ReinoutdV, Unison
I am now collecting parts for the amp due to vast amounts of inspiration from this wonderful thread.
I was wondering whether you could help
My problems with making this amp are
1. purchasing and shipping this tube and the types of 833a/c and brands. Would have to talk to frank to organize a group buy.
2. The connectors esp the fillaments holders, i believe the anode and grid are the same connectors for 866a/811a that is easy to find. There is no way to source the fillament holder from my country unless i fabricate one here. Is there a source to order this
The rest are easily done just pay money to do so.
I would do custom winds for opt and power trans. At the moment i have 2* 1.5kva 700,980volts idling away collecting dust beggin to be used and some 866a too.
Probably would go with low voltage too. something like 850 200-250ma like the wavacs. With a 5k trans too. With a 300b driver and a pentode driving the 300b. Would use the Inverted interstage thingy of wavac to reduce the air gap for the interstage trans.
What do u think of the op points
I am now collecting parts for the amp due to vast amounts of inspiration from this wonderful thread.
I was wondering whether you could help
My problems with making this amp are
1. purchasing and shipping this tube and the types of 833a/c and brands. Would have to talk to frank to organize a group buy.
2. The connectors esp the fillaments holders, i believe the anode and grid are the same connectors for 866a/811a that is easy to find. There is no way to source the fillament holder from my country unless i fabricate one here. Is there a source to order this
The rest are easily done just pay money to do so.
I would do custom winds for opt and power trans. At the moment i have 2* 1.5kva 700,980volts idling away collecting dust beggin to be used and some 866a too.
Probably would go with low voltage too. something like 850 200-250ma like the wavacs. With a 5k trans too. With a 300b driver and a pentode driving the 300b. Would use the Inverted interstage thingy of wavac to reduce the air gap for the interstage trans.
What do u think of the op points
Hi Nick,
Getting the valves and connectors is the easy bit
Haflin have both 833As and 833Cs and filament and anode/grid connectors. Just ask via the web site Haflin
I'll leave those with working amps to comment on the op. points but the topology sounds good. The only potential problem I see is with the inverted IT, the inverted connection needs special winding to preserve bandwidth.
Good luck!
ciao
James
Getting the valves and connectors is the easy bit
Haflin have both 833As and 833Cs and filament and anode/grid connectors. Just ask via the web site Haflin
I'll leave those with working amps to comment on the op. points but the topology sounds good. The only potential problem I see is with the inverted IT, the inverted connection needs special winding to preserve bandwidth.
Good luck!
ciao
James
Hello Nick.
For the 833A amp, my operating point is 1000V/+20Vbias/180ma into 5K SE. I tried 800V and 1200V too, but settle on 1000V for power output reason, at 1200V more power but the tube run quite hot, 800V not enough power for me.
Rfparts has chineese socket for 833A not that expensive. The anode cap is the same as 811/866 but I do not use the heat dissipation cap because of exposing plate with 1000V is dangerous. Even with the anode cap, it is still exposed. I did not run 1200V because I was afraid that the extra heat would melt the solder in the anode cap and the wire would pop out.
The 866A tube, I have not had good luck with it, even with long warmup, sometime the tube does spark and cause terrible noise through the speaker. I have bought 10 NOS 866A and still has problem. The 3B28 is a good substitute, the noise problem is gone, but it does not has that blue glow.
For the 833A amp, my operating point is 1000V/+20Vbias/180ma into 5K SE. I tried 800V and 1200V too, but settle on 1000V for power output reason, at 1200V more power but the tube run quite hot, 800V not enough power for me.
Rfparts has chineese socket for 833A not that expensive. The anode cap is the same as 811/866 but I do not use the heat dissipation cap because of exposing plate with 1000V is dangerous. Even with the anode cap, it is still exposed. I did not run 1200V because I was afraid that the extra heat would melt the solder in the anode cap and the wire would pop out.
The 866A tube, I have not had good luck with it, even with long warmup, sometime the tube does spark and cause terrible noise through the speaker. I have bought 10 NOS 866A and still has problem. The 3B28 is a good substitute, the noise problem is gone, but it does not has that blue glow.
parts and stuff
Hi Nick,
as James D already pointed out: Halfin in Belgium got most of your wanted goodies. They have the 833A on stock and can order the 833C for you if you want. To be more precise: the have the Tungsram OT400 and it works very well. I have to admit: i found no real differences between the Amperex 833A and the Tungsram OT400 !
