Hmm...in 25 years in this insane obsession...er...crazy hobby, I've seen only one tubed preamp, NOT an ARC, with a pentode in it. Said another way, ALL active tubes in ALL tubed preamps (but this one) were all triodes. I wonder why your suggestist even mentioned this.
Just to be confident, I suppose you could ask if the preamp you're considering is all triode.
ARC makes great stuff. Conrad-johnson and others, too, do.
Understand that some tubed preamps have much-higher-than-normal output impedance. This will somewhat limit your choices in length and types of IC and poweramps driven. Ask about that, too.
Don't limit yourself to Audio Research. There are many tubed brands (Sonic Frontiers, BAT, deHavilland, Joule, Supratek, Conrad Johnson, Rogue, etc.) which will offer you better performance at comparable pricing. Check out the number of used ARC pieces for sale. Serious audiophiles don't use them very long after hearing the sonic deficiencies in their own systems.
Your last paragraph is probably the most important factor. I'm going thru it right now. I have a very nice preamp that unfortunely is a mismatch with my amp. Even after lowering the amps input impedance the pre has too much output impedance and overloads the amp causing a distortion.
Kora makes a nice tubed pre-amp, called the Equinoxe, I believe. I had very good success with its predecessor, the Triode. I ran the Triode with both the (SS) Plinius SA-100 and the (SE) Melos MAT-185, both with good success. There is a Triode for sale on the Audiogon right now for $400, I think.
Of course as Jeffreybehr points out all low level signal amplification is done with triodes, often the ubiqutous 12AX7, and its clones. The alternative to a triode is the pentode, which is used in power amps that have transformers. The extra grid in the tube is used to apply feedback from the transformer secondary winding so as to correct frequency response deficiencies of the transformer, and, as a secondary purpose, to reduce distortion.
IMHO your shopping list should not be constrained by arbitrary factors like the type of tube. You might not like the sound of triodes.
Audiogabby - sounds like you have a gain mismatch as opposed to an impedance mismatch. An impedance mismatch will usually result in prematurely rolled-off bass and treble. You are seemingly describing overloading the input stage of your amp. You need to pad down the output of your preamp. The easiest way is to get an outboard attenuator of some kind. The best way though is to see if the manufacturer of your preamp is able to lower the gain structure and if so send it in for updating.
Judy426 Is it actually a deficency with the AR or just a compatabilty mismatch between componets and ICs? I have been pretty fortunate with my matching and get very nice sound but I have been careful as to what I had and how I've changed. Also I have a great counsouler to toss opinions off of too. Right now I was looking as to how I tell differences between a pentode design and/or Triode, are all the AR Pre Amps/line stages Triode or what design would they be? Wanting AR is my personal choice I have always loved them and they were always out of reach for me, it's my personal dream. Now if Sonic Frontiers or another Pre was a better choice I am open to it I'm not being closed minded by any means, when I make a consideration for a seperate amp it will be a Classe though, becuse that was the reference for my speakers and I am hearing the joy of that matching and from the power cord changes I've made, so there I'm being unflexable at this time but, a Pre Amp to match might not be the AR as I would like and I'll have to ask at the time of that impemding change still again. We all have dreams and at this time AR is my first choices.
You seem to be emotionally attached with this dream of owning a ARC product. If that's the case follow your dream but also know you have not purchased the best value for your money. Time was when ARC was one of the best high end lines available. Unfortunately that time has passed and many newer and more innovative manufacturers have stepped all over ARC. Once again check out products from Sonic Frontiers, BAT, VAC, Rogue, Joule, Aesthetix, Supratek,etc. They are demonstrably better, more engaging, and sonically superior to ARC which has long been living off past laurels. There will inevitably be some ARC defenders posting to the contrary because they have invested unwisely in the line and can't deal with it.
Judy426, I do want to thank you for your opinion and your suggestions, I don't want to be close minded concerning my future choice so when I am in position to be doing so I hope that you will be available to offer me an opinion when I have selected an amp at that time. But still what makes a Triode configuration different from say a Pentode? and what are some basic considerations in matching a Solid State amp with a tube Pre Amp? I'm not clear as to how the impedance matching works? (I do understand impedeance on a more simple level though).
While I don't disagree with Judy426's assertions. and my last ARC product was purchased more than two decades ago, my own take on this is that many audiophiles who have toiled through the process of learning what listening is all about (I bought my first component system in 1964), soon discover that personal taste can override reality.
In addition to those recommendations, I'd have to include any number of the currently available Chinese products that appear to offer performance bettering many of their higher-priced domestic counterparts. Having just recently heard the new ModWright Labs preamp, I'd have to include this among those I might have to concede is better than your garden variety ARC piece.
As to your question about impedance matching of a SS amp to a tube preamp, I'm confident in saying that the good designs are within tolerances that most makers are using, and that this would be less of a problem than you seem to think it will be. Nonetheless there are issues between components that need to be addressed. Some, like the Rogue, invert phase/polarity -- which means that you will need to reverse your speaker cable's leads unless your amplifier also inverts. Beyond that, you will find that tonal balance varies, so you would want to select a preamp that is complimentary to that balance and bandwidth of your chosen amplifier.
In the end, though, the ultimate decision as to what works for you should be your own. It's what makes you happy that counts most.
"...what makes a Triode configuration different from say a Pentode?"
Tiodes and pentodes are different kinds of vacuum tubes. A triode has 3 active parts, a pentode 6. A pentode has more voltage gain than a triode, but, GENERALLY, triodes sound better. (Some triode fans say that pentodes sound more like transistors.) GENERALLY, triodes are used in Voltage-gain situations such as preamps and the frontends of poweramps, while pentodes and beam tetrodes are used in the output sections of tubed poweramps.
But lots of us prefer triodes all around, the most-extreme execution of that being the SET or Single-Ended Topology (or Single-Ended Triode). ('Single-Ended' means NOT having amplifying devices in push-pull configuration.) I have a pair of Antique Sound Labs Explorer 805 SET poweramps that I love. To confuse the issue, pentodes and beam tetrodes can be wired into triodes. They then have less Voltage gain and (maybe) they sound better. Triode-wired pen- and tetrodes are used in poweramp output sections or as output-tube drivers and NOT in Voltage-gain situations.
So, again, if you're considering a tubed preamp, simply ask the manufacturer if it's all triode.
A pentode has 5 active parts - the prefix "penta" means 5 -
as in Pentagon.
Those 5 parts are cathode, plate, control grid, screen grid,
and suppressor grid. [ One doesn't count indirect heaters.]
Dr. Gregory Greenman
Thx, Doc. Obviously didn't think about THAT one!
You are right, i have a gain mismatch. The power amp's input sensitivity is too high. I have a decision to make since padding down the preamp would change the sonic signature.
Jeffery, Thank you for that explaination that helped greatly and I think I understand better now. Yeah I know that the audio world has changed over the years and I'm holding on to some older goals, can't help that I've always loved AR, Levinson and Classe products (I'm an old SS fan) that's all. I have heard some very nice CJ line stages before and yes it was nice. as well as ARs mated with the before mentioned SS amps and they were simply georgous! Now a days I won't go back to shopping for new due to cost, so I do a ton of inquiry to help educate myself. My musical tastes are all over but centeralize mostly on softer rock, I could go back to an Aragon Amp again (that was a nice peice) mated with a Tubes Pre but I would like to concentrate on a Classe as that was Apogee's reference and maybe an earlier amp would have just a bit more bottom end extention as well again. Thanks to everyone your help has been greatly appreciated.