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Old 1st May 2013, 05:44 AM   #11
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Join Date: Apr 2013
Good Day All...thanks for your posts.. I appreciate it

I will be basing my design on Loren's design and take in consideration the Williamson updates stated earlier above.

Thus my preamplifier section will consist of 12AX7 and 12AU7 if I can not get my hands on the 6SN7GT. I would liek to use the 5751 as they have a biot more gain in them than the 12AU / 12AX and the 6SN.

I would liek to use a PCB design rather than point-to-point wiring.

Loren42: Do you still have some PCB's left?

The Transformers will be coming from Edcor

Output Transformer CXPP60-MS-4.2K - As this amplifier would be 50Watts rated and I think you can not get more that 50watts out of the KT88 unless you drive them parallel, thus I feel that the 100W version would never be used to its potencial and I would rather save the $40.

Power transformer can not be the XPW133 stated as our primary voltage here in Australia is 'n bit higher than 110VAC. thus I am waiting for Edcor to respond if they can supply a 240VAC version of the XPWR133.

Color on the Edcor would be black if I can choose...

Enclosure will be custom and would be a stereo setup rather than a Mono block setup.

Once Edcor has confirmed availability and my order to them I will start with my enclosure design and component placement .. If I can get some PCB's nice...otherwise I will do point-to-point.. (Might think making my own PCB's... if my financial officer don't mind an extra $500 expense for the PCB's..)
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Old 1st May 2013, 12:31 PM   #12
rmyauck is offline rmyauck  Canada
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Get the 100W OPT as the bandwidth will be much better at full power & with less distortion. Many 6550/KT-88 amps got 60W/CH (Dynaco & Harman Kardon) and at least one with 70W (Heatkit) was made. The bigger OPT's will support KT-120 tubes better also if you want to try them latter also!

Anyway when your doing it you may as well do it right for only a very small % of the total cost more. The OPT's are what define the ultimate sonics of your tube amp also, so if you can afford the extra on PCB's look for better OPT's.

Don't rush, do your due dilligence!

Best PP OPT 30-100W range

Last edited by rmyauck; 1st May 2013 at 12:36 PM.
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Old 1st May 2013, 08:36 PM   #13
rongon is online now rongon  United States
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Location: Across the river from Rip's big old tree...
Williamson circuit has enough gain as it is, doesn't it? Why add 12AX7? Also, there are Russian 6SN7GT available. That's what it is in the pretty picture from earlier in this thread. In addition, 12AU7 does not perform as well as 6SN7.
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Old 1st May 2013, 09:16 PM   #14
multi is offline multi  Australia
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Default KT88 50 watt

Best to stick with Lorens design maybe changing some of the resistor values.
12AX7's 5751's are best left to Guitar amps and pre-amps, you don't need extra gain with the Williamson. Other driver tubes are 12BH7, Russian 6N6 or ECC99.
the design by Triode Dick is also very good.
The 6550/KT88 can easily give 100 watts, but last longer at 70 watts or less.
R18 is better reduced to 470r not 1k may be printing mistake on the input voltage amp used on Triode Dicks Monobills classic, circuit
Attached Images
File Type: jpg MonoBill-Classic-schema.jpg (121.7 KB, 555 views)
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Old 1st May 2013, 09:27 PM   #15
multi is offline multi  Australia
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One advantage of Triode dicks circuit is the grid resistor on the KT88' of 39k.
Current production 6550's, KT120's recommend less than 50K, Fixed bias. Original GEC KT88's could handle 100K, but even so many of GEC's circuits used 39k and 68K, to extend tube life. Not sure but 6SN7's may have trouble working into 39K, the 6N6 has very low plate resistance so easily drives 39K..
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Old 1st May 2013, 09:32 PM   #16
TiMBoZ is offline TiMBoZ  Australia
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I was considering transformers also: Lundahl transformers are also available in Aussie at Golden Age Audio.
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Old 1st May 2013, 11:06 PM   #17
Loren42 is offline Loren42  United States
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Location: "Space Coast" Florida, USA
Originally Posted by rongon View Post
Williamson circuit has enough gain as it is, doesn't it? Why add 12AX7? Also, there are Russian 6SN7GT available. That's what it is in the pretty picture from earlier in this thread. In addition, 12AU7 does not perform as well as 6SN7.
I am now running some NOS PhillipsECG JAN 6SN7WGTA tubes instead of the Russian tubes and the KT88s have been replaced with reissue Gold Lions.
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Old 2nd May 2013, 03:16 AM   #18
limono is offline limono  United States
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I would build Jadis clone . The design has been ridiculed by all best electricians here so all the chances are it sounds sensational
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Old 2nd May 2013, 11:03 PM   #19
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Join Date: Apr 2013
Good day my fellow Valve heads ()

Thanks for the advise..

Ok..I will be sticking to Lorens design as I have all the info I need. It is a sweet amp and it looks the parts as well.

I had a look at the Jadis amplifier and even found a Defy 7 schematic..But looking at that I would have to start from scratch again.. What Power Transformers do they use? what OPT do they use..

Loren was kind enough to share his design and all the info required to build the amplifier. For first time builders and Novices like myself this is to me the best option.

I have placed my order with EDCOR.. The OPT is the CXPP100-MS-4.2K as advised by people with better knowledge (and I can understand the madness behind the argument for a bigger OPT). The Power Transformer is the XPWR133.. but with a $40 charge they are making the XPWR133-240 for me.

So next step will be to layout my Enclosure and get it laser cut and folder .. I was looking at a few posts where stereo enclosure seem to have a weakness due to the weight and the available enclosures in the market.. Thus I am opting for a 2mm stainless enclosure designed.

I am currently looking into a few volume controls ..either ALPS or a
23 Step Attenuator.. Inputs would be selectable between 3 sources..

Seems I will be doing a point to point wiring at this stage as budget was taken up with the transformers. But this might be a good point as this would provide me with easy changes if any resistors needs changing and then it would also allow me to upgrade and do design changes if I require to update with KT120 as mentioned prior in this threat..

Will keep you guys posted and on my progress...
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Old 19th June 2013, 10:32 PM   #20
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Join Date: Apr 2013
Good Day my fellow Valve lovers

Finaly got my Transformers from Edcor. I must say..Wow..they look great..hope they sound as good as they look.

Loren42... Wow man..the output transformers are actually bigger than the power transformers.

Now for my enclosure... I had a good and hard thought and I have decided I will be doing a single enclosure.. Might be heavy and big but I would rather have one than three enclosures to build.

Enclosure design is still up in the air..still looking for acceptable enclosure from supplier or maybe design my own..

Will keep you posted and start loading photos

Happy building
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