The Polyaron GU-48 and the Penta 833C are really different in sound. At this moment i already have a IT833 which looks building-wise also somewhat different and/so i expect differences in sound as well.
The OT400 will set you back € 87,50 a piece. And the packing & handling at Halfin is very good. The tube-socket/filament-holders are from China. Not bad.....but if you can score original Johnson's or RCA's please do that. The same for the topcaps. They're pretty common and to be found for reasonably low prices. At hamfest here i can score them never used for € 3 a piece. They are superior to the chinese variety for their clamping is still strong after some time. And the China-ones begin to wobble....
The next hamfest is in 2 months.....if you need them i'll score a few for you.
Unison845 and me use almost the same operating points. Both A2: 1000V/+20/5K. I'm running a couple of mA's more.....but almost the same. I went for this voltage: the 833 came really to live here and i found no real changes when switching to 1400 V.
I'm pretty settled with these op points and with the 833's as well. Now i'm tube-swapping to find the optimum input-tube and driver. Currently "on stage" are the Sylvania 6SN7W (metal base) and the RCA 6SN7M (yes....a metal tube !)(picture include...low quality !).
Lots of building pleasure...and listening pleasure of course !
Reinout
(the included picture shows the RCA 6SN7M and the Sylvania 6SN7W. The latter has a teflon tube ring in order to tame microphonics)
Hi Nick,
as James D already pointed out: Halfin in Belgium got most of your wanted goodies. They have the 833A on stock and can order the 833C for you if you want. To be more precise: the have the Tungsram OT400 and it works very well. I have to admit: i found no real differences between the Amperex 833A and the Tungsram OT400 !
The Polyaron GU-48 and the Penta 833C are really different in sound. At this moment i already have a IT833 which looks building-wise also somewhat different and/so i expect differences in sound as well.
The OT400 will set you back € 87,50 a piece. And the packing & handling at Halfin is very good. The tube-socket/filament-holders are from China. Not bad.....but if you can score original Johnson's or RCA's please do that. The same for the topcaps. They're pretty common and to be found for reasonably low prices. At hamfest here i can score them never used for € 3 a piece. They are superior to the chinese variety for their clamping is still strong after some time. And the China-ones begin to wobble....
The next hamfest is in 2 months.....if you need them i'll score a few for you.
Unison845 and me use almost the same operating points. Both A2: 1000V/+20/5K. I'm running a couple of mA's more.....but almost the same. I went for this voltage: the 833 came really to live here and i found no real changes when switching to 1400 V.
I'm pretty settled with these op points and with the 833's as well. Now i'm tube-swapping to find the optimum input-tube and driver. Currently "on stage" are the Sylvania 6SN7W (metal base) and the RCA 6SN7M (yes....a metal tube !)(picture include...low quality !).
Lots of building pleasure...and listening pleasure of course !
Reinout
(the included picture shows the RCA 6SN7M and the Sylvania 6SN7W. The latter has a teflon tube ring in order to tame microphonics)
Attachments
tube sockets
Hi Nick,
these are what you are looking for: Johnson 124-212-1 (or the RCA equivalant for which i do not have the number).
I stumbled across them...and bought the lot !
They were not cheap...but worth their money. If i find more of these items i surely will buy them: they are really sought after.
Reinout
Hi Nick,
these are what you are looking for: Johnson 124-212-1 (or the RCA equivalant for which i do not have the number).
I stumbled across them...and bought the lot !
They were not cheap...but worth their money. If i find more of these items i surely will buy them: they are really sought after.
Reinout
Attachments
tube sockets 2
Nick,
in the above posted picture you'll see the original top caps. No isolation whatsoever !! So for home-use seriously to be avoided. I'll enclose a picture of a 833-based transmitter with a couple of 833's hanging upside down using these items. Then you can see also how well these "old" original tube sockets clamp the tube !
With regards,
Reinout
Nick,
in the above posted picture you'll see the original top caps. No isolation whatsoever !! So for home-use seriously to be avoided. I'll enclose a picture of a 833-based transmitter with a couple of 833's hanging upside down using these items. Then you can see also how well these "old" original tube sockets clamp the tube !
