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Maggie 8600 \ DG-SE1 'Super Build' - The fun begins!

Wharfcreek

Wharfcreek

Jack of all trades, master of none!!
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Well, perhaps I'm jumping the gun here, as I'm still awaiting a few parts to arrive, most significantly the power transformer. The PT in the pics is just an old 'dead' unit I use as a door stop. Anyway, I've received a few inquiries about 'posting' some shots of the Transcendar OTs as related to the AES units. So, I received them today, took a few pics, and also put them atop the new chassis....just to confirm in my own mind that everything is going to fit. Looks good so far. Easy to note the size distinctions. Also, take a look at the 'new' choke being provided by Dynakitparts.com. As you'll see, it's now 'shielded'...which I figure is a good thing. It's also about the same price and size as the Hammond, and it comes from a good place! It's also 1.75H vs 1.5, the same 200ma, and 62 vs (I believe) 56 ohms of resistance. As I'll be using the 5AR4 in this build, the 6 ohms if difference won't add up to the proverbial hill of beans. The Hammond chassis is from CE....the same as that available from AES (they're the same company). This build will use all axial caps underneath, though I still rather like the 'vintage' look of a multi-cap. But, the costs at this point have escalated to a point where I'm probably saving about $30 by going with the axial caps underneath. So....that choice has been made. Still have to source out some gold RCA jacks, and I'm going to do the EIA connector on this one as well. It looked good on the #4 'rat' build..... I think I have most everything else at this point. So, here's some preliminary shots, with more to come as the final parts arrive.

Oh....please forgive any perceived 'arrogance' with my 'super-build' comment. I am NOT a 'super builder'!!! After seeing what Fernanindo and JohnW have done under their Maggie chassis....... I think an award should be handed out to those guys for 'Build Practices'. In fact, I think I'll get with a couple of the AK 'brass' and see if, when they do their 'member of the year' award....they can't perhaps do some 'recognition' of some of these incredible works of 'under-chassis' art!! Hope that clears that issue up. WC
 

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Tom, did you try your new Transcenders yet (on another build)? anxious to to see how the compare to the Edcors... I was tossed up between them and Edcors for the 811 amp and went cheaper!!!, and I got em in 10days, instead of the 5-6 weeks they advertised...
Are you planning on installing them next to each other on teh chassis like the pics show? I think I'd put teh PT between em, turned 90* just to guard against hum...
 
If I do that, I'm gonna need a bigger chassis. And I think hiding the OPTs under the top panel is simply not feasible. I might be following you down this particular rabbit hole, Tom.

Is there a problem with having the driver tube smack-dab between the OPTs if the tube is shielded?

-D
 
Shaping up to be a real nice build. Can't wait to see the completed shots and get your impressions of what the Transcendars bring to the table.:thmbsp:
 
OK, did some more thinking about this 'placement' stuff.....and I'm going with the PT in the middle as suggested by John. Actually John, I got the Hammond PT from UPS today at about 5....and opened it and played with placement then. I liked that configuration better......and 'yes', I do have a 90 degrees out of phase from the OT cores. OTs will straddle on either side of the PT along the back of the chassis (did anyone say ST-70? ) and that will pretty much take up the whole width of the 12" chassis. Derek.... I do think you'll want to forget about burying these underneath. Besides....the way this is shaping up..... I think it's going to look pretty good.

Note the current placement of the choke. It's going to stay right were it is, only I could use some advice on which direction it ought to face. Should it's core align with the PT....or should it too be 90 degrees out? Also, I plan to give it a coat of Satin Black BBQ paint. That will make ALL the iron and chassis kind of 'stealth' mode! The 5AR4 will be to the left of the choke, the two OPTs and the driver tube will go in much like they did on the Edcor version. I'll actually have less room for them since these PTs are larger....and I had both of the Edcor OTs next to each other. I also had the 6CA4 in that build....and the larger 5AR4 also just make this amp look 'bigger'! I've got to laugh; I have one of those odd-ball tubes..... I don't recall the number now, something like G47R or something weird like that. I got told long ago that it was some 'special' version of a 12AU7 that was coated in black as 'shielding' and was used in some of the early Atomic Bomb development labs. Sounds like Hog Wash...but the tube IS coated in black. If I had a 12AX7 like that, I'd use it!! But, I think they make some nice little black anodized 3-ring tube guards.....and I'm going to try to find one. Pics forth coming tomorrow. WC
 
Wharfcreek said:
But, I think they make some nice little black anodized 3-ring tube guards.....and I'm going to try to find one. Pics forth coming tomorrow. WC
Click to expand...

