[Martyn]

Happy New Year!

Over the summer of the year gone by, I read John Rider's "Inside The Vacuum Tube" and Mullard's "Tube Circuits for Audio Amplifiers", having decided that it was time that I had a basic appreciation of the vacuum tube. I've since forgotten most of it, but the main points I took away were that a push-pull pentode with negative feedback is a good way to go and that the EL34 and EL84 are good choices, although the 6550 might be a better (I might be over-simplifying a bit).

After reading these books, I decided that I'd like to build a stereo pair of the Mullard 20W amplifier together with the Mullard stereo pre-amp. On the assumption that there's probably no shortage of people who have improved on these designs over the years, I started looking for designs that are within my capabilities, kits that are relatively foolproof, or fully built products that are sensibly priced. Of course, I quite quickly became bogged down in audiophile marketing techno-babble. Nonetheless, it became apparent that tube amps can provide quite a lot of power these days and possibly without dimming the lights when turned on and being unbearably hot during the summer months!

Here are some of the amplifiers that caught my attention:

Pete Millet's "Engineer's Amp": a 20W p-p pentode design that is probably within my capabilities, but probably isn't powerful enough (http://www.pmillett.com/DCPP.htm).
Menno Vanderveen's UL40-S2: a 30W EL34 or 6550 kit (http://www.mennovanderveen.nl/eng/index.html).
Eastern Electric's M520 and M88 integrated amps: 40W fully built (http://www.morningstaraudio.com/shop/item.asp?itemid=7&catid=4).
Rogue Audio's "Cronus" integrated amp: 100W fully built (http://www.rogueaudio.com/Products_Titan.htm).
Music Reference RM-10: 35W fully built (http://www.ramlabs-musicreference.com/rm10mk2.html).

If I were to build or buy a tube amp, I'd want it to exceed the SQ of Hugh Dean's AKSA 100N+. I use this without a pre-amp (just a Goldpoint stepped attenuator and selector switch). I use Jim Hagerman's "Ripper" as a phono amp on the rare occasions that I play vinyl. I prefer DIY if I can, although the overall objective here is to achieve outstanding sound quality at an affordable cost, rather than to build the next interesting project. I listen to a wide range of music, so getting a decent low-end response is a requirement.

So my question is this: what tube amps would you recommend that can drive conventional speakers of typical sensitivities to reasonable volumes in a room about 16' x 22' x 8' with a sound quality better than an AKSA 100N+? Let's assume a budget of around $2k - less would be good, more might be OK if justifiable.

I realise that this might all be a little vague, but in essence I'm looking for informed opinions based on the considerable knowledge and experience of some of the people who hang out here, or on objective comparisons between various amplifiers.

Thanks very much for your help!

[glynnw]

I have been running a passive/tube setup for several years.  Probably any of those amps will sound good.  Check the input sensitivity and make sure your source has enough output to drive the amp to levels you desire with your speakers.  I have noticed the Music Reference will do well in this situation, but I haven't really looked at the specs on any of the others.  And while I am admittedly  a hopeless fanboy of the following, check out the Tortuga LDR3X DIY passive volume control.   This is working extremely well for several of us driving tube amps.

[paul79]

I've always had issues with the low end of most tube amps, until I bought NOS Valves VRD Mono Amps. They are end all amps and have ran circles around everything I have ever tried.

[Martyn]

Check the input sensitivity and make sure your source has enough output to drive the amp to levels you desire with your speakers.  I have noticed the Music Reference will do well in this situation...

What specifically am I looking for here? My source is usually a Squeezebox, but aren't source outputs typically 2V? Am I just looking for a high input sensitivity on the power amp (quoted as 950 mV for the Music Reference)? Is anything around this figure going to be OK?

[Martyn]

I've always had issues with the low end of most tube amps, until I bought NOS Valves VRD Mono Amps. They are end all amps and have ran circles around everything I have ever tried.

Thanks, Paul, but getting a little expensive!