With regards,
Reinout
Attachments
i do like 6SN7's and 6C45's
Hi Unison845,
although we share our 833-ideas we do not agree on 6SN7 use. I really like the 6SN7. It's a versatile tube with lots of uses. Not to much asking in way of power/voltages/ etc, and sounding nice as well. Of course there are extremely bad types (forget the Russian and Chinese ones. Not to forget the RCA coin base disaster) but on the whole you've got very meny types and brands to chose from in searching for the optimum mix/combination in you tube-device.
I certainly do not call the 6SN7 (or any tube) the "best". That simply does not exist. But the 6SN7 has some really handy characteristics and uses.
Yes...i heared
For the 6C45: i was looking for a high mu tube for my phonostage. I wanted to stick to triodes and not go for penthodes and with lots of money you can buy m167/3A's, EC8010/8020, and so on. They sound really nice. But the characteristics of the 6C45 was really interesting. The audio community did not have discovered this Russian triode when i bought a box of 50 in Lithuania for peanuts compared to the 167/3a prices.
Mu of 50. 1,2K impendance....nice for a phono.
So here's a picture of my phonostage. Maybe your ultimate nightmare......but let me assure you: it's a good sounding nightmare !
Some data:
- external power supply
- 6C45 as first stage
- passive RIAA
- 6C45 as second stage
- interstage (not very common in a phonostage)
- 6SN7 as output tube ( ,, )
- output transformer ( ,, )
Yes: the 6C45/riaa-combination was enough gain, but with the interstage/6SN7/opt combination added i was able to run long cables AND searching for a optimum sound-combination cartridge and phonostage.
Still friends ?
Now back to the 833-issue. Currently i'm experimenting with tube rings on my tubes. You can see them in a earlier post on the 6SN7. But i'm going to extend that to the 833. I'll post the results in this thread. Did you have done some microphonic-experimenting ?
With regards,
Reinout
(seriously impressed with your pre-amp !)
Hi Unison845,
although we share our 833-ideas we do not agree on 6SN7 use. I really like the 6SN7. It's a versatile tube with lots of uses. Not to much asking in way of power/voltages/ etc, and sounding nice as well. Of course there are extremely bad types (forget the Russian and Chinese ones. Not to forget the RCA coin base disaster) but on the whole you've got very meny types and brands to chose from in searching for the optimum mix/combination in you tube-device.
I certainly do not call the 6SN7 (or any tube) the "best". That simply does not exist. But the 6SN7 has some really handy characteristics and uses.
Yes...i heared
For the 6C45: i was looking for a high mu tube for my phonostage. I wanted to stick to triodes and not go for penthodes and with lots of money you can buy m167/3A's, EC8010/8020, and so on. They sound really nice. But the characteristics of the 6C45 was really interesting. The audio community did not have discovered this Russian triode when i bought a box of 50 in Lithuania for peanuts compared to the 167/3a prices.
Mu of 50. 1,2K impendance....nice for a phono.
So here's a picture of my phonostage. Maybe your ultimate nightmare......but let me assure you: it's a good sounding nightmare !
Some data:
- external power supply
- 6C45 as first stage
- passive RIAA
- 6C45 as second stage
- interstage (not very common in a phonostage)
- 6SN7 as output tube ( ,, )
- output transformer ( ,, )
Yes: the 6C45/riaa-combination was enough gain, but with the interstage/6SN7/opt combination added i was able to run long cables AND searching for a optimum sound-combination cartridge and phonostage.
Still friends ?
Now back to the 833-issue. Currently i'm experimenting with tube rings on my tubes. You can see them in a earlier post on the 6SN7. But i'm going to extend that to the 833. I'll post the results in this thread. Did you have done some microphonic-experimenting ?
With regards,
Reinout
(seriously impressed with your pre-amp !)
Attachments
welcome !
Good morning James D,
you more than welcome to visit. Please do send a mail in advance ?
Geee....that was a serious strange experiment / job you had at Decca. But you've learned to work with less normal voltages. And that's worth a lot.
I'm working with radars. The last one was a 220 kW-device. So i'm not unfamiliar with lethal voltages as well. In radars there are still tubes to be found, but less and less. Lower output radars are surely switching over to solidstate-devices. The high power ones are still tube based.
From the radarwork i came across hexfred's as rectifiers. With these items i had good results in my other projects (phonostage, preamp, headphone amp) so why not give it a try in the 833 amp ? Certainly i had a look at 866's (i simply love the looks), but as said earlier in this thread: they are not stable and sometimes for whatever reason you get funny noises. With a good choke/coil/capacitor combination you can get a decent powerline with solid state stuff.
