Hi people,
Here's a link to a tube stage I intend to build for my pioneer pd-s 703,
http://www.ultranalog.com/cdenhancer/cdenhancer2.html
Here's the schematic, http://www.ultranalog.com/cdenhancer/cdenhancer2_3a5.pdf
I live in the UK and on some investigation, I have managed to find stockists of the tubes, and output transformers (sowter).
However I can not seem to find a required mains transformer to provide the exact 100v outputs for the circuit. I do know that maplins do have mains isolation transformers which provide around 115v, perhaps I could use one of these instead, and drop the voltage with a resistor???
Or does anyone know of an off the shelf type which is suitable?
I ask this as it may be cheaper than having a custom tranny wound for me.
Also the 4H choke, does anyone know of a stockist in the UK, Sowter does have them but not at this value which means I need a custom one, this might be expensive?????
I do know that Maplins have a 10H choke which is quite cheap, and if possible I would like to use this.
Just thought I would ask more experienced people before making assumptions on how to get the correct rail voltages and filtering by using substitute parts.
I am reasonably confident I can do this, I have built SS kits before, and can now read schematics well enough to understand how this links together.
Thanks
Raja
Here's a link to a tube stage I intend to build for my pioneer pd-s 703,
http://www.ultranalog.com/cdenhancer/cdenhancer2.html
Here's the schematic, http://www.ultranalog.com/cdenhancer/cdenhancer2_3a5.pdf
I live in the UK and on some investigation, I have managed to find stockists of the tubes, and output transformers (sowter).
However I can not seem to find a required mains transformer to provide the exact 100v outputs for the circuit. I do know that maplins do have mains isolation transformers which provide around 115v, perhaps I could use one of these instead, and drop the voltage with a resistor???
Or does anyone know of an off the shelf type which is suitable?
I ask this as it may be cheaper than having a custom tranny wound for me.
Also the 4H choke, does anyone know of a stockist in the UK, Sowter does have them but not at this value which means I need a custom one, this might be expensive?????
I do know that Maplins have a 10H choke which is quite cheap, and if possible I would like to use this.
Just thought I would ask more experienced people before making assumptions on how to get the correct rail voltages and filtering by using substitute parts.
I am reasonably confident I can do this, I have built SS kits before, and can now read schematics well enough to understand how this links together.
Thanks
Raja
Hi,
I don't see much of a problem with the powerxformers being a little hotter than needed.
Prior to buying the chokes have a look at their DC resistance, 10H choke normally have higher DCR than say, a 4H choke.
BTW, Ultranolg is a member here although it's been quite awhile since he last posted.
Maybe you could buy all the iron where he had it made?
AE is contactable here:
Automatic Electric Europe.
Mr. Wil Blauw is the man behind the iron.
Cheers,
I don't see much of a problem with the powerxformers being a little hotter than needed.
Prior to buying the chokes have a look at their DC resistance, 10H choke normally have higher DCR than say, a 4H choke.
BTW, Ultranolg is a member here although it's been quite awhile since he last posted.
Maybe you could buy all the iron where he had it made?
AE is contactable here:
Automatic Electric Europe.
Mr. Wil Blauw is the man behind the iron.
Cheers,
Tried contacting ultranalogue, but he's knda reluctant to tell too much (for the simple reason of not having anyone blaming him for mishaps I suppose!), didn't manage to get past him telling me to buy a scope - fair play to him!!!!
Yeah I suppose I could always use the 115v isolation transfo, and tthe 10H choke and measure the rail once it's up and running, I don't suppose say 2-5v either way should result in catastrophe???
Thanks once again for your kind help,
Raja
Yeah I suppose I could always use the 115v isolation transfo, and tthe 10H choke and measure the rail once it's up and running, I don't suppose say 2-5v either way should result in catastrophe???
Thanks once again for your kind help,
Raja
Hi,
Ah...that was you?
Nah, Remco (Ultranalog) is a busy fellow...he just doesn't have the time to help everyone out.
