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 Post subject: Re: KT120 Oddblocks
PostPosted: 29 Sep 2011, 10:09 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi Everyone, The amps live and breathe. Check the posts at the end of the Oddblock thread for some details. As they are rather similar to the earlier amps (more an evolution than a design change) they can probably go on either thread.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 12 Oct 2011, 13:21 
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Hi, An update.... The pair of demo KT120 amps was just auditioned by a guy with good ears on a massive system that used the BG 6 foot tall ribbon tweeters. He previously had a pair of quite costly ($30K for the pair) name withheld to protect the guilty SS amps on them. The SS amps are now on the sub woofers. He wants the first pair of kit 120s. He (and a high end dealer we work with who set them up) thought they were a lot louder sounding than the 45 WRMS I rate them at. Class A tube amps are like that. Need I say more? Any one that needs lots of power and wants to use tubes should get a matched quad of the 120s and build something along the lines of the most recent schematic. Not a cheap build, but could be the last you will ever need. 8-)

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 12 Oct 2011, 15:06 
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Bruce good to hear your gear is getting accolades. The KT120s maybe the power amp to have when you need lots of power or have hard to drive speakers.

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 Post subject: Re: KT120 Oddblocks
PostPosted: 04 Oct 2012, 22:15 
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Might have missed it, but is there an Edcor part number for Power Transformers for this KT120? Thanks.


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 Post subject: Re: KT120 Oddblocks
PostPosted: 04 Oct 2012, 22:53 
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Hi, No you didn't miss it. The final version uses a special transformer OEM to Oddwatt. But the Edcor XPWR002-120 was used in the original amplifiers with good results. You need to series the 5 and 6 volt heater windings to get a little over 11 volts and then rectify it with a bridge and probably have to include one or two series rectifiers (or a big power resistor) to bring it down to the 12 volts DC used on the heaters. An alternative is to use AC heaters on the tubes as the 6 volt winding on the trannie has the capacity. You will then need to use a 6SL7 in place of the 12SL7. BTW I used the 12SL7s as I found a stock pile of NOS ones made under a Western Electric contract that have wonderful sound. (we bought them out) They were quite reasonable in cost as well. The new Sovtek 6SL7 is a good choice for 6 volt use. NOS RCA and Sylvania are fine as well but not cheap. I'm sure there are plenty of other NOS ones as well for tube rolling. BTW the Edcor transformer has another winding (60V at 800ma) that is not used. I have no idea what the original use of an 800 ma 60 volt winding would be. Way too much for a bias circuit. BTW these are big heavy trannies at about 10 pounds each. Plan on using a strong chassis.

Good listening
Bruce

EDIT: with the Edcor trannie you will need to use a standard two rectifier full wave rectifier arrangement in place of the bridge as the 002 trannie is a 720VCT and the OEM one is 360 not CT. The current rating of the 002 will deliver 440ma at 360 AC and the OEM is just a tad larger at 450ma.

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 Post subject: Re: KT120 Oddblocks
PostPosted: 04 Oct 2012, 23:20 
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Thanks Bruce, and my oddblocks have been going strong for nearly 2 years with 6NO45s, JJ KT88, and 12SL7.


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 Post subject: Re: KT120 Oddblocks
PostPosted: 05 Oct 2012, 07:56 
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Weston Electric 12SL7? Now they could be nice. Would love a pair of their re-issued 300Bs ($900 a pair).

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 Post subject: Re: KT120 Oddblocks
PostPosted: 05 Oct 2012, 12:59 
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Yes, me too on the 300Bs. When I get around to it I have a 300B Oddwatt on the drawing board. But I will use ones a whole lot less costly.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 05 Oct 2012, 18:27 
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A little off-thread but which 300Bs would you go for Bruce?

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 Post subject: Re: KT120 Oddblocks
PostPosted: 05 Oct 2012, 20:19 
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Hi Mark, since is all about Oddblocks... not too far OT. I probably would initially try EH ones. Readily available and not all the costly. I have tentative plans for a 300B Oddwatt. Not all that different from the others, but the directly heated filament does make for a few changes. There are other projects ahead of it so it may be a while. (a stereo KT88 amp and a guitar amp for starters). My main consideration is noise level. It might be a challenge to get it down into the -90dbv range that I prefer.

Good listening
Bruce

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