And if you look inside a power supply of a high voltage devise....you can see the same way of building as my power supply for the 833 amp. I like to work tidy; logical building; no mess of wires.
So what next.......of course there is fine-tuning to do with the 833-amp. But my hands are already itching for a new project. I've got 2 options;
- a tube based DAC;
- a new preamp;
Still haven't decided yet.
Maybe till summer ?
Reinout
Good morning James D,
you more than welcome to visit. Please do send a mail in advance ?
Geee....that was a serious strange experiment / job you had at Decca. But you've learned to work with less normal voltages. And that's worth a lot.
I'm working with radars. The last one was a 220 kW-device. So i'm not unfamiliar with lethal voltages as well. In radars there are still tubes to be found, but less and less. Lower output radars are surely switching over to solidstate-devices. The high power ones are still tube based.
From the radarwork i came across hexfred's as rectifiers. With these items i had good results in my other projects (phonostage, preamp, headphone amp) so why not give it a try in the 833 amp ? Certainly i had a look at 866's (i simply love the looks), but as said earlier in this thread: they are not stable and sometimes for whatever reason you get funny noises. With a good choke/coil/capacitor combination you can get a decent powerline with solid state stuff.
And if you look inside a power supply of a high voltage devise....you can see the same way of building as my power supply for the 833 amp. I like to work tidy; logical building; no mess of wires.
So what next.......of course there is fine-tuning to do with the 833-amp. But my hands are already itching for a new project. I've got 2 options;
- a tube based DAC;
- a new preamp;
Still haven't decided yet.
Maybe till summer ?
Reinout
Attachments
To everyone thanks for the almost instant reply to my problem
James D.
The only potential problem I see is with the inverted IT, the inverted connection needs special winding to preserve bandwidth
James from my understanding of current loops if primary draws current say 40ma, we have to gapped for 40ma. But if secondary draws current due to grid current i.e. 811a/833a say 20ma then we only need to gap the core for 40-20ma=20ma only instead of 40ma thus inlarging the primary inductance. However the current loop in primary should be clockwise and secondary anti-clockwise to have some cancelation. Is my assumption correct?
James i have access to a custom trans winder, he has z11 core and i have made and design 1 opt for 300b and 1 interstage now. He charges peanuts for trans. like my 300b trans is like 96mm and 45mm for only 40 usd. Any my gm70 i wounded today 111m and 68mm for only 80usd only. gm70 would be 10k:8. So the interstage i am playing around with that. If you have any suggestions for the inverted IT do shoot me a mail or post, would love to try something out.
ReinoutdV
Thanks for explaining the the proper sockets. They really look great the sockets for the 833a but i deem unsafe. I keep dogs in my house. Don't one them go and lick them. but from a mechanical point of view i have always wonder on how to mount them properly. Might give your clamps a try looks better for stability. Just i need to enclose the amp. How 's does yours stand up without cracking the base. Is allright to mount like yours reinout? I see Unison also did the same and so does wavac. But i find the proper way/unsafe way better as when the tubes are hot it might cause the glass to break under horizontal loading due to in proper area of the tube(not balance symetically in construction). I would be glad if you score me some holders for the fillament. I inted to build this in the future a push pull. If could get me 4 fillament holders and top caps would be great. Thanks again, hope it is not burdening you. My country doesnot support hams, not a popular hobby here.
Unison
I might try the 1kv approach, looks allright to. Might check up on rfparts for the tube sockets. Would be terrible not to use the 866as they looks so good. WHILE THE 3B28 looks terrible in shape and operation color better just stick with HV diodes.
James D.
The only potential problem I see is with the inverted IT, the inverted connection needs special winding to preserve bandwidth
James from my understanding of current loops if primary draws current say 40ma, we have to gapped for 40ma. But if secondary draws current due to grid current i.e. 811a/833a say 20ma then we only need to gap the core for 40-20ma=20ma only instead of 40ma thus inlarging the primary inductance. However the current loop in primary should be clockwise and secondary anti-clockwise to have some cancelation. Is my assumption correct?
James i have access to a custom trans winder, he has z11 core and i have made and design 1 opt for 300b and 1 interstage now. He charges peanuts for trans. like my 300b trans is like 96mm and 45mm for only 40 usd. Any my gm70 i wounded today 111m and 68mm for only 80usd only. gm70 would be 10k:8. So the interstage i am playing around with that. If you have any suggestions for the inverted IT do shoot me a mail or post, would love to try something out.
