Bandersnatch said:
plate diss is rated 100watts, but for class B amp duty, idle at 34watt then 60watt full power, this is per plate, i am not sure now but forced air cooling was never mentioned on data sheet.
here is how it looks like: http://tubedata.tigahost.com/tubedata/photos/030/q/QE08-200H.jpg
datasheet here: http://tubedata.tigahost.com/tubedata/sheets/030/q/QE08-200H.pdf
Here is some information from the person that built the 4-65A amp indicated in the second post.
The 4-65 Stereo Amplifier that I built for VSAC started out as a Stereo Triode 45 Amp that I built for VSAC 2003. More about the 45 to 4-65 conversion at the end of this e-mail.
First, the details of a 4-65 Tetrode:
3000 V Max Plate Voltage
150 mA Max Plate Current
65 Watt Max Plate Dissipation
Transconductance is 4000 umhos (with plate V = 500, and Screen V=250)
400V Max Screen Voltage
10 Watt Max Screen Dissipation
Grid 1 to Grid 2 gain u = 5 (with plate V = 500, and Screen V=250) Grid 2 is the Screen Grid
Filament 6.0 Volts
Filament 3.5 Amps
This tube uses a Thoriated Tungsten Filament (there is no Cathode, direct emission is used).
The Plate resistance is higher than the Screen resistance in Triode mode, at or below the Screen 400V limit (do not exceed 400V).
That means that most of the current is Screen current, not Plate current in Triode mode.
Since u = 5 above and transconductance of 4000 umhos, the lowest the Screen resistance can possibly be is 5/(4000x10-6) = 1250 Ohms
Note: in the VSAC amplifier below, it is estimated that the parallel Screen and Plate resistance was about 2000 Ohms, because the transconductance (and probably the u) is lower in triode mode and at low plate voltages.
The idea for this amplifier was to use the Screen as a "plate", and let the actual plate add whatever it can to the total current.
Second, Cashe:
The filament glows White, which is one beauty of this tube. More beauties are its Glass, Shape and Size.
Third, the details of the amplifier:
the following lists the values just one side of the stereo pair, the total current and power are double of that.
Output Stage:
The 4-65 was operated in triode mode
About 355V on the Screen and Plate (Self bias was about 55 Volts in a 1600 Ohm resistor from filament to ground, the resistor was bypassed with an electrolytic to ground). That only puts 300V from Screen & Plate to Filament. There was about 34 mA Screen + Plate current (total). 300V x 34 mA = 10.2 Watts Screen and Plate dissipation
If you disconnect the plate, there was only about a 2 mA change in current (for triode mode, the screen has much lower "plate resistance" than the plate does).
300V x 34.4 ma
The Screen & Plate load was a One Electron # UBT2 (4800 Ohm primary)
The 4-65 filament was run on 6.0VDC
The output power was about 1.5 to 2 watts. You really have to use higher screen voltage, and much higher plate voltages to get real power from this tube (and operate in Tetrode mode).
Driver Stage:
Both halves of an ECC99 were connected in parallel, each half was run at 10 mA and about 220 to 250V (2 ECC99s, one for left channel and one for right channel, 40 ma for all 4 triode sections).
The plates were loaded with an Electra Print 1:1 # 3634 interstage transformer.
Filaments were run on 6.3VAC
Power Supply:
300VCT; Silicon Full Wave Rectifiers; Cap Input; Choke; Cap (4-65 Plate voltage); Resistor; Cap; (ECC99 Plate Voltage)
12.6V CT Silicon Full Wave Rectifiers; Cap; Resistor; Cap 4-65 Filament
6.3VAC ECC99 filaments, ground one side (no floating filaments)
Fourth, how did all this come about:
On Wednesday at 10:00 PM, the week VSAC 2003 started (Friday), I finished building a Stereo Triode 45 Amp (same ECC99 and 3634 interstage, same UBT2). It sounded VERY good, so I listened till 2:00AM Thursday morning, and finally went to sleep.
