2a3 amp mono blocks

[Alberto86]

hello everybody,

I’m looking for Welborne Labs 2A3 Moondog Monoblocks kit to assembly myself but looks like I’m having an hard time in finding any online.

Anybody knows if they are still in production (the kit).

If no luck there I’m open to any other suggestions of good kit to build for 2a3 amps (mono blocks preferred).

I have to pair them with my khorn 1971 and I’m really looking forward to do so. I heard once khorn with a 2a3 and now I’m in love.

Thanks for any help in advance.

AB

 

[mhardy6647]

Ron Welborne ended up making a lot of enemies due to allegations of some (very) questionable business practices.

What country are you in?
If you can get one without outrageous shipping cost & duties, I'd say go for the 2A3 amp from "Doc Bottlehead" (Dan Schmalle).

https://bottlehead.com/product/stereomour-ii-stereo-single-ended-integrated-2a3-amp/

Not in the same league as the Moondogs but a reliable and great sounding amplifier kit from a successful and dependable company.

I've owned a pair of their predecessors (the monoblock Paramours) since the kit was originally introduced (indeed, I think our kit was one of the first he shipped) and I have no reason to ever wish to part with them. I reckon they're closing in on twenty years old, come to think of it.

DSC_8376 (2) by Mark Hardy, on Flickr

If you're feeling slightly more adventuresome, source the appropriate parts and build yourself one of these from scratch. A slightly more "traditional" design than the Paramour/Stereomour (no parafeed outputs, so a large air-gapped SE OPT is required "for best results"), the "Simple 2A3" is indeed simple, customizable (e.g., spend as much or as little as you like on OPT iron, passive parts, choke, etc.) and sounds great.

http://jelabsarch.blogspot.com/2012/06/je-labs-simple-452a3.html

http://audiokarma.org/forums/index.php?threads/the-je-labs-angela-se-2a3-amp-done-my-way.112767/

DSC_0586 by Mark Hardy, on Flickr

Here's a current "simple 2A3" build project, just reaching fruition...
http://www.hifihaven.org/index.php?threads/je-labs-angela-simple-2a3-build.2473/

 

[mhardy6647]

A typical "Ron Welbourne" thread from about a decade ago.
http://db.audioasylum.com/mhtml/m.h...e&sortOrder=DESC&sortRank=Forum&forum=general

oops, I got the name wrong, didn't I? It's Welborne, and here's another 2007 thread, from AK:
http://audiokarma.org/forums/index.php?threads/welborne-labs-business-in-trouble-be-aware.115112/

I will say that I ordered a smattering of parts from Welborne many years ago for a build of Pete Millett's "Low voltage hybrid headphone/line amp", and I got my stuff quickly and sans any drama... but his reputation was pretty tattered even by 2007.

I also note this thread, from 2016 (offered strictly 'as-is' and FWIW):
http://www.dslreports.com/forum/r30595415-Welborne-Labs-is-no-more

 

[Alberto86]

Mhardy your advices are great!!!
Thank you very much for taking time for that.

I live in California. The 2a3 would be the 2nd amp I’d build. I built a dynakit st35 from dynakitparts and this is my current amp. It sound really good but not as what i heard with the 2a3.

I won’t sell my st35 until I can compre the 2 in my own system.

My skills allow me to solder in a good way and to follow instructions. But i do need instructions to follow.

I’ll look into the bottle head amps. Hopefully I can get one and give a try with no problems.


I really appreciate your help.

Best

AB

 

[Kim G]

I second the Bottlehead products. Though a quick check just now and the don't have any mono block kits available. I built my Paramounts as 2A3s years ago and will never part with them. The present stereomour would be an excellent project.

 

[mhardy6647]

Bottlehead kits are a little harder to build, being point to point wired, than the ST-35... the instructions are good, though, and there's an excellent resource of enablers at the Bottlehead forum.

California, fortunately, is still part of the US
Bottlehead's in Washington state -- maybe you (the OP) could take a field trip up there some time!