ReinoutdV
Thanks for explaining the the proper sockets. They really look great the sockets for the 833a but i deem unsafe. I keep dogs in my house. Don't one them go and lick them. but from a mechanical point of view i have always wonder on how to mount them properly. Might give your clamps a try looks better for stability. Just i need to enclose the amp. How 's does yours stand up without cracking the base. Is allright to mount like yours reinout? I see Unison also did the same and so does wavac. But i find the proper way/unsafe way better as when the tubes are hot it might cause the glass to break under horizontal loading due to in proper area of the tube(not balance symetically in construction). I would be glad if you score me some holders for the fillament. I inted to build this in the future a push pull. If could get me 4 fillament holders and top caps would be great. Thanks again, hope it is not burdening you. My country doesnot support hams, not a popular hobby here.
Unison
I might try the 1kv approach, looks allright to. Might check up on rfparts for the tube sockets. Would be terrible not to use the 866as they looks so good. WHILE THE 3B28 looks terrible in shape and operation color better just stick with HV diodes.
Hello ReinoutdV,
What a beautiful Phono stage! That's a lot of work ReinoutdV, I am sure it sounded great. You did lots of nice work.
Regarding the 6SN7, I guess it is a matter of taste, I have bought about 100 tubes ten years ago, and still have them, I tried about three different circuits but decided it was not the type of sound that I liked, then I started experimenting other tubes. I hope there is no hard feeling ReinoutdV, there are lots of people that used 6SN7 out there and liked them, I must be wrong.
Regarding the 833A, mine do not have much microphonic, even if I tap the tube slighly while playing music, so I did not think about microphonic control device. I am sure evry damping device will help sonically including unpotted output transformer.
Regarding next project, go for the DAC. I am using a modified tube DAC with passive filtering. The output of the DAC drive 100 ohms, then LC filter then drive the 12AX7 output tube. This, I did ten years ago and still use it. I wanted to build a new DAC but did not due to time consuming regarding PC layout.
What a beautiful Phono stage! That's a lot of work ReinoutdV, I am sure it sounded great. You did lots of nice work.
Regarding the 6SN7, I guess it is a matter of taste, I have bought about 100 tubes ten years ago, and still have them, I tried about three different circuits but decided it was not the type of sound that I liked, then I started experimenting other tubes. I hope there is no hard feeling ReinoutdV, there are lots of people that used 6SN7 out there and liked them, I must be wrong.
Regarding the 833A, mine do not have much microphonic, even if I tap the tube slighly while playing music, so I did not think about microphonic control device. I am sure evry damping device will help sonically including unpotted output transformer.
Regarding next project, go for the DAC. I am using a modified tube DAC with passive filtering. The output of the DAC drive 100 ohms, then LC filter then drive the 12AX7 output tube. This, I did ten years ago and still use it. I wanted to build a new DAC but did not due to time consuming regarding PC layout.
hello again
Good afternoon,
you must admit.....this thread is getting longer/better every time. It started all with Protos asking for 833-amps and now it seems there are serious plans and even builded amplifiers with this tube !
NickC: your right about the open structure of the tube socket. It is rather exposed. Nonetheless the anode-connection with 1000 V (in my case) is more a problem. A standard topcap will fit perfectly for the wire, but a part of the connection (metal !) is still exposed. Although the heat of the tube will certainly make you think twice of touching it........can you take the risk with children ? That's why i've build an open frame with ventilation holes in it. If there are visitors with children i simply install the frame. The tube cn still loose it's heat but the holes are to small for even tiny fingers to touch the 833 at all. It works but i do not like it; so now i'm experimenting with a teflon pipe that slides over the top cap. If i'm happy with it i'll post a picture. Now you have to do with the frame-solution (picture in next post).
Back to the tube sockets. I am happy to have found a pair. But asking for 4 for your PP-design is pushing. But i will be on the look-out for you (and all other 833-builders).
There are 2 varieties of sockets:
- the Johnson. Altough a rather simple clamping-system the mounting can be swiffeled 90 degrees ! And that is very handy indeed. The ceramic base can be fixed to a wall or base (horizontal or vertical) and the tube can be how YOU want it ! Which is in almost all designs standing proudly vertical. I'm going to post a picture some post from now which is absolutely NOT good. And that's even a commercial item.
