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 Post subject: Re: KT120 Oddblocks
PostPosted: 08 Sep 2018, 00:53 
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Joined: 21 Aug 2018, 14:09
Posts: 5
Hi, in your opinion, Bruce, (or others) to drive my speakers that are these
http://www.troelsgravesen.dk/Jenzen-ATS.htm
would a kt120 monophonic pair be sufficient? or better, a stereo pair in vertical biamplification?
Sorry for the silly question but I've never built valve amplifiers up until now but only SS amplifiers
thank you


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 Post subject: Re: KT120 Oddblocks
PostPosted: 08 Sep 2018, 15:45 
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Joined: 04 Jun 2008, 20:59
Posts: 3842
Location: Arizona, USA
Hi, Unless your room is huge or you listen to music at extremely high levels a single amp per speaker should be fine. You can always add the second to bi-amp later if you feel the need. They look like pretty decent speaker BTW. If you do bi-amp you might consider a Behringer CX3400. Inexpensive. I use one and they seem to be innocuous in the system. I use it to split the 45HZ and down to the subs (monster 200L with 30cm drivers) and everything above that to my ESLs.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 09 Sep 2018, 01:02 
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Joined: 21 Aug 2018, 14:09
Posts: 5
Thank you so much Bruce for the answer, now piloto my speakers with two Krell ksa50 clone in vertical biamplification and I must say that they do it very well, just wanting to try to build tube amplifiers (to give a little more sweetness to the upper middle) I was positively impressed by your beautiful project and I'll give you my warmest congratulations for both the project and the patience you put into sharing.
According to you, building a stereo I could use the same power scheme of the mono by increasing only the power of the power transformer (which is obviously adequate for two channels for both the + B and filaments) and putting the two channels in parallel with a single power supply ( obviously using them in a vertical biamplification configuration)?
Thanks again
P.S Good idea of the electronic crossover for the bass part in bi-amplification, in this way the amplifier would exploit the maximum power including that which would "eat the crossower


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 Post subject: Re: KT120 Oddblocks
PostPosted: 09 Sep 2018, 08:54 
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Joined: 04 Jun 2008, 20:59
Posts: 3842
Location: Arizona, USA
Hi, Yes you could put two channels on one chassis just increase the capability of the power supply to handle it. The Behringer is quite inexpensive here at just over $100US. It has many features that can be useful. 2-3 way with or without subs, summing, phase reversal, woofer delay and so on. The only limitation is it uses three pin "Pro" style connectors. Fortunately adapters to RCA are quite inexpensive and work fine. True you lose the benefits of balanced cables and in theory about 3 db S/N. But since you didn't have balanced circuitry before it probably doesn't matter, particularly at line level drive to power amps. A nice feature is it has separate channel and separate gain controls for each output and input. Very handy to balance the L-R and High-Low.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 09 Sep 2018, 11:48 
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Joined: 21 Aug 2018, 14:09
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Excuse me Bruce when you say "Yes you could put two channels on one chassis" mean only one power circuit for both channels as per your scheme (one bridge with diodes of adequate power , a single capacitor circuit 100 + 100uf + 47uf, a single LR8K4 and so on) with a more powerful transformer, I meant this....
As for the output trasformers, I read that someone wanted to use the "Toroidy" brand: does anyone have any opinions about it?


Last edited by maxst67 on 09 Sep 2018, 11:54, edited 1 time in total.

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 Post subject: Re: KT120 Oddblocks
PostPosted: 09 Sep 2018, 11:53 
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Joined: 07 Mar 2017, 03:14
Posts: 80
On the power supply circuit, there are 0.1 uF type X2 and 220R parallel to K1 on the relay. Which one should be on the transformer side (360VAC) first? 0.1 uF cap or 220R?


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 Post subject: Re: KT120 Oddblocks
PostPosted: 09 Sep 2018, 16:53 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, It doesn't matter.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 16 Sep 2018, 08:10 
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Joined: 07 Mar 2017, 03:14
Posts: 80
I finally finished power supply circuit and tested it. It was exciting. I took safety precautions as much as I can: A switch controlled electric outlet, even a fire extinguisher :)) Do not forget discharging high voltage capacitors after the test. They can be very dangerous even after powering off the circuit.

By the way, here are the measured results:
Outlet voltage: 226 VAC
Tranny ouput1: 369 VAC
Tranny output2 (heater side): 11.37 VAC

B+ : 520 VDC
SRPP: 296 VDC
Heater: 14.50 VDC

Relay switch closing time: 53 seconds

These measurements are taken when there is no load on the circuit. I mean no tubes are connected.

Outlet voltage is 6 volt over expected 220 VAC. As a result, I get 369 VAC on the output of tranny. After AC to DC conversion, Is it normal to see 520 VDC B+ ? It looks high to me. What do you think?

Is 14.5 VDC usual for heater?

My bests,
Ozan


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 Post subject: Re: KT120 Oddblocks
PostPosted: 16 Sep 2018, 08:47 
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Joined: 04 Jun 2008, 20:59
Posts: 3842
Location: Arizona, USA
Hi, Seems about right. You can not measure the heater voltage or B+ without having tubes in place. The voltage will drop under load because of the resistance in the rectifiers and transformer windings. Same goes for the B+. It will drop considerably under load.

Good listening
Bruce

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 Post subject: Re: KT120 Oddblocks
PostPosted: 16 Sep 2018, 12:25 
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Joined: 31 Oct 2016, 03:59
Posts: 1
Hi,i'm planning to do two KT120 monoblock,i have a question,is Edcore XPWR264 right for this project? has only 2A at 10.9 so two KT120 running in series at 12v aren't rated to 1.9A + 1.9A?i need 4A 12V to run two Kt120 or i'm wrong? Any of you is buiding with some modding KT120 stereo with integrated ecc802 SRPP tube preamp? can XPWR264 run at 12V two KT120 and two preamp tube?

My best
Marco


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