ChrisMmm said:
Yes, measure the primary DCR and the secondary DCR. Also measure voltage at the primary and the secondary, with the secondary unconnected. Right click on the transformer icon and you will see a dialog box labeled "edit transformer properties". Then click on the Ohms button in that dialog box and you will get a second dialog box ("source impedance calculator") to enter your measurements. PSUD will calculate the voltage and source impedance from those values.
Sheldon
power supply questions
I changed the PS filter to add an RC filter stage to drop the voltage - B+ now sitting on 291V. I also took the voltage and impedance measurements as suggested by Sheldon - PSUD is now within 5v of the actual result - I guess the 5U4 voltage drop is the last variable.
Also I did a comparison between my RH84 with SS diodes and the one I built my friend with the tube rectifier. The only difference between the two amps is the P/S (FRED diodes with CRCRCRC filter against 5U4 with CLC filter), we even used the same tubes. The SS version was clearly the better in terms of bass - much better definition. It also sounded more dynamic than the tube version which was a little veiled in comparison.
So why the difference? My assumption is that this was a result of the voltage "sag" in the 5U4 rectifier, in a sense I somewhat expected this (why I opted for SS). However, as I understand it, you get voltage "sag", to differing degrees, as a result of any component that has DCR in the PS chain (trafo secondary, resistor or choke). In the transistor/chip amps I have built in the past the PS never had chokes or resistors in order to minimise DCR - simple cap filter are the rule (possibly with snubbers). I know we are talking class "A" here which has less dynamic demand than the classic transistor AB amp but even class A transistor amps usually just have capacitor power supplies. So why the difference with tube amps? Am I correct in assuming you should always seek to minimise any resistance in the power supply?
Cheers
I changed the PS filter to add an RC filter stage to drop the voltage - B+ now sitting on 291V. I also took the voltage and impedance measurements as suggested by Sheldon - PSUD is now within 5v of the actual result - I guess the 5U4 voltage drop is the last variable.
Also I did a comparison between my RH84 with SS diodes and the one I built my friend with the tube rectifier. The only difference between the two amps is the P/S (FRED diodes with CRCRCRC filter against 5U4 with CLC filter), we even used the same tubes. The SS version was clearly the better in terms of bass - much better definition. It also sounded more dynamic than the tube version which was a little veiled in comparison.
So why the difference? My assumption is that this was a result of the voltage "sag" in the 5U4 rectifier, in a sense I somewhat expected this (why I opted for SS). However, as I understand it, you get voltage "sag", to differing degrees, as a result of any component that has DCR in the PS chain (trafo secondary, resistor or choke). In the transistor/chip amps I have built in the past the PS never had chokes or resistors in order to minimise DCR - simple cap filter are the rule (possibly with snubbers). I know we are talking class "A" here which has less dynamic demand than the classic transistor AB amp but even class A transistor amps usually just have capacitor power supplies. So why the difference with tube amps? Am I correct in assuming you should always seek to minimise any resistance in the power supply?
Cheers
DELIGHTED
Dear all,
a reply to thread reminder caught my attention a few days ago: and what do I see? A lot of people is still making the RH84 amp. I am, simply, delighted to see that people still enjoy my design after all this time, and still find it interesting and competitive.
I am also happy to see that in the end the amp design has achieved what I was hoping for: the audio section design is followed closely (and frankly it should be) while on the other hand there is much experimenting with various power supplies. The original power supply was just 47uF - 10H (approx) - 220uV... and was deliberately simplified to encourage experimenters.
I personally prefer tube rectifiers, to the point that I frankly cannot imagine using solid state diodes any more (except in hybrid graetz configuration where they come in handy without changing the sound).
Finally, I must add that I envy you all for the fact that you can embark on the DIY journey and make amps and experiment... I have not built anything for years now, but hope and plan to be back relatively soon with the finalization of RH 2nd generation designes which are better, more powerful (other tubes involved, obviously) and simpler than the first generation was.
Regards to all,
Alex
Dear all,
a reply to thread reminder caught my attention a few days ago: and what do I see? A lot of people is still making the RH84 amp. I am, simply, delighted to see that people still enjoy my design after all this time, and still find it interesting and competitive.
I am also happy to see that in the end the amp design has achieved what I was hoping for: the audio section design is followed closely (and frankly it should be) while on the other hand there is much experimenting with various power supplies. The original power supply was just 47uF - 10H (approx) - 220uV... and was deliberately simplified to encourage experimenters.
I personally prefer tube rectifiers, to the point that I frankly cannot imagine using solid state diodes any more (except in hybrid graetz configuration where they come in handy without changing the sound).
Finally, I must add that I envy you all for the fact that you can embark on the DIY journey and make amps and experiment... I have not built anything for years now, but hope and plan to be back relatively soon with the finalization of RH 2nd generation designes which are better, more powerful (other tubes involved, obviously) and simpler than the first generation was.