- The RCA and ITT. Their clamping system is more sophisticated, but the whole tube socket is fixed....so less flexible in your design.
Enclosed is a picture of a ITT (=fixed) socket and a Johnson with one of the filament clamps 90-degrees swiffeled as an example.
Reinout
Good afternoon,
you must admit.....this thread is getting longer/better every time. It started all with Protos asking for 833-amps and now it seems there are serious plans and even builded amplifiers with this tube !
NickC: your right about the open structure of the tube socket. It is rather exposed. Nonetheless the anode-connection with 1000 V (in my case) is more a problem. A standard topcap will fit perfectly for the wire, but a part of the connection (metal !) is still exposed. Although the heat of the tube will certainly make you think twice of touching it........can you take the risk with children ? That's why i've build an open frame with ventilation holes in it. If there are visitors with children i simply install the frame. The tube cn still loose it's heat but the holes are to small for even tiny fingers to touch the 833 at all. It works but i do not like it; so now i'm experimenting with a teflon pipe that slides over the top cap. If i'm happy with it i'll post a picture. Now you have to do with the frame-solution (picture in next post).
Back to the tube sockets. I am happy to have found a pair. But asking for 4 for your PP-design is pushing. But i will be on the look-out for you (and all other 833-builders).
There are 2 varieties of sockets:
- the Johnson. Altough a rather simple clamping-system the mounting can be swiffeled 90 degrees ! And that is very handy indeed. The ceramic base can be fixed to a wall or base (horizontal or vertical) and the tube can be how YOU want it ! Which is in almost all designs standing proudly vertical. I'm going to post a picture some post from now which is absolutely NOT good. And that's even a commercial item.
- The RCA and ITT. Their clamping system is more sophisticated, but the whole tube socket is fixed....so less flexible in your design.
Enclosed is a picture of a ITT (=fixed) socket and a Johnson with one of the filament clamps 90-degrees swiffeled as an example.
Reinout
Attachments
safety cage
For security reasons when "new" children are entering or when the experienced "free-education" by their parents.....i put the safety cage in place.
Of course you lose a lot of optic impact. But it still sounds good and there are no fried children in you house.
Reinout
For security reasons when "new" children are entering or when the experienced "free-education" by their parents.....i put the safety cage in place.
Of course you lose a lot of optic impact. But it still sounds good and there are no fried children in you house.
Reinout
Attachments
not good !
Hi all,
when reading the 833 tube data:
"type 833A requires special mounting and may be operated in vertical position with filemant end up or down, or in horixontal position with all terminals in the same vertical plane".
Very clea, i thought. So i was very surprised to see the Legend 200Se (so a 200 Watt SE 833-based amp). Although nice in set up:
- external power supply with 866's;
- nice lay out;
the 833 is lying horizontal BUT WRONG !!!!! (see picture). The tube data specifically tells you that all the terminals have to be in the same vertical plane. Which is logically: the filaments will expand during "on" and are in the Legend-case prone to actually touch the gridwire. and that will have a funny effect.
When i contacted the Legend-manufacturor about this there was total silence.......
Reinout
Hi all,
when reading the 833 tube data:
"type 833A requires special mounting and may be operated in vertical position with filemant end up or down, or in horixontal position with all terminals in the same vertical plane".
Very clea, i thought. So i was very surprised to see the Legend 200Se (so a 200 Watt SE 833-based amp). Although nice in set up:
- external power supply with 866's;
- nice lay out;
the 833 is lying horizontal BUT WRONG !!!!! (see picture). The tube data specifically tells you that all the terminals have to be in the same vertical plane. Which is logically: the filaments will expand during "on" and are in the Legend-case prone to actually touch the gridwire. and that will have a funny effect.
When i contacted the Legend-manufacturor about this there was total silence.......
Reinout
Attachments
Reinout
So much for my dreams of PP 833a. Better stick with se then. I think the rca/itt design seems fine. I don't need the swivel action. Will mount it like how you mount yours upright. At this moment i only see this mounting bracket to be a major hurdle. The rest is managable
Thanks for the pictures they explain alot. I might go with the wavac style, a plastic cage over it. That way still beautifull without the burning smell of burn fingers.
Cheers
So much for my dreams of PP 833a. Better stick with se then. I think the rca/itt design seems fine. I don't need the swivel action. Will mount it like how you mount yours upright. At this moment i only see this mounting bracket to be a major hurdle. The rest is managable
Thanks for the pictures they explain alot. I might go with the wavac style, a plastic cage over it. That way still beautifull without the burning smell of burn fingers.