Do a search on eBay for 'IERC tube shield' - there is a short version that is ideal for this application.

-D
 
Wharfcreek said:
O.

Note the current placement of the choke. It's going to stay right were it is, only I could use some advice on which direction it ought to face. Should it's core align with the PT....or should it too be 90 degrees out? WC
Click to expand...

I always try to put the transformers at right angles,,, PT,FT and chokes... haven't had any noise or hum.... There are six of em on this chassis all at 90*...
 

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John, does it take two people to lift that amp? Sheesh!! That's a LOT of iron!! Thanks for the advice.

Jaz, I think the Transcendars cost about $140 including shipping to me in Baltimore. The upgraded choke from DKP was $22 shipped, the chassis from CE Dist was about $35, the PT (also from CE Dist) was $65, and I'm figuring about $40 to $50 in other 'misc' parts, which includes the filter caps, RCA Jacks, Speaker terminals, sockets, and other passive parts. So, what is that; right around $300? I suppose that's pretty costly when you consider that a 'bigger' PP amp could probably be built for the same costs. But..... I'm putting this into the same category as doing a 300B type build, as the results in performance are about the same. As I understand it, a build like that would be MUCH higher in costs....... so, this amp 'should' represent a significant cost savings over the 300B project, and it should deliver about the same level of performance. I guess a lot will depend on just how well the Transcendars work. Time will tell on that one. I'm also hoping that perhaps Dave would consider running this build through his shop to do a 'formal' evaluation of it.... just to validate any perceived enhancement I feel might come from the upgraded OTs. Dave, if you're reading this, how 'bout considering that?

Derek, here's a link to the cover I'm using. Realistically, this is purely cosmetic, as I don't think it does too much in the way of RF protection. But, I've not had ANY issues with that aspect of any of these amps I've built. So, while Dave maybe measured some noise that he eliminated with the shield..... I'm not 'hearing' any noise that I'm feeling as if I need to remove. So, maybe I've just been lucky, but this is really just about adding a 'touch of class' to the thing.

http://www.ebay.com/itm/1pc-Tube-Gu...2-Audio-Amp-/400843233999?hash=item5d541e5acf

I may opt for the 'Chrome' or 'Gold' versions..... but these look cool, while I'm pretty confident they do little else!

WC
 
Wharfcreek said:
John, does it take two people to lift that amp? Sheesh!! That's a LOT of iron!! Thanks for the advice.
WC
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HA,,, I don't have two people... its still in the shop!!!
Good luck with your project, looks promising,,, waiting to hear your opinion of the Transcendar vs Edcors...
When I was looking for OPTs for that amp,, I looked at 15W Edcors vs 10W Trancendars,,, figured its about 13W output, Jeri at Transcendar said their 10W would be OK for it... but they still were 50% higher cost... Didn't price the 15W Trans...
 
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Wharfcreek said:
Jaz, I think the Transcendars cost about $140 including shipping to me in Baltimore. The upgraded choke from DKP was $22 shipped, the chassis from CE Dist was about $35, the PT (also from CE Dist) was $65, and I'm figuring about $40 to $50 in other 'misc' parts, which includes the filter caps, RCA Jacks, Speaker terminals, sockets, and other passive parts. So, what is that; right around $300? I suppose that's pretty costly when you consider that a 'bigger' PP amp could probably be built for the same costs. But..... I'm putting this into the same category as doing a 300B type build, as the results in performance are about the same. As I understand it, a build like that would be MUCH higher in costs....... so, this amp 'should' represent a significant cost savings over the 300B project, and it should deliver about the same level of performance. I guess a lot will depend on just how well the Transcendars work.

