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Heathkit W-6

76.179.20.144
Posted on April 5, 2015 at 14:46:07
mark.korda@myfairpoint.net
Audiophile

Posts: 1253
Location: Maine
Joined: August 16, 2011
 Hi, I don't know if a lot of you mugs peruse Ebay looking for vintage stuff like I do. If there are, did anyone see that Heathkit W-6 that was going for 1200 bucks? The wiring shown underneath would give Airtime and Samra a hi-fi hard#n. While not mentioned at all it looked like it was wired by Vladimir Lamms soldering teacher! I tried for 2 days to post that picture on the Vintage forum but have forgotten the proper way to (copy and paste) correctly.Could anyone give me a quick,slow,understandable to a cave man,instruction.Thank you in advance.....Mark Korda

 

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Copy and paste pictures?, posted on April 5, 2015 at 15:01:04
1973shovel
Audiophile

Posts: 10117
Location: Greenville SC
Joined: February 25, 2007
 If I see a picture on the net that I want to post to the Asylum, I right click on it, select "save image as" from the menu, and save it to my desktop.

Then I upload the picture to my Asylum post, using the "upload image" button I've circled in red in the image below. If you have multiple images to upload, click the "preview message" button and upload the second one, etc.

Hope that helps.





 

RE: Heathkit W-6 , posted on April 5, 2015 at 15:11:01
bcguitar
Audiophile

Posts: 1328
Location: Maryland
Joined: March 2, 2005
 I saw it, holy crap thats a nice wiring job.

 

RE: Heathkit W-6 , posted on April 5, 2015 at 15:29:34
Steve O
Audiophile

Posts: 12362
Location: SE MI
Joined: September 6, 2001
 Like this one? Notice it didn't sell. Non-stock meter looks out of place.


 

RE: Heathkit W-6 , posted on April 5, 2015 at 16:40:28
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 I see a selenium rectifier, which is another good reason to pass it buy. :>(( IMO, that's a major flaw in a unit that is supposedly in tip/top condition.


Eli D.

 

RE: Heathkit W-6 , posted on April 5, 2015 at 17:11:57
unclestu
Dealer

Posts: 5851
Joined: April 13, 2010
 The most under rated of the vintage amps IMHO. Properly set up , even stock. it can run the mot difficult speaker load w t to it. Simple great transformers.

A

 

RE: Heathkit W-6 , posted on April 5, 2015 at 21:29:11
mark.korda@myfairpoint.net
Audiophile

Posts: 1253
Location: Maine
Joined: August 16, 2011
 Hi, Shovel,thats perfect,your a great teacher! BCGuitar,(HolyCrap) thanks for verifying that wiring job.When you said that I knew I was not dreaming. Steve,thanks for the picture,it sure looks like the one I saw. Eli, you know a ton about tube amps and I want to learn from you.I still have copied answers from you on how to remove tone controls from the Dyna PAM's and am almost ready to start that project after a slight delay. Eli, that Heathkit was a giant 70 watt Colossus and maybe the rectifier tube could not maintain the AC to DC current or voltage transfer as do the diodes in a bridge....I don't know and I wish you would tell me. I do know most tube guys want the (soft start) of the diode tube. Uncle Stu for your input now and later too as I consider you a great teacher of the tubes. Thanks all you guys.....Mark...Shovel,I'll try your instructions tomorrow.

 

RE: Heathkit W-6 , posted on April 6, 2015 at 05:40:34
johnmil
Audiophile

Posts: 527
Location: Texas
Joined: December 21, 2002
 Good morning,
The Heath W-6 Mr. Korda mentions has been shown on E-Bay previously.
The seller listings are cash only - local pickup only.
Another W-6 recently sold for $1,050 dollars on E-bay. It, also,
was in very nice condition. Both amplifiers were offered with no tubes.
Readers should realize the Heath W-6 utilizes a solid state
bridge-diode and does not have a tube rectifier.
One internet source mentions about 2,200 of these amps were
produced.