Cheers
Hello Reinout,
Forget Legend Audio! Their 200W 833AE amp is a joke. It was meant for display only to get free puplicity for their line of product. Their last display at San Francisco Stereophile show was an amplifier with the tube submerge in water! Of course DIY knows that was another joke, their amp never made any sound. If you ask to purchase their amp, they never is available.
Only tube builder know how to align the filament when the tube is mounted in horizontal position.
Forget Legend Audio! Their 200W 833AE amp is a joke. It was meant for display only to get free puplicity for their line of product. Their last display at San Francisco Stereophile show was an amplifier with the tube submerge in water! Of course DIY knows that was another joke, their amp never made any sound. If you ask to purchase their amp, they never is available.
Only tube builder know how to align the filament when the tube is mounted in horizontal position.
Hello Reinout,
Back to the 833A again, did you ever thought of building a Parafeed 833A using PP output transformer? I have a nice pair of Tamura 2012 5K PP 100 watts and I would like to hear some feedback of Parafeed amp builder using PP xformer. The SE transformer that I have do not perform very well if the bias current is high in the bass, my guess is that the core is starting to saturate and the Inductance is not efficient.
Back to the 833A again, did you ever thought of building a Parafeed 833A using PP output transformer? I have a nice pair of Tamura 2012 5K PP 100 watts and I would like to hear some feedback of Parafeed amp builder using PP xformer. The SE transformer that I have do not perform very well if the bias current is high in the bass, my guess is that the core is starting to saturate and the Inductance is not efficient.
parafeed opt
Hello Unison845,
just spotted the pictures of the Legend. i never seen them "live". And with your comments: nobody heared them playing at all. What a fraud !! Trying to lure possible customers to you with non-functioning items. But now i do understand why i never got an answer from them !
About the opt:
- a SE opt has a air-gap in order to resist the saturation which is bound to happen with the continiously presence of DC. Simplified: a SE opt is chopped in 2 pieces so that the saturation level never will take place. That's why a SE opt has to be so extrmely well designed. For it will be "chopped" on purpose and still has to function ! No small feat.
- a PP opt has no DC (te be more correct: cancelled out), so there is no need for an air-gap. In these opt's the laminations are optimally used. Purely theoretical a PP opt is more efficient given its weight. The "problem" of PP is the introduction of a splitter, etc. But NOT the opt !
- a parafeed, or in my case ultra-parafeed also does not see DC in it's opt. Not by cancelling out as PP does, but by using a plate choke. The result is the same.
So i would certainly take the Tamura PP opt.
That the SE opt you've used does not "sound" nice is not because of core saturation. In a (ultra-)parafeed there is near zero DC-flux across the opt...so the basis of saturation is missing. And even if there was some DC....the airgap would prevent saturation.
What can be possible is indeed the Henry-item you already mentioned. The SE airgap does introduce a lot of Henrys..... And the SE opt is by definition a chopped up device trying to be as good as it can: but is is split/chopped/not-optimal.
So when going for (ultra-)parafeed stick to PP opt's and/or go all the way and chose really sensitive laminations like permalloy for there is almost nothing to saturate. You'll get the super-detail form the high nickel content core.
For there was not very much available when i did my 833-amps, i chose classic M6X. Nice and stable. Off course there is better (read: more sensitive), but it is sufficient for now. Maybe when finding very large permalloy laminations or something like that i'll switch to more exotic metals. Now it is a E126 opt. I have the opt been layered with kapton-foil. A very nice electrical insulating foil which is "safe" up to 8 kV ! More than spare.....
And because the theory does say....."near-zero" DC-flux i had a micro air-gap been placed just to be on the safe side. Now i've built and measured the amp.....i would not make that micro air-gap again and go for a PP-opt with fully interleaved laminations.
If you don't use the Tamura's.....i'm interested in them. does that says enough ?!
Included a picture of the innards of the amp. The opt is in the left upper corner. The E150 plate choke is in the top/middle. The small E96 transformer in the middle of the amp is the 300B-833 interstage.
With regards,
Reinout
Hello Unison845,
just spotted the pictures of the Legend. i never seen them "live". And with your comments: nobody heared them playing at all. What a fraud !! Trying to lure possible customers to you with non-functioning items. But now i do understand why i never got an answer from them !
