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Old 15th April 2008, 07:37 PM   #2011
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Yes, the copper is on one side: http://aycu05.webshots.com/image/351...6628899_rs.jpg
The good quality copper covered board should be white. The glass fibre is mixed with glue, and if they use bad quality glue, the board became darker. The best board should be almost transparent. It was used for high frequency electronic.
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Old 16th April 2008, 07:44 AM   #2012
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many thanx, now I know what to look for
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Old 23rd April 2008, 05:15 AM   #2013
Rodango is offline Rodango  United States
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Default Audio Augustus Imperator (AAI)

Here is the latest fine product of Ranch Rodango - the Audio Augustus Imperator or AAI for short. It is the most fantastic sounding amp I have ever heard, due mainly to the Coveted Clandestine Cochraine Circuit (C4). My implementation is nothing short of extravagant! From the Soviet mil-spec teflon coupling capacitors (imported especially for this amp) to the mil-spec wiring and no concern for cost approach to construction.

The tube complement is as follows. First are a pair of '59 Soviet Svetlana 6C3S rectifuers which, by the way, are the toughest 5U4Gs I have ever seen. Regular 5U4Gs will arc-over in this amp. Next are a pair of '50 Raytheon 6J5G preamps followed by a pair of '44 Sylvania JAN CHS 6SN7s and into the JJ KT88s.

I used no cheap parts at all. The cathode resistor bypass caps are Solen fastcaps, all of the resistors are metal film and at least 1 watt. All of the tube sockets are gold plates and all of the wiring is silver plated mil-spec. It has 4 chokes, two outputs, a CG UTC power transformer and weighs in at 97 pounds.

The results? Utterly awesome! It actually sounds clearer and more real than my 300B SET amp! And about 10 times the power.

Click the image to open in full size.
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Old 23rd April 2008, 05:45 AM   #2014
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Good work Rod, .Since no expense is spared ?: Be interested if you swap the JJ88's for other brands and discover any sonic differences.
I found the JJ88's rather shrill, typical of a frame grid application.
What is the anticipate spec of the Imperator ?

From family history, the name of your amp was also the same name of a large German ocean liner, 52,116 tons. British seamen called it the "Limperator" as it was found to have an inbuilt list. After 14/18 it was renamed Berengaria. My grandfather tried to sink it !
No discouragment!


richhj
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Old 23rd April 2008, 06:24 AM   #2015
Rodango is offline Rodango  United States
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Hi Rich,

Yes I'm going to see how it likes SEDs but I don't think I'll be going for NOS GEC Gold Lions any time soon. It's about 100W per channel, Class A and I have yet to connect it to my dstortion analyzer and see what it's made of. But that sounds fun!

Dave
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Old 23rd April 2008, 10:56 AM   #2016
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Nice building Rodango.

For centerpoint class A drive of KT88 the Ua 320V and Ia 100mA, does not produce any 100W out of two valves to speaker use.

But you certainly meant klass AB.
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Old 23rd April 2008, 01:32 PM   #2017
Rodango is offline Rodango  United States
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Thanks, you're correct. I haven't measured and calculated everything out yet but here's what I have so far:

Push-Pull Ultra-Linear Cathode Bias

Va 550V
Ia 55Ma
Vg1 58V
Rk 1K
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Old 23rd April 2008, 02:48 PM   #2018
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With those AB figures, then it looks like around 50W per ch. I think you meant V cathode = 58V, not Vg1. If Rcath = 1K seems a trifle high. What is the power rating of those cathode resistors ?

I know the JJ88 bias is 20% lower than other 88's so if you swap'em , you might have to check the output stage is running correctly.

As Ragnwald mentions, you have to drop B+ way down-- as with my amp I am just skimming class A at 265V B+ using UL parallel pairs. Iq = 90mA, Ifload =110mA. Pout LS = 25W. With such conditions, the performance is exemplorary.

richj
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Old 23rd April 2008, 03:03 PM   #2019
Rodango is offline Rodango  United States
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Yea I had to go 1K on the Rks because I was getting over current popping with my 820 ohm Rks. It was running about 65ma and with the 1ks it's running about 55ma now on my set of SEDs. The Rks are 10W.

Perhaps I'll put the thing on my variac and idle it down to about 60% and see how it all sounds. Of course I'd need to rebias to do it right.

I need quick change Rks.

Or I could just leave it all too... That idea sounds best to me!
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Old 23rd April 2008, 07:10 PM   #2020
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When using a variac to fudge the B+; don't forget to keep the heaters around 6.3V otherwise the tubes become emission sensitive, i.e creating anode currents based on emission = upping the Ra (tube internal res)

richj
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