Regards to all,
Alex
Re: DELIGHTED
It's probably safe to say that the RH G-2 (series?) will be on many a project list once the schema are made available. I built a pair of monoblocks several years ago based on the RH topology that are still putting a smile on faces.
An updated version for either EL34 or 6550 would be very interesting.
Alex Kitic said:
It's probably safe to say that the RH G-2 (series?) will be on many a project list once the schema are made available. I built a pair of monoblocks several years ago based on the RH topology that are still putting a smile on faces.
An updated version for either EL34 or 6550 would be very interesting.
Hi Alex,
Good to see your post. I came accross and built your design well after you put it up but it still seemed to be the best of the bunch for my first tube amp build.
Appreciate your comments about power supply. As I had posted when we compared SS to tube rectifier versions the SS one appeared to be better (mainly bass). However I subsequantly change the PS on the tube rect. one adding an RC after the CLC filter to drop the voltage (we had 330v originally, got it down to just over 290v now). I have not listened to it but my friend says it now equals the SS version in the bass so maybe the culprit was the high B+ voltage.
I have also briefly substituted some better OPTs on my SS version and the bass is even better - tighter, more controlled.
About to embark on a RH807 for my friend who needs a few more watts, will be using some quality OPTs in it so I am eager to see how that turns out.
Thanks again for a great design and sharing.
Good to see your post. I came accross and built your design well after you put it up but it still seemed to be the best of the bunch for my first tube amp build.
Appreciate your comments about power supply. As I had posted when we compared SS to tube rectifier versions the SS one appeared to be better (mainly bass). However I subsequantly change the PS on the tube rect. one adding an RC after the CLC filter to drop the voltage (we had 330v originally, got it down to just over 290v now). I have not listened to it but my friend says it now equals the SS version in the bass so maybe the culprit was the high B+ voltage.
I have also briefly substituted some better OPTs on my SS version and the bass is even better - tighter, more controlled.
About to embark on a RH807 for my friend who needs a few more watts, will be using some quality OPTs in it so I am eager to see how that turns out.
Thanks again for a great design and sharing.
Since I originally posted this thread I am pleased to announce that I finally built a SE EL84 amp. The RH84 was the the amp of choice and I must say it is a beauty; sound wise that is. Looks wise it's not so great due to it being built as a bread board with junk box parts but it does sound great!
Now to get some quality parts and see where this takes me...
Thanks Alex for sharing your design with the DIY world. Can't wait for your 2nd generation amp designs.
Lastly, does anyone have design tweeks in which I could try? P10's mod might cost a bit more $$$ but might be interesting...
Now to get some quality parts and see where this takes me...
Thanks Alex for sharing your design with the DIY world. Can't wait for your 2nd generation amp designs.
Lastly, does anyone have design tweeks in which I could try? P10's mod might cost a bit more $$$ but might be interesting...
Not having heard of a Graetz bridge I google it and find in Wiki that its a bridge rectifier! Surely I am missing something here? And Alex mentions hybrid graetz, this the sort of thing
http://www.radiomuseum.org/forumdata/upload/EZ%2DBr%FCcke2%2Epng
What are the advantages?
Dave, if you are using Solens I assume they aren't as large capacitance as one would use with electrilytics? I have some 20uf ones lying around from a speaker project that didn't get built, they would be a good start I guess (must check voltage).
Cheers
http://www.radiomuseum.org/forumdata/upload/EZ%2DBr%FCcke2%2Epng
What are the advantages?
Dave, if you are using Solens I assume they aren't as large capacitance as one would use with electrilytics? I have some 20uf ones lying around from a speaker project that didn't get built, they would be a good start I guess (must check voltage).
Cheers
ChrisMmm said:
A bridge is more efficient than a full wave rectifier. The peak inverse voltage is also half of that for a FWR. With a hybrid bridge, the tube gives a slower turn on, and it also controls the diode cut off. The latter attribute minimizes hash from the SS diode cut off. The tube characteristics dominate the character. If you want that character, only one rectifier tube is required for a hybrid bridge.
Sheldon
Thanks, I have been to that site before but not that page - some very useful stuff there.
Interesting snippets from there "The main reasons for using a valve rectifier are to create 'sag' in a Class-AB amp..." then later "Valve rectifiers do not produce such pronounced switching spikes as silicon diodes..."
I am assuming the main reason to use tube rectifiers in a class A amp is to eliminate the spikes/noise of SS and that sag is not an issue due to the more constant current needs of class A. I am still undecided if I should use SS or tube rectification in my next project however it seems the majority of tube amp builders prefer tube rectifiers.
Cheers
Interesting snippets from there "The main reasons for using a valve rectifier are to create 'sag' in a Class-AB amp..." then later "Valve rectifiers do not produce such pronounced switching spikes as silicon diodes..."
I am assuming the main reason to use tube rectifiers in a class A amp is to eliminate the spikes/noise of SS and that sag is not an issue due to the more constant current needs of class A. I am still undecided if I should use SS or tube rectification in my next project however it seems the majority of tube amp builders prefer tube rectifiers.