[pehare]

The MR RM-10 Mk II is the way to go.  It's perfect for passive pre's or a source w/a volume control.  I've owned a lot more expensive SS (Pass, Classe, Conrad Johnson) & tube amps (ARC, Cary, Rogue, Conrad Johnson) & this is my keeper

[Martyn]

The MR RM-10 Mk II is the way to go.  It's perfect for passive pre's or a source w/a volume control.  I've owned a lot more expensive SS (Pass, Classe, Conrad Johnson) & tube amps (ARC, Cary, Rogue, Conrad Johnson) & this is my keeper

Thanks, it's encouraging to hear about comparisons. Any comments on performance relative to a good quality SS amp?

I've just checked the RM-10 pricing - $2,950 for the 35W version, so this one is getting up there too. I'd have to save up for this one!

Anyone know of a DIY kit alternative with similar performance?

[WGH]

The Van Alstine Ultravalve is $1999. Always musical with rave reviews. I have heard it at RMAF and agree with the reviewers an all points. A friend has the kit and is rebuilding a Dynaco ST-70 this weekend turning it into a Ultimate 70, a kissing cousin to the Ultravalve, with any luck I'll hear it in my system soon.

AVA Ultravalve
http://www.avahifi.com/index.php?option=com_content&view=article&id=250&Itemid=235



Wayne

[Bob in St. Louis]

Before you spend two grand on the recommendation of somebody, have you tried to find someone in your area with a tube amp that would be willing to bring it to your house?
I (obviously) can't speak of the section of Canada you're in, but where I'm at, I have no doubt there's like minded individuals near me who'd be willing to share an adult beverage, some great tunes, all in the name of me auditioning their amp with my speakers.

After all, the amp needs the synergy of your equipment and room to sound good which can't be predicted accurately here.

For what it's worth.....

Bob

[Martyn]

Wayne, the VA amp is an interesting option. I hope you do get to hear your friend's amp soon and look forward to your comments. In your own system would be even better!

Bob, that's a good idea. I think there are several AC members in the Victoria area - I'll look into it and perhaps start a new thread after this one has run its course. It's always fun to hear other people's gear, especially when accompanied by a beer or two.

[nnck]

The MR RM-10 Mk II is the way to go.  It's perfect for passive pre's or a source w/a volume control.  I've owned a lot more expensive SS (Pass, Classe, Conrad Johnson) & tube amps (ARC, Cary, Rogue, Conrad Johnson) & this is my keeper

pehare, martyn, all-

I've been interested in learning more about tube amps and have been reading up on Music Reference amps as well. I've always been curious about the difference between the RM-10 MkII amps you are talking about vs the RM-200 MkII amps he sells as well:  http://www.ramlabs-musicreference.com/music_reference_rm-200_hybrid_power_tube_amplifer.html

Other than the obvious points (the RM-200 has more power, more expensive, uses different KT-88 or 6550 tubes), what would be the most likely differences in theses Music Reference amps?

The original post mentioned 6550 as being potentially a better choices. I'm not sure I know why. But I usually see the RM-200 with KT-88 tubes. Can anyone explain some of the differences with these different tubes?

[pehare]

everything you want to know about MR amps can be found in the threads on the MR circle here on a'circle.  I agree w/Bob - hearing is believing to see if its your cup 0f tea.  There are plenty of folks who love amps that weren't good synergy or my preference in my system.  See if you can find someone on the MR circle w/an amp you could hear locally.

[Ericus Rex]

Hi Martyn,

I have some direct experience with the last two amps you mention, so I'll leave my comments to just those.

As for the Rogue, I have had that amp in my system and compared it directly to my other Rogue components (99 pre and Stereo 90 amp).  It sounds very good but I would recommend you get a Rogue Tempest III integrated instead.  The wattage is roughly the same and they can both use the same types of power tubes but the Tempest (the integrated version of the Stereo 90 amp which I owned at the time) sounds much more powerful and 'larger' with better slam and darker background.  Since you're musical tastes vary largely and you want good low end I think it's a better choice for you.  There's one on Audiogon right now for $1,830.  Rogue does offer a tubed phono board for this model if you need one.  If you can swing it, I'd recommend getting the new Rogue ST-100 amp as it trumps both the Tempest and Cronus and has solid-state-like command of the lo-end.

The MR is a great little amp.  I've never had one in my system but have heard a couple in various other systems.  It's a great amp, no doubt.  It's an unusual pairing with the Rogue as they are very different amps.  There's, of course, an obvious difference in wattage; 100 vs 35. With the RM10, you'll be very limited in your tube rolling options.  The Cronus/Tempest can support many different types of octals: 6L6, 6P3S, 6CA7, EL34, KT66, KT77, 6550, KT88, KT90 AND KT120 (Magnum version only on the Cronus).  But you can only put EL84 equivalents in the RM10.  Power tube rolling can drastically change the sound of an amp so you'll have a larger palette available to you with the Cronus/Tempest.  But I'm sure you'll be very happy with the RM10 if you get one.  I'm hoping to get one for myself whenever I can swing the dough.  Too bad the price recently went up on it....

Good luck!

[nnck]

I've also been curious about Decware amps. Do these fit the sort of specifications that the original poster is interested in?

http://www.decware.com/newsite/tubes.html

IS there anyone out there familiar with these amps? Can you compare to Music Reference or some of the other amps being discussed here?

[Ericus Rex]

Forgot to mention that Morgan Jones in his book "Valve Amplifiers" systematically poo-poo'ed some of those Mullard designs.  It's been a while since I read that section and don't remember exactly which circuits he mentioned but you might think about getting that book if you want to learn more.  It goes by at lightning fast speed though.

[DavidS]

if I had your building / engineers skills I'd love to build one of the Audio Note EL34 kits - the monos for example would be nice match for average efficiency speakers and not too big a room.

http://www.ankaudiokits.com/index.html#

Martyn haven't talked in long time - good to see you still have your AKSA amp - still envious.

David in Victoria

[Martyn]

...If you can swing it, I'd recommend getting the new Rogue ST-100 amp as it trumps both the Tempest and Cronus and has solid-state-like command of the lo-end.

Thanks, Ericus. The introductory price of $2,995 (and 60 lb to Canada is going to be painful too). I'll find out how long the price is good for. I should probably add to my original requirements by saying that I'm a bit of a buy-and-hold guy when it comes to expensive electronics...I don't feel the need to "up-grade" my gear every couple of years, so I am sometimes prepared to increase my budget for a product that offers high performance and long-term reliability.

It seems like prices are falling into two groups: around $2k and around $3k. Tube-rolling sounds like another expensive hobby (!) and one that introduces another random walk towards the goal of faithful sound reproduction. I was rather hoping that I could find an amp that provides that elusive high fidelity without having tweak further, but perhaps I'm being too simplistic.

Interesting that no-one's commented yet on direct comparisons with high quality SS amps or on comparable kits. Also, can anyone offer a cross-reference between Rogue and VA?

[geowak]

I've got a Line Magnetic Audio integrated tube amp that I like alot. Here http://donbetteraudio.com/products/amplifiers/ at top of page.
I did a review of this amp here- http://www.audiocircle.com/index.php?topic=104440.0
They also have other models and some SET amps too. FWIW

[tull skull]

Martyn I am not sure of the current status but I know Roger (Music Reference) has discussed amp kits in the past. Maybe you could talk to him and get an idea if he has anything available or if there is something in the works.

[Martyn]

if I had your building / engineers skills I'd love to build one of the Audio Note EL34 kits - the monos for example would be nice match for average efficiency speakers and not too big a room.

http://www.ankaudiokits.com/index.html#

Martyn haven't talked in long time - good to see you still have your AKSA amp - still envious.

David in Victoria

Hi, David.

Good to hear from you! I drive past your house quite often and always wonder what you have in your listening room these days. As it happens, I had an AudioNote amp on my list and then deleted it on price (and they've changed their website to a format that I don't have the patience to navigate). I should probably put the L4 on my list since I seem to be considering equipment in that price range now.

I've built a few more speakers since you were here - I'll invite you around as soon as I have a little more time!

Martyn