It often doesn't matter that much.
I'd pay more attention to the OPTs which are the most important components, i.e. quality is usually linear to what is paid for those OPTs.
Are you planning to use the 3A5?
Cheers,
Ah...that was you?
Nah, Remco (Ultranalog) is a busy fellow...he just doesn't have the time to help everyone out.
It often doesn't matter that much.
I'd pay more attention to the OPTs which are the most important components, i.e. quality is usually linear to what is paid for those OPTs.
Are you planning to use the 3A5?
Cheers,
3A5 = yes
Hi mate,
3a5 is the one that I would like to build, I think the review of this given on the website tickles my interest. I will cost cut though and use the sowter output transformers, which seem to be more than adequate. Really looking forwards to getting this together, to provide that musical magic
Thanks
Raja
Hi mate,
3a5 is the one that I would like to build, I think the review of this given on the website tickles my interest. I will cost cut though and use the sowter output transformers, which seem to be more than adequate. Really looking forwards to getting this together, to provide that musical magic
Thanks
Raja
I'm afraid I have to advise you NOT to use the AE trannies. Their amorphous cores did not reach my specified impedance and regular C-cores turned out to be 10x under impedance. This led to unacceptable phase shift in the bass department.
For more info, read
AE impedance measurement
The amorphous core is useable for the stage, but too expensive by far.
Instead, I recommend the Sowter 8650. Whilst being much smaller, it has always performed excellent given it's modest price. Also, the Sowter service is much better. I haven't heard from AE after their promise to take my trannies back.
On another note:
I did not go into DAC details not because of protectionism or arrogance but since Raja refuses to buy a scope. This is DANGEROUS! He found a scope too expensive. It may one day save your life, which cannot be expressed in money.
For more info, read
AE impedance measurement
The amorphous core is useable for the stage, but too expensive by far.
Instead, I recommend the Sowter 8650. Whilst being much smaller, it has always performed excellent given it's modest price. Also, the Sowter service is much better. I haven't heard from AE after their promise to take my trannies back.
On another note:
I did not go into DAC details not because of protectionism or arrogance but since Raja refuses to buy a scope. This is DANGEROUS! He found a scope too expensive. It may one day save your life, which cannot be expressed in money.
scope
Hi,
Sorry Remco, I did have a look at scope prices and they seemed to cost from say £300 to over £1000, and this put me off, although you are correct, the cost of life is far more valuable.
You see I have a DMM and I thought that this was adequate for diy that I undertake.
In this instance I wrongly thought you were only suggesting a scope to find the audio pinouts (sine) on the dac, and I thought I could get this info via yourself or via a forum, as proved to be the case.
As such no-one had ever really recommended me to buy an oscilloscope before, and I had only deemed them useful for measuring distortion etc.
Thanks
Raja
Hi,
Sorry Remco, I did have a look at scope prices and they seemed to cost from say £300 to over £1000, and this put me off, although you are correct, the cost of life is far more valuable.
You see I have a DMM and I thought that this was adequate for diy that I undertake.
In this instance I wrongly thought you were only suggesting a scope to find the audio pinouts (sine) on the dac, and I thought I could get this info via yourself or via a forum, as proved to be the case.
As such no-one had ever really recommended me to buy an oscilloscope before, and I had only deemed them useful for measuring distortion etc.
Thanks
Raja
It's working
HI Guys,
Well thanks to the people on this forum, I got the output stage up and running, everything works just fine!!!!
Frank, I connected the B+ to the 3a5's and the voltage dropped to around 105-110v (have given time for warmup).
I've listened to some tunes on my senn hd580 'phones, and I must say that this is a very good ouput stage.
Getting a bit of hum thru the phones - heater tranny is noisy and mounted on top cover, and I still need to star eart both ouputs properly...... will investigate..........
The sound is much smoother than I'm used to with solid state...... The tone and timbre of the sound is what this stage excels at...........
Bass isn't as powerful, but maybe bass was overblown before---- listening will tell.......
