That is about right for an 18 WPC version as of 5 years ago when we did all of that stuff. More power means bigger transformers.
Today the 100 watt Edcor OPT's cost $100 each, and I think it cost me about $30 to get them shipped when I lived in Ft. Lauderdale. So we are at $230 for decent, but lowish cost OPT's. I powered mine with a pair of Ebay sourced transformers that cost $15 each, but those are gone. The easiest way to get 600 volts, and 300 volts for the 125 WPC version is to build two 300 volt supplies, and wire them in series. You could use Edcor and get there for about $130 plus shipping, other builders used one Edcor and one Antek to save money. I built an amp that used two Anteks for power, and two Edcors for OPTs for about $350 in transformers including shipping.
I plan on building a version on my own PC boards at the 400+ WPC power level using the two Plitrons seen in the photo in post #438. Those are the ultimate OPT, but cost about $400 each today. Power will be by Antek toroids. There will be 4 output tubes per channel.
The rest of the BOM is pretty much the same as Petes, except for the tubes. We all used 6HJ5's for the 125 WPC version, but they all got sucked up by speculators when we talked about them in that thread. There are several choices for output tubes that are under $10, and we all used 6GU5's for the drivers, they are still cheap and plentiful.
Today the 100 watt Edcor OPT's cost $100 each, and I think it cost me about $30 to get them shipped when I lived in Ft. Lauderdale. So we are at $230 for decent, but lowish cost OPT's. I powered mine with a pair of Ebay sourced transformers that cost $15 each, but those are gone. The easiest way to get 600 volts, and 300 volts for the 125 WPC version is to build two 300 volt supplies, and wire them in series. You could use Edcor and get there for about $130 plus shipping, other builders used one Edcor and one Antek to save money. I built an amp that used two Anteks for power, and two Edcors for OPTs for about $350 in transformers including shipping.
I plan on building a version on my own PC boards at the 400+ WPC power level using the two Plitrons seen in the photo in post #438. Those are the ultimate OPT, but cost about $400 each today. Power will be by Antek toroids. There will be 4 output tubes per channel.
The rest of the BOM is pretty much the same as Petes, except for the tubes. We all used 6HJ5's for the 125 WPC version, but they all got sucked up by speculators when we talked about them in that thread. There are several choices for output tubes that are under $10, and we all used 6GU5's for the drivers, they are still cheap and plentiful.
You get what you pay for... High quality OPT's cost a lot. That's why your options are limited to domestic, off-the-shelf OPT's.
About the same as a scheduled maintenance trip to the Ferrari dealer on a 355 F1!!!
Conversely, are those Hashimotos $1100 better than the Edcor's. To a select few with fat budgets, the answer may be yes. To a retired person on a fixed income (me), no.
I lucked into the pair of Plitrons several years ago for a nice price (about $300 for the pair). They will go into my ultimate amp someday when I decide to build it. For now I use Edcors.
Unfortunately there isn't too much out there in the middle ground between those extremes. Like, say a Corvette.
Transcendar now has some high power P-P OPT's on their web site, but I don't know anyone who has tried them. Their mid sized SE OPT's are good though.
Hammond's larger SE OPT's have problems in the high frequency ranges. Again I have no experience with the big P-P stuff in a HiFi application. Their 120 W OPT worked good in a guitar amp, but that was 10 years ago.
Iron and chassis is what drives a DIY tube amplifier cost.
Heck, even working on the stingiest budget I could, making a stereo single-ended pentode amplifier using 1625 tubes cost me ~$800. This was with Edcor CXSE iron and Allied PT and chokes, a Front Panel Express top, and a wood box that I had laying around from another project.
Best bet - buy a used amplifier for under a kilobuck. Getting 100Ws will be difficult but you can get close - an ARC D-75, CJ MV-75, a pair of Dynaco Mark IIIs, a pair of Eico HF-60s, etc etc. For vintage monoblocks, be patient and buy 'em in singles for price savings. Upgrade with your favorite parts and choice mods.
