Is it a 272JX?
I'd like to see the 5.0 and 6.3 as close to spec as possible. You certainly don't want them more than 10% over spec (no more than 5.5 and 6.9).
If the filaments are running more than 10% over, consider installing a small bucking autoformer under the chassis. It'll help drop all the voltages closer to where they ought to be.
Maybe read this thread from post #14 down...
http://www.diyaudio.com/forums/showthread.php?postid=1672114#post1672114
I'd like to see the 5.0 and 6.3 as close to spec as possible. You certainly don't want them more than 10% over spec (no more than 5.5 and 6.9).
If the filaments are running more than 10% over, consider installing a small bucking autoformer under the chassis. It'll help drop all the voltages closer to where they ought to be.
Maybe read this thread from post #14 down...
http://www.diyaudio.com/forums/showthread.php?postid=1672114#post1672114
Yes Is it a 272JX hammond would the Hammond 272FX ( 300-0-300, DC mA: 150, Fil. #1 Rectifier: 5.0V/3A CT, Fil. #2 Heater: 6.3V/5.0A CT) be a better choice? if it is i rather exchange the PTX altogether than to do the bucking trans , i dont think i have enough room under the chassis. i will know if the filament voltage is within spec when i get home. by your experence it seem like it wont be.
Unfortunately, all the Hammond 200 series power transformers are wound for 115VAC on the primary. If you put more than 115 in, you'll get more than the rated voltage out. Dropping down to smaller rated 272 might lower the B+ a bit, but probably won't have a whole lot of effect on the filament voltages.
You could use their 300 series transformers. One of the 370 models would probably be perfect, perhaps the DX or maybe the EX. These transformers have a "universal" primary, which can be connected for a variety of different input voltages. I used a 374BX on one of my projects, and all the voltages came out pretty much exactly where they should. The down side is that the 300 series units cost a lot more. They're also physically larger than the 200 series.
You could also put small (~0.1 ohm) resistors in series with the heater leads. At a 2 amp draw, each tenth of an ohm will drop two tenths of a volt. They will get hot, and they need to be cemented wire-wound types - probably 3 watters or so.
Check it first and see. Maybe there is no problem to be fixed.
You could use their 300 series transformers. One of the 370 models would probably be perfect, perhaps the DX or maybe the EX. These transformers have a "universal" primary, which can be connected for a variety of different input voltages. I used a 374BX on one of my projects, and all the voltages came out pretty much exactly where they should. The down side is that the 300 series units cost a lot more. They're also physically larger than the 200 series.
You could also put small (~0.1 ohm) resistors in series with the heater leads. At a 2 amp draw, each tenth of an ohm will drop two tenths of a volt. They will get hot, and they need to be cemented wire-wound types - probably 3 watters or so.
Check it first and see. Maybe there is no problem to be fixed.
HIGHER AND LOWER
I design my amps and preamps around the preamble that "everyone should be able to do it" and taking care that the equipment functions without problem within a wide range of B+.
Therefore, the RH84 would work without problems between some 150V and 300+V... from a point where tubes are starving to a point where the output tube is subject to "cherry anodes". Obviously, the best way is to make it work at near 12W anode dissipation at the output tube (almost 100%) where the power and everything else would be at its prime.
There is no need to worry about the ECC81 -- it will work in all the conditions the output tube can endure (never too much voltage, or current).
When it comes to filaments, I tend to "overheat" to 6.6 for the 6.3 and 5.2 or 5.3 for the 5V needed by the rectifier. I prefer the "heated and faster" sound. Of course, never too much, as there is no need to "kill the tubes".
There are several ways to lower the AC on the primary, but the BEST is to find a transformer which is fit for the task -- not too large and not too small.
Regards to all,
Alex
I design my amps and preamps around the preamble that "everyone should be able to do it" and taking care that the equipment functions without problem within a wide range of B+.
Therefore, the RH84 would work without problems between some 150V and 300+V... from a point where tubes are starving to a point where the output tube is subject to "cherry anodes". Obviously, the best way is to make it work at near 12W anode dissipation at the output tube (almost 100%) where the power and everything else would be at its prime.
There is no need to worry about the ECC81 -- it will work in all the conditions the output tube can endure (never too much voltage, or current).
