Modifications on ASL Hurricane 200 DT ?


I am contemplating purchasing a used pair of ASL 200DTs that have been modified by Milan Bogdan, apparently a well-respected Nashville recording engineer.

Has anyone had any modifications done by this gentleman on their Hurricanes ? Has anyone heard of what kind of work he does on the amplifiers? By all accounts he can cut a great record, but is his choice of capacitors equally wise ?

Any information is greatly appreciated.

Dimitry
dimitry

Showing 5 responses by jeffreybehr

Bill Baker at Response Audio will do a FINE job of making them better, but YOU or someone who knows how to solder can make them sound a good bit better by further upgrading the 10 0.22µF couplers per amp with SoniCap Platinums. The Platinum uses a film that's an alloy of teflon; they sound VERY quick, clean, smooth, detailed, and tonally neutral while being significantly less expensive than the V-H teflons that Bill uses. My ASL dealer loves the sound of Jensen paper-in-oil-copper-foil caps, but others tell me they sound artificially warm.

I just received a new pair of 'Canes and have chosen the Platinums for the 1st position and Cardas Golden Ratio solids (which are close to the SC-Ps sonically) for the 2nd position.

What are you using for 'N7s and '88s? I'm collecting new and used 'N7s, but, not being a GEA, it takes me a long time to determine the character of the input tubes. I'm still using the stock Chinese '88s, but probably I'll buy a set of the Penta '88SCs with closed plates; they're getting rave reviews on the Tube Asylym.
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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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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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Dennis, the ASL 'Cane uses NO overall or local feedback loops. E-mail me at jefreybehr(at)cox(dot)net and I'll send you (or anyone who asks) a JPG image of the schematic. Let me know if you have hi-speed or dial-up service, as the file CAN be quite large.
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