Heck, even working on the stingiest budget I could, making a stereo single-ended pentode amplifier using 1625 tubes cost me ~$800. This was with Edcor CXSE iron and Allied PT and chokes, a Front Panel Express top, and a wood box that I had laying around from another project.
Best bet - buy a used amplifier for under a kilobuck. Getting 100Ws will be difficult but you can get close - an ARC D-75, CJ MV-75, a pair of Dynaco Mark IIIs, a pair of Eico HF-60s, etc etc. For vintage monoblocks, be patient and buy 'em in singles for price savings. Upgrade with your favorite parts and choice mods.
Well, the service maintenance for a 348/355F1 was around $5K in 2004.
You get what you pay for is not necessarily true these days. The are a lot of things ridiculously overpriced, but it is to the appeal to the very rich and snob.
People who buy high priced, "exotic" audio equipment are more than ever in need of advice and protection. For over a quarter of a century the high-end market has become a jungle, where rip-offs are possibly even more frequent that they used to be on the low end of the business years ago, in the primitive days of the hi-fi boom.
During the glory days, the true age of hi-fi, this country made the best audio equipment in the world. The purity of the iron, wonderful PCB-capacitor dielectric, cobalt for the metal-magnet alloy Alnico, the Japanese rushed in to grab everything audio made in USA. Now, it is the Chinese.
As a retired person, I have a fixed income, like George said in a previous post, and have to allocate different budgets. In Miami, the cost of insurance [flood, hurricane, auto, you name it] plus personal taxes are way over what we paid in No. Virginia.
Cheers,
You get what you pay for is not necessarily true these days. The are a lot of things ridiculously overpriced, but it is to the appeal to the very rich and snob.
People who buy high priced, "exotic" audio equipment are more than ever in need of advice and protection. For over a quarter of a century the high-end market has become a jungle, where rip-offs are possibly even more frequent that they used to be on the low end of the business years ago, in the primitive days of the hi-fi boom.
During the glory days, the true age of hi-fi, this country made the best audio equipment in the world. The purity of the iron, wonderful PCB-capacitor dielectric, cobalt for the metal-magnet alloy Alnico, the Japanese rushed in to grab everything audio made in USA. Now, it is the Chinese.
As a retired person, I have a fixed income, like George said in a previous post, and have to allocate different budgets. In Miami, the cost of insurance [flood, hurricane, auto, you name it] plus personal taxes are way over what we paid in No. Virginia.
Cheers,
The OP's speakers are "difficult". There's every reason to believe that an amp whose B+ PSU is vacuum rectified will be unable to deliver the peak current needed. I say thumbs down to a pair of Dyna MK3s.
For "hot and low" operating condition KT88s, 2X (1/channel) AnTek AS-3T325 toroidal power trafos will provide for B+ and heater needs at a quite reasonable $80.
FWIW, I'm more comfortable with Mullard style circuitry, as opposed to Williamson style, when Edcor O/P "iron" is employed. The Class "AB2" idea of the Heath W6M will work just fine with a Mullard front end. At $98.51 each, Edcor's CXPP100-MS-2.2K seems to be THE budget choice.
Juggling costs and performance is such fun.
O/P tubes are another area cost control can be applied to. The ElectroHarmonix (EH) KT88 is a bit lacking in the bass extension dept., but is FINE everywhere else and cost about 50% of the premium "reissue" GEC KT88.
For "hot and low" operating condition KT88s, 2X (1/channel) AnTek AS-3T325 toroidal power trafos will provide for B+ and heater needs at a quite reasonable $80.
FWIW, I'm more comfortable with Mullard style circuitry, as opposed to Williamson style, when Edcor O/P "iron" is employed. The Class "AB2" idea of the Heath W6M will work just fine with a Mullard front end. At $98.51 each, Edcor's CXPP100-MS-2.2K seems to be THE budget choice.
Juggling costs and performance is such fun.
O/P tubes are another area cost control can be applied to. The ElectroHarmonix (EH) KT88 is a bit lacking in the bass extension dept., but is FINE everywhere else and cost about 50% of the premium "reissue" GEC KT88.
