The GM70 require dc filaments with any kind of loudspeakers due to the higher amplification factor and the trimmer are useless. Any amplifiers with dc filaments should use a separated transformer for the filaments because using a single transformer the noise generated by the rectification process in input capacitor power supply is amplified to ...

2010年3月3日 · Thanks for your valuable and detailed info. Iam surprised how many GM70 amps are being manufactured. This GM70 looks a good tube for the price, in view of a 500dollars 845 single. Go ahead it worth the work.

GM70 copper plate specifications: . filament voltage: 20V filament current: 3A . max plate voltage: 1.5kV long-dissipated anode power: 125W height 185mm, diameter 68mm - Plate resistance calculation 2300ohm - Amplification factor 8x - Amplification factor on 10Kohm load 6.7 The sockets show has been created by Jakeband, he produce a very good teflon socket with copper terminal at a right price.

The GM70 and the 813 (FU-13) in a direct comparison with the 845 have the same sound quality but these tubes have the great advantage of a higher voltage gain to allow an simple driver stage. The GM70 and the 813 with graphite plate are not very good so you should use only copper plate for the GM70 and metal plate for the 813 (FU-13 Shuguang).

The GM70 has been produced in the 1960/70's and 80's and there are only 2 versions , Carbon plate and Copper plates. So not much tube rolling possibilities but at least its NOS which IMHO is better then current production anyway. Datasheet 845, Part 2 datasheet 845. Datasheet GM70. And to our eyes when we mean special , it means something out ...

2010年10月8日 · With an anode voltage 300-600V for GM70 and a driver will not get more classic than 12-15W sinus unlimited power. Actually, if you look at the triode curves for 6E5P; put a constant current source on the anode and use an operating point of 15mA,160V+ you can easily swing a few hundred volts peak to peak which should be plenty to drive the GM-70 ...

2019年3月27日 · The GM70 needs, as you know, a lot of volts on its grid. R. rufus74pz. Member. Joined 2010. 2019-03-28 4:44 pm #6 2019-03-28 4:44 pm #6 Hello. As for the voltage for G2 for EF55 applies to the connection of pentode for triode is not important. I have a dismantled EF55 tube and the distances between the grids are 50% greater than in EL84.

gm70单端输后级做好了，性能不错，这是用ef37a作前置放大，2a3b用输入牛推动gm70作单端输出的，gm70这管子线性很好，栅负压较深，介于211和845之间，比845容易推动，用牛交连去推时的屏极效率比较高，在b+1050v.100ma屏流时的输出功率达到35瓦rms，对喇叭的驱动能力十分好，其音色有点像845，感觉没有211 ...

2016年11月13日 · 買了兩隻銅屏gm70剛拆封測試了一下燈絲 阻抗相差還算大 心裡開始毛毛了 覺得是不是管子有問題 一般805-845-211-gm70測試燈絲會在0.1歐姆以下居多 第一次測到這麼高 於是先送10vdc燈絲預熱一下30分 再送15vdc電壓30分 接下來再送20vdc電壓

Direct-heating triode GM70 Equipped with direct-heat triode GM70 tube with Pp=125W, which is larger than 845 (Pp=100W) and has low impedance. Output power is 30W + 30W (4Ω load) and 20W + 20W (8Ω load), driving even low-frequency speakers that have become mainstream in recent years.《There are two models: graphite plate and copper plate.》