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Old 7th February 2012, 09:18 PM   #1
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Default KT88 Stereo Schematic and help

So I think I may have jumped in to purchasing some components a little quick and I'm not 100% sure what to build yet.

I have no experience building audio equipment and don't own any either... but I REALLY want to get into it and purchased the following:

(2x) Gold Lion KT88
(2x) Sovtek 5751
(1x) EDCOR CXPP25-MS-8K
(1x) EDCOR XPWR105-120

I was planning on building: THIS PROJECT and I still may... just looking for some input.

Then, I was looking at THIS PROJECT but I would have purchased the wrong Iron, I believe (forgive me.. I am even new to circuits in general)

So what I am looking for is some confirmation that I should build the first project that I originally purchased the parts for or if there is a more simple project to start with that would perhaps sound as good (or better).

Thank you for any suggestion!

Im sure I'll come back with some more questions when I confirm which project to do...

Here is a rendering I did just getting excited:

Click the image to open in full size.
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Old 7th February 2012, 09:44 PM   #2
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Did you by chance mean this amp using the 5751 as the driver?
OddWatt Audio 5751 SRPP / KT88 Push-Pull Monoblock Tube Amplifier Kits

If so, that would make a nice amp but it is a mono-block. The title of your post says "stereo". If your intention is to build two mono-blocks, you will need 2 more KT88, 1 more output transformer, 1 more power transformer.

edit: my mistake, the 5751 or 12SL7 can be used interchangeably, with the exception of the heater voltage.
edit 2: the KT88 require 1.6A heater current. The Edcor you have specified can only provide 6.3V at 3A. I believe you will need a different transformer or auxiliary heater supply.

Last edited by scott17; 7th February 2012 at 09:54 PM.
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Old 7th February 2012, 11:05 PM   #3
Loren42 is offline Loren42  United States
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I vote the OddBlock (1st one).

OddBlock is about as simple as they come.

Last edited by Loren42; 7th February 2012 at 11:07 PM.
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Old 7th February 2012, 11:07 PM   #4
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The schematic in MY FIRST CHOICE shows KT88s with (1x) EDCOR CXPP25-MS-8K
and (1x) EDCOR XPWR105-120.

Is that incorrect? Will that not work?
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Old 7th February 2012, 11:08 PM   #5
Loren42 is offline Loren42  United States
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Quote:
Originally Posted by scitizen17 View Post
Did you by chance mean this amp using the 5751 as the driver?
OddWatt Audio 5751 SRPP / KT88 Push-Pull Monoblock Tube Amplifier Kits

If so, that would make a nice amp but it is a mono-block. The title of your post says "stereo". If your intention is to build two mono-blocks, you will need 2 more KT88, 1 more output transformer, 1 more power transformer.

edit: my mistake, the 5751 or 12SL7 can be used interchangeably, with the exception of the heater voltage.
edit 2: the KT88 require 1.6A heater current. The Edcor you have specified can only provide 6.3V at 3A. I believe you will need a different transformer or auxiliary heater supply.
OddBlock uses a separate SMPS for the heaters.
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Old 7th February 2012, 11:25 PM   #6
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Quote:
Originally Posted by Loren42 View Post
OddBlock uses a separate SMPS for the heaters.
Maybe I'm confused, but the transformer he has will only supply 3A at 6.3VDC. The KT88s are 1.6A each. The transformer spec'd for the 5751 version is 6.3VAC at 4A. I did not see a SMPS in the bill of materials. The addition of the SMPS for the KT88s would do it. The 5751s can run from the transformer that is specified.

Last edited by scott17; 7th February 2012 at 11:31 PM.
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Old 7th February 2012, 11:31 PM   #7
Loren42 is offline Loren42  United States
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Quote:
Originally Posted by scitizen17 View Post
Maybe I'm confused, but the transformer he has will only supply 3A at 6.3VDC. The KT88s are 1.6A each. The transformer spec'd for the 5751 version is 6.3VAC at 4A. I did not see a SMPS in the bill of materials. The addition of the SMPS for the KT88s would do it.
It's shown in the power supply schematic of the first link.
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Old 7th February 2012, 11:39 PM   #8
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Quote:
Originally Posted by Loren42 View Post
It's shown in the power supply schematic of the first link.
I understand, although it is not listed in the BOM. I suppose that's where I made the assumption and resulting mistake in my post.
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Old 7th February 2012, 11:39 PM   #9
chrish is offline chrish  Australia
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Have you already got the parts from Edcor or have you just ordered them? I understand there is some lead time from order, so you might be able to change the order to something more appropriate when you have decided on a design. The Edcor site is down at the moment, but the output transformer looks like its load is a bit too high for KT88, EL34, 6L6 etc (best around 6.6K). 8K looks best for EL84. Anyway, for PP you will need 4 KT88s, 2 output transformers and probably a different power transformer. With that power transformer perhaps you could go single ended and just need 2 KT88, but still 2 different output transformers.

For single ended I would suggest Tubelab SSE, stereo PP perhaps the Pete Millet universal driver board Push-pull KT88 class A amp with "universal" driver PCB Both are respected engineers with well designed products.

Last edited by chrish; 7th February 2012 at 11:53 PM.
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Old 8th February 2012, 12:30 AM   #10
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I haven't received them yet, I ordered them on Friday (Feb 3rd).

In reading info on the Tubelab.com website, it doesnt look like I could use any of the parts I ordered in their SE or PP.... are you suggesting returning my items and going with something more simple like that to start off? Or could I somehow use the stuff I bought to make one of the Tubelab amps?

If I was going to change my Edcor order to power the ODDBLOCK PP KT88 project better, which transformers should I change to?
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