Late Thursday morning when I got up, I turned the amp on to listen again; unfortunately one of the 45s went gassy, oscillated, and I turned the amp off. I did not have any spare 45s.
What was I going to do? I had planned to leave very early Friday AM for VSAC.
I had already purchased a pair of 4-65s with the idea of using the Screens as a "45" substitute. I had 4-65 sockets.
Drill new holes, Mount the 4-65 sockets, add input capacitance to raise the B+ voltage, increase the filament voltage and current, etc. Thursday at 10:00 the amp was finished, I listened till 12:00 midnight (I had to catch up on lost sleep from the night before). Friday afternoon I got to VSAC at Silverton.
The Triode mode did work, the 4-65s looked pretty, and the amplifier sounded OK. But they did not sound as good as the 45 amp.
Either build a "45" amp; or if you want to use 4-65s, really go for the gusto and put 500V on the plate and 250 Volts on the screen, and use it in Tetrode mode. I do not have any idea what the plate resistance is in Tetrode mode.
The 4-65 Stereo Amplifier that I built for VSAC started out as a Stereo Triode 45 Amp that I built for VSAC 2003. More about the 45 to 4-65 conversion at the end of this e-mail.
First, the details of a 4-65 Tetrode:
3000 V Max Plate Voltage
150 mA Max Plate Current
65 Watt Max Plate Dissipation
Transconductance is 4000 umhos (with plate V = 500, and Screen V=250)
400V Max Screen Voltage
10 Watt Max Screen Dissipation
Grid 1 to Grid 2 gain u = 5 (with plate V = 500, and Screen V=250) Grid 2 is the Screen Grid
Filament 6.0 Volts
Filament 3.5 Amps
This tube uses a Thoriated Tungsten Filament (there is no Cathode, direct emission is used).
The Plate resistance is higher than the Screen resistance in Triode mode, at or below the Screen 400V limit (do not exceed 400V).
That means that most of the current is Screen current, not Plate current in Triode mode.
Since u = 5 above and transconductance of 4000 umhos, the lowest the Screen resistance can possibly be is 5/(4000x10-6) = 1250 Ohms
Note: in the VSAC amplifier below, it is estimated that the parallel Screen and Plate resistance was about 2000 Ohms, because the transconductance (and probably the u) is lower in triode mode and at low plate voltages.
The idea for this amplifier was to use the Screen as a "plate", and let the actual plate add whatever it can to the total current.
Second, Cashe:
The filament glows White, which is one beauty of this tube. More beauties are its Glass, Shape and Size.
Third, the details of the amplifier:
the following lists the values just one side of the stereo pair, the total current and power are double of that.
Output Stage:
The 4-65 was operated in triode mode
About 355V on the Screen and Plate (Self bias was about 55 Volts in a 1600 Ohm resistor from filament to ground, the resistor was bypassed with an electrolytic to ground). That only puts 300V from Screen & Plate to Filament. There was about 34 mA Screen + Plate current (total). 300V x 34 mA = 10.2 Watts Screen and Plate dissipation
If you disconnect the plate, there was only about a 2 mA change in current (for triode mode, the screen has much lower "plate resistance" than the plate does).
300V x 34.4 ma
The Screen & Plate load was a One Electron # UBT2 (4800 Ohm primary)
The 4-65 filament was run on 6.0VDC
The output power was about 1.5 to 2 watts. You really have to use higher screen voltage, and much higher plate voltages to get real power from this tube (and operate in Tetrode mode).
Driver Stage:
Both halves of an ECC99 were connected in parallel, each half was run at 10 mA and about 220 to 250V (2 ECC99s, one for left channel and one for right channel, 40 ma for all 4 triode sections).
The plates were loaded with an Electra Print 1:1 # 3634 interstage transformer.
