I wanted a Jeff Korneff Clone Build. I had not seen a Mono Block Version of this Amp, so I contacted Min Yang of Tube Audio Labs to do a Custom Build last fall. Min had built quite a few Korneff Clone Stereo Amps, But had never built them in a Mono Block Configuration. So, I went 'All Out' with Hashimoto Transformers, Mundorf Silver Oil Caps, Cardas Connectors etc.... Min was very easy to work with, as he let me design a Chassis Layout of the Tubes, Transformers, Hum pot and all of the connections on the back of the Amps. -- Mirror Image etc. I got to select a Walnut Hammond Chassis as well.

When I first hooked up these Amps on my System, I adjusted the Hum Pots, so that any noise from my 115db Oris Horns was only barely audible by sticking my Ear into the Horns.... These Amps were the quietest amps, I've had Hooked up to my Oris Horns.. Almost Dead Silent.

Since I Bi-Amp my System, I had my Bass Amps (Which are hooked to my Khorn Bass Bins) Balanced with my Welborne Star Chief 45 Amps. To my Surprise, The Bass was overwhelming at first. I had to drop the volume of the Hypex Amps by 17db from the Welborne Amps to balance with the TAL Korneff Amps.

So, now I have got these Amps pretty well matched and 'dialed in' and am now listening to these Amps.... So, the Korneff Design is everything that people say it is... I am enjoying them immensely... And I will also say that the Welborne Star Chief 45 Amps are 'In the Same League'.... I could not pick one over the other ....Yet (Maybe in a few months - They are both lovely 45 amps) .... The TAL Korneff Design has a simpler circuit and is Tube Rectified. The TAL Korneffs are much quieter at idle than the Welbornes (Probably Less Power) Maybe only about 1.5 watts instead of 1.8 on the Welbornes. (I Don't know for sure). But it is nice knowing that I am listening to the Korneff Design. I had contacted Jeff Korneff and he was nice enough to send me a schematic and design notes, which is 'nuts on' to this build. So, I longer have to wonder how a Jeff Korneff Design sounds.

I have been Hooked on the 45 'Amp Sound' now for about 18 years (This is my 3rd pair of 45 Mono Block Amplifiers).... And These Amps 'Fill the Bill'.... I highly recommend Tube Audio Labs and Min Yang if you want the 'Amplifier of your Dreams' and a Custom Build... I am wondering if I have one of the only Pairs of Jeff Korneff Clone Monoblocks??

 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Salectric 13:33:35 03/29/21 (5)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Cut-Throat 13:51:07 03/29/21 (4)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Salectric 13:59:17 03/29/21 (3)

