I'm using a 5v4ga, one 12sn7 and two 45's. It's real low power so I was thinking about rebuilding it with 275 PK, two filament transformer for the 45's and a high quality .22uf for coupling cap if I get that for. I'm listening to a direct coupled 2a3 as I write this and I'm blown away how it sounds.
And it usually depends on your speakers.........
But, is your 45 amp the 'real' Korneff Clone? -- Is their a 'real' Korneff Clone Schematic?
But, is your 45 amp the 'real' Korneff Clone? -- Is their a 'real' Korneff Clone Schematic?
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I built the glory amp back when that article first came out using some peerless opts. I ended up salvaging the parts as it never really worked out with the speakers I was using at the time. If I were to build it again, I would use a larger cap on the driver cathode bypass something like 33u rather than the 20u shown in the schematic. Not sure if the scan in post 4 is showing the coupling cap correctly. I see 2u there but .2u makes more sense to me. The bugle driver is better if sims are to be believed, mid band harmonics are lower across the board especially above the 3rd where higher harmonics are 10dB lower using the srpp.
Indeed it is, as I contacted Jeff Korneff a couple days ago and he sent me the same Old Glory page that is listed here. He also sent me the following notes and said that I was free to share them.
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That 45 amp was a take off on Eric Barbour's Single Ended Glory for under $100. I attached that schematic. You can download and enlarge. I never bothered with a written schematic of my own, the changes I made were all in my head. You could build the amp exactly as shown, PP transformers and all, and it will sound great. My first build was a mono version very similar to this one, even using the Sansui/Hashimoto outputs, just to see what might be there. I was totally taken in. Don't forget Eric was using junk box parts to build a great sounding amp. Genius.
The changes I would make as a final build to get the full 2 watts, not in any particular order:
use a Hammond 372FX power transformer (a nice transformer, better than 200 series)
use a 5u4 (octal) or 5Z3 (4 pin) rectifier with 20uf/500V electrolytic input cap and 20K 12W load resistor at B+ take off
use separate filament transformers for the 45's with 100 ohm 2W hum balance pots
use 1500 ohm -5W or better- 45 cathode resistors (if separated, above) with say 30uf-100uf / 100V bypass caps
use a pair of true SE 5K outputs from Electraprint- or your maker
use a pair of 50-50 uf/500V dual section electrolytics after the choke pairs
the Heath W series 46-12 (#?) chokes look nice refinished, seems to me they were ~10H, 150 ohm?
use min 2W 6SN7 plate load resistors
suggest using coupling caps to be 0.22uf (not 2.0), 400V or better, try Mundorf silver Foil in Oil
I would personally skip the mylar bypasses across the electrolytics
seems to me I used a 50 or 100uf/16V electrolytic for the 6SN7 bypass cap
It all fits nicely on a 10 x 17 chassis- photo attached. Aluminum.
You're looking for 275 plate volts for the 45 (plate to cathode), 56 volts dropping across the 45 cathode resistor, about 160 plate volts at 6SN7. You will need approx a 335V supply off the rectifier to get to these voltages. Using any other rectifier choices than those I mentioned may/will necessitate the use of a different power transformer rating.
Other notes: I did tidy up the 6SN7 and 45 filament supply voltages with 5W cement dropping resistors to put them "on the money". The amp was buss grounded to a power transformer mounting bolt. Also, the amp was dual switched to allow for preheating the 45's before B+ voltage could be applied- the B+ switch will do nothing without the 45 preheat switch being on. Don't be tempted to use high capacitance values.
The amp was built to run USA old stock 45's. If using overseas versions you would want to consider their specifications.
It's a power amp and will want a preamp ahead no matter that it could be driven directly from some sources. Seems to me the input sensitivity was around 2.6vac .. not sure now. But more than 2.5 and less than 3.
OK folks ... without further ado ... here is the Korneff 45!
I have been working with Jeff nailing this down over the last several months. I recently built it and it is one of the best tube amps I have ever heard! There is something to be said about simplicity and detail retrieval!
This is shared with Jeff's blessing too BTW ...
I have been working with Jeff nailing this down over the last several months. I recently built it and it is one of the best tube amps I have ever heard! There is something to be said about simplicity and detail retrieval!