Regards to all,
John

 

RE: Copy and paste pictures?, posted on April 6, 2015 at 06:27:22
Awe-d-o-file
Dealer

Posts: 21037
Location: 50 miles west of DC
Joined: January 10, 2004
 That's what I do since I found "optional image URL" doesn't always work.


E
T

ET

"If at first you don't succeed, keep on sucking till you do suck seed" - Curly Howard 1936

 

Glad I got my two...:), posted on April 6, 2015 at 09:07:28
PakProtector
Audiophile

Posts: 12363
Joined: May 14, 2002
 And for a lot less than that each...LOL Their PS got upgraded; choke installed, SiC recitifers...500V caps and a whole new E-Linear circuit built around 6CL6's. The Cit.II went away, the W6m stay.
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

RE: Heathkit W-6 , posted on April 6, 2015 at 09:52:43
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 The B+ PSU in a W-6M is a "full wave" voltage doubler, not a 4 diode bridge rectifier. The diodes are series wired pairs, to increase PIV capability.

That topology is cost effective and can be HIGH performance. It's found in some McIntosh models, the Harman/Kardon Citation 2, and the Marantz 8B. :>D While nothing more need be said, superior bass behavior is a big benefit of SS rectified B+. The better amps employ a choke between the doubler stack and the reservoir position. The W-6M is cheaper.

Only vacuum rectifiers with cathode sleeves, like the 5AR4 and 5V4, exhibit a "soft" start. Directly heated types like the 5U4 and 5R4, turn on almost as quickly as SS diodes do.

I see some obvious areas of improvement in the W-6M.

Extra heater current is available. So, rewire pins 4,5, and 9 of the I/P 12AU7 socket and install the much more linear 6CG7/6FQ7.

Replace the OEM B+ diode pairs with 2X 600 PIV/2 A. Schottky diodes. Install a CL-130 inrush current limiter in the line between the rectifier winding and the center of the doubler stack. Increase the value of the doubler stack capacitors. Install a low DCR 1 H. choke between the doubler stack and the reservoir position. Increase the capacitance in the reservoir position. An additional B+ PSU refinement is inserting a "hash" filter between the doubler stack and the main filter choke. Increases in the decoupling capacitance value could also be of benefit.

Improve the bias supply by installing a 4X Schottky diode bridge and CRC filtering the rail.


Eli D.

 

RE: Heathkit W-6 , posted on April 6, 2015 at 14:41:36
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 Hi Eli,

Why are their so many stages in the driver section?

Dave

 

The best output transformers ever, posted on April 6, 2015 at 16:43:12
garymuffley
Dealer

Posts: 445
Location: Maryland
Joined: March 29, 2006
 The quality of the W-6 output transformers is simply phenomenal.

 

RE: Heathkit W-6 , posted on April 6, 2015 at 17:31:31
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 It's Williamson style, with an added "twist". Cathode followers are DC coupled to the "finals". Blocking distortion can't occur and a bit of positive g1 current, for which KT88s/6550s are rated, can occur.

Considering that the differential gain block is a 'X7, cathode followers are a damned good idea. The 'X7 triode "can't fight it's way out of a wet paper bag".

A 2nd look at the schematic suggests that reducing the open loop gain might be reasonable. Notice the attenuating resistor network, right at the I/P jack. FWIW, I prefer a simple 100 Kohm grid to ground resistor, along with a CC grid stopper.

I like high gm in circuits that employ GNFB. Open loop gain could be reduced and gm improved by changing the tube used in the differential gain block to a 12AV7. Heck even a 12AY7 would (IMO) be an improvement over the OEM 12AX7.


Eli D.