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 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Salectric 13:33:35 03/29/21 (5)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Cut-Throat 13:51:07 03/29/21 (4)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Salectric 13:59:17 03/29/21 (3)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Cut-Throat 14:02:27 03/29/21 (2)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Salectric 14:14:57 03/29/21 (1)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Cut-Throat 14:17:02 03/29/21 (0)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - bouncy ball 08:39:45 03/27/21 (0)
 The Korneff 45 was an audio-life changing event for me. - The Killer Piglet 07:21:16 03/27/21 (6)
 RE: The Korneff 45 was an audio-life changing event for me. - Cut-Throat 07:47:48 03/27/21 (5)
 RE: The Korneff 45 was an audio-life changing event for me. - The Killer Piglet 05:25:19 03/28/21 (4)
 RE: The Korneff 45 was an audio-life changing event for me. - Cut-Throat 06:27:56 03/28/21 (3)
 RE: The Korneff 45 was an audio-life changing event for me. - The Killer Piglet 07:54:35 03/28/21 (2)
 RE: The Korneff 45 was an audio-life changing event for me. - Cut-Throat 09:24:57 03/28/21 (1)
 RE: The Korneff 45 was an audio-life changing event for me. - The Killer Piglet 12:30:31 03/28/21 (0)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - deathtube 667 06:28:00 03/27/21 (44)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Cut-Throat 07:05:37 03/27/21 (43)
 RE: sounds good to me ... - deathtube 667 08:29:20 03/27/21 (0)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Tre' 07:20:45 03/27/21 (41)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Cut-Throat 07:29:23 03/27/21 (40)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Tre' 07:41:54 03/27/21 (39)
 RE: tried the input cap mod ... - deathtube 667 18:54:14 03/28/21 (5)
 I asked the guy that Designed my Horn System this question ......... - Cut-Throat 13:11:03 04/01/21 (0)
 I have no explanation for that. nt - Tre' 17:27:00 03/30/21 (1)
 RE: It might be ... - deathtube 667 02:51:42 04/01/21 (0)
 RE: tried the input cap mod ... - Cut-Throat 07:01:48 03/29/21 (1)
 RE: tried the input cap mod ... - deathtube 667 07:40:53 03/29/21 (0)
 "100k input impedance of the 45 amplifier"........ - Cut-Throat 14:49:33 03/27/21 (1)
 I was looking at the wrong schematic, yours is 1meg nt - Tre' 17:26:31 03/27/21 (0)
 My 300B monoblocks have a 100K input resistor to ground... - Ivan303 11:36:43 03/27/21 (2)
 Yes and yes. nt - Tre' 13:47:12 03/27/21 (1)
 except I get 72.34Hz for that combo. nt - Tre' 13:49:16 03/27/21 (0)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Tre' 08:01:35 03/27/21 (0)
 OK, Thanks ........... - Cut-Throat 08:00:45 03/27/21 (25)
 That's not the circuit I thought it was - Tre' 08:10:05 03/27/21 (24)
 OK, Great ........................ - Cut-Throat 08:12:38 03/27/21 (23)
 RE: OK, Great ........................ - Tre' 08:40:01 03/27/21 (22)
 RE: OK, Great ........................ - 91derlust 17:02:12 03/27/21 (3)
 RE: OK, Great ........................ - Tre' 17:30:17 03/27/21 (2)
 RE: OK, Great ........................ - 91derlust 20:36:56 03/27/21 (1)
 "some of the compromises mentioned can be overstated". Agreed. nt - Tre' 06:50:37 03/28/21 (0)
 Why did he select 100 Hz ? .... Why not 200 Hz or ?? ........nt - Cut-Throat 08:53:46 03/27/21 (16)
 No, I selected it - Tre' 09:19:31 03/27/21 (15)
 Got a Source for some .0015 uf Caps ? .................. - Cut-Throat 13:05:51 03/27/21 (13)
 RE: Got a Source for some .0015 uf Caps ? ......yes............ - awsjr 04:07:39 03/28/21 (0)
 RE: Got a Source for some .0015 uf Caps ? .................. - Tre' 13:28:17 03/27/21 (11)
 E-Bay has quite a few .......................... - Cut-Throat 14:27:48 03/27/21 (1)
 RE: E-Bay has quite a few .......................... - Tre' 14:46:42 03/27/21 (0)
 On my setup... - Tre' 13:40:33 03/27/21 (2)
 Here are some very Spendy Ones from England ...... - Cut-Throat 13:44:31 03/27/21 (1)
 RE: Here are some very Spendy Ones from England ...... - Tre' 14:19:21 03/27/21 (0)
 "Why is the grid resistor 1 meg?" ....................... - Cut-Throat 13:39:48 03/27/21 (5)
 Well, if your preamp don't mind... - Tre' 13:52:23 03/27/21 (4)
 RE: Well, if your preamp don't mind... - RPMac 15:32:47 03/28/21 (3)
 RE: Well, if your preamp don't mind... - Tre' 16:24:21 03/28/21 (2)
 RE: Thanks a lot nt - RPMac 05:00:20 03/29/21 (0)
 Link to online calculator - Tre' 16:47:46 03/28/21 (0)
 OK, makes sense..................... nt - Cut-Throat 10:21:40 03/27/21 (0)
 I'll definitely try this ...................... - Cut-Throat 08:44:17 03/27/21 (0)
 A .015uf cap will do the job. nt - Tre' 07:49:21 03/27/21 (0)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - 6bq5 15:35:55 03/26/21 (4)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - HiFiOd 18:13:47 03/26/21 (3)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Cut-Throat 05:01:13 03/27/21 (2)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - HiFiOd 09:53:01 03/29/21 (1)
 RE: Listening to my New Korneff Clone 45 SET Amps ................. - Cut-Throat 10:10:55 03/29/21 (0)

http://www.bd-design.nl/contents/en-us/d71.html

I did try a Marchand Active Crossover once, that would filter out the Bass before it reached the Amp, but it was a Mass of extra cables and added more hum to my system than I've ever heard before.

• http://www.bd-design.nl/contents/en-us/d71.html

Even though you have a passive crossover keeping the bass out of the horn, if you don't do something to keep the bass out of the 45 SET amplifier the load line for the mids and highs will follow an elliptical load line because of the presents of the bass. No gapped output transformer has enough inductance to properly deal with low bass frequencies. This leads to distortion of all the frequencies.

Try this, add your best .015uf capacitor in series with the 100k input impedance of the 45 amplifier. I like the Russian Silver mica caps.

This will create a 6db high pass filter at about 100Hz and greatly improve that amplifiers performance in the mids and highs without changing your 270Hz crossover point. The load line for the mids and the highs will become much more "resistive" leading to less harmonic distortion.