When it comes to filaments, I tend to "overheat" to 6.6 for the 6.3 and 5.2 or 5.3 for the 5V needed by the rectifier. I prefer the "heated and faster" sound. Of course, never too much, as there is no need to "kill the tubes".
There are several ways to lower the AC on the primary, but the BEST is to find a transformer which is fit for the task -- not too large and not too small.
Regards to all,
Alex
rookie mistake
first of all i want to thanks everyone for helping me out , the problem was not the hardwares it was me , i miss something that was very basic. the 5u4 was not wired correctly
i connect the 300V to pin 4 & 5 instead of 4 & 6 (oops) dumb i know.so thats explain the low B+ i was getting, so after all the headache i've put you guys through " SORRY ". its now running perfectly with the old PTX all measure verry close to desire voltage ,
oh and its sounds allot better. but on the bright side of thing i have learn so much from this build .
Thanks again guys.
TIM
first of all i want to thanks everyone for helping me out , the problem was not the hardwares it was me , i miss something that was very basic. the 5u4 was not wired correctly
i connect the 300V to pin 4 & 5 instead of 4 & 6 (oops) dumb i know.so thats explain the low B+ i was getting, so after all the headache i've put you guys through " SORRY ". its now running perfectly with the old PTX all measure verry close to desire voltage ,oh and its sounds allot better. but on the bright side of thing i have learn so much from this build .
Thanks again guys.
TIM
6p14p/6p15p
I've made plenty of mistakes and asked lots a stoopid questions - its one of the best ways to learn
Talking of which I have been playing around with my RH84 to learn about other ways of hooking up the output tube and the effects.
1. Removed feedback and hooked the output tube up triode mode via 900ohm resistor (I know its usually 1-200ohm but more on this later)
2. hooked up cathode bypass cap for cathode feedback
3. hooked up fou UL operation
All worked well - UL and cathode feedback seemed to give tighter bass response.
Then tried replacing the 6p14p with a 6p15p as I had heard these have a slightly more dynamic sound than the EL84. This was in the UL setup with 900ohm resistor from G2, G3 left floating. This, other than UL, is much as used in the ZEN EL84 amp. But there was gross distortion, the tube was not happy like this.
I know that G2 needs to be a lower voltage in this tube, does that mean using in UL is out? I will try triode hookup tonite but any insight into what is happening very welcome.
Cheers,
I've made plenty of mistakes and asked lots a stoopid questions - its one of the best ways to learn
Talking of which I have been playing around with my RH84 to learn about other ways of hooking up the output tube and the effects.
1. Removed feedback and hooked the output tube up triode mode via 900ohm resistor (I know its usually 1-200ohm but more on this later)
2. hooked up cathode bypass cap for cathode feedback
3. hooked up fou UL operation
All worked well - UL and cathode feedback seemed to give tighter bass response.
Then tried replacing the 6p14p with a 6p15p as I had heard these have a slightly more dynamic sound than the EL84. This was in the UL setup with 900ohm resistor from G2, G3 left floating. This, other than UL, is much as used in the ZEN EL84 amp. But there was gross distortion, the tube was not happy like this.
I know that G2 needs to be a lower voltage in this tube, does that mean using in UL is out? I will try triode hookup tonite but any insight into what is happening very welcome.
Cheers,
TRIODE, UL, AND PENTODE MODE
My RH84 - long time ago given to a friend - had a switch enablig shifting from triode to pentode RH mode. The switch did two functions:
1) disconnect Rfb
2) disconnect Rg2 from B+ and connect to anode.
I even used to switch it "hot" (EL84s are small money if you live in Serbia where Ei produces them) without having any problems (good switch, one per channel) in doing it (tubes are very tough).
It is logical to swith Rfb off when in triode mode, since the general idea was to test the sound of the triode mode vs the sound of the pentode mode -- and then compare the available power (how loud can you go).
On the other hand, I never had at hand UL transformers, therefore I was never contemplating the alternative to put some switch for comparison or use purposes (I have first encountered those switches on VTL amps, particularly their 807PP amp with switchable triode/tetrode and feedback modes). BUT, if I were to use it in UL mode, I would most certainly leave the Rfb (because that is where the game is, actually). Of course, the gain would be lower, since the UL path represents a form of feedback, to put it simple.