Filaments were run on 6.3VAC
Power Supply:
300VCT; Silicon Full Wave Rectifiers; Cap Input; Choke; Cap (4-65 Plate voltage); Resistor; Cap; (ECC99 Plate Voltage)
12.6V CT Silicon Full Wave Rectifiers; Cap; Resistor; Cap 4-65 Filament
6.3VAC ECC99 filaments, ground one side (no floating filaments)
Fourth, how did all this come about:
On Wednesday at 10:00 PM, the week VSAC 2003 started (Friday), I finished building a Stereo Triode 45 Amp (same ECC99 and 3634 interstage, same UBT2). It sounded VERY good, so I listened till 2:00AM Thursday morning, and finally went to sleep.
Late Thursday morning when I got up, I turned the amp on to listen again; unfortunately one of the 45s went gassy, oscillated, and I turned the amp off. I did not have any spare 45s.
What was I going to do? I had planned to leave very early Friday AM for VSAC.
I had already purchased a pair of 4-65s with the idea of using the Screens as a "45" substitute. I had 4-65 sockets.
Drill new holes, Mount the 4-65 sockets, add input capacitance to raise the B+ voltage, increase the filament voltage and current, etc. Thursday at 10:00 the amp was finished, I listened till 12:00 midnight (I had to catch up on lost sleep from the night before). Friday afternoon I got to VSAC at Silverton.
The Triode mode did work, the 4-65s looked pretty, and the amplifier sounded OK. But they did not sound as good as the 45 amp.
Either build a "45" amp; or if you want to use 4-65s, really go for the gusto and put 500V on the plate and 250 Volts on the screen, and use it in Tetrode mode. I do not have any idea what the plate resistance is in Tetrode mode.
Here is a link to a page showing how to take the screen grid out of the circuit with a diode between the plate and Sg. This could help a lot with using big transmitting tubes as triodes if it works. Anyone try it?
http://www.webace.com.au/~electron/tubes/triode.htm
http://www.webace.com.au/~electron/tubes/triode.htm
Just a couple of thoughts.
First re switching supplies: I tested a TY4-400 (see avatar) to see if it could be any use for audio - I had a pair of them. Filament is 5V at 14A. I checked with a scope and there was very little noise and I suppose that this could be reduced still further with some filtering.
As for G2 limits, I think that provided one is sensible, they can be exceeded substantially in triode connection. I have tested 13E1s (G2 limit 300V) triode-strapped at 500V and 200mA without problems. For 6146 Philips provided information for triode operation at 400V and 6146 is notorious for fragility with an absolute maximum rating of 250V for G2.
Of course 813 with its 1100V g2 limit is the really safe option!
7N7
First re switching supplies: I tested a TY4-400 (see avatar) to see if it could be any use for audio - I had a pair of them. Filament is 5V at 14A. I checked with a scope and there was very little noise and I suppose that this could be reduced still further with some filtering.
As for G2 limits, I think that provided one is sensible, they can be exceeded substantially in triode connection. I have tested 13E1s (G2 limit 300V) triode-strapped at 500V and 200mA without problems. For 6146 Philips provided information for triode operation at 400V and 6146 is notorious for fragility with an absolute maximum rating of 250V for G2.
Of course 813 with its 1100V g2 limit is the really safe option!
7N7
What a weird way of doing things
Don't let that put you off , Eimac actually quote 600V as the g2 rating . I measure 0.75 volts across the 90 ohm G2 strapping resistor , total drawn by the 4-65A 52mA . It's not a problem at all at higher voltages . 4-65A seem perfectly happy running as triodes at 550V and could easily go much higher IMO .
dshortt9 said:
Yuck !!! Just use a resistor , something like a nice meaty carbon comp 100 ohms or less . For triode strapping my advice is to tie all the grids apart from the control grid if at all possible . This is possible with valves such as S11E12 , 2E22 and EL34 which have all individual grids brought out to the socket
(currently running with LCL DC filaments on the 4-65A . Amp is at present choke loaded 316A into 4-65A)
cheers
316a
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