[Pez]

I am looking for a low powered tube amp that is capable of output in the range of 5-8 watts for my RM40s tweeter. I would like something that can be switched from triode to pentode.  I really haven't found anything out there that meets these parameters (other than the miniwatt and the ASL wave 8s if I could find a pair still in existence, not that either one can switch modes), does anyone have any suggestions? the Pentode/triode thing isn't a requirement, but it would be preferrable.

[soewhatman]

If you are open to DIY...

http://www.engineeringvista.com/audio/AudioKits/Model-1/index.htm

Has jumpers on the board to switch between UL, Triode & Pentode mode.  Could be wired up with a switch instead of jumpers I imagine.

Vista Audio used to sell this as a complete assembled unit  called the i82.  You may be able to find a used one.  I bought one (used) a number of months back and have enjoyed it with headphones.  I have used it very little with speakers though.

Rick.

[mcgsxr]

Does vintage cut it?

My old Magnavox console pull is a single ended pentode design, using EL84's.  I think it only outputs 3-5wpc though, so it might not have enough guts for what you want.

In terms of quality output though, it remains my main amp since Sept 2006...

http://www.audiocircle.com/index.php?topic=31096.0

[JimJ]

Doesn't meet your power requirement, but if you can live with less power (2 watts), Decware Zens can be had for around that price. Especially the older SE84B or non-Select C versions.

[Wayne1]

Jason,

You also may want to look at the S-5 electronics kits. You can get a 12 watt stereo amp with case for about $270.00. These are fairly well thought of.



S-5 Electronics

Lot of mods can be done to these. 

[doug s.]

this one already sold, but if you are patient, you may be able to find another, not too much over your budget:

http://cgi.audiogon.com/cgi-bin/auc.pl?ampstube&1251682235


5wpc, single-ended pentode.  these are killer amps, imo; a great deal even at retail, if you only need 5w...

doug s.

[doug s.]

oh i forgot - shameless spam here...     i have two amps that might do it for you - completely refurb'd electrohome p-p amp, w/wintage nos french 6aq5 tubes.  makes ~8wpc; better than the wave 8's i used to own, imo.  i'd like $300 for it:



it comes w/a nos wintage philips rectifier, as well as the ruby tube pictured.  i did a simple mod, (lifting one wire) recommended by the builder of the amp below, to allow using the philips tube, which softens the start-up woltage the 6aq5's see, lengthening thier life.  i also have schematics/manual/etc... 

or a custom made/designed set amp, by a chinese guy living in australia, w/nos 6v6 tubes making ~4.5wpc.  switchable negative feedback - 0db, -1.5db, -3db.  i also have the schematics for it; this one is a bit spendier - $450:




there's more pics in my "doug's stuff" gallery, if interested...  actually, the pics are there, even if you're not interested!   

doug s.

[JimJ]

Man, I'd be all over that PP amp if I could afford it now

How much for the Pantera? 

[doug s.]

Man, I'd be all over that PP amp if I could afford it now

How much for the Pantera? 

actually, i would consider selling the pantera.  i really would love to get a used lotus elise or exige.     but, if you can't afford the electrohome, i think the pantera would be a stretch for you.   

doug s.

[JimJ]

but, if you can't afford the electrohome, i think the pantera would be a stretch for you.

I hate when math gets in the way.

[Pez]

Lots of great suggestions here guys! I'm liking some of the DIY stuff.  I am thinking that might be the way I go, but keep em coming. Honestly if someone has a 20-30 watt option I would love to here that as well, hopefully price won't exceed the stated amount. 

[doug s.]

pez, if you want more power, look for a wintage scott, sherwood, stromberg-carlson integrated amp.

doug s.

[Wayne1]

Triode Electronics offers an updated kit version of the Dynaco ST-35 for $470.00

17.5 watts per channel

MANY posts about this amp on DIYTube

I would be willing to help you with assembly, if you choose the DIY route.

There is even an assembled one for sale on Audiogon for $350.00 or best offer

ST-35 assembled

[Wayne1]

Another great kit amp is the Simple SE offered by Tubelab



I think this one meets all your requirements. It can be built for as low as $250.00 or you can spend as much as you like with more exotic parts. It can have a switch for Triode/Pentode or even Ultralinear operation. The amp can produce 10 to 14 watts per channel in ultralinear mode and 5 to 8 watts in triode mode depending upon tube choice. More power is available in pentode mode. It can be built with either tube or solid state rectification.

Compatible with a large variety of tubes:



I believe a few members of AC have built this amp. This may be the one for you, Jason.

[Pez]

I think you're right Wayne! That amp looks spectacular! I even found a cool little box for it just lying around the house. I think we have a winner!

Dang, it can operate KT88s? OHHHH so sold!!! 

[Mariusz]

Interesting thread.
And please do not let me stop you.

Mariusz

[soewhatman]

I built a Tubelab SimpleSE last year and found it to be an easy built for a novice to such things.  It is not a kit per se, but actually just the circuit board you buy from tubelab.  You need to purchase the rest of the components yourself, though there is a parts list with Digikey and Mouser part numbers in the instructions.  There are tons of options when building this amp, and some very good threads on www.diyaudio.com about different parts and configurations.

He also has a push-pull el84 amplifier board that is nearly done and should be available soon to get you a bit more power.

Rick.

[Pez]

Thanks for the info soewhatman, I should be able to get the SPL I want out of the 5-15 watts from the simple SE through triode or UL. Plus I like the fact that I can roll a ton of tubes. I am ordering the board for the Simple SE today, but lets keep this topic rolling. There are a lot of neat low cost amps here!

[JoshK]

For your tweeters, I recommend SE over PP.  I don't think you need dampening factor that PP offers for ribbon tweeters, plus the second order harmonics are going to be more pleasing than third (SE makes more 2nd, PP cancels 2nd leaving mostly 3rd).   I like the SimpleSE for you application and it is cheap.

I am building a Tubelab SE amp right now, its a more complicated version than the SimpleSE for use with DHTs rather than standard audio pentodes.  It still was a pretty easy build.  George is a talented engineer (by day) and made the kit so that beginners could tackle it without frustration.  I think it is pretty high performance for this style of amp.  You can get into exotica but you will pay handsomely.  His kit looks like a high performance to modest cost design.

If you aren't inclined to build a kit, which is sounds like you are, then I like Doug's suggestion for the Almarro, a Magnavox console pull EL84 SE amp or any other 6V6/EL84/6AQ5 type SE amp.  You can't go wrong with the EL84 types for 1.5-5watts (depending on operating mode), its hard to mess them up as they are so linear and easy to drive.