About the opt:
- a SE opt has a air-gap in order to resist the saturation which is bound to happen with the continiously presence of DC. Simplified: a SE opt is chopped in 2 pieces so that the saturation level never will take place. That's why a SE opt has to be so extrmely well designed. For it will be "chopped" on purpose and still has to function ! No small feat.
- a PP opt has no DC (te be more correct: cancelled out), so there is no need for an air-gap. In these opt's the laminations are optimally used. Purely theoretical a PP opt is more efficient given its weight. The "problem" of PP is the introduction of a splitter, etc. But NOT the opt !
- a parafeed, or in my case ultra-parafeed also does not see DC in it's opt. Not by cancelling out as PP does, but by using a plate choke. The result is the same.
So i would certainly take the Tamura PP opt.
That the SE opt you've used does not "sound" nice is not because of core saturation. In a (ultra-)parafeed there is near zero DC-flux across the opt...so the basis of saturation is missing. And even if there was some DC....the airgap would prevent saturation.
What can be possible is indeed the Henry-item you already mentioned. The SE airgap does introduce a lot of Henrys..... And the SE opt is by definition a chopped up device trying to be as good as it can: but is is split/chopped/not-optimal.
So when going for (ultra-)parafeed stick to PP opt's and/or go all the way and chose really sensitive laminations like permalloy for there is almost nothing to saturate. You'll get the super-detail form the high nickel content core.
For there was not very much available when i did my 833-amps, i chose classic M6X. Nice and stable. Off course there is better (read: more sensitive), but it is sufficient for now. Maybe when finding very large permalloy laminations or something like that i'll switch to more exotic metals. Now it is a E126 opt. I have the opt been layered with kapton-foil. A very nice electrical insulating foil which is "safe" up to 8 kV ! More than spare.....
And because the theory does say....."near-zero" DC-flux i had a micro air-gap been placed just to be on the safe side. Now i've built and measured the amp.....i would not make that micro air-gap again and go for a PP-opt with fully interleaved laminations.
If you don't use the Tamura's.....i'm interested in them. does that says enough ?!
Included a picture of the innards of the amp. The opt is in the left upper corner. The E150 plate choke is in the top/middle. The small E96 transformer in the middle of the amp is the 300B-833 interstage.
With regards,
Reinout
Attachments
Hi Reinout,
is the paper in oil cap between choke/transformer the parafeed coupling cap?
What value? and did you try others?
what's the inductance for the choke?
That coupling cap is what I find the - point of parafeed, it's easier to find a high power pp transformer, and a high current choke too, compared with a high power, high current, high inductance SE transfromer.
BUT you need to use a capacitor to remove the dc for the output transformer. And in this case a very high voltage one, so there isn't much choice/availability as compared to 300b parafeed's.
I still have a couple of big russian pio's, 4uF, 1600v rated.
They would work well in this position, but I have no idea if they sound well.
Filip.
is the paper in oil cap between choke/transformer the parafeed coupling cap?
What value? and did you try others?
what's the inductance for the choke?
That coupling cap is what I find the - point of parafeed, it's easier to find a high power pp transformer, and a high current choke too, compared with a high power, high current, high inductance SE transfromer.
BUT you need to use a capacitor to remove the dc for the output transformer. And in this case a very high voltage one, so there isn't much choice/availability as compared to 300b parafeed's.
I still have a couple of big russian pio's, 4uF, 1600v rated.
They would work well in this position, but I have no idea if they sound well.
Filip.
Hello Reinout,
The Tamura F2012 is an excellent transformer. I have build a PP845 using it and it sounded very good, especially in the bass, it seems to go down much lower than SE. Measurement confirm this too.
Sorry but mine is to keep!
Now the problem is to find a plate choke that match the quality of the 2012, not very easy, the 2012 rated 200H, so to find a 200H/200-250ma choke is pretty tough. There is nothing available out there. I probably have to call and ask some winder regarding a big custom choke.
The Tamura F2012 is an excellent transformer. I have build a PP845 using it and it sounded very good, especially in the bass, it seems to go down much lower than SE. Measurement confirm this too.
Sorry but mine is to keep!
Now the problem is to find a plate choke that match the quality of the 2012, not very easy, the 2012 rated 200H, so to find a 200H/200-250ma choke is pretty tough. There is nothing available out there. I probably have to call and ask some winder regarding a big custom choke.