I have a good amp, an Electrocompaniet 100-DMB Anniversary dual mono, 125W/Ch, but I still miss the "sound" of the tubes, the Radford STA 25, Berning EA 230, Quad II, the fantastic but low powered Acrosound UL 25/25 and the Paragon 12A preamp. I still wonder how the Aerials would fare with a tube amp.
I also thought of selling the Aerials and try the Pure Audio Project Trio 10 for $3,300 the pair in kit form. [http://www.pureaudioproject.com/] But I don't think they will work in the family room, there is not enough space on that wall to separate them, I cannot make any changes due to the room size.
I also thought of selling the Aerials and try the Pure Audio Project Trio 10 for $3,300 the pair in kit form. [http://www.pureaudioproject.com/] But I don't think they will work in the family room, there is not enough space on that wall to separate them, I cannot make any changes due to the room size.
I just guessed the $1300 based on the $900 my brother paid for his 12,000 mile service on his new Boxster.
I know, I grew up in South Miami not far from you. In fact I took guitar lessons for several years at a music store in the Dadeland mall.
I moved to Broward in 1973 and left Florida last year when Citizen's raised my windstorm insurance premium to $5,500 per year on a $200K house. 36 years in that house and never filed a single claim. I paid $40K for the house in 1978, and almost $100K to insure it and another $50K in taxes over the 36 years,
I agree that peak current capability is needed for a dynamic high powered amp into any large speaker system. Some speakers do need more peak current than others.
Let's say you have a hefty power supply with a large low ESR reservoir cap, AND a lowish DCR in the OPT primary, what's the limiting factor now? It's the peak current handling capability of the cathode in the output tubes......Nothing beats a good sweep tube. KT88, 300 to 450 mA. 6LW6, 1.4 AMPS! Even wimpy sweep tubes are in the 850 mA territory. Most are cheaper than KT88's too.
Many a good sounding rig has been assembled using tube preamplification and SS power amplification. Per the 100-DMB manual, 1 V. of drive is needed for full power and the I/P impedance is 220 Kohms. No line stage gain is needed, but a touch of 2nd order HD seems to be in order. Scan the archives for 12B4 based designs. Given the 100-DMB's "friendly" I/P impedance, resistive loading to obtain a net AC load of at least 3X RP will be easy enough.
Although too many suggested variations advance this thread mainly horizontallly, perhaps to chime in with a slightly different approach used by me.
I opted for a cathode feedbacked distributed load output stage. More simply put: As used in the Quad II but with 25% cathode windings so as to approach beneficial UL conditions. (The required hefty grid signal is provided by an E182CC driver, preceeded by an ECF80 as input stage and cathodyne phase splitter. An ECC85 cathode follower drives the inverted NFB mode for distortion reduction reasons, etc.)
My power stage is not as ambitious as using the KT-umpteens - I use four 6L6GCs in p.p. parallel mode to get a reasonable 110W output/channel. (Locally two 6L6GCs sell for less than one KT120, same dissipation, apart from some reduncancy.) Further, so far a not to be sneezed at 0,25% distortion at 100W; further efforts to get it down to 0,1%.
Because of mentioned sky-high cost, I decided to wind my own transformers, C-core; OPT bandwidth some 8Hz - 230kHz at 20W. This not to boast; simply to show that it is quite possible home-wound. And the whole effort mentioned to show that perhaps going the way of tubes with a reputation at better economy could be considered a worthwhile option.
I opted for a cathode feedbacked distributed load output stage. More simply put: As used in the Quad II but with 25% cathode windings so as to approach beneficial UL conditions. (The required hefty grid signal is provided by an E182CC driver, preceeded by an ECF80 as input stage and cathodyne phase splitter. An ECC85 cathode follower drives the inverted NFB mode for distortion reduction reasons, etc.)