A far more musical experience than the solid state device that was in the stock player (pd-s703)..........
If you have a voltage output dac this is a must consideration................
I'll see if I can post pics soon.............
My thanks go out to Fdegrove, Dhaen, Paul Barker and all other who helped me thru building this thing, sorry for the stress you guys........
Also thanks to Ultranalog for the design..............
Regards
Raja
HI Guys,
Well thanks to the people on this forum, I got the output stage up and running, everything works just fine!!!!
Frank, I connected the B+ to the 3a5's and the voltage dropped to around 105-110v (have given time for warmup).
I've listened to some tunes on my senn hd580 'phones, and I must say that this is a very good ouput stage.
Getting a bit of hum thru the phones - heater tranny is noisy and mounted on top cover, and I still need to star eart both ouputs properly...... will investigate..........
The sound is much smoother than I'm used to with solid state...... The tone and timbre of the sound is what this stage excels at...........
Bass isn't as powerful, but maybe bass was overblown before---- listening will tell.......
A far more musical experience than the solid state device that was in the stock player (pd-s703)..........
If you have a voltage output dac this is a must consideration................
I'll see if I can post pics soon.............
My thanks go out to Fdegrove, Dhaen, Paul Barker and all other who helped me thru building this thing, sorry for the stress you guys........
Also thanks to Ultranalog for the design..............
Regards
Raja
I've also been looking into what's the best way to get sound from a current output dac. Im designing a mono AD1955 based DAC unit.
I was thinking along the line of using a Sowter 9545 transformer right at the DAC as an IV stage, and a basic triode line stage buffer.
How would this compare?
I'm beginning to think around the lines of killing the line stage buffer & driving my tube power amp directly from the transformer, however, as I change volume, there is a small difference in input load & capacitance which may alter the sound.
(sowter transformer specs: http://www.sowter.co.uk./specs/9545.htm )
I was thinking along the line of using a Sowter 9545 transformer right at the DAC as an IV stage, and a basic triode line stage buffer.
How would this compare?
I'm beginning to think around the lines of killing the line stage buffer & driving my tube power amp directly from the transformer, however, as I change volume, there is a small difference in input load & capacitance which may alter the sound.
(sowter transformer specs: http://www.sowter.co.uk./specs/9545.htm )
hum
Hi all,
Brian you may want ask ultranalog your questions directly, as he'd probably have some good answers for you.....
Can't seem to get rid of the hum,
I have tried earthing the outputs, moving the choke, output transformers, twisting cables etc.........
Interestingly enough the hum gets real loud if I touch the chassis of either the cd player or preamp (being used with headphones)
Out of interest how close should R7 be to the socket pins, at present I habe a long length (20-30 cms) of cable running into pcb mounted terminal block which is then connected to R7.?????
Thanks
Raja
Hi all,
Brian you may want ask ultranalog your questions directly, as he'd probably have some good answers for you.....
Can't seem to get rid of the hum,
I have tried earthing the outputs, moving the choke, output transformers, twisting cables etc.........
Interestingly enough the hum gets real loud if I touch the chassis of either the cd player or preamp (being used with headphones)
Out of interest how close should R7 be to the socket pins, at present I habe a long length (20-30 cms) of cable running into pcb mounted terminal block which is then connected to R7.?????
Thanks
Raja
Hi,
Groundloop, I reckon.
That's the cathode bias resistor which is shared between the two output valves.
Its' top should go close to the cathodes' midpoint.
IMHO, using two separate 300R cathode resistors would make life easier on you.
Maybe UA would like to comment on his design choices?
Cheers,
Groundloop, I reckon.
That's the cathode bias resistor which is shared between the two output valves.
Its' top should go close to the cathodes' midpoint.
IMHO, using two separate 300R cathode resistors would make life easier on you.
Maybe UA would like to comment on his design choices?
Cheers,
groundloop
Hi,
Does the groundloop issue come from the output (interconnects to starearth at preamp), or more from my implementation of earthing on the pcb to the 3a5's???
