I have the same dream in the same time of my childhood. With a old radio that i destroy with my first experiments at 13.
Just an update,
I have connected the pre/driver board.
I have only one 6sn7 in the driver/splitter position.
And because I have almost done all connecting I thought I would just put some 6sl7's in the pre to see if anything comes out of the speakers. (because I don't have any SN7's yet!)
So power on, hiss in speakers only very quiet, connected the ipod h/p out to input 1.
Music with good sound stage. Only at very quiet levels. If I turn it up It clips to be expected i guess. So I have some SN7'S on order.
So still ongoing
If the sound level comes up with the SN7's it should be very very interesting. So watch this space!
I will have to mod the top plate, the inside is cool however the top plate is picking up the heat from the tubes so some more design required!
I have measured the mains current with different settings, if anyone is interested I will post the results.
Regards
M. Gregg
I have connected the pre/driver board.
I have only one 6sn7 in the driver/splitter position.
And because I have almost done all connecting I thought I would just put some 6sl7's in the pre to see if anything comes out of the speakers. (because I don't have any SN7's yet!)
So power on, hiss in speakers only very quiet, connected the ipod h/p out to input 1.
Music with good sound stage. Only at very quiet levels. If I turn it up It clips to be expected i guess. So I have some SN7'S on order.
So still ongoing
If the sound level comes up with the SN7's it should be very very interesting. So watch this space!
I will have to mod the top plate, the inside is cool however the top plate is picking up the heat from the tubes so some more design required!
I have measured the mains current with different settings, if anyone is interested I will post the results.
Regards
M. Gregg
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Ha! There is sound!
Great stuff! Congratulations!
I just tried a 6SL7 in my amp for the first two stages, the phase-splitter is a 6J5 in mine (Guess you're using the single piece of 6SN7 you have in the phase-splitter for both channels?)
Anyway, I duplicated the thin, low output, no-bass sound you describe, that clipped very early on.
You wait till you got some 6SN7 in there--Completely Different, plenty of output and loads of bass in comparison!
'Soundstage'?--You'll get that in buckets too......
Great stuff! Congratulations!
I just tried a 6SL7 in my amp for the first two stages, the phase-splitter is a 6J5 in mine (Guess you're using the single piece of 6SN7 you have in the phase-splitter for both channels?)
Anyway, I duplicated the thin, low output, no-bass sound you describe, that clipped very early on.
You wait till you got some 6SN7 in there--Completely Different, plenty of output and loads of bass in comparison!
'Soundstage'?--You'll get that in buckets too......
That's great,
I will wait and see what happens. Is the Russian 6N8S any good in the first stage?
I am running on one heater per 6c33c. Should be interesting.
I will work on modifying the top plate. Its fine with one heater but the full power version gets hot quite quick so a bit more design there I think.
Thank's for the help so far...
Regards
M. Gregg
I will wait and see what happens. Is the Russian 6N8S any good in the first stage?
I am running on one heater per 6c33c. Should be interesting.
I will work on modifying the top plate. Its fine with one heater but the full power version gets hot quite quick so a bit more design there I think.
Thank's for the help so far
...Regards
M. Gregg
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Aye, the Russian 6N8S is fine...
Its a direct version to the American 6SN7 as far as I know, and I have a number Ive used to good effect.
One or two of the 7 odd I have, show a little michrophony and a little hum, but most are pretty quiet.
I'm using those so-called, 'Tung-Sol re-issues', and they are surprisingly good --they again are Russian made....
Its a direct version to the American 6SN7 as far as I know, and I have a number Ive used to good effect.
One or two of the 7 odd I have, show a little michrophony and a little hum, but most are pretty quiet.
I'm using those so-called, 'Tung-Sol re-issues', and they are surprisingly good --they again are Russian made....
Russian 6N8S (actually marked 6H8C in cyrillic) equals 6SN7. And 6H9C is a match for 6SL7. I'm running my OTL (and other OT) amp on them very well.
Those 6H8C and 6H9C nowadays are a real NOS tubes from 50-60-70's, you can get for a reasonable price. Sure you have to check and pick them before using as you should do with all older NOS tubes.
Thank's for the info,
Just some more progress.
I am working on the top plate now to cut down the heat transfer across the surface. The heat does not pass the shield between Pre and power sections.
Still waiting for the 6SN7's.
B+ relay is in the top left corner of the picture.
Just for interest if I power between different heater settings you don't hear anything except a slow increase / decrease in clip level.
Also it drives my Alpair 7's quite a surprise. Just want to hear the difference with the SN7's.