Voltsecond did a study of inductance and elliptical load lines and made the very point I am trying to share with you.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

A .0015uf would work just fine.

This is a big deal. You will hear immediately the mids and highs "clean up".

Do yourself a favor and just try it.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

All output transformers have a limited amount of inductance. Single ended output transformers need to have a gap so the idle current for the output tube doesn't saturate the core. When a gap is placed in the core of a transformer the inductance goes way down. The inductance can be brought back up by winding more wire around the core but there are limits. Too much wire and you will began to lose highs because of the winding capacitance. The end result of all the this is that SET transformers do not have a ton of inductance. The lack of inductance means that the reactance of that inductance will be small for the lower frequencies and that is what causes the elliptical load line.

If you allow the lower frequencies to reach the output transformer the load line becomes elliptical instead of the straight load line we think of when we're dealing with a plate resistor. An elliptical load line causes the tube to operate in a less linear part of the operating curve for part of the wave form.

The part that most people miss (and the part that Voltsecond points out) is that once there are low frequencies present in the output transformer all the frequencies have to follow that elliptical load line, not just the bass frequencies. If you can keep the low frequencies out of the transformer the load line will be much more like a resistive load line and there will be less distortion.

Even if you don't follow what I am trying to explain or if you don't believe me, it costs very little to try this and it is totally reversible.

After reading Voltsecond's paper, I placed caps in front of my SET 300b amps driving my midrange and tweeter and was shocked at the improvement.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

I find the Russian silver mica caps to be very transparent. I use them in my phono preamp also.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

• https://www.hificollective.co.uk/search/site?title=.0015

Let me explain a little more. I don't play bass using SET transformers for three reasons. One, not enough power, 2 too low a damping factor and 3 the subject at hand.

I have seen sims that show the elliptical load lines for a "normal" SET output transformer at low frequencies and it's not pretty. I have also seen sims of the load line when the bass is limited to 200Hz for the same "normal" SET output transformer. With the bass frequencies limited the load line almost looks like a resistive load line resulting is much less harmonic distortion.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

As far as your SET Journey, you took a wise shortcut.. I started with a cheap pair off 300b amps that I built (Billies).. Moved on to Welborne 300B Amps, Then Welborne 2A3 Moondogs, then Welborne DRD45 Amps. OK that convinced me that the 45 Amp was where I needed to be, So why not upgrade to the Welborne 45 Star Chiefs (Ultimate 45 Welbornes) -- Stayed there for about 15 years --- Bored with COVID I wanted to see what the Korneff Circuit was all about (Just to make sure I wasn't missing anything).

Where do you live currently in Miami? -- We have a place rented in the Keys next year (Islamorada) --- Maybe they'll open up the West Indies this year and we'll go there instead.

So now someday someone will be looking like I was, will see you comments, and say 'ok, I'll just step off into the deep end.'

I am in the north beach area, next to the husk of the Deauville.
Big legal fight going on over that.

I am right at the water, so got sun, beach, and Cuban food within easy reach. Just came back from a walk, we got a haul of croquetas, empanadas, guarapo, pan con bistec, pan con lechon, and a Cuban sandwich. Lots of 'pan.'

KP

• http://www.learningaboutelectronics.com/Articles/High-pass-f

No, I did not listen.

I might reinvestigate with some different film caps to see if the distortion issue happens again or not.

FWIW, I also noted an small increase in THD at 100Hz as well.

Not what I was hoping to see.

I would leave the TAL SE 45's unmodified.

Don't void the warranty.

DT 667

The emission labs tubes are a higher power tube. In fact some people say that they are really not a 45 tube at all, and are more like a 2a3.... One reason a lot of people like them, is that they probably can use the extra power, with their less sensitive speakers. I for one do not desire more power and was not impressed at all with the Emission Labs Tubes. I sent them back immediately.

According to the Builder of my Korneff Clones, I can use 2a3 tubes in my New Amps without a circuit change. The Builder tried them when he had the amps and admitted a lot of the '45 magic' was gone with the 2a3 tubes... He had Altec Valencia Speakers (About 97db) and he was impressed with the extra power of the 2a3 tubes.... I won't ever need to go there with my 115db Horns. Old Stock 45 Tubes is what I Stick With!

My ARTA test setup uses a 100K pot to trim voltage coming out of the sound card. It is housed in a plastic box with rca jacks for in/out.

For some reason, I am getting odd THD readings from on the left channel, so I think the grid might be going into oscillation as I turn the pot.

A test signal directly from the soundcard into the amp causes no problems.

I will have to investigate further and try to input cap mod again.

DT 667

Edit : found an issue related to power supply returns.

Once corrected, ARTA measurements seemed to normalize.

I will need to re-test the input cap mod again.