Therefore, when experimenting, try the UL with Rfb.
Another issue is the CRk on the output tube, absolutely necessary (no need to go into cathode degeneration here, really). On the other hand, the driver tube needs not to have a CRk to allow the RH circuit to function properly.
When it comes to putting other tubes, like the SV83, you must take into account that those are indeed different tubes. The SV83 is mostly used at lower voltages, with more current being drawn, and has different curves... The fact that it is used in the Zen Amp which has extremely simple circuitry without any additional toughts hidden inside, does not mean that it will serve as replacement elsewhere. Furthermore, the SV83 does not have the same pin connections -- I cannot possibly remember every single detail for years but I remember that there is a small but important difference (like two pins that are the same connection on the EL84 are separate on the SV83, and the g3 is not connected to the anode inside the tube, but has its own pin like in signal pentodes...). If you did not connect the g3, or made a similar involontary mistake, that would explain the problems experienced!
Regards,
Alex
My RH84 - long time ago given to a friend - had a switch enablig shifting from triode to pentode RH mode. The switch did two functions:
1) disconnect Rfb
2) disconnect Rg2 from B+ and connect to anode.
I even used to switch it "hot" (EL84s are small money if you live in Serbia where Ei produces them) without having any problems (good switch, one per channel) in doing it (tubes are very tough).
It is logical to swith Rfb off when in triode mode, since the general idea was to test the sound of the triode mode vs the sound of the pentode mode -- and then compare the available power (how loud can you go).
On the other hand, I never had at hand UL transformers, therefore I was never contemplating the alternative to put some switch for comparison or use purposes (I have first encountered those switches on VTL amps, particularly their 807PP amp with switchable triode/tetrode and feedback modes). BUT, if I were to use it in UL mode, I would most certainly leave the Rfb (because that is where the game is, actually). Of course, the gain would be lower, since the UL path represents a form of feedback, to put it simple.
Therefore, when experimenting, try the UL with Rfb.
Another issue is the CRk on the output tube, absolutely necessary (no need to go into cathode degeneration here, really). On the other hand, the driver tube needs not to have a CRk to allow the RH circuit to function properly.
When it comes to putting other tubes, like the SV83, you must take into account that those are indeed different tubes. The SV83 is mostly used at lower voltages, with more current being drawn, and has different curves... The fact that it is used in the Zen Amp which has extremely simple circuitry without any additional toughts hidden inside, does not mean that it will serve as replacement elsewhere. Furthermore, the SV83 does not have the same pin connections -- I cannot possibly remember every single detail for years but I remember that there is a small but important difference (like two pins that are the same connection on the EL84 are separate on the SV83, and the g3 is not connected to the anode inside the tube, but has its own pin like in signal pentodes...). If you did not connect the g3, or made a similar involontary mistake, that would explain the problems experienced!
Regards,
Alex
Thanks Alex,
Maybe I will confine my experiments to EL84 type tubes for now!
Thanks for the guidance, I will try the feedback resistor in UL as well and see how that sounds.
Re the cathode capacitor - I have not removed it but rewired it for "cathode feedback" as suggested by tubelab for his Simple SE design to improve cheaper OPTs such as the Edcor ones I have in the RH84. This is achieved by connecting the "-" capacitor lead to the output of the OPT while the other output terminal of the OPT is earthed. Which is earthed and which is connected to the cap varies with the OPT make apparantly. Sorry if I am explaining something you already understand!
Maybe I will confine my experiments to EL84 type tubes for now!
Thanks for the guidance, I will try the feedback resistor in UL as well and see how that sounds.
Re the cathode capacitor - I have not removed it but rewired it for "cathode feedback" as suggested by tubelab for his Simple SE design to improve cheaper OPTs such as the Edcor ones I have in the RH84. This is achieved by connecting the "-" capacitor lead to the output of the OPT while the other output terminal of the OPT is earthed. Which is earthed and which is connected to the cap varies with the OPT make apparantly. Sorry if I am explaining something you already understand!
Alex:
I've mentioned this before (actually just looked at some dated sketches, and it was over 4yrs ago!), but another very interesting driver for the RH84 is a triode connected EF86.
I built a pair of monoblocks, which due to the nature of frugally salvaged components, ended up as a hybrid of the RH feedback technique and parafeed output stage.
Choke filtered supply with 270volts on plate of EL84 (@ 38mA), and 150V on EF86 (@ 1.8mA ) - this was a much sweeter sounding combination for me than a stereo version with ECC81 & variants.
I've been a bit busy with speaker projects since, and didn't follow up - did you ever contemplate or complete a version for the EL34?
I've mentioned this before (actually just looked at some dated sketches, and it was over 4yrs ago!), but another very interesting driver for the RH84 is a triode connected EF86.
I built a pair of monoblocks, which due to the nature of frugally salvaged components, ended up as a hybrid of the RH feedback technique and parafeed output stage.
Choke filtered supply with 270volts on plate of EL84 (@ 38mA), and 150V on EF86 (@ 1.8mA ) - this was a much sweeter sounding combination for me than a stereo version with ECC81 & variants.
I've been a bit busy with speaker projects since, and didn't follow up - did you ever contemplate or complete a version for the EL34?
Sorry for my double-post,
but I feel I have to say something...
First of all, sorry Alex that I was so eager to post your schematic,
I mean, it's your design...
However, I made the RH34SE and I love it.
Never got to painting / polishing the case further,
it's still in the state of the pictures.
Still, I find the RH84SE a wee bit more refined, more detailed.
It can be due to the output transformers I used, or maybe a
difference in the PSU (The RH84 using solid state diodes),
maybe it's just the '84 compared to the '34.
....apples & oranges....
Unfortunatly, my RH84 is on a loan at a friends house,
and he somehow keeps forgetting to give it back
It's the first single-ended amp he ever heard on his system...
But, what I wonder, is will a RH-mode push-pull amp work ?
I got a pair of nice input transformers I could use as phase
splitters, and then basically two RH..SE's connected to a PP-opt ?
Only thing about the input-transformers is they are 1:0.5+0.5,
so I'm gonna need an additional stage to boost the input so I can
get maximum output with my DAC (putting out 2,1V max)
Anyone got a good idea to make a refined driver stage for
my input transformers ?
Cheers !
Empee
but I feel I have to say something...
First of all, sorry Alex that I was so eager to post your schematic,
I mean, it's your design...
However, I made the RH34SE and I love it.
Never got to painting / polishing the case further,
it's still in the state of the pictures.
Still, I find the RH84SE a wee bit more refined, more detailed.
It can be due to the output transformers I used, or maybe a
difference in the PSU (The RH84 using solid state diodes),
maybe it's just the '84 compared to the '34.
....apples & oranges....
Unfortunatly, my RH84 is on a loan at a friends house,
and he somehow keeps forgetting to give it back
It's the first single-ended amp he ever heard on his system...
But, what I wonder, is will a RH-mode push-pull amp work ?
I got a pair of nice input transformers I could use as phase
splitters, and then basically two RH..SE's connected to a PP-opt ?
Only thing about the input-transformers is they are 1:0.5+0.5,
so I'm gonna need an additional stage to boost the input so I can
get maximum output with my DAC (putting out 2,1V max)
Anyone got a good idea to make a refined driver stage for
my input transformers ?
Cheers !
Empee
EF 86 as driver
It is quite possible that the EF86 fits the bill very nicely in triode mode. I should check the cruves (and characteristics) of the EF86 in triode mode to see which triode tube it fits best -- but I presume it looks similar to the ECC81.
Personally, I have used the E180CC as a "better sounding substitute", although frankly I think that it is not only about the tube type, but the workmanship of the tube itself (it DOES matter whether it is black anode or not, whether it is premium construction or not...).
The important issue for a substitute is a combination of mu and transconductance, whereas the ECC83 with highest mu and lowish transconductance can be used as driver in the same schematics, but the 5751 cannot due to a lower mu than ECC83 and still lowish transconductance. Other tubes, with mu around 45 and high transconductance might replace the ECC81 fitting the bill even better.
Just a short note, for now, on PP application: as I wrote somewhere earlier, imagine two channels placed as two halves of the PP amp. Now all you need is a phase splitter: and there is where the pain begins. Frankly, the main reason why I do not design PPs and do not build them, as well, is the phase splitter (always a compromise, never symmetric enough to satisfy my wish).