Difference in power taken from mains supply with one heater on the 6c33c's is 100W..I think its worth the effort.
Regards
M. Gregg
Just some more progress.
I am working on the top plate now to cut down the heat transfer across the surface. The heat does not pass the shield between Pre and power sections.
Still waiting for the 6SN7's.
B+ relay is in the top left corner of the picture.
Just for interest if I power between different heater settings you don't hear anything except a slow increase / decrease in clip level.
Also it drives my Alpair 7's quite a surprise. Just want to hear the difference with the SN7's.
Difference in power taken from mains supply with one heater on the 6c33c's is 100W..I think its worth the effort.
Regards
M. Gregg
Attachments
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Great progress, and impressive power-reduction running single-heater...
(Just had my eleccy bill, gawd its gone up--Nowt to do with the OTL, although makes you think, turn off the Plasma unless you're actually watching it!)
I'm driving a pair of smallish, large bookshelf 6 ohm speakers and in my medium sized room I can play it to that 'too-loud' sorta level--Sounds wonderful on full-bandwidth movie-soundtracks, before they went digital!
Really, at the moment your amp isnt working anywhere near as it should with the 6SL7, as its DC coupled to the phase-splitter, not only are the two gain stages not running correctly/optimum, its upsetting the phase-splitter balance too....
--It will be sounding awful to what it should sound like!
Its a shame you're not closer, I could give you a couple of 6SN7 to get it running right, until you get your ordered ones.
I am anxiously waiting to hear your impressions when its got the right valves in there!
Not sure what you can do about the heat issue, Maybe you could squeeze a PC fan in there somewhere..
--Or maybe not! You have enough space between the tubes, so unless you're worried about someone burning themselves, I wouldnt worry about the top panel heating up....
(Just had my eleccy bill, gawd its gone up--Nowt to do with the OTL, although makes you think, turn off the Plasma unless you're actually watching it!)
I'm driving a pair of smallish, large bookshelf 6 ohm speakers and in my medium sized room I can play it to that 'too-loud' sorta level--Sounds wonderful on full-bandwidth movie-soundtracks, before they went digital!
Really, at the moment your amp isnt working anywhere near as it should with the 6SL7, as its DC coupled to the phase-splitter, not only are the two gain stages not running correctly/optimum, its upsetting the phase-splitter balance too....
--It will be sounding awful to what it should sound like!
Its a shame you're not closer, I could give you a couple of 6SN7 to get it running right, until you get your ordered ones.
I am anxiously waiting to hear your impressions when its got the right valves in there!
Not sure what you can do about the heat issue, Maybe you could squeeze a PC fan in there somewhere..
--Or maybe not! You have enough space between the tubes, so unless you're worried about someone burning themselves, I wouldnt worry about the top panel heating up....
Wow--Just looked up the specs for the Alpair-7 drivers....
3.6 ohm at the coil, so--4 ohm nominal at a guess....
Thats a hell of a difficult load for any OTL to drive, let alone a small powered twin-tuber like this! I thought I was pushing my luck running 6 ohm...
--Mine seems to cope OK at 6 ohms, but realistically 8 or above would be much happier impedance...
Still, If it works and you're happy with the end results with the new 6SN7, thats all that really matters!
Forgot to say--Beautiful job of construction there.....!
3.6 ohm at the coil, so--4 ohm nominal at a guess....
Thats a hell of a difficult load for any OTL to drive, let alone a small powered twin-tuber like this! I thought I was pushing my luck running 6 ohm...
--Mine seems to cope OK at 6 ohms, but realistically 8 or above would be much happier impedance...
Still, If it works and you're happy with the end results with the new 6SN7, thats all that really matters!
Forgot to say--Beautiful job of construction there.....!
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I have modified the top plate,
It still gets quite warm, however you can touch and hold your hand on it, tested after 2 hrs with B+ on.
Yes I just tried the Alpair 7's for a laugh. Its only at very low volumes, I am just surprised it ran them at all.
I may mod further. I cannot say for sure if all is well until I get the SN7's.
Then perhaps a fine tune.
So I guess its still ongoing...
Regards
M. Gregg
It still gets quite warm, however you can touch and hold your hand on it, tested after 2 hrs with B+ on.
Yes I just tried the Alpair 7's for a laugh. Its only at very low volumes, I am just surprised it ran them at all.
I may mod further. I cannot say for sure if all is well until I get the SN7's.
Then perhaps a fine tune.
So I guess its still ongoing...
Regards
M. Gregg
Attachments
What happened to all the capacitors?