Cheers
HYBRID GRAETZ
The main reason I made the first hybrid bridge was necessity: I had no adequate HT transformers at hand and had to make do with what I had (let us call it poverty. It may seem preposterous, but at the time I did not know that the topology was relatively widely known, and was almost under the impression that it was an invention of mine
Thus I tried the hybrid bridge before the regular valve rectifier as it was meant to be used... and later found out that the sound is the same (almost, but very convincingly so) as if I was using the valve rectifier in a conventional application.
I continue using both configurations, hybrid and conventional valve rectifier to this day, depending on the HT power transformer at hand. Also, when ordering a new transformer, possibly toroidal (space concerns), it is always cheaper and simpler (and most probably safer) to order a conventional secondary as opposed to a secondary with center tap.
Finally, an idea, if others have not come to that already is paralleled or even series transformers. Imagine you need several LT secondaries, and a higher current from the HT secondary. Or, that you need higher B+ and put two secondaries in series, lowering the B+ by adoption of a LC type PS (choke first)... in the end, you might end surprised by the sonic advantage of an inefficient power supply (the more V you loose thru chokes and stuff, the better).
Regards,
Alex
The main reason I made the first hybrid bridge was necessity: I had no adequate HT transformers at hand and had to make do with what I had (let us call it poverty. It may seem preposterous, but at the time I did not know that the topology was relatively widely known, and was almost under the impression that it was an invention of mine
Thus I tried the hybrid bridge before the regular valve rectifier as it was meant to be used... and later found out that the sound is the same (almost, but very convincingly so) as if I was using the valve rectifier in a conventional application.
I continue using both configurations, hybrid and conventional valve rectifier to this day, depending on the HT power transformer at hand. Also, when ordering a new transformer, possibly toroidal (space concerns), it is always cheaper and simpler (and most probably safer) to order a conventional secondary as opposed to a secondary with center tap.
Finally, an idea, if others have not come to that already
is paralleled or even series transformers. Imagine you need several LT secondaries, and a higher current from the HT secondary. Or, that you need higher B+ and put two secondaries in series, lowering the B+ by adoption of a LC type PS (choke first)... in the end, you might end surprised by the sonic advantage of an inefficient power supply (the more V you loose thru chokes and stuff, the better).Regards,
Alex
Hi Alex!
I found this thread and your website after a friend of mine wanted to build a simple single-ended tube amp.
After reading through all these pages I found it to be very informative and I'm glad I found your RH84 design.
My friend built his already and is waiting for the new caps to burn-in, but he is "stoked" at how nice it sounds and now I'm looking at building one for myself.
I will have a pair of One Electron UBT-3 SE trannys coming my way soon but they are 3K ohm primaries. Could I use 8 ohm speakers on the 4 ohm taps and have a reflected impedance of 6 k ohms back to the output tube?
My other trannys are smallish console amp type and it would be a way for me to use some nicer trannys with this design!
Regards and thanks for sharing your design with us!
Ron
I found this thread and your website after a friend of mine wanted to build a simple single-ended tube amp.
After reading through all these pages I found it to be very informative and I'm glad I found your RH84 design.
My friend built his already and is waiting for the new caps to burn-in, but he is "stoked" at how nice it sounds and now I'm looking at building one for myself.
I will have a pair of One Electron UBT-3 SE trannys coming my way soon but they are 3K ohm primaries. Could I use 8 ohm speakers on the 4 ohm taps and have a reflected impedance of 6 k ohms back to the output tube?
My other trannys are smallish console amp type and it would be a way for me to use some nicer trannys with this design!
Regards and thanks for sharing your design with us!
Ron
UBT-3 info
http://www.one-electron.com/Trans/UBT3_10.pdf
Just in case anyone was interested in knowing what trannys these were.
Regards, Ron
http://www.one-electron.com/Trans/UBT3_10.pdf
Just in case anyone was interested in knowing what trannys these were.
Regards, Ron
hi guys.
i built one of the rh84 last week and it was my first build it turn out
very nice so far but for some reason am not getting 300b+. mine's at 265b+ and 261 at the plate 8v at cathode to ground screen at 154
the only thing different is that i use a 15h-75ma choke and 250ohm cathode resister instead of the 270ohms.
as of now am very satisfied with it but i would like to get closer to the intended designed .
BTW: all tube tested strong but ptrany run very hot after about an hour.
i built one of the rh84 last week and it was my first build it turn out
very nice so far but for some reason am not getting 300b+. mine's at 265b+ and 261 at the plate 8v at cathode to ground screen at 154
the only thing different is that i use a 15h-75ma choke and 250ohm cathode resister instead of the 270ohms.
as of now am very satisfied with it but i would like to get closer to the intended designed .
BTW: all tube tested strong but ptrany run very hot after about an hour.
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