[rlee8394]

Here is a short review of an Insight 170 built in a Dyna ST-120 chassis. I'm not one for purple prose or other glowing adjectives such as palpability, velvetty, sweet, luscious, etc. I'm just going to tell you what I hear and let you be the judge of the review for better or worse.

First, let me tell you what I didn't hear. The amp. That's right. I put my ear to my B&W 601S3 speakers, and I couldn't hear any hiss or other thermionic generated noise when powered on. Only when I powered up the preamp did I hear and noise from the system. This I feel, is justification that the amp will pass on whatever it is fed, nothing more, nothing less.

Second, I have been comparing the Insight 170 to my AVA Ultra 70 tube amp. Both amps were driven by either an AVA Super PAS 3 or AVA T7 preamp. Source was a Denon CD player's digital output feeding an AVA Insight + DAC. The speakers as mentioned are B&W 601 S3 with crossover modification performed by me based on Dennis Murphy's redesign for this speaker. The two amps sound similar, but I'd like to state what I hear as obvios differences between them.

With the U70, after the latest rewiring mod, I could hear things that I couldn't before. Little bits of sound that just comes through the mix that either you didn't notice or didn't distinguish itself from the mix. The soundstage was nice and wide with good depth as you would expect from a decent system. With the Insight 170, not only could I hear different instruments in the mix, I could hear them equally as well regardless of the level of the instrument. That is, louder instruments did not mask the softer ones. This I feel the the geatest virtue of the Insight 170, it resolving power for the lack of a better word. It manages this feat effortlessly. You don't find yourself "straining" to hear what's in the mix. It just happens, if the information is there. Frank has said before..."You will want to listen to all of your music all over again." I can't over emphasize how true this statement is.

Soundstage presentation seems a bit wider and deeper than with the U70. I don't know, maybe I just wanted to hear it wider and deeper, who knows. Like I said, I'm not very good in describing exactly what I hear, but I can hear the differences between the two amps. Maybe I'll slap in my Weber Copper Cap in place of the 5AR4 rectifier to see if that makes any difference in the U70.

Both of these amps are winners in my book. I think Wayner has mentioned that he likes the U70 a bit better than his Insight 170. I on the other hand find myself listening to the Insight 170 more that the U70. Maybe it's because we are liking the newer of the two amps in our systems. I believe that it was Wayner who also stated that the Insight 170 puts you on stage with the musicians while the U70 puts you in the fifth row, or something to that effect. I'd have to agree.

The bass from this little amp is quite enjoyable, even through the 601's. Very authoritative. By that I mean that it goes low without becoming loud or boomy. The mids and highs are free from any solid state artifacts whatsoever. I intend on doing some more listening, you know, play the rest of my collection to see if I hear/discover more accolades for this amp.

Next I will compare the Insight 170 against two U70's runing through my Fet-Valve Phase Inverter Bridge and into a pair of B&W 801FS loudspeakers. The two U70's will generate about 120 watts compared to the Insight's 90 watts. Close enough in power, I'll keep them adjusted to the same volume. Hell, I'm afraid I'm going to like the Insight better than the U70's in which I'll have to send Frank my Musical Concepts DH-500 unit in to upgrade to the Insight. What's next? Getting an Insight+ preamp instead of the Ultra that I've been saving for? Maybe I should send in the Super PAS pre in for the new current buffers? Too many options!!!!

Stay tuned for the next installment!

Ron

[avahifi]

Thanks for the kind comments Ron.

One caution:  Is that "copper cap" replacement for the 5AR4 tube actually a solid state diode bridge in one plug in package?

If so, don't use it.  It will raise the operating voltages to be in excess of the output tube or power supply capacitor's ratings!  The original power transformer was designed to take into consideration the 50V forward drop across the 5AR4 tube.  A solid state diode bridge does not have this drop and the voltages go up too much.  In addition, the 5AR4 turns on slowly.  The solid state bridge bangs on instantly, before the tube have warmed up and are pulling current.  This causes an additional voltage overshoot at turn on.  BAD!

This is true of any ST-70 amplifier, not just our Ultimate 70 circuits.

Regards,

Frank Van Alstine

[Wayner]

Nice write-up Ron! I keep switching between the U70 and the Insight170, both powering my Dynaco A25XLs with the Insight EC preamp at the helm and always fed by ARMod. I am a soundstage slut, and the 170 excels at that while I also agree that it tends to bring out all of the instruments. I sometimes like the natural cymbak crash I get with the U70, more natural, fast and with a nice natural decay, but the 170 is a big picture window, at least to me. In near field applications, the vinyl can be breathtaking, regardless of which amp, but I think over time I've become wishy-washy over which one is my favorite. Maybe it's the weather or my mood, or my imagination, but it's fun to have these kinds of problems.

Bridging two U70s certainly sounds fun. I'd like to bridge 2 170s to see what that will sound like. Also, if someone wants a 170 and doesn't have the cabinet, I think Frank will put it in the small DAC housing. It is also the same amp in the integrated. Oh yes, sometimes the bass just surprises me.

Have fun!

Wayner 

[oneinthepipe]

Good review, Ron.  There is something about earthy vocals, cymbal crashes, piano notes, and guitar plucks with the U70 that surpasses the reproduction of those sounds with the Insight 440, in my brief comparisons in my system.  Additionally, for example, the reverberation on the first track of Martha Wainwright's self-titled album is more prominent through the U70.  On very complex and bass-heavy passages, the Insight 440 handles everything, where the U70 seems less defined.

Regarding the rectifier, I replaced the generic Russian rectifier tube in my U70 with an NOS Philips that I received from Jim McShane, and the improvement is remarkable.

[rlee8394]

oneinthepipe,

I do remember actually hearing the reverb of a bass drum in one of my recordings! I though, how often does one hear reverb in low bass notes?

I bought a pair of the Chinese 5AR4's from Jim McShane recently and that is what I'm using. They are supposed to be quite rugged and reliable. I didn't see any NOS units from him. Were they not listed? How much did they set you back?

Frank, the Copper Cap has two series diodes, 1N4007 I think, per leg of the rectifier with two 39 ohm 10W power resistors and a CL90 inrush current limiter. The voltage drop is fine, but the slow turn-on is not optimal, only about 2 seconds compared to the 10 - 30 seconds or so of a 5AR4. I don't use it all of the time, just for a quick test. I actually found out about them from another user in this forum. Can't remember who.

Ron

[oneinthepipe]

Jim doesn't have any more NOS 5AR4 tubes.

Here is a NOS 5AR4 made by BEL in India for Philips/Mullard for 47.00.  http://www.tubemonger.com/Rectifiers_s/3.htm

This vendor has GE NOS tubes in stock for 90.00. http://kcanostubes.com/products/148/NOS-GE-5AR4-GZ34.htm 

[oneinthepipe]

I'm gonna be dropping a NOS Mullard 5AR4 into my U70 in a few days. I expect to hear entire universes of things I haven't heard before, or even dared to imagine were possible.

    

[Listens2tubes]

With so many having both amps, have any of you bi-amped your system?