Modifications on ASL Hurricane 200 DT ?

Dimitry, I summarized my thoughts on couplers for the 'Canes here http://www.audioasylum.com/forums/tubediy/messages/94704.html . If you were ready to spend upwards of $5K at Bill's, you definitely can afford the SoniCap Platinums. And...they're $23 each less expensive than the V-Cap TFTFs, = $460 for the 2 amps.

Do you have detailed notes on modifications already performed? If so, if you share them, probably I can give you more to consider. Pls e-mail me at jeffreybehr(at)cox(dot)net. I've ordered the couplers and other parts and am currently co-designing a serious upgrade of the main PS. I'll let you know how that goes with my advisor who has LOTS more experience at this than I.

Where are you? Maybe I can physically help you improve your amps.

I've bought about 4-dozen* 'N7s, NOS and used, and I know they work in the amps, but I've yet to characterize them.

* Just another example of why my wonderful wife calls me Mr. Excess.
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Wow, you seem very involved in improving your amps. Keep me posted on you endeavors. I am a sometimes tweaker, but some of the things you are contemplating are a bit above my level. However, there is always something to learn from knowledgeable people ! I am in Massachussetts, by the way. If you decide to go commercial, let me know. I am especially interested in you 6SN7 experiments.

On 6SN7s, here's what I wrote to my audio buddies tonite:
"Wow are my ears and brain (?) tired. Just listened carefully to a half-dozen samples of 'N7s in the frontend* of the 'Canes. Of the 6 samples, I made notes on only 4, that is, I think I heard character in only 4 tubes--3 were a little edgy/bright, and one seemed a little warmer. After listening to all 6, several more than once, I replaced the 2 Chinese inverter/driver tubes** with RCAs and left them in; that seemed to increase the spaciousness a bit.

I hope Pat's coming over tomorrow to help!

* 2 Voltage-gain stages in series...cascade, I believe it's called.
** one section of the dual triode is half of the amp's long-tail phase splitter and the other section is the cathode-follower driver."

Listening carefully to stuff like this is WORK for me. Oh well...it must be a labor of love or I wouldn't be doing it.

My 'Cane mods are in 4 general areas--the coupling caps, the decoupling (= frontend) dropping resistors and storage caps (currently 4 'lytics), the main PS, and the grounding wiring and rest of chassis. For the decouplers, I'll be tossing all the 'lytics and replacing them with Solen 'propylenes bypassed with SoniCap-2s. I've ordered them, but I'll soon be determining if the sizes I chose will work. On the PS, I'll be increasing the total capacity a little and putting most (about 80%) in the 1st pole and using only 200µF of Blackgate 500s in the 2nd pole, probably with a little MC-RTX bypass.

I'm going to try to install one piece of 14g. solid copper wire as the ground wire and run it around the chassis instead of having all those little (18g.? 20g.?), stranded wires running all over. I thought about using solid silver but decided that was overkill. I will be using double-20g. solid-silver conductors in teflon airtubes for signal or high-Voltage wiring I feel like replacing. Probably will be replacing few resistors, as resistors generally have far less character than caps, and the resistors ASL uses are plenty good enough for me.

Did you get details on your amps' mods done by Mr. Bogdan?
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Sounds like you have great plans !

The modifications on my amplifiers were all coupling caps (front and side, so to speak) to MIT RTX and silver wire to from the jacks to the front end. I don't think he did anything else. I replaced the binding posts, some of which had cracked bases (flipping them over, if you are not careful, can put a big bending moment on the posts), with the same kind from the manufacturer. The tops of the transformers have scuffs on them (apparently from several trips to the repair place, where the amps were placed upside down to work on them), which I need to paint.

HI Dimitry,
The Hurricanes are exceptional amplifiers right out of the box. Like any good valued product, there is a lot more potential to be brought forward.

The coupling capacitors make a huge difference and one recommendation I would have for you is that if you cannot go Teflon throughout the unit, use the V-Caps in the input stage (the two caps mounted on the face plate up front of each unit) and then a good film cap of your choice for the 8 coupling capacitors. That first stage is critical.

The other areas that I find to be very important is the grid stop and screen grid resistors. Here you want a good carbon resistor.

There are a few other resistor applications that are also very important and this is where choosing teh right components for the proper application come into play.

In my mods, I replace EVERY resistor in the circuit on the Canes. When developing these mods, I spent a lot of time doing single stage upgrades to see what the outcome was. Then, in the end, I found that the sum of the whole was justified. I had over 80 hours of labor in the first pair of Canes I modified just doing trial and error.

As far as the power supply goes, I agree with Jeffrey in that some upgrades here would be justified but I will not do anything that alters the original circuit. There are fartoo many liabilities to consider when you start doing this.


Another thing I do in these mods is remove a LOT of the wiring. I recently finished up a pair that I ended up with 7 feet of wire that was removed.

There is a lot of labor that [can] go into these amps. I realize what I do is more than what others would have the patience to do but I like to address even the smallest details. I want to make sure that every pair that comes in, goes out the door never to return with any "issues". I still spend 15-20 hours in each pair and I have done a good number of these amps. I treat every pair like it is my first. I have 5 pair here now.

For a DIY'er, these amps are intense and even intimidating to work on. There is a LOT of stuff in there. If you want to take on the venture, just take your time and obviously work on only one unit at a time. If something goes wrong, you always have the other half to get you back. Be patient, work in stages and you will end up with one hell of an amp. Most important: Have fun and be careful.

TUBES: Lots of options here. The KT88s that most my customers like are the EH. I am at the point that now I use the Sovtek 6550WE for system testing these amps when completed. I choose these tubes because they are inexpensive and I can easily have 2-4 pair of Hurricanes running at a time. That's a lot of expensive KT88s. For my personal amps (as soon as I get the time to build a few pair for myself) I will be using the Valve Art in one and the EH in the other. Same with the Monsoons I have on the list. YMMV.

The 6SN7 that I like is the RCA, I have a couple Canes running now with these as inputs across the board. You will have to experiment to see what you like.