My power stage is not as ambitious as using the KT-umpteens - I use four 6L6GCs in p.p. parallel mode to get a reasonable 110W output/channel. (Locally two 6L6GCs sell for less than one KT120, same dissipation, apart from some reduncancy.) Further, so far a not to be sneezed at 0,25% distortion at 100W; further efforts to get it down to 0,1%.
Because of mentioned sky-high cost, I decided to wind my own transformers, C-core; OPT bandwidth some 8Hz - 230kHz at 20W. This not to boast; simply to show that it is quite possible home-wound. And the whole effort mentioned to show that perhaps going the way of tubes with a reputation at better economy could be considered a worthwhile option.
Tabulation of common sweep tubes:
With list of knee currents for g2 = 150 V, g1 = 0 V, Vp = 60 to 80 V
(given for g2 drive selection)
(note that the peak current rating is typically 3X to 4X the DC max current given here)
(anything from 6ME6 on up in the list would probably handle 100 Watts out into a difficult speaker easy)
Data Format:
<tube> <Watts> <mA knee@150Vg2> <gm> <Mu> <maxDCmA> <registered by> <date>
6LF6 40W 1144mA@150V 15K@125mA Mu3 500mADC Amperex 1968
6KG6/EL509 34W 1135mA@150V 13K@150mA Mu3.2 500mADC Amperex 1965
6MC6 33W 1130mA@150V 14K@125mA Mu4 400mADC RCA (6LX6 clone) 1972
13E1 90W(absmax) 1120mA@150V 35K@500mA Mu4.5 800mADC AEI 1961
6MH6 38.3W 1100mA@150V 14K@125mA Mu4 500mADC GE (up-rated 6LX6,6KD6,26HU5) 1972
6MB6 38W 1085mA@150V 14K@110mA Mu3.5 400mADC Sylvania 1971
6LR6 30W 1085mA@150V 16K@140mA Mu3.5 375mADC Sylvania 1968
6LX6/6KD6/26HU5 33W 1080mA@150V 14K@125mA Mu4 400mADC GE 1969/1965/1969
6LW6 40W 1050mA@150V 12K@125mA Mu3.7 400mADC GE 1971
6KN6 30W 1050mA@150V 16K@100mA Mu4.5 400mADC Sylvania 1965 (later versions are 6KD6)
6LZ6 30W 940mA@150V 11K@140mA Mu3 350mADC RCA 1971
6LB6/A 30W/35W 825mA@150V 13.4K@105mA Mu4 315mADC GE 1967
6JE6C/6JS6C 30W 789mA@150V 10.5K@130mA Mu3 350mADC Sylvania 68/69
6JE6 24W 762mA@150V 9.6K@115mA Mu3 315mADC RCA 1962
6JS6/6HF5 28W 749mA@150V 11.5K@130mA Mu3 315mADC GE 1964/1963
6MJ6 30W 740mA@150V 11K@100mA Mu3.6 350mADC RCA 1973
6LG6 28W 740mA@150V 11.5K@90mA Mu3.6 315mADC GE 1967
6LQ6 30W 715mA@150V 7.5K@95mA Mu3 350mADC RCA 1967
6ME6 30W 700mA@150V 9.6@130mA Mu3.5 350mADC RCA 1971
6DQ5 24W 690mA@150V 10.5K@110mA Mu3.3 315mADC RCA 1957
6JF6/6JG6 17W 660mA@150V 10K@80mA Mu4.1 275mADC RCA 1965/1964
6KM6 20W 630mA@150V 9.5K@80mA Mu4 275mADC RCA 1965
6HD5/6HJ5 24W 630mA@150V 10K@80mA Mu4.2 280mADC Raytheon 1962/1963
6JR6/6JU6 17W 600mA@150V 7K@45mA Mu4.7 275mADC RCA 1968/1966
6JZ6/21HB5A 18W 560mA@150V 9K@46mA Mu4.8 230mADC GE 1966/1964
12HE7 10-15W 540mA@150V 8.8K@60mA Mu4.2 200mADC GE (15W if damper disabled) 1964
6CL5 25W 514mA@150V 6.5K@90mA Mu3 240mADC Sylvania 1955
6GB5/29KQ6/EL500 17W 500mA@150V 13K@100mA Mu5.1 275mADC Amperex 1961/Matsushita 1959/Philips 1961?
