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In Reply to: Re: Are you implying better go passive as much as possible? (nt) posted by morricab on March 8, 2007 at 01:17:40:
Hi.I share the same 'less means more' idea with you.
Since I love LPs more than my DVD-audio & CD, a good phono premap is needed for me. I use both SS & tube.
My tube pre-amp is a basic two-stage phonostage plus a programme selector, followed by a non-reactive passive volume attenuator. I so designed-built this simple pre-amp to accept MM cartridge, DVD-audio & CD inputs WITHOUT any grounding loop isolation device, e.g. I/P transformer (very popularly used to kill ground loop hums due to multi inputs), & yet neglegible hum at phono I/P full volume.
My SS 'pre-amp' is only a two-stage phonostage employing two NPN bi-polars. Fully monoblock design with 17V battery power supply. I always try not to use any chips. The SS phonostage, being my second phono source, is hooked up to my tube phono-preamp occasionally. Frankly, I prefer my tube phonostage better.
I never got the problem of not enough gain even on playing LPs though many worry about not enough drive with passive linestages. More headroom makes music sound more engaging & more enjoyable.
Follow Ups:
If you want to cut down on opamps and such in your cd player/DAC then try the Monarchy Audio M24 DAC. I am using it and its fantastic. The analog output stage is a passive IV conversion followed by an SRPP tube output stage. It also has a full tube preamp that I don't use because I really don't need it and it adds an extra stage (it is also SRPP and very good sounding though with a normal power amp). This is how I get only 1 gain stage in the cd player. My amp (kr audio VA350i) uses 3 stages because the "preamp" is passive. So JFET input, MOSFET driver and KR audio T-100 output tubes (1 per channel good for 30 watts). Yep a MOSFET driving an output tube and it works better than any tube driver I have yet heard.I am using a Silvaweld SWH650 phonostage. Its tube rectified and tube regulated (the only transistor in the whole darn thing is the one for the MC input). Simple passive RIAA equalization means no negative feedback here either.
My TT rig is a Voyd "The Voyd" (3 motor concept with big ass power supply making pure sine waves) with Helius Cyalene arm and Benz Micro H2 cartridge (weakest link IMO).
Hi.Better than tubes-driving-tubes? That's news to me.
My experience was reversing yours. The very best power amp I ever heard so far, dollar for dollar, is the Belgian desinged but
Canadian built Tenor Audio 75WP 75W all-triode OTL-OCL power amp monoblock. It was famed a very fine sounding amp beating amps cost many times more, by critics worldwide.It uesd the cheapest tubes imagineable, with SS regulators throughout, yet its sound was good musical & yet so powerful I was very impressed.
Unfortunately, this affordable sonic jewel was discontinued & now replaced by a tubes-driving-MosFETs power monoblock, being more powerful & "less adjustment than the older all-tube model" per the amp distributor.
I was saddened as I missed bigtime the musically being-there from the new hybrid amp.
c-J
"Better than tubes-driving-tubes? That's news to me."Glad I could be the first to break it to you. It shocked me too, believe me. However, I started reading about how difficult it is to really get the driver of the output stage right and where a couple of guys claimed that this was the primary source of distortion in many tube amps. This high voltage MOSFET really controls the output tube such that there is NO sloppiness in the bass (also great output trannies) and yet the mids and highs sound like pure SET. The secret I think is that there is no feedback and the fets are running single ended class A with no feedback, which should produce mostly low order products like a good tube stage (actually according to Boyk and Sussman's model it should produce only 2nd and 4th harmonics due to the quadratic nature of the mosfet).
I know the Tenor OTLs. Fantastic sound and you can really hear how the regulation tightens up the sound compared to some other OTLs. I know this because I had a pair of Silvaweld OTL Tube Reference amps using a similar tube complement to the Tenors. The sound was crystal clear and extremely dynamic. Truly a beautiful sounding amp; however, they were not as well regulated and as a result the bass was somewhat sloppy. The mids and highs were nearly perfect (when biased correctly...too low bias and they began to sound a bit cold). I only sold them though due to the unbearable heat they generated (500 watts per monoblock all the time). The room went up at least 5 degrees C in a couple of hours!!
However, the KR hybrid is just as dynamic and clean sounding as the Tenors with even better bass. Hard to believe but at least to my ears true. Here is a link to the smaller brother of the amp I own. You will see that it has pretty nice measurements for a tube amp in general (let alone a SET).
http://www.vi-fi.nl/assets/s2dmain.html?http://www.vi-fi.nl/xtrartikelen/testen/100000982d090451e/index.html
The one I have gets about 10 more watts. Notice the linearity of the output vs. frequency (no sharp rise in the bass due to tranny saturation big key to good bass performance). Notice also the -3db point is 80Khz...without negative feedback! Distortion at 1 watt has only to the 5th harmonic at about -105db. At 10 watts some higher harmonics but all below -110 db. Even a decent damping factor (always above 5).
The Tenor at 10 watts looks like this:
http://www.soundstagemagazine.com/measurements/tenoraudio_75wi/
Not too bad either but there are more higher order harmonics and there is more power supply noise in the distortion spectrum. Also, the progression is not as smooth probably for two reasons, 1) it is essentially a pushpull amp and 2) it uses negative feedback. Also running in Class AB it will perhaps have a bit more mismatch in the zero crossing (a SET has no discontinuity there). Finally, it has a more complicated circuit which means more active stages with each adding some distortion.
Honestly much of this is made up for by not having the output transformer. OTLs really do sound amazingly transparent and the KR is first tube (output) amp that I have heard that really measures up in this regard. I have found that the OTLs though that are using negative feedback (this means Graaf, Tenor, Silvaweld, and some Atmasphere) to lower the output impedance to a reasonable level do sound a bit less rich harmonically than the best zero feedback tube amps. Not so cold as most solid state and a bit different but not perfect either. Call OTLs my second favorite amps :), with "normal" hybrids my third favorite (I still love the tone of my Sphinx Project 14 hybrid...tubes in Mosfets out). I have heard one, from AcousticPlan, that is very close to sounding like a good OTL.
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