WC
Click to expand...
The cost is actually quite reasonable, let us know if the expensive irons pay off or not... As you said, the 300B SE will cost quite a bit more, but on a dollar per watt basis, perhaps it is still in the same ballpark (ok, just a budget build with generic Chinese tubes and run of the mill OPTs). But it is still hard for me to imagine that the two could be in the same catagory, or having the same level of performance, there are just too many differences between the two... just me 2c.
 
Derek, I fear you're thinking 'function vs form' where I'm thinking 'form'....only. I'm HOPING that the 'function' part will be un-needed...which is how it's been on the previous 4 builds. Which leads me to ask the question: Have you seen any difference on your amp 'with' or 'without' the use of a shield on the 12AX7......or have you even had a reason to consider the use of one? As it stands now, my builds have had NO noise issues that have prompted me to consider the use of a shield for anything other than an 'aesthetic' adornment....which I think the one I picked out will add in a rather complimentary way. I'm not so sure the one you've reference is what I'd consider 'classy'. "Functional"......probably! But, if I don't need the 'function' part, then the 'dress-up' becomes the objective...... kinda like the wood trim on all these amps...which I've skipped altogether. I'd LIKE to do that....but sadly, I'm just NOT a good woodworker. It would be interesting to know just why Dave added that shield and ground wire at the end of all this? I'm assuming that he was doing his usual thing and running further 'tests' on the amp and determined that he could remove some content of noise by placing the grounded shield on the tube. However, in the event that I hear no noise.......then that shield becomes superfluous....though perhaps not when being evaluated by sophisticated diagnostic gear....of which my ears are not. Anyway....that's where I'm at. I've ordered the gold RCA jacks.....and may start drawing up the 'drill' plans tonight. Had a busy day with a potential 'new job'. At 63, this is a big deal!! Wish me luck!! TSD
 
I want to see the shrine to these little amps when your done.:D you will have enough to heat a room! Good luck with the new job!
 
LOL....thanks Paul! Believe me, I have enough tube 'watts' to heat a room! I do plan to take a picture of the 'migration' of these amps....... from 1 through 5....... then at some point I think one or two will go on the auction blocks. Can only afford to keep so much of a good thing......so to speak! But, ..... who knows. I have a few family members that might be interested in one. If it 'inspires' one of them to get more 'in' to tube amps......it would be worth it!

Lions on 1 yd line!! RG3 out ..... AGAIN!! TD Lions!! Not looking good for DC!
 
Adding the tube shield had nothing to do with noise, but rather, making the supersonic performance the same between the two channels. On the 8600 chassis, the input tube is physically close enough to the left channel output tube, such that this fact, combined with the significant open loop gain of the design, allowed some coupling taking place between these tubes at very high frequencies -- whereas this of course did not happen with the right channel. Therefore, it was simply a measure to level the playing field between the channels, and nullify the effects of the physical layout that Magnavox used -- one last effort to wring out the max possible performance from what could be built into the original chassis. The original design has such a convoluted HF response that it really didn't matter if the input tube was shielded or not.

Dave
 
Good to know this Dave! My first two builds had the driver tube on the end.....similar to the way the Maggie had the layout. However the second two had the driver tube 'between' the two output tubes. All of them have the driver what I'd call 'further' from the output tubes than on the Maggie chassis...... I guess I'm curious as to just how far the driver tube needs to be from the output tubes to be 'far enough' away to avoid this problem? Also, is there a 'symptom' that I might actually find ...... or 'hear' ...... or is this 'supersonic' problem something that is discernible only on test equipment? Like I said, I've not 'heard' even the slightest of problems.....but now you've got me worried that there might be something going on I can't hear or perceive. Thanks Dave. Tom

EDIT: Lions lost! HTTR (I can't believe I did that!)
 
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Usually, a couple of inches (center to center) will suffice. This is nothing you would directly hear, but more about choosing the ideal compensation cap for the NFB loop for one channel versus that for the other. Without the shield, the optimum value was different by 30pF between the channels. By shielding the input tube, the optimum value was the same for both.

Dave
 
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