Folks,
Has anyone ever used a seven pin, sub-miniature 6HA5? I have four I'd love to try out; 1963 tube, GE, branded 'Sears'.
This tube is a 14.5mA/V, mu 72 12mA single triode for use in VHF as a grounded grid amplifier. Plate dissipation is 2.6W.
Anyone know what the sonics are?
Cheers,
Hugh
Has anyone ever used a seven pin, sub-miniature 6HA5? I have four I'd love to try out; 1963 tube, GE, branded 'Sears'.
This tube is a 14.5mA/V, mu 72 12mA single triode for use in VHF as a grounded grid amplifier. Plate dissipation is 2.6W.
Anyone know what the sonics are?
Cheers,
Hugh
Why don't you give 'em a try? Data sheet: http://frank.pocnet.net/sheets/135/6/6HA5.pdf
I have a couple of dozen myself, 6HA5, 6HM5, 6HQ5 all seem to be close equivalents - some are marked with more than one number.
I have a couple of dozen myself, 6HA5, 6HM5, 6HQ5 all seem to be close equivalents - some are marked with more than one number.
Thanks Guys,
Just set it up on the workbench.
With B+ of 280, 136V on the plate and 11.75K plate load (12.2mA), cathode resistor/cap is 150R//470uF. In this configuration it will easily pull 160Vpp output with 4.5Vpp input. 3dB points are 4Hz and 140KHz, square wave battlement to about 15KHz.
For a stated mu of 72, this is an Av of just 35.5, disappointingly low, I'm quite surprised.
Really need more voltage gain. Might have to move to the 6GK5.
Cheers,
Hugh
Just set it up on the workbench.
With B+ of 280, 136V on the plate and 11.75K plate load (12.2mA), cathode resistor/cap is 150R//470uF. In this configuration it will easily pull 160Vpp output with 4.5Vpp input. 3dB points are 4Hz and 140KHz, square wave battlement to about 15KHz.
For a stated mu of 72, this is an Av of just 35.5, disappointingly low, I'm quite surprised.
Really need more voltage gain. Might have to move to the 6GK5.
Cheers,
Hugh
I'm not suprised, you're encroaching mighty close to Rp. It's what, 5k? (Rp = mu/Gm) I'd guess less current.
Tim
Tim
Tim,
This is not a particularly linear tube, designed for grounded grid CRT VHF duties. It was running -1.77V of bias at 12mA with a cathode resistor of 150R.
I find a convenient way to figure voltage gain for audio tubes with bypassed (common) cathode at Class A plate currents is quite simple.
Divide the plate load by rp. In this case, 11.75/5 gives 2.35.
Now, multiply the published mu by 2.35/1 + 2.35. This factor is around 0.7, so Av should be around 50. It isn't, it's quite a bit less. This, I feel, is a comment on the linearity of the tube, and perhaps the fact that it's really not designed for common cathode.
It's a real pity, because they are dirt cheap, and run up to 22mA in a tiny package 3/4" in diameter and 1 1/4" long.
Ah, well, I'll try the 6GK5 next........
Cheers,
Hugh
This is not a particularly linear tube, designed for grounded grid CRT VHF duties. It was running -1.77V of bias at 12mA with a cathode resistor of 150R.
I find a convenient way to figure voltage gain for audio tubes with bypassed (common) cathode at Class A plate currents is quite simple.
Divide the plate load by rp. In this case, 11.75/5 gives 2.35.
Now, multiply the published mu by 2.35/1 + 2.35. This factor is around 0.7, so Av should be around 50. It isn't, it's quite a bit less. This, I feel, is a comment on the linearity of the tube, and perhaps the fact that it's really not designed for common cathode.
It's a real pity, because they are dirt cheap, and run up to 22mA in a tiny package 3/4" in diameter and 1 1/4" long.
Ah, well, I'll try the 6GK5 next........
Cheers,
Hugh
UHF triodes
Hope you have more luck with these things than I did . A few points to note with most UHF triodes :
Device inconsistency between samples
Rarely meet book spec for gm
Microphony !
Others to try are PC900 and EC97 . Why not go the whole hog and look for some 416B ? These have stupendous gm and mu of about 250
316a
Hope you have more luck with these things than I did . A few points to note with most UHF triodes :
Device inconsistency between samples
Rarely meet book spec for gm
Microphony !
Others to try are PC900 and EC97 . Why not go the whole hog and look for some 416B ? These have stupendous gm and mu of about 250
316a
Located and tested a 6GK5.
With 295V B+, 15K plate load, and 89R cathode resistor, it pulls 11.2 mA with -1V of bias and 135V on the plate. Gain is 55.5, and it will pull around 170Vpp before visible distortion is apparent on the CRO. Zout is just under 4K, and square wave is battlement to around 30KHz.
Very good tube..... I will continue R&D and move towards a hybrid amp using it. It's a corker.
Cheers,
Hugh
With 295V B+, 15K plate load, and 89R cathode resistor, it pulls 11.2 mA with -1V of bias and 135V on the plate. Gain is 55.5, and it will pull around 170Vpp before visible distortion is apparent on the CRO. Zout is just under 4K, and square wave is battlement to around 30KHz.
Very good tube..... I will continue R&D and move towards a hybrid amp using it. It's a corker.
Cheers,
Hugh
Apologies, for ressurecting this thread, but I was looking through my stash and have several 6HM5, and a few 6GK5's and I have a few 6ER5's also. It may not make a good RIAA preamp but if I use it in a grounded grid config. or I would call it a common grid config? Anyway it may make a good MC headamp, and maybe introduce some negative feedback to the grid to tame it a little. Bad Idea??
ARC had a Headamp for a short run that had a similar setup, but I felt they should have used a mu-follower setup instead of a cascoded setup, a much better PSRR than the cascode I think.
No, I use 6HM5 in my DAC as an I/V stage, bias -500mV, Rk 16R, gain ~70x and I can say that it is a great tube. A little neglected and unusual, but if used in the linear area it sounds great.
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