 

[Alberto86]

Is there any guide online you guys are aware of that would guide me in building my own. That would require an explanation of what kind of parts and ideally connections I’d need.

In February i may have some time off and it would be an awesome project i could follow.

Cheers all

 

[Redboy]

s there any guide online you guys are aware of that would guide me in building my own. That would require an explanation of what kind of parts and ideally connections I’d need.

The real value in a Bottlehead kit, in my opinion, is the set of good instructions that come with it. Getting everything you need in one box is super convenient, and having the support of a community of builders on their forum makes for a singularly excellent experience in the DIY hobby.

 

[Shadowdog]

If you've got a tight budget , diy what many say sounds great, with a PCB to start with from tubelab.com George Anderson has a forum
on diyaudio they are still selling well after more than 10 years and you pick the output transformer which define a tube amps ultimate sonics.

All his boards are very affordable with great instructions online a forum help & he also has a PCB board's for a simpler SE & PP circuits.

Elekit of Japan (they have distributors in Canada & the US) makes well regarded kits for SE or SET DHT tubes with everything , allowing upgrades to Lundahl output transformers.

Consider adding Dave Gillespie's EFB mod to your ST-35 if you haven't to noticeably enhance the sonics & as a bonus improve output tube life. Tronola Electronics site has all the info & PCB's if you want them.

 

[lordgarth]

Looking at Mhardys last photo -0586, why do some DIY's place the rca connectoers in the front of the amps???. IMHO it just ruins the look.

 

[Dadbar]

Looking at Mhardys last photo -0586, why do some DIY's place the rca connectoers in the front of the amps???. IMHO it just ruins the look.

Keeps the signal path short.....less chance for bad things to happen. I usually put them on the side....it beats putting them on the back where they are hard to reach. I do the same with the output connectors, too.

 

[Palustris]

The Moondog kit was the initial SE amp offering from Welbourne. The Moondog was a three stage RC coupled amplifier and was state of the art for the early 1990s. Towards the end of the 1990s, Jack Eliano recognized that a two stage direct coupled amplifier was far more transparent and revealing than a three stage RC coupled amp, and so the second SE amplifier marketed by Welbourne, using Eliano's power and output transformer, was the "DRD" or Direct Reactance Drive amplifier designed by Jack Eliano.

All that said, I have a couple of the Welbourne DRD 300B amplifiers that I have extensively modified (and converted to 2A3) that I bought as an assembled kit over a decade ago. In the subsequent years I have built and designed several amps that use a variation of the topology. My present amps are still direct coupled and two stages, but I have experimented with many driver tubes and several complementary topologies such as a CCS on the driver as opposed to the plate choke. In the end, though, for the formula for a great sounding SE amplifier remains the same: two stages, direct coupled with a high transconductance medium mu triode (or triode connected pentode) as the driver stage; although I admit that the 6K5 is an extraordinarily good sounding tube despite the low transconductance.

So it seems doubtful that you will find either a Moondog or a DRD amp in the used market since they are decades old and were rare to begin with. There are several choices, but perhaps Bottlehead is the best of them if quality and ease of assembly are paramount. If you are up for scratch building your amps your possibilities are endless, just be certain to purchase the best output transformers possible. The 3k ohm SE transformers by Eliano, Magnequest, Lundahl, etc are excellent, but for those with deep pockets there are even more exotic and better performing transformers.

 

[Palustris]

My decision to put the input RCA jacks on the front of the amp has nothing to do with aesthetics and everything to do with performance. The wire from the input jack to the volume control is a couple of inches of silver wire and the length of wire to the grid of the first tube is another couple of inches and none of that wire needs to go anywhere near the power supply which is usually situated towards the rear of the chassis. When you build your own amps you can do whatever you want. Note WRT the amp in the photo it originally had a stereo volume control on the right and a pilot light on the left, but the two pots on the stereo volume control didn't track exactly right to left so I had to install a second volume control for perfect tracking.