At present I have a common earth wire running the length of the pcb, all negative ends from the caps etc come to this line, from here I have connected the ouput ends of this to a pcb mounted 3 terminal block. The cathode bias resitor has it's own terminal with a wire running from the block to the pins respectivley. One of the other blocks is the B+ to the output transformers. The third block supplies earth to the 4 1800pf caps. Perhaps I shold have just one earth block output to the tube pins instead of 2? I was thinking of connecting the c bias resistor close to the pins, and using the bottom end of the resistor for the earth supply to the caps also, hence negating the need for 2 wires carrying earth to the tube sockets..........
Any thoughts and advice???
Thanks
Raja
Hi,
Does the groundloop issue come from the output (interconnects to starearth at preamp), or more from my implementation of earthing on the pcb to the 3a5's???
At present I have a common earth wire running the length of the pcb, all negative ends from the caps etc come to this line, from here I have connected the ouput ends of this to a pcb mounted 3 terminal block. The cathode bias resitor has it's own terminal with a wire running from the block to the pins respectivley. One of the other blocks is the B+ to the output transformers. The third block supplies earth to the 4 1800pf caps. Perhaps I shold have just one earth block output to the tube pins instead of 2? I was thinking of connecting the c bias resistor close to the pins, and using the bottom end of the resistor for the earth supply to the caps also, hence negating the need for 2 wires carrying earth to the tube sockets..........
Any thoughts and advice???
Thanks
Raja
Ground loop
Taking a look at the pdf of the circuit I noticed I did not explicitly state that one side of the tranny secondary needs to be grounded.
Sorry for the blurry picture, but I only found out recently how to transfer spectra digitally to my computer.
It may save you some hum.
Sowter also recommends terminating the secondary with a resistor to dampen eventual ringing. You can try and measure or listen to a variation of terminating resistors.
I'd check the circuit for ground loops first.
Another cause for humming may be excess PSU hum combined with bad matching of the 3A5. The hum should cancel out. First measure the PSU residual hum (with a scope, Raj!), then check the matching.
About the hum, a picture says more than a thousand words. Ground loops definitely look different than PSU AC remains. Hope by now you see why you need a scope? It's hard to be of any assitance since I don't know what I'm looking at.
Weak bass may be a result of poor DC matching saturating the Xformer core, but then again it's also a characteristic of the Legato dac. Need some objective numbers (pictures) to decide what's what.
A cap over the cathode resistor may eliminate some mismatch, but it'll have to be quite large (> 2200 uF). It will solve difficulties arising from eventual layout problems (I once picked up radio with a cathode resistor) but that only comes into play when the layout is extremely poor (in the forementioned case, the heater wires were 5 meters long). I prefer no capacitor there (well, actually, I prefer a current sink there).
Would be, but the cathode is internally shared between the triodes. Which indicates the midpoint should be fairly accurate, since differential operation was intended.
Remco
Taking a look at the pdf of the circuit I noticed I did not explicitly state that one side of the tranny secondary needs to be grounded.
An externally hosted image should be here but it was not working when we last tested it.
Sorry for the blurry picture, but I only found out recently how to transfer spectra digitally to my computer.
It may save you some hum.
Sowter also recommends terminating the secondary with a resistor to dampen eventual ringing. You can try and measure or listen to a variation of terminating resistors.
I'd check the circuit for ground loops first.
Another cause for humming may be excess PSU hum combined with bad matching of the 3A5. The hum should cancel out. First measure the PSU residual hum (with a scope, Raj!), then check the matching.
About the hum, a picture says more than a thousand words. Ground loops definitely look different than PSU AC remains. Hope by now you see why you need a scope? It's hard to be of any assitance since I don't know what I'm looking at.
Weak bass may be a result of poor DC matching saturating the Xformer core, but then again it's also a characteristic of the Legato dac. Need some objective numbers (pictures) to decide what's what.
