|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
In Reply to: 6BL7GT and 6BX7GT as drivers posted by gman on March 10, 2003 at 09:39:44:
HEy-Hey!!!,
I have not tried them on DHT but the triode strapped KT90. I slightly prefer the 5687. I found the 6BL7 a bit fuzzier and the 6BX7 a bit too sharp sounding. And the 5687 was juuuuust right. Kidding there. None of them sounded bad, minor nuance stuff. I am currently running a pair of 12B4A in an octal adapter I built and haven't taken them out after the first few swaps. The split plate 12B4 also looks cool with the exposed cathode glowing orange.
By the plate curves, teh lower gain tubes will give a bit more swing, but it is a small thing. I point to 7N7 and other's work to look for a tube with lower odd harmonic distortion and 5687 is about a quarter of the others. I will make another adapter or maybe a hole filler to use them direct wired. part of the 12B4 attraction is the gain is almost perfect. may try 5998 there if I can find one or two.
Tried a half dozen 7119 and did not like the sound, hard to describe why, but it wasn't as nice as any of the alternatives. Grainy and bland is probably as good as I can do without a shared listen.
regards,
Douglas
Follow Ups:
I have experience with both of these types - and indeed some of the others mentioned.I have used 6BX7 to drive a pair of 813s which it did very well. 6BL7s I am using in my line stage which like most of my stuff is "temporary".
I do not like E182CC/7119 - it is the one valvbe that I would say sounds nasty - a sort of sharp edge; 6350 is better if you like a sharpish sound - it is much smoother. 6463 is good too and these types are cheap although they are nowhere near the 6SN7 class when it comes to distortion.
5687 will work properly only if a lot of current is run through it; a glance at the composite curves will show that those exciting figures put out by the makers apply to 40mA anode current!
Choice of driver ultimately depends on how much gain is required; if there are to be two stages, then my favourite choice at present would be either 6EW7 (or the 10, 15 or 19V variants) or 6DN7. For those who do not know these, they are "dissimilar" double triodes used as line osc./amp in old TV sets. Both 6EW7 and 6DN7 have a section that roughly approximates to half a 6SN7, the other half being a beefy triode with mu of around 6 and gm of about7 - Ra is therefore in the order of 800 ohms or so depending on the current you care to run.
I have tested these thoroughly and their distortion performance is excellent..
Recommended.
What current is optimal for the 6BX7 and the 6BL7?
This depends to a certain extent on a) the amount of HT you have available and b) how many volts you wish to swing.Having a higher anode resistance, 6BL7 should have a higher value of load resistor.
I would say aim for 20mA per section minimum for both types
5998a is the sledgehammer and the grid of the KT90 is the nut ! I've often wondered what this valve would sound like as a driver . The 7236 (computer grade 5998a) I have test very close between sections , as an output valve they are very good , but as a driver ?
Send it over, I'll plug it in and report. I have ooodles ov heater corrent, the power trans used to run a pair of 6336A's and the socket is already based 8BD....
As to the sledgehammer and nut thing, I've done my share of work on Milwaukie's finest 2-cylinders so I know how to weild a big hammer. In defense fo the KT90, it is triode strapped so it is just a bit harder than a tetrode connected valve might be to drive.
regards,
Douglas
I just can't bring myself to do it though ! A 7236 is bigger than an S11E12 which is what I'm using for the output valve , would possibly work very well , even with only 400V HT . Being a power valve itself , the drive problems would be moved upstream a stage
This post is made possible by the generous support of people like you and our sponsors: