Thoughts on Audio Research D70

Johnsonwu,

Thanks for your input. I think the current ARC cap is the TRT Stealth cap. No outside reviews that I've been able to find. I do know that Aesthetix also uses these in their Eclipse series. From what I've read, I'm not sure these are teflon - they sound simular to the Clarity MR's if you read the write up. If you look closely at ARCDB for the Ref 110, there's a side photo that shows the gold & red Stealth cap with a small silver cap which looks to bypass the Stealth. I would venture a guess that the small silver cap is teflon.

Another interesting cap is the duelund Alexander's. In the smaller size range, they are not nearly as expensive as the teflon caps.

JohnsonWu, you say that every time you have used vintage ARC amps, even after replacing the caps, that they still exhibit smear and glare but at higher headroom.
In my system and with the original caps in the ARC, I am not exhibiting this symptom. As I asked before, could it be something else in your system that is the cause of what you are hearing? How sensitive are your speakers and what tap are you using on the amps to connect them to? I have a small dedicated room, so I am not driving the amp that hard ( which could be why I am not hearing your symptom ;))), what size is your room?

@Daveyf: I meant even after replacing the Rel+Wonders with the class B caps like Auricaps there is still glare remaining. Not so this time, I am using oil caps, not polyprop.

My 2 main pairs of speakers are Avalon Eidolons (too big for my 14 x 18ish room) and a highly modified pair of Utopia Divas. The Eidolons with their Accuton ceramic tweeter tend to exacerbate the glare and hardness more so than the Utopia.

I use the 4 Ohm taps.

I never have a glare problem with my Phi70s (well after all its an expensive amp with all 300Bs and Infinicap-S, they MUST not have glare) or my Counterpoint NPs (Vcap TFTF).

With the stock caps, and if you are not driving the amp hard, you wont hear a lot of details in the recordings.
Thats my main complaint of the Rel+Wonder combo... low volume and its muddy, high volume and it pounces at you.

Anything oil or Teflon will convey the microdetails better and be a lot more linear when going from soft to loud. I never got a chance to discuss with Leonard about teflon caps but figure why he recommended Infinicap and later on Audio Research went from Rel+Wonder to Dynamicap and now Teflon (in some of their amps), not sure about the TRT Stealth which should be a modern version of Dynamicaps.

Johnsonwu, i am following this thread with interest. I have has several ARC amps and preamps modded by GNSC )Steve Huntley) over the last 10 years.

I still own a pair of Classic 120's which i hope to put head to head with a REF150 soon. I also have a REF3 LE and REF Phono 2 both modded by Steve.

The only thing that Steve did not replace in the critical signal path are the interstage coupling caps (4 in each unit). He felt that the stock caps were good enough and need not be replaced. What ARC use in their SE upgrades for the REF5 and REF2's are teflon 150 vdc 10.0uf =/- 10%.
What similar caps would you recommend as replacement (Vcaps?). I doubt that ARC would release those proprietary caps for installation in the field. Any recommendations much appreciated. Thanks again.

@Smoffat: The reason why I sold my CL120 (and CL150 of course) was the solid state input and gain stages.
I believe in the Counterpoint (Michael Elliot) philosophy of getting the small signal stage as tubey and transparent as possible and use whatever as the output stage as it has the least influence to the sound.

The 10uF caps had to be output caps (from pre to power) or from phono to pre. Upgrading those to any exotic brand like Duelund or Mundorf or VCap would be cost/size prohibitive.

The coupling caps within each device had to be 2uF or under I imagine. But until I get to see the schematic I cant comment.

Anyway, upgrading the small signal coupling caps would have a more noticeable benefit than the output caps.