A cap over the cathode resistor may eliminate some mismatch, but it'll have to be quite large (> 2200 uF). It will solve difficulties arising from eventual layout problems (I once picked up radio with a cathode resistor) but that only comes into play when the layout is extremely poor (in the forementioned case, the heater wires were 5 meters long). I prefer no capacitor there (well, actually, I prefer a current sink there).
Would be, but the cathode is internally shared between the triodes. Which indicates the midpoint should be fairly accurate, since differential operation was intended.
Remco
Hi Remco,
Okay what I'll do is attach 0v from b+ and output secondries to a single star ground which is already in the cdp.......
Remco I've seen a few scopes around that use a pc to work are these okay for this kind of work? I don't know much at all about scopes, and I've seen prices starting from say £150 all they way upto £1000. Do pc versions generally have what I would need to make measurements?
Thanks
Raja
Okay what I'll do is attach 0v from b+ and output secondries to a single star ground which is already in the cdp.......
Remco I've seen a few scopes around that use a pc to work are these okay for this kind of work? I don't know much at all about scopes, and I've seen prices starting from say £150 all they way upto £1000. Do pc versions generally have what I would need to make measurements?
Thanks
Raja
Thanks Remco for the link,
I've done the star earthing and the hum is virtually gone..........
All I'm left with is a slight hf hiss thru one channel, which goes if I press on the chassis near the 3a5 representing that channel. I've tried it with a plastic handle also just to check I wasn't acting as a ground, the chassis is slightly warped on this side......
It's not noticable when the music's on so I may leave it.........
But I must say I'm extremley impressed with the smooth sound of this output stage, it's made my harsher sounding discs sound so..............analogue. The bass is good, I initially thought it to be weak but I figure this was due to no star earth for the ht supply, A very different listening experience to the solid stage output, which was perhaps cleaner but also more fatiguing
Well Remco do you have any plans for a tube headphone amp, perhaps SE?
Thanks
Raja
I've done the star earthing and the hum is virtually gone..........
All I'm left with is a slight hf hiss thru one channel, which goes if I press on the chassis near the 3a5 representing that channel. I've tried it with a plastic handle also just to check I wasn't acting as a ground, the chassis is slightly warped on this side......
It's not noticable when the music's on so I may leave it.........
But I must say I'm extremley impressed with the smooth sound of this output stage, it's made my harsher sounding discs sound so..............analogue. The bass is good, I initially thought it to be weak but I figure this was due to no star earth for the ht supply, A very different listening experience to the solid stage output, which was perhaps cleaner but also more fatiguing
Well Remco do you have any plans for a tube headphone amp, perhaps SE?
Thanks
Raja
The hiss sounds like a bad socket or dirty tube pins. Try cleaning those and check the sockets for firmness. The easiest check is to swap the 3A5's and see if the problem moves to the other channel. Could also be a bad solder joint btw.
Can't say more on the hum without some measurements, I'm afraid. You could try increasing psu buffer capacity, but be aware of the AZ1 internal resistance. Try psud2 simulations.
Glad you like the sound. I recognize and acknowledge the comments you made.
A headphone amp is not in the planning. But if your headphones are 300 Ohms or higher, try driving them directly from the CD enhancer II output. Rout is about 100 Ohms. I could drive even my 32 Ohms Sony headphones to quite reasonable, undistorted power levels. You'd only miss a volume control but could add one in between the dacs and the tube stage.
Can't say more on the hum without some measurements, I'm afraid. You could try increasing psu buffer capacity, but be aware of the AZ1 internal resistance. Try psud2 simulations.
Glad you like the sound. I recognize and acknowledge the comments you made.
A headphone amp is not in the planning. But if your headphones are 300 Ohms or higher, try driving them directly from the CD enhancer II output. Rout is about 100 Ohms. I could drive even my 32 Ohms Sony headphones to quite reasonable, undistorted power levels. You'd only miss a volume control but could add one in between the dacs and the tube stage.
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