Frank is one of the oldest in the forum to have published starved circuitry by the way (for low level signal)
Purpose of this schematics is almost the same - for those, who want to make/own "construction with glowing bottle", but, unlike "chinese" this is really tube construction, which does not have any solid state elements in a signal flow.
Please, understand me right. Maybe I am wrong with thread choice and I am offtopic, I don't mean this schematics are the same. But I think there are also similar ideas.
I did not critique, I just analyzed the way it works. Of course it is to tempt the non familiar with high voltages today's digital storage music lover to make something small but with tubes. "Safe exotic". Its more original. There are eBay items with only the heaters connected even but almost all have the proverbial blue LED in the noval base center.🙂
Anyone tried the 6V6 gain stage with a cathode follower ?
I don't want to spend time making another board so maybe I'll rig the CF on top of this board. I plan to use a 6SN7 of which I have a few .
If it turns out very well I might get the other 6V6 brands for comparison. Mullard, EH and Genalex. My friend already has the JJ version and I'll get it later some time.
I've made a rudimentary layout for the EL84 tube. Basically rehashed what I used for the 6V6. Maybe I will complete it by the weekend. Time is in short supply at he moment ! 🙂
Since more stages are being added , it might eventually be interesting to add a couple more and build an Aikido for comparison ! Of course the whole purpose of using a 6V6 and keeping it simple will be lost ! 😉
I would like to do this as I have all the parts...but unfortunately not the time ! 🙂 Maybe after June.
I don't want to spend time making another board so maybe I'll rig the CF on top of this board. I plan to use a 6SN7 of which I have a few .
If it turns out very well I might get the other 6V6 brands for comparison. Mullard, EH and Genalex. My friend already has the JJ version and I'll get it later some time.
I've made a rudimentary layout for the EL84 tube. Basically rehashed what I used for the 6V6. Maybe I will complete it by the weekend. Time is in short supply at he moment ! 🙂
Since more stages are being added , it might eventually be interesting to add a couple more and build an Aikido for comparison ! Of course the whole purpose of using a 6V6 and keeping it simple will be lost ! 😉
I would like to do this as I have all the parts...but unfortunately not the time ! 🙂 Maybe after June.
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Zero Vgk operation
Did someone bring up the usage of the 6922 or 6DJ8 with zero grid bias voltage for use as a MC input stage for a RIAA preamp ? I thought I saw that a few years ago.
Did someone bring up the usage of the 6922 or 6DJ8 with zero grid bias voltage for use as a MC input stage for a RIAA preamp ? I thought I saw that a few years ago.
I haven't seen it with additional 6V6 CF stage presented here, but enough use it as 6V6 in CF mode itself. I suggest you rewire it and listen to it that way also. There is a first post link. If you don't need the gain that is. Its a very good CF subjectively so I also suggest you make it with 6V6 again if it must be a cascade preamp with gain and buffer stages.
Hi,
Indeed. If I can help with that just let me know.
I do fail to see the purpose when signal levels average or exceed +2V at the grid's input even though a 6DJ8 is quite forgiving in that respect.
As for cathode followers in this particular application, IMHO if you go down that road then at least pick one that can deliver some current so the interconnect cable and next input stage is driven properly if needed.
Otherwise you'll end up with a low Zout stage that's crippled for all intends and purposes. IOW, a meaningless number on a spec sheet.
WCF stages are good at that for instance.
Contrary to what I quickly read here, a CF reduces overall distortion levels since these are local negative feedback topologies.
So, unless you adhere to uber minimalistic designs, they're quite useful, generally speaking.
Cheers, 😉
Indeed. If I can help with that just let me know.
I do fail to see the purpose when signal levels average or exceed +2V at the grid's input even though a 6DJ8 is quite forgiving in that respect.
As for cathode followers in this particular application, IMHO if you go down that road then at least pick one that can deliver some current so the interconnect cable and next input stage is driven properly if needed.
Otherwise you'll end up with a low Zout stage that's crippled for all intends and purposes. IOW, a meaningless number on a spec sheet.
WCF stages are good at that for instance.
Contrary to what I quickly read here, a CF reduces overall distortion levels since these are local negative feedback topologies.
So, unless you adhere to uber minimalistic designs, they're quite useful, generally speaking.
Cheers, 😉
Frank can we start a thread saying " using tubes ( 6922?) at zero Vgk " for mc gain ahead of a regular MM stage ?
Thanks.
Thanks.
6N14P can be a good candidate for a cathode follower. Look at it's datasheet.
Also, of course my favourite 6P15P.
An externally hosted image should be here but it was not working when we last tested it.
Also, of course my favourite 6P15P.
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Yes at some 7-8 mA they start looking good for the purpouse of taking on some difficult load without changing in gm to much with current. Could always be higher in mu but it looks linear enough not having to be highly reduced with the CF negative feedback.
Hi,
@Ashok:
If that's the intended usage then why not just build the stage as has been posted here by me years ago?
It's been discussed many times. Admittedly scattered a little all over the Tubes section but still.
Cheers, 😉
@Ashok:
If that's the intended usage then why not just build the stage as has been posted here by me years ago?
It's been discussed many times. Admittedly scattered a little all over the Tubes section but still.
Cheers, 😉
I suspect that pentodes like 6Z5P, 6Z9P, 6Z51P, in triode mode also can have something to say in the subject. 6P15P looks great indeed.
Tube Tester Files - 6J51P
http://www.bartola.co.uk/valves/2013/02/23/russian-pentodes-in-triode-mode/#more-1264
The 6V6 sounds noticeably better with a film cap at the output as compared to the electrolytic I had earlier. Maybe I should get a Russian teflon type to see what others have found. But sounds nice right now. I have not fixed the hum which I think will require more time. Maybe the dc heater voltage itself. I have not checked that on the scope. So much to fix and so little time..🙁
Thanks Frank. That's what I saw long ago.
So does the grid actually draw current on a positive transition of the input signal at low mV levels ? Vgk = 0 of course . There is no coupling cap as usual.