6KV6/A 20-28W 488/610mA@150V 6K@40mA Mu4 275mADC RCA (re-rated 6KM6?) 1967/1969
6HB5/6GY5/21JV6/6KE6/16KA6 18W 475mA@150V 9.1K@50mA Mu4.7 230mADC GE/GE/GE/Ray/Tung 1962/1962/1965/1965/1964
6EX6 22W 460mA@150V 7.7K@67mA Mu4.2 220mADC Raytheon (up-rated 6CD6) 1959
6CB5/A 23W 440mA@150V 8.8K@90mA Mu3.8 240mADC RCA 1954/1956
6CD6/GA 15/20W 422mA@150V 7.7K@75mA Mu3.9 200mADC RCA/GE 1949/1954
6GT5/6GJ5/6JT6/6JB6/6GW6 17.5W 380mA@150V 7.1K@70mA Mu4.4 175mADC RCA 1961/1961/1964/1962/1961
6GE5 17.5W 350mA@150V 7.3K@65mA Mu4.4 175mADC GE 1961
6GF5 9W 345mA@150V 4.7K@34mA Mu4.2 160mADC GE 1961
6JM6/6JN6/6FW5/6GC6 17.5W 340mA@150V 7.3K@70mA Mu4.4 175mADC GE 1964/1964/1960/1960
6DQ6B/6GV5 17.5W/18W 330mA@150V 7.3K@65mA Mu4.4 175mADC GE 1959/1962
6DQ6/A 18W 280mA@150V 6.6K@55mA Mu4.1 120/155mADC CBS/RCA 1955/1956
6JA5/10JA5 19W 276mA@150V 10.3K@95mA Mu5.5 110mADC GE 1971
6LU8/6LR8//6MY8 14//16W 265mA@150V 9.3K@56mA Mu6.5 75mADC Sylvania 1964/1964//1970(Toshiba)
6AV5/GA///6BQ6/GA 11W 255ma@150V 5.9K@57mA Mu4.3 110mADC CBS/GE 1949/1955 /// CBS/Syl 1949/1953
KT120 60W 221ma@150V 190mADC
KT90 50W 220mA@150V
6Y6G/GT/GA 12.5W 200mA@150V Ray 1937/KenRad 1939/Syl 1954
6550A 35W/42W 190mA@150V 11K@140mA 190mADC
6W6GT 10W 185mA@150V 8K@46mA Mu6.2 65mADC CBS 1939
KT88 35W 170mA@150V 175mADC
6CA7/EL34 25W 107mA@150V 11K@100mA Mu10.5 150mADC Philips 1952
6JC5 19W 80mA@150V 4.1K@43mA Mu7 75mADC Sylvania 1971
6L6/G/GA/GB/GC 30W 77mA@150V 4.7K@40mA Mu8 110mADC RCA 1936/Ray 1936/Syl 1943/Syl 1954/GE 1958
6HB6 10W 70mA@150V 20K@40mA Mu33 60mADC Raytheon 1961
6GK6 13.2W 65mA@150V 11.3K@48mA Mu19 65mADC CBS 1959
6BQ5/EL84 12W 65mA@150V 11.3K@48mA Mu19.5 65mADC Rogers 1956
6V6G/GT 14W 45mA@150V 4.1K@45mA Mu9.8 40mADC KenRad 1936/CBS 1939
With list of knee currents for g2 = 150 V, g1 = 0 V, Vp = 60 to 80 V
(given for g2 drive selection)
(note that the peak current rating is typically 3X to 4X the DC max current given here)
(anything from 6ME6 on up in the list would probably handle 100 Watts out into a difficult speaker easy)
Data Format:
<tube> <Watts> <mA knee@150Vg2> <gm> <Mu> <maxDCmA> <registered by> <date>
6LF6 40W 1144mA@150V 15K@125mA Mu3 500mADC Amperex 1968
6KG6/EL509 34W 1135mA@150V 13K@150mA Mu3.2 500mADC Amperex 1965
6MC6 33W 1130mA@150V 14K@125mA Mu4 400mADC RCA (6LX6 clone) 1972
13E1 90W(absmax) 1120mA@150V 35K@500mA Mu4.5 800mADC AEI 1961
6MH6 38.3W 1100mA@150V 14K@125mA Mu4 500mADC GE (up-rated 6LX6,6KD6,26HU5) 1972
6MB6 38W 1085mA@150V 14K@110mA Mu3.5 400mADC Sylvania 1971
6LR6 30W 1085mA@150V 16K@140mA Mu3.5 375mADC Sylvania 1968
6LX6/6KD6/26HU5 33W 1080mA@150V 14K@125mA Mu4 400mADC GE 1969/1965/1969
6LW6 40W 1050mA@150V 12K@125mA Mu3.7 400mADC GE 1971
6KN6 30W 1050mA@150V 16K@100mA Mu4.5 400mADC Sylvania 1965 (later versions are 6KD6)
6LZ6 30W 940mA@150V 11K@140mA Mu3 350mADC RCA 1971
6LB6/A 30W/35W 825mA@150V 13.4K@105mA Mu4 315mADC GE 1967
6JE6C/6JS6C 30W 789mA@150V 10.5K@130mA Mu3 350mADC Sylvania 68/69
6JE6 24W 762mA@150V 9.6K@115mA Mu3 315mADC RCA 1962
6JS6/6HF5 28W 749mA@150V 11.5K@130mA Mu3 315mADC GE 1964/1963
6MJ6 30W 740mA@150V 11K@100mA Mu3.6 350mADC RCA 1973
6LG6 28W 740mA@150V 11.5K@90mA Mu3.6 315mADC GE 1967
6LQ6 30W 715mA@150V 7.5K@95mA Mu3 350mADC RCA 1967
6ME6 30W 700mA@150V 9.6@130mA Mu3.5 350mADC RCA 1971
6DQ5 24W 690mA@150V 10.5K@110mA Mu3.3 315mADC RCA 1957
6JF6/6JG6 17W 660mA@150V 10K@80mA Mu4.1 275mADC RCA 1965/1964
6KM6 20W 630mA@150V 9.5K@80mA Mu4 275mADC RCA 1965
6HD5/6HJ5 24W 630mA@150V 10K@80mA Mu4.2 280mADC Raytheon 1962/1963
6JR6/6JU6 17W 600mA@150V 7K@45mA Mu4.7 275mADC RCA 1968/1966
6JZ6/21HB5A 18W 560mA@150V 9K@46mA Mu4.8 230mADC GE 1966/1964
12HE7 10-15W 540mA@150V 8.8K@60mA Mu4.2 200mADC GE (15W if damper disabled) 1964
6CL5 25W 514mA@150V 6.5K@90mA Mu3 240mADC Sylvania 1955
6GB5/29KQ6/EL500 17W 500mA@150V 13K@100mA Mu5.1 275mADC Amperex 1961/Matsushita 1959/Philips 1961?