 

RE: Heathkit W-6 , posted on April 7, 2015 at 08:15:49
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 Now it makes sense to me. The cathode followers are to give the 12AX7 enough drive to power the KT88's/6550's, which I understand are difficult to drive. It gets the job done, but it does seem like a lot of circuits go out of there way to use 12AX7's when another tube would be a better choice.

Is this circuit more or less stable than a traditional 6SN7 Williamson without the CF? (I suspect less.) will the traditional 6SNZ Williamson drive PP KT88's/6550's sufficiently?

TIA!

Dave

 

RE: Heathkit W-6 , posted on April 7, 2015 at 09:00:50
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 "Is this circuit more or less stable than a traditional 6SN7 Williamson without the CF? (I suspect less.) will the traditional 6SNZ Williamson drive PP KT88's/6550's sufficiently?"

The number of RC poles in the W-6M is the same as in a "textbook" Williamson setup. Therefore, no significant difference in stability is present.

A "routine" 2X 6SN7 Williamson setup is quite capable of driving KT88s. OTOH, the W-6M is Class "AB2". That's good for a bit of extra power and immune to blocking distortion.

Overall, the OEM W-6M is a fairly decent effort. A corner was cut in omitting a PSU choke and the gain structure (IMO) could have been thought out better. The weaknesses are shored up easily enough and I'd be glad to own a pair.


Eli D.

 

RE: Heathkit W-6 , posted on April 7, 2015 at 09:00:52
bcguitar
Audiophile

Posts: 1328
Location: Maryland
Joined: March 2, 2005
 just replace it?

 

Great information as usual, Eli!, posted on April 7, 2015 at 09:44:27
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 I had not considered the extra demand of class AB2, even though I had read this before about the Heath/Williamson circuit. They also run the tubes UL instead of triode, if I remember correctly.

Dave

 

RE: The best output transformers ever, posted on April 7, 2015 at 15:16:57
Jim McShane
Dealer

Posts: 5910
Location: Chicago
Joined: January 13, 2003
 One of the very best? Sure, no question in my mind... THE best? Not in my opinion. Once you get to a certain level the "bestness" of the VERY top trafos is a matter of personal preference.

It is indeed VERY good!

 

Arrrrgh, the pain returns!, posted on April 8, 2015 at 05:12:30
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 15 or 20 years ago I found a WM-6 in a thrift store complete with a set of golden lion tubes for $1.50 (that's right one dollar and 50 cents!). I flipped it for $300 and thought I had done extremely well. That was before I had started working on and restoring gear and before there was so much info on the web. I did not find out until several years later how rare they are and how special. Been kicking myself ever since. The one that got away, after I landed it!
Of course the flip side is the second one would have cost me quite a bit more, but it probably would have been worth it.

 

RE: Arrrrgh, the pain returns!, posted on April 8, 2015 at 05:37:01
PakProtector
Audiophile

Posts: 12363
Joined: May 14, 2002
 Lol...that is about what I paid for each of mine. They were not tubed IIRC. Running Type III KT90 sourced from Jim( from the end of their decent production), and have a set of Type II's waiting as replacements. I'll not be parting with them.
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

RE: Arrrrgh, the pain returns!, posted on April 8, 2015 at 14:31:49
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 Which the $300 or the buck fifty? I would truly love to hear a pair in stereo.

 

RE: Arrrrgh, the pain returns!, posted on April 8, 2015 at 16:23:04
PakProtector
Audiophile

Posts: 12363
Joined: May 14, 2002
 nah...the $300. I would have been willing to spend more( and thus get the second quicker ), if I only paid $1.50 for the first...:)
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

real numbers?, posted on April 9, 2015 at 06:02:28
PakProtector
Audiophile

Posts: 12363
Joined: May 14, 2002
 I have seen that ~2k production number too. Any other independent source that either backs it up or says otherwise? It would be nice to know just what the production was...:)
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

RE: The best output transformers ever, posted on April 15, 2015 at 08:03:56
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 No doubt the HK Citation transformers are high on you list!

Dave

 

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