This is shared with Jeff's blessing too BTW ...
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The drawing has a typo. You don't really want the 2.5 volt filament transformers' CTs grounded. Also, are you really sure you want a shunt resistor to adjust B+?
YOS,
Chris
YOS,
Chris
Good catch! Sorry ... I forgot to update the grounded CT's. I used a custom Heyboer single power transformer so mine is wired differently. I am not a fan of the dropping resistor but that is what he used. My power transformer was custom made to have the proper HV without needed that resistor.
5842, e180f, e186f, e810f, ef184, D3a, e55l, 8010 choke loaded will cut 6sn7's throat any day. Why run after 6sn7 after all these years? Please try a better driver.
Regards
Regards
I tried 6sn7 and 12au7 (9pin derivative), 5842, C3m, ef184, 2a3, e810f, e280f, e180f etc. Humble question, have you tried any of them?
Low gm vs. high gm, don't know you understand. If you have used both type and still prefer 6sn7 type driver then no question asked because SQ is subjective and I have high respect for that.
N.B. George uses 5842 in all of his boards.
Regards
Low gm vs. high gm, don't know you understand. If you have used both type and still prefer 6sn7 type driver then no question asked because SQ is subjective and I have high respect for that.
N.B. George uses 5842 in all of his boards.
Regards
We don't use 6sn7 family tube as driver for low mu DHT output tube any more. We don't use resistor as any triode driver load any more. Those days are long gone, we have grown older.
Regards
Regards
I agree. These tubes would make a much better driver (triode connected) than a 6SN7. I would add C3g to the list.
How exactly are these tubes "better" than a 6SN7. Sure, they are different. But which specifications make them "better" than a 6SN7, and why?
I have heard 5842, 12AU7 as a driver. If the driver can supply the proper Vp-p swing the output tube requires on the grid WITHOUT distortion, Gm is irrelevant. A 45 is a very easy tube to drive! Not so much for the 2A3 or 300B. Look at the load lines of a 6SN7 and I challenge you to find that kind of linearity on anything you mentioned above.
Triode connected EF184 is pretty good, and has a mu about 50. But the high-Gm telephone line valves aren't amazingly linear as drivers. At low levels, they're great, but not first rank drivers for low mu output valves.
YOS,
Chris
YOS,
Chris
Quote from Jeff Corneff:
'That 45 amp was a take off on Eric Barbour's Single Ended Glory for under $100. I attached that schematic. You can download and enlarge. I never bothered with a written schematic of my own, the changes I made were all in my head. You could build the amp exactly as shown, PP transformers and all, and it will sound great. My first build was a mono version very similar to this one, even using the Sansui/Hashimoto outputs, just to see what might be there. I was totally taken in. Don't forget Eric was using junk box parts to build a great sounding amp. Genius.'
-So after all, it's a budget design.
-We are talking about two stage DHT amp, so the first stage is voltage amp as well driver for the output DHT.
-6sn7 gain is low for full output.
-AC wise better load for driver tube is CCS/gyrator or plate choke, for 6sn7 plate choke is not practical because it's plate resistance is too high.
Please think tube linearity in the context of its electrical environment. 6sn7 is ok as driver (not as voltage gain device) for 45 but for a better design it's not adequate.
Regards
'That 45 amp was a take off on Eric Barbour's Single Ended Glory for under $100. I attached that schematic. You can download and enlarge. I never bothered with a written schematic of my own, the changes I made were all in my head. You could build the amp exactly as shown, PP transformers and all, and it will sound great. My first build was a mono version very similar to this one, even using the Sansui/Hashimoto outputs, just to see what might be there. I was totally taken in. Don't forget Eric was using junk box parts to build a great sounding amp. Genius.'
-So after all, it's a budget design.
-We are talking about two stage DHT amp, so the first stage is voltage amp as well driver for the output DHT.
-6sn7 gain is low for full output.
-AC wise better load for driver tube is CCS/gyrator or plate choke, for 6sn7 plate choke is not practical because it's plate resistance is too high.
Please think tube linearity in the context of its electrical environment. 6sn7 is ok as driver (not as voltage gain device) for 45 but for a better design it's not adequate.
Regards