6KV6/A 20-28W 488/610mA@150V 6K@40mA Mu4 275mADC RCA (re-rated 6KM6?) 1967/1969
6HB5/6GY5/21JV6/6KE6/16KA6 18W 475mA@150V 9.1K@50mA Mu4.7 230mADC GE/GE/GE/Ray/Tung 1962/1962/1965/1965/1964
6EX6 22W 460mA@150V 7.7K@67mA Mu4.2 220mADC Raytheon (up-rated 6CD6) 1959
6CB5/A 23W 440mA@150V 8.8K@90mA Mu3.8 240mADC RCA 1954/1956
6CD6/GA 15/20W 422mA@150V 7.7K@75mA Mu3.9 200mADC RCA/GE 1949/1954
6GT5/6GJ5/6JT6/6JB6/6GW6 17.5W 380mA@150V 7.1K@70mA Mu4.4 175mADC RCA 1961/1961/1964/1962/1961
6GE5 17.5W 350mA@150V 7.3K@65mA Mu4.4 175mADC GE 1961
6GF5 9W 345mA@150V 4.7K@34mA Mu4.2 160mADC GE 1961
6JM6/6JN6/6FW5/6GC6 17.5W 340mA@150V 7.3K@70mA Mu4.4 175mADC GE 1964/1964/1960/1960
6DQ6B/6GV5 17.5W/18W 330mA@150V 7.3K@65mA Mu4.4 175mADC GE 1959/1962
6DQ6/A 18W 280mA@150V 6.6K@55mA Mu4.1 120/155mADC CBS/RCA 1955/1956
6JA5/10JA5 19W 276mA@150V 10.3K@95mA Mu5.5 110mADC GE 1971
6LU8/6LR8//6MY8 14//16W 265mA@150V 9.3K@56mA Mu6.5 75mADC Sylvania 1964/1964//1970(Toshiba)
6AV5/GA///6BQ6/GA 11W 255ma@150V 5.9K@57mA Mu4.3 110mADC CBS/GE 1949/1955 /// CBS/Syl 1949/1953
KT120 60W 221ma@150V 190mADC
KT90 50W 220mA@150V
6Y6G/GT/GA 12.5W 200mA@150V Ray 1937/KenRad 1939/Syl 1954
6550A 35W/42W 190mA@150V 11K@140mA 190mADC
6W6GT 10W 185mA@150V 8K@46mA Mu6.2 65mADC CBS 1939
KT88 35W 170mA@150V 175mADC
6CA7/EL34 25W 107mA@150V 11K@100mA Mu10.5 150mADC Philips 1952
6JC5 19W 80mA@150V 4.1K@43mA Mu7 75mADC Sylvania 1971
6L6/G/GA/GB/GC 30W 77mA@150V 4.7K@40mA Mu8 110mADC RCA 1936/Ray 1936/Syl 1943/Syl 1954/GE 1958
6HB6 10W 70mA@150V 20K@40mA Mu33 60mADC Raytheon 1961
6GK6 13.2W 65mA@150V 11.3K@48mA Mu19 65mADC CBS 1959
6BQ5/EL84 12W 65mA@150V 11.3K@48mA Mu19.5 65mADC Rogers 1956
6V6G/GT 14W 45mA@150V 4.1K@45mA Mu9.8 40mADC KenRad 1936/CBS 1939
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You guys know a LOT more about sweep tubes than I do. AFAIK, screen grid fragility is a serious concern. Those expensive Plitron separate screen grid winding O/P trafos neatly dispose of that issue. Can the "crowd" suggest a PP pair of sweep tubes that will yield 75-80 W. running in Class "AB1", that also mate well with the 2 Kohm end to end impedance of the Plitron "iron"? The OP's speakers need an amp with a good damping factor and GNFB (obviously) is a path to meeting the requirement. Whenever GNFB is employed, magnetic headroom in the O/P "iron" and infrasonic noise filtering at the amp's I/Ps are (IMO/IME) essential.
Does the thought of sweep tube finals in a Mullard circuit, along the lines of the H/K Cit. 5, meet with approval? I'm thinking 6CL6 voltage amplifier and a CCS tail loaded ECC99 as the LTP.
Does the thought of sweep tube finals in a Mullard circuit, along the lines of the H/K Cit. 5, meet with approval? I'm thinking 6CL6 voltage amplifier and a CCS tail loaded ECC99 as the LTP.
Attachments
that is why ultralinear operation with sweep tubes are not common...
unless a separate screen grid winding is made wth lower G2 supply,
but to me this is hard work as far as winding OPT's are concerned...
the EL509 should do it....
the HK Cit 5/Mullard 5-20 topology has been my choice ever since i made one to drive a pair of Shuguang El34's.....
unless a separate screen grid winding is made wth lower G2 supply,
but to me this is hard work as far as winding OPT's are concerned...
the EL509 should do it....
the HK Cit 5/Mullard 5-20 topology has been my choice ever since i made one to drive a pair of Shuguang El34's.....