You could try input transformers, but those are going to cost and add additional complication to the amp. Maybe the best solution would be some long tail or similia?
Regards,
Alex
It is quite possible that the EF86 fits the bill very nicely in triode mode. I should check the cruves (and characteristics) of the EF86 in triode mode to see which triode tube it fits best -- but I presume it looks similar to the ECC81.
Personally, I have used the E180CC as a "better sounding substitute", although frankly I think that it is not only about the tube type, but the workmanship of the tube itself (it DOES matter whether it is black anode or not, whether it is premium construction or not...).
The important issue for a substitute is a combination of mu and transconductance, whereas the ECC83 with highest mu and lowish transconductance can be used as driver in the same schematics, but the 5751 cannot due to a lower mu than ECC83 and still lowish transconductance. Other tubes, with mu around 45 and high transconductance might replace the ECC81 fitting the bill even better.
Just a short note, for now, on PP application: as I wrote somewhere earlier, imagine two channels placed as two halves of the PP amp. Now all you need is a phase splitter: and there is where the pain begins. Frankly, the main reason why I do not design PPs and do not build them, as well, is the phase splitter (always a compromise, never symmetric enough to satisfy my wish).
You could try input transformers, but those are going to cost and add additional complication to the amp. Maybe the best solution would be some long tail or similia?
Regards,
Alex
rh 2nd generation schematics
Apologies to all those who are still waiting for my reply: I must find a few (more than a few, actually) moments to sit by my computer at home and reply to all emails -- forwarding schematics for the RH88 and of course the RH300B.
Also, I should find a few more moments to draw a classical schematic which is more straightforward than my simulation that I usually forward
Those who have already received the schematics and eventually tried some of it... might post their opinions.
Regards,
Alex
Apologies to all those who are still waiting for my reply: I must find a few (more than a few, actually) moments to sit by my computer at home and reply to all emails -- forwarding schematics for the RH88 and of course the RH300B.
Also, I should find a few more moments to draw a classical schematic which is more straightforward than my simulation that I usually forward
Those who have already received the schematics and eventually tried some of it... might post their opinions.
Regards,
Alex
Re: rh 2nd generation schematics
I received the RH88 schematic from Alex and quickly modified my Mikael Abdellah's SE KT88, replaced the driver tube with 12at7 and wired the KT88 in pentode.
Sound is more dynamic, faster and have better slam. To me the RH88 sounded in between an SE KT88 and a PP KT88. You can say it is the best of both topologies.
I will wire a switch for Triode strapped, Ultralinear and Pentode, just to see how it compares (If my friend will ever return my amp, he begged me to loan it to him after I re-wired it to the RH88 circuit).
More impressions later.
-AlexG
Alex Kitic said:Apologies to all those who are still waiting for my reply: I must find a few (more than a few, actually) moments to sit by my computer at home and reply to all emails -- forwarding schematics for the RH88 and of course the RH300B.
Also, I should find a few more moments to draw a classical schematic which is more straightforward than my simulation that I usually forward
Those who have already received the schematics and eventually tried some of it... might post their opinions.
Regards,
Alex
I received the RH88 schematic from Alex and quickly modified my Mikael Abdellah's SE KT88, replaced the driver tube with 12at7 and wired the KT88 in pentode.
Sound is more dynamic, faster and have better slam. To me the RH88 sounded in between an SE KT88 and a PP KT88. You can say it is the best of both topologies.
I will wire a switch for Triode strapped, Ultralinear and Pentode, just to see how it compares (If my friend will ever return my amp, he begged me to loan it to him after I re-wired it to the RH88 circuit).
More impressions later.
-AlexG
Re: Re: Re: rh 2nd generation schematics
Emailed the schematic to you, did you get it?
It will work but with severely diminished gain, 12bh7 have only 1/3 of the gain of 12at7.
On the RH88, I used 12at7 as recommended by Alex Kitic, and it sounded nice. I might try 12sl7 next time, I have a few of these octal tubes.
korneluk said:
Emailed the schematic to you, did you get it?
It will work but with severely diminished gain, 12bh7 have only 1/3 of the gain of 12at7.
On the RH88, I used 12at7 as recommended by Alex Kitic, and it sounded nice. I might try 12sl7 next time, I have a few of these octal tubes.
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