiers as well."

I tried virtually all combinations, including using all the same tube, i.e., three RCA grey glasses. The synergies of having difference tubes kind of surprised me. I alway thought the closer the matching of the drivers tubes the better. The strength of these three tubes combines to keep the tonality fairly neutral, but improved all other aspects of the sound. The biggest improvement is in the bass extention and control.

I have to note the ECC32 where very seductive - if someone prefered a warmer/lush sound these would be a good choice in leau of the Sly W metal bases.

The only 6sn7 I have still to try are the Raytheons and the National Unions. The NU are supposted to sound alot like the Ken-Rad Dark Glass, which I did not care for. The Raytheons could possibly be a good choice. I'll let you know.

Thanks for sharing your experiences with tube rolling in your ASL amp.

Best regards.
You should try some mil spec RCA 5692s if you can find some.

PS- I see they pulled the other Hurricane thread.
Kana813 - I wonder why?

I'll try RCA 5692s. Thanks.
Hmmm...I have to disagree with the poster who indicated that one needed to change the stock tubes to get "anywhere near" the performance capabilities of the Hurricanes. They are magnificent as they are: the imaging size of instruments in the back of the stage do not shrink AT ALL, which is quite different from any other amplifier I've ever heard -- and this with the stock tubes.
When someone says tubes need to be changed, what I hear is that they want a different "sound," but the sound of, say, a double bass has its own integrity and does not need a tube change for anyone to hear what a double bass sounds like. The idea in much of the tube rolling seems to be to orient the SOUND to what we want, not to orient an acoustic instrument: the instrument makes its own sound.
The amps need NO tube changing to sound excellent. They might need tube changing to improve EVEN FURTHUR their many excellences AS IS.
Pardon my opinions, but it seems that the SOUND is what many people look for, not the music. I rarely see anyone discuss how a tube change makes the harmonic overtones of the violins appear more vividly, or the body of a double bass, or the strike of a hammner on a piano string. It's always "better bass" (what does that mean?! I truly am puzzled about it).
Having said that, I am also experimenting with "tube rolling" for the first time, because I am fascinated by how change can take place in the amps, but I know what real instruments sound like, and if the tubes reduce that "realness" then they do not serve the music, and I take 'em out.
Right on, Gbmcleod. I have only changed the 6sn7's (big improvement but not the KT88's. My 'canes sound "wonderful"!

It's been sometime since your post. What has been your experience in changing the 6SN7s? Do you prefer the stock tubes?

I would be interested to hear which tubes you've tried.

My experience is the NOS tubes I wrote about (still using the same combination) improved every aspect of the sound while remaining nuetral in terms of the "stock" sound.

I would love to hear your comments
I have been considering a Hurricane. What happens to the amp when a tube fails? Does it blow a resistor or you simply replace the bad tube? Are there any reliability problems?
I lost one tube KT88). I never realized it. I found out when I tried to biais it. The meter read 000. I just got a new tube and that was that.
Hi RB:
It's been forever since I posted, I see.

I did put in two other types of tubes: Sylvania 6SN7 and RCA 6 SN7.

I didn't like the Sylvanias as much as I thought: they're certainly "extended" on top, but it seems a "glazed" sort of extension, besides which the treble seems a bit "white." Also, the body of instruments in the lower midrange/upper bass wasn't quite right. I replaced it with an RCA tube and it sounds fine.
I'm not much for the tube-rolling experience. I DO understand they "change" the sound, but I prefer to listen to which tubes come with it: also, my partner, a pianist and baritone opera singer, usually tells me which tubes make the piano sound most like a piano. That way, I don't bother wasting my time trying to create a "flavor" that I like. Frankly, I was always happy with the Chinese tubes that came with the amp.