Teaching my Moondogs upgrade tricks

[Erik Mandaville]

Yah, I know...lots of talk lately about Moondogs. I was just so impressed with Ed's amps, that I have begun looking into modeling aspects of mine (purchased in the least expensive form) after Ed's. I have never priced Black Gate power supply capacitors, but man are those things expensive! They were so fine sounding, though, that I might try to get a couple...maybe to install over the summer vacation (I'm a high school art teacher).

He also has the great Teflon tube sockets with silver plated pins (Ed: I put a little tension on those, since tubes weren't being held as securely as they could have been). Each one of those beauties is around $40.00 at Welborne Labs, so I might go for the much less costly but good ceramic sockets. I have the black phenolic jobs (plastic) that have pins that grip so tightly, I once couldn't get out one of the 6SN7s without snapping the guide pin off the bottom of the tube.

All in all, I think the reason Ed's amplifiers sounded the way they did was not just because of one or two high quality capacitors. Rather, it was the combined effects of all of the elements combined.

Edster's amplifiers were shipped back to him this morning, but I can't let go of the way they sounded. My wife and I were taking turns jumping up to try our favorite CDs, and we were continually surprised at the difference between my own amps and Ed's. Yes, they were that good! Mine are not too far behind, I think, and the volume control issue has helped. It's also time to snip out my cheapo mylars, to be replaced by some Jensens. Kelly (where is he?) liked them; Leo uses them; Ed's got 'em; and now I know why!

[leok]

Erik,

I think, if you install a Solen 50uF polyprop. for C4A, you don't have to worry about the PS caps because audio won't be going that way any more.

As for the Jensens .. they're a sure bet. I am listening to Andrew Manze (violin) & Richard Egarr (harpsichord) do Corelli's Violin Sonatas through RB-5s, driven by pp using two Jensens each. All those nice upper partials in place and No harshness AT ALL.

leok

[Cut-Throat]

OK - I had to chime in here, because I just (This afternoon) bagged a pair of Moondogs with the Ultimate parts upgrade. They even have Wenge wood Chassis like the 'Final Dog'.?

The Ultimate upgrade includes the Black Gate Caps, The upgraded tube Sockets, Mullard recifiers. Did I leave anything out?

Mine also has the KR 2A3 tubes. Yes I will be doing tube rolling and performing minor surgury as wanted. Any suggestions?

[edster00]

Congratulations Cut-Throat! I just saw that they were sold and was going to ask if anyone here snagged them. You got 'em at a great price too! They were available for about 6 hours at best.

One thing you might want to ask the seller if you haven't already, is what voltage the amps are running on the 2A3's. The KR 2A3's can run at higher voltage than "mere mortal" 2A3's and if you run non-KR tubes at the higher voltage they may burn up relatively quickly. I am sure Erik or leok or someone with more technical knowledge will give you a better explanation.

If your Moondogs are set to run at a "normal" 2A3 voltage (like mine are) I would recommend that you pick of a pair of Sovtek 2A3's for "everyday" tubes. At ~$60 a pair the really sound great. I shipped my KR 2A3's to Erik today so he can give us a review of them when he has a chance to check them out.

[Cut-Throat]

Edster,

Yup, I already asked the seller if he knew if they had been modded for the 4.5 watts instead of the stock 3.25. He did not know as he was the second owner. Do you happen to know how to tell if they have the Mod? - Visually would be nice, although I could take Voltage measurements.

[leok]

Congrats Cut-Throat. The Moondogs are great as they are and easy to modify if you want to make changes. Perfect for horns.

leok

[jazman]

Cut throat,

Congratulations on your Moondogs purchase, and at a fantastic price for a factory built set with the Ultimate Moondog option. You also received what I consider a great sounding pair of 6SN7s, and my personal favorite for use with my Moondogs.

