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Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #70547 is a reply to message #68729] Wed, 21 December 2011 12:33 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1446
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi Everyone, An update on these beasts. The initial components are on hand and the first kit builds (so we can write the instructions) will probably begin next week. Price is still open a bit as we haven't been billed for all the work yet. Since the design first was posted, I made a few small changes and these amps are special (even if I do say so myself). The changes are going to be posted for the smaller (relatively as KT88s are not really all that small Rolling Eyes ) amplifiers. Raises them a notch or two as well.

Good Listening
Bruce
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #70551 is a reply to message #70547] Wed, 21 December 2011 14:33 Go to previous messageGo to next message
ROCKMANDRAKE is currently offline  ROCKMANDRAKE
Messages: 3
Registered: December 2011
Location: France
Esquire
Dear Sir,

congratulations for your work...

I am amazed as you are using only one 12AX7 as a first stage Shocked

Could you please share schematic ?


Best regards from France 'n' happy christmas


Rock
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #70558 is a reply to message #70551] Wed, 21 December 2011 19:24 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1446
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi, If you keep a design clean and simple you do not need as much gain. My sense with many designs is they start out with a more or less standard configuration and then when it is built find flaws. They then add things to fix the flaws. My projects generally start out with an idea of what needs to be done. Then I figure out what configurations will do it best (at least in my opinion). Then I build it and do a lot of testing and tweaking to get it to do what it should. I use configurations that many designers shy away from for various mostly historical reasons. I am also not afraid of using solid state devices when I feel they will do best what I want. All the power supplies in my projects are SS, I use SS regulators in the B+ on the preamps and IC constant current sources in the power amps. Purists cry foul but the results are what I care about. A good example is the distortion level in the latest KT88 monoblocks. At one watt it is at the thresholds of what I can generate and measure (around 0.05%). I also strive for high signal to noise levels. My usual target is -90dbv. I don;t want any hum or noise at the speaker. So what all this means is that the power amp designs are deceptively simple. No parts that don't contribute to purpose. You will observe that there is only one capacitor in the signal path. Also I use a rather trivial amount of negative feedback (3-4 db) to insure stability with any kind of load, not to fix the distortion or frequency response as is often done in other designs. The various parts (like the particular transformers and capacitors)are chosen to work together. The end result is amplifiers that perform excellently. I have attached the schematic of the amp below. How you build the power supply is your choice, but it does need to be clean. I recommend against tube rectifiers because of their higher internal impedance, but with careful application they can be used.

index.php?t=getfile&id=659&private=0


Good Listening
Bruce
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #70566 is a reply to message #70558] Thu, 22 December 2011 02:10 Go to previous messageGo to next message
ROCKMANDRAKE is currently offline  ROCKMANDRAKE
Messages: 3
Registered: December 2011
Location: France
Esquire
Dear Sir,


thank you very much Very Happy

Best regards from France


Rock
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #70567 is a reply to message #70558] Thu, 22 December 2011 05:00 Go to previous messageGo to next message
ROCKMANDRAKE is currently offline  ROCKMANDRAKE
Messages: 3
Registered: December 2011
Location: France
Esquire
Dear Gofar 99,

if you like clean and simple design, please have a look at my blog


http://petitesfabricationsmusicales.blogspot.com



Regards


Rock Very Happy
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #70571 is a reply to message #70567] Thu, 22 December 2011 10:16 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1446
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi, Like you said nice clean designs. Tres bon. Smile We are clearly targeting different folks with our products though. Both in cost and tube vs solid state. I do some projects in SS and like them as well, just I like the challenges tubes present. I also like the sound. There are many individuals that say one kind of sound (SS, valve, triode, SE) is the best. I try to steer clear of that stuff. I just build and design what I like to hear without prejudice to what others like. Some folks like the same things and we sell kits to them (or freely give diy assistance on building from scratch). A bit OT here, but my two biggest passions are to (1) design audio equipment that excels and (2) to encourage new diyers to get into the audio field. If pressed, the second one is really the one I like best.

Good listening
Bruce


Good Listening
Bruce
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #70860 is a reply to message #67330] Fri, 06 January 2012 13:36 Go to previous messageGo to next message
OWRODNEY is currently offline  OWRODNEY
Messages: 1
Registered: January 2012
Location: Michigan
Esquire
Hi Everyone

My Name is Rodney and I am the other half of OddWatt along with Bruce.

I have been working on 4 pre production versions of the KT120 amp which we are officially calling the OBHO (ODDBLOCK HIGH OUTPUT).

I have one of the 4 up and running and the results were great. I expect to have 2 of these in Bruces hands for testing in a week or 2 for his testing and input.

If all goes well, expect kits in mid March.

Replay with any questions.

Rodney


OWRODNEY
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #70865 is a reply to message #70860] Fri, 06 January 2012 18:56 Go to previous messageGo to next message
Wayne Parham is currently online  Wayne Parham
Messages: 17478
Registered: January 2001
Illuminati (33rd Degree)

Dude, that sounds reeeaaally sweet. Can't wait to hear 'em at LSAF 2012.

Didn't you guys bring an earlier version of that amp last year? I remember that you had one new powerful amp there. The one I heard in your room was really nice.

And I ran one of your amps on Sunday too, as you recall. Not the big amp, but definitely enough power for my needs. Very nice sound!

Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #70896 is a reply to message #70865] Sat, 07 January 2012 19:27 Go to previous messageGo to next message
gofar99 is currently offline  gofar99
Messages: 1446
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi Wayne, yes we had some early ones there. The present versions are far better. The originals were rather good, but the level of detail and "air" in the new ones is so much greater you would thing they are different amps. And as what would be obvious, they are really powerful. True to form, though, my belief in the first watt concept, they are quite clean at lower power levels. They just cross the 1% distortion level at 25 watts RMS. Smile Not to bad for a class A design. There is nearly 25 more on tap to keep your speakers busy.

The amp you tried at LSAF was a Poddwatt. I only rate them at 5 watts per channel, but they are really nice sounding watts. We will be bringing one or more of them this year.


Good Listening
Bruce
Re: KT120 Class A Push-Pull U/L Mono-Blocks [message #71466 is a reply to message #70896] Wed, 22 February 2012 16:34 Go to previous messageGo to previous message
gofar99 is currently offline  gofar99
Messages: 1446
Registered: May 2010
Location: Southern Arizona
Illuminati (3rd Degree)
Hi Everyone, An update. I have a pre-production set of KT120 mono blocks. I have been using them for about a week now. These amps are not for the faint of heart. Rolling Eyes Powerful, stunning sound, heavy (37 pounds each)and just plain awesome looking. I will have them at LSAF so you can see for yourselves what a pair of push pull class A U/L tube amps can do.

Good Listening
Bruce
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