The hill is getting less steep
I think your on the move now!Regards
M. Gregg
Originally Posted by flatheadmurre
Heater toroid has arrived.
How are you controlling the inrush current and back EMF from the toroids? I fitted CL 60’s (thermistor) and MOV protection. In the past I have seen power switches weld closed with no protection and I think the inrush will be high.
It will be interesting to see your amp progress. How are you going to construct the PSU? IE what type of rectifiers?
Just for interest I think there is a lot of energy stored in the capacitors on this PSU, high capacitance across each rail. It made me very aware the voltage is 350 V and high caps value high current shock risk.
(Thinking discharge times and bleeder resistors).
I have a 10W 100K across mine and with no tubes on after power down, it takes a while to discharge!
When testing (PSU lashed up before the build)
I powered off and came back 10 mins later I had only used high value bleeders, by accident as I tested for dead (meter leads moved a cable) touched a cable to a piece of earthed aluminium and " Bang" a 2mm hole through 1.5 mm aluminium plate- cap discharge.
Still waiting for the donkey bringing the SN7's....
Regards
M. Gregg
Heater toroid has arrived.
How are you controlling the inrush current and back EMF from the toroids? I fitted CL 60’s (thermistor) and MOV protection. In the past I have seen power switches weld closed with no protection and I think the inrush will be high.
It will be interesting to see your amp progress. How are you going to construct the PSU? IE what type of rectifiers?
Just for interest I think there is a lot of energy stored in the capacitors on this PSU, high capacitance across each rail. It made me very aware the voltage is 350 V and high caps value high current shock risk.
(Thinking discharge times and bleeder resistors).
I have a 10W 100K across mine and with no tubes on after power down, it takes a while to discharge!
When testing (PSU lashed up before the build)
I powered off and came back 10 mins later I had only used high value bleeders, by accident as I tested for dead (meter leads moved a cable) touched a cable to a piece of earthed aluminium and " Bang" a 2mm hole through 1.5 mm aluminium plate- cap discharge.
Still waiting for the donkey bringing the SN7's....
Regards
M. Gregg
Mains intake filter from old SMPS unit.
I have some softstarters i designed for magnetron duty the will do the trick i think.
M Gregg i agree with you that it´s a scary amount of energy stored in the caps.
Perhaps a relay and some large disharge resistors activated at power off.
On my wishlist to fit inside amp is 3 toroids, 22 caps, heater rectifier/reg for small signal, 2 fans with reg.
A remote controlled input selector/volume control perhaps.
Getting crowded !!!!
I have some softstarters i designed for magnetron duty the will do the trick i think.
M Gregg i agree with you that it´s a scary amount of energy stored in the caps.
Perhaps a relay and some large disharge resistors activated at power off.
On my wishlist to fit inside amp is 3 toroids, 22 caps, heater rectifier/reg for small signal, 2 fans with reg.
A remote controlled input selector/volume control perhaps.
Getting crowded !!!!
Sounds good,
The reason I mentioned the PSU is because I am used to working with MV/HV, however I am used to a few hunderd of uF in valve circuits and had over looked the energy in the caps. I thought you might too..LOL.
Have you thought of using TARDIS theory?
(Dr Who, little on the outside)..
Keep reaching for the volume (turn it up!)...can't LOL ! Where is me tubes..awwwww..LOL Feed the donkey give it some Caffeine..
Regards
M. Gregg
The reason I mentioned the PSU is because I am used to working with MV/HV, however I am used to a few hunderd of uF in valve circuits and had over looked the energy in the caps. I thought you might too..LOL.
Have you thought of using TARDIS theory?
(Dr Who, little on the outside)..
Keep reaching for the volume (turn it up!)...can't LOL ! Where is me tubes..awwwww..LOL Feed the donkey give it some Caffeine..
Regards
M. Gregg
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M Gregg never choose 20 mule express for delivery .
I have a good one about delivery.
I ordered 10 Omron relays USPS from Questcomp.
USPS is handled by Swedish postal service with their own custom people.
The $2/hour clerk read that it was milspec. and asked for my permission to import military equipment.
After 2 month of arguing with the Swedish foreign department the relays had to go back to Questcomp.
Lesson learned everything is from now "sample" fits in the easy dictionary.
.I have a good one about delivery.
I ordered 10 Omron relays USPS from Questcomp.
USPS is handled by Swedish postal service with their own custom people.
The $2/hour clerk read that it was milspec. and asked for my permission to import military equipment.
After 2 month of arguing with the Swedish foreign department the relays had to go back to Questcomp
.Lesson learned everything is from now "sample" fits in the easy dictionary.
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