You evidently have the mod for using the KR2A3 tube, so depending on the original owners specs, you may find a switch underneath the amps to allow selecting voltage for the KR2A3 or the normal 2A3 tube. Some may have opted for using the KR2A3 only. I have a mod to use either tube with my Moondogs and I'll try to get a shot of the underside of my amps posted on my web space for you within the next day or so. I have chosen not to use the KR2A3 based on comments of Asylum inmates and Kelly, so I have no personal impressions or experience to relate on that tube. I currently use 1943 RCA 2A3 Black plates.

The "Ultimate Moondog" upgrade package included..."Caddock resistors, Blackgate Muse electrolytic power supply capacitors, Jensen Copper Foil paper-in-oil capacitors and precision machined Teflon tube sockets." I think you're in for many hours of great listening. Enjoy!

Klipsch out.

[Erik Mandaville]

Real quick!

Jazman: Give the tubes a try! Despite what others have said, you may in fact like them...it never hurts to give them a try, and it can only confirm what others have said if you don't care for the sound. I can't wait to try them!

Cutthroat! Please know you just acquired one of the best SET amps currently available -- at any cost! I'm serious about that. With the upgrades you got (I'm jealous!), you will be very happy.

By the way: to tell if your amps were wired for the higher voltage capability of the KR tubes, you can take a voltage reading between the plate of the tube and ground. R13 is the main dropping resistor in the power supply, and this is normally bypassed with bare wire, providing the 2A3 with full B+ voltage. But! many who have done this don't realize that they are also substantially increasing the voltages in the input and driver stages, since those also come off the main high voltage rail. I'm going to do the change in my amps, but make sure plate voltages in the 6SN7s remain with spec.

Leo: I was wondering the same thing last evening about the Black Gate cap. There is no point in making that expense since it is effectively moved out of the audio porting of the circuit -- plus they are very expensive capacitors. Thanks for making that important distinction. Ed's amps were just lots better than mine, even with C4 in the ultrapath version -- I made a quick check to compare, tacking C4 in and out from the bypass the ultrapath locations. I'm sure parallel feeding is taking this to the outer limits, though. I sincerely wish I was close enough to you to have a listen and look at what you did.

Gotta run!

Erik

[Randy Bey]

Kevin,

rawr!

I am dying to hear the diff between the Billie and the Moondog.

That 2A3 is supposed to be one of the BEST in the WORLD, at any price.

I'll be back next week; although I might be going to Virginia then. I'll definately call and see if we can hook up.

FWIW, my Laurels have the Ultimate upgrades, and I've switched from Hovlands (not a bad cap!) to copper Jensen PIOs in the coupling stage. I think the caps alone underneath that beast must be $1000.

Lordy (have to sound like MH for a second,) you made quite a jump. From here on out it will be very very hard to get much better power amp action.

[sprocket]

Hey Cut Throat

Grear deal on your Moondogs.

My M-dogs came with both KR and Sovtek 2a3 pairs. The rca input was moved to the

top plate to shorten the distance to the 6sn7 input (I think Leok has a similar configuration).

The hole vacated by the original location of the rca input was fitted with the voltage switch for

alternating between the Sovtek and KR tubes. I recall that switch bypasses R13 on the power supply

cap. Leok, Erik or Jazz can confirm this. Kelly kindly posted 2 picktures of my moon-puppies where

the wiring bypass can be seen under her skirt (search Leok's "Moondogs are up").

Jazman's amps look like the switch is accessed after the bottom plate is removed.

BTW I think things were more interesting when Kelly was around.

[Deang]

The KR's are the best tubes in the world.

Sure wish they made an EL-34.

Randy, UPS site is still showing "Billing Information Received" on the 5692's I dropped off at Mailboxes E. I'm starting to worry UPS didn't see our little box. I'm going to call them here in a few minutes.

[Cut-Throat]

Thanks guys! - Yes I feel lucky to have picked these up.

Jazman,

My system is starting to look like yours now.

Belles and Moondogs.

Have you tried the TJ Meshplate 2A3's? I have the 300b's and they

are very good!

Erik, Leok, Jazman, Sprocket

As far as the KR2A3 tube, The way I read the details on this tube is that you can run it either way. For either the 3.25 watts or 4.5 on the moondogs. It will just last a lot longer at 3.25 watts. The seller did say in his add that the KR tubes would probably outlast me.

That is the way I also read the Welborne Statement on this tube with the Moondogs. Am I correct here?

Randy,

You will get to hear both amps! - I'll send you an e-mail of my upcoming schedule.

[Erik Mandaville]

The way you are going to get the higher wattage from the KR is by increasing the voltage. But you might not need the extra headroom depending on the speakers you have. Some rewiring of the amplifier PS must be done in order to achieve this. Bypassing the primary dropping resistor (2A3 B+ voltage)will give you probably nearly 400 VDC, or so. However, keep in mind that the actual voltage across the tube is taken between the plate and cathode, not plate and ground, so based on this, we're talking about 350 volts on the 2A3 plate. Maximum voltage for the 2A3 (RCA manual) is 250.

Installing a switch is a good idea, which is exactly what I plan to do. I also have my input jack (I bought some very, very high quality BNC jacks off ebay for a great price -- these have grounds isolated from the chassis) on the top plate, and will be using the normal input jack location for plate voltage manipulation. I had the volume controls in there before (God, I'm glad those are out, now!)

If you don't have overly sensitive speakers, an extra watt might not make that much of a difference -- but will if you do have some kind of sensitive horn loading going on.

[LonestarBlues]

Congratulations CutThroat on your Moondog purchase. You got those Dogs at an excellent price. I also

have a factory assembled pair of Moondogs with the ultimate upgrade

package-Sovtek 2A3, Brimar 6SN7, Mullard GZ-37. I picked up a used factory assembled Revellie preamp

2 weeks ago off of Audiogon at an excellent price. The Revellie is my first tube preamp, I like the Welborne's with my 1977 Cornwalls. I have 3 set of 6SN7 tubes for the Revellie-JAN Philips WGTA, NOS Slyvania, don't know what year vintage-has yellow printing on tube-FA in yellow square & AAK underneath the box, the top of the tube is silver & the base is brown. Is this Slyvania a chrome dome? The Philips top of the tube is also silver. I picked up a pair

of NOS RCA Redbase 5692 tubes from Welborne Labs at a really good price-$48 for a pair. I still need

to pick up a spare set of tubes for the Moondogs. I have an intermittent microphonic tube in my right channel Moondog. Most of the time it doesn't act up. I don't know if it is one of the Brimar 6SN7 tubes or the Mullard GZ-37. When the tube is microphonic, I can gently tap on the wood base of the amp and it quits. I have read about the Halo tube dampners and I am thinking about buying some. I envy you guys

that have amp building and trouble shooting skills. I am a tube novice, never built any tube amp kits-don't know how to solder. And I have zero knowledge for trouble shooting. Enjoy your Moondogs Cut-

Throat.

Regards, Mike

[Cut-Throat]

Mike,

Thanks,I have had my eye open for a while for a pair of Moondogs.

Great price on the 5692's! - How come so cheap? - I'm assuming that he won't sell me a pair at that price?

Erik,

I have been researching this mod because I only plan on 3.25 watts and if the mod has been done, I'll undo it. All you need is to bypass the resistor. If it's there it's putting out about 3.25 watts. If the resistor is gone it will put out about 4.5 watts.

Here is what I got from Ron Welborne this Morning at the Welborne Forum.

***************************************************************

The resistor that goes across the PS cap (Cerafine or BlackGate) is the one that makes the difference; if it's in place the amp is set to run with standard 2A3's.

Without the resistor the B+ is raised approximately 40V which is enough to squeeze another watt from the amp.

The resistor is a Mills 1K 12W non-inductive wirewound.

Any 2A3 can be used with the resistor in place. Removing the resistor allows for higher power from KRs, Sovteks, TJs and other higher power 2A3s.

Ron W.

*****************************************************************

[Erik Mandaville]

Of course Ron W. is exactly right -- he knows his amps inside and out, since he is their papa!

The 1K power resistor he references is actually two 1.8K resistors connected in parallel (paralleling resistors results in half the value). But, this may in fact be a single resistor on some of the newer moondogs. Mine is an older version.