For this size of amplifier, the larger Sweep tubes would be the "ones". Unfortunately, the 6.3 V filament versions of the big Sweeps are hard to come by (expensive, and likely to get more so) since the CB rigs ate them up long ago. So you are left with higher filament V versions. You don't have tube matching services available for these either, so will want to buy a bunch to roughly match and insure future stock.
I would make sure to provide individual DC bias and an AC balance control in this type of amplifier. The larger Sweeps (30 Watt +) only come with plate caps, unless you want to go with paralleled tubes. In which case most any of the 18 Watt or 24 Watt tubes could work. (they are cheap, some just $3 or $4)
Probably something like a 26LX6, 26LW6, 35LR6, 36LW6 or 6KN6 pair, (or 42KN6), would be reasonable on price. EL509/6KG6 I guess are available new, but pricey (available matched?). George (Tubelab) may have some ideas here. The 26__6 tubes could be run from an Ebay 24VDC regulated supply for heaters with the Vadj pushed up a skosh.
If you have a Plitron high bandwidth OT, with a separate UL winding (around 150 V on grid 2), then that would probably work fine with just global Fdbk, IF the percent UL is around 15% or 20% (43% is too high for LV g2 sweeps). (some 20% CFB OTs might be pressed into UL service) UL mode MAY NOT provide good peak current capability however, which is what one is pursuing here for a difficult speaker. (When you want the peak current, the Vg2 is flogged out. Use the biggest tubes for UL mode.)
Otherwise, cheaper OTs can be accommodated by using some local feedback(s) to the driver stage inside of a global Fdbk loop. Schade, or crossed plate to driver grids, or plate to driver cathodes. RCA had a Schade + plate to driver cathodes design (the 50 Watt design in the RCA tube book). Cit V/Mullard with the Plitron OT (for global Fdbk only). Plitron CFB if you want to get complex. Edcor winds custom OTs for a reasonable fee I think (still), but they don't seem to like CFB or extra windings. (you might get a 20% custom UL version though, and then use two smaller OTs in a Crowhurst Twin configuration, which can be circuit modded easily for just 20% CFB)
I would make sure to provide individual DC bias and an AC balance control in this type of amplifier. The larger Sweeps (30 Watt +) only come with plate caps, unless you want to go with paralleled tubes. In which case most any of the 18 Watt or 24 Watt tubes could work. (they are cheap, some just $3 or $4)
Probably something like a 26LX6, 26LW6, 35LR6, 36LW6 or 6KN6 pair, (or 42KN6), would be reasonable on price. EL509/6KG6 I guess are available new, but pricey (available matched?). George (Tubelab) may have some ideas here. The 26__6 tubes could be run from an Ebay 24VDC regulated supply for heaters with the Vadj pushed up a skosh.
If you have a Plitron high bandwidth OT, with a separate UL winding (around 150 V on grid 2), then that would probably work fine with just global Fdbk, IF the percent UL is around 15% or 20% (43% is too high for LV g2 sweeps). (some 20% CFB OTs might be pressed into UL service) UL mode MAY NOT provide good peak current capability however, which is what one is pursuing here for a difficult speaker. (When you want the peak current, the Vg2 is flogged out. Use the biggest tubes for UL mode.)
Otherwise, cheaper OTs can be accommodated by using some local feedback(s) to the driver stage inside of a global Fdbk loop. Schade, or crossed plate to driver grids, or plate to driver cathodes. RCA had a Schade + plate to driver cathodes design (the 50 Watt design in the RCA tube book). Cit V/Mullard with the Plitron OT (for global Fdbk only). Plitron CFB if you want to get complex. Edcor winds custom OTs for a reasonable fee I think (still), but they don't seem to like CFB or extra windings. (you might get a 20% custom UL version though, and then use two smaller OTs in a Crowhurst Twin configuration, which can be circuit modded easily for just 20% CFB)
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