With the stock resistor in place, you will get (+ or - several volts)about 350 volts on the 2A3 plate. Subtract about 50 of that which is cathode related, and you'll have around 300 volts. This is still 50 volts higher than the maximum listed for the tube. I know of some current, well-regarded SET amp designers and builders who would not push tubes that high. The fabulous-or-the-money Sovtek 2A3s (used as the work horse tube by Edster, Kelly H. and some others...including me)can handle that voltage without strain. Before I got Sovteks, I was using some vintage and expensive RCAs. I in fact lowered the stock voltages for those tubes -- to exactly 250 volts.

When Ron says take that resistor out, he means it must be either bypassed by a length of hookup wire or completely taken out of the circuit with a lead in its place.

I have respect for Ron, but I don't entirely agree with the practice of using any 2A3 run at voltages beyond established operating parameters. They would be fine for a time, but likely wouldn't last as long as they would otherwise. When I asked him about this, he said he thought specs in tube manuals are over-rated. I don't agree with that philosophy, but don't say that I am right and he is wrong. I know for a fact that some who have done this modification have ended up with noticeably more power and higher volume ability, but with a companion increase in background noise. To me, that tradeoff is not worth-while.

But you must be excited about this great new purchase! This weekend will be fun, I'm sure!

To Lonestar:

A very respectable post! Not having tech. knowledge with this stuff (Man, I'm still learning how little I know! and my understanding of computers is rediculous!)has nothing to do with serious appreciation of music and listening to hi quality playback at home. I sometimes will listen for an hour or two, and 5 minutes later the amps or preamp or whatever will be upside down on my workbench again. A terrible state of affairs for someone who really loves to listen to music!

[leok]

Cut-Throat,

Tube preference for the Moondogs is very personal. But, I've found that general characteristics that others have described generally apply to what I've heard.

TJ Meshplate is lively, somewhat dark, with a high end that I find hard to tame with the proper 6SN7 driver .. but the sound is generally a lot of fun and sometimes very musically revealing.

1947 RCA dual black plate sounds better damped, is very detailed, but can sound clinical with certain 6SN7s.

The RCA sounds best with the Sylvania 6SN7s and the TJ goes well with the electro-harmonix.

Other 6SN7s .. mid-60s RCAs are a little intense in the high end. 50s and ealry 60s GEs have a very pleasant clean but softened upper mid and high end.

Your mileage will certainly vary.

Enjoy

leok

[Erik Mandaville]

Leok says much with an economy of words! (I obviously need to learn some of that)

Erik

Hey! That had to be my shortest post ever

[LonestarBlues]

CutThroat,Ron Welborne had 2 pair

of NOS RCA Redbase 5692 tubes listed at $48 a pair on his cable remnant closeout sale. I snagged a pair and someone else bought the other pair. Being the tube nube that I am, I had read that they are a good tube. I did a little looking around at various tube resale sites to discover that $48

a pair was an excellent price. I am still learning about tubes and tube equipment. I had never rolled

tubes before. Started out using the JAN Philips WGTA 6SN7 tubes in the Revellie for several days. Switched out to the Sylvanias for several days and now have the RCA

5692's in the Revellie. I still need to buy a spare set of backup tubes for the Moondogs. I have been reading about the various sonic attributes of different brands & vintages of NOS tubes. I have not made a decision yet in what I am going to buy. I just don't want to spend an arm & leg on some of the real high dollar tubes.

Regards, Mike

[Cut-Throat]

I have respect for Ron, but I don't entirely agree with the practice of using any 2A3 run at voltages beyond established operating parameters. They would be fine for a time, but likely wouldn't last as long as they would otherwise. When I asked him about this, he said he thought specs in tube manuals are over-rated. I don't agree with that philosophy, but don't say that I am right and he is wrong. I know for a fact that some who have done this modification have ended up with noticeably more power and higher volume ability, but with a companion increase in background noise. To me, that tradeoff is not worth-while.

******************************************************************

Erik,

Were Edster's amps and yours both running the same Voltage on the Tubes? - If not, could this explain some of the difference you were hearing?