"Does you're schema include RIAA correction ?"
Unfortunately not. I have had great success with Leosch's El Cheapo phono stage. Unfortunately it uses a higher +B than my circuit.
I don't see why the suggested PS wouldn't work excellently. I used a simple CRCRCRCR type power supply and it worked well. Can't say whether Leosch would sound better, though it probably will.
Shoog
Unfortunately not. I have had great success with Leosch's El Cheapo phono stage. Unfortunately it uses a higher +B than my circuit.
I don't see why the suggested PS wouldn't work excellently. I used a simple CRCRCRCR type power supply and it worked well. Can't say whether Leosch would sound better, though it probably will.
Shoog
Shoog said:
Hi Shoog,
Wow that's fast
The reason I searched for another PSU is that I read that the RCRCRCRCR PSU-design has quite a lot of voltage-drop and dissipation.
Furthermore I really think you're design deserves a very good PSU-design. Because I am looking for a really good (neutral and fast) sounding phono-design, I hope to combine best of you're and Loesch's world.
I have to tell you that I base my choices on what I read on different fora on the internet (thanx to google).
I have a basic knowledge of electronics. And as much as no practical-experience...
I have to start somewhere
Anyway, I really appreciate you're effort and suggestions.
PS: I have to find a way to recalculate the output voltage of this PSU design.
Within reason an overvoltage PS can be trimmed down to any voltage simply by insertion of a series resistor in the positive leg. You have to know the current draw of the design to do this accurately (about 20mA for my design), but using a power potentiometer allows you to trim a variable amount. You can then substitute a fixed resistor of the appropriate value.
This works because the preamp draws a constant current.
If you started out with a 280-300V supply you could tap off at 250V for EL CHEAPO, and then add another stage of RC filtering in order to get down to the 165V(I think thats the right voltage) you need for my preamp.
I find that a practical approach is often the best when you aren't to certain of the underlying theory.
Shoog
This works because the preamp draws a constant current.
If you started out with a 280-300V supply you could tap off at 250V for EL CHEAPO, and then add another stage of RC filtering in order to get down to the 165V(I think thats the right voltage) you need for my preamp.
I find that a practical approach is often the best when you aren't to certain of the underlying theory.
Shoog
Hi Shoog
You probably know the price of a FVP5 kit is $3500
(per www.tnt-audio.com/ampli/vse_fvp5a_e.html - did they slip a n extra digit in?
What was the approx all-up cost of yours?
Thanks
You probably know the price of a FVP5 kit is $3500
(per www.tnt-audio.com/ampli/vse_fvp5a_e.html - did they slip a n extra digit in?What was the approx all-up cost of yours?
Thanks
Depending on what you spend on a case really. Assuming you spend next to nothing on the case, expect to spend about €200.00.
I used an old Pioneer amplifier case for mine. All the valves are inside and I didn't have to buy any phono or power sockets. I would guess that would probably have saved me about €50.00
I personally don't much like having the valves out on show as they are more vunerable and also it makes it much harder to accommodate the finished unit.
I would point out that mine hasn't got a phono amplifier section or the superregs. Also mine only uses 3 PCC88's where as the original uses 5. Compared to many other high end kit out there I would say that the original was still good value for money.
Going back to the power supply. I tried using a bipolar transistor capacitance multiplier in my power supply. It definately sounded worse than a simple CRCRCRC power supply. I cannot comment on the power supply asked about before, as it uses FETs. Still it may not sound better than a simpler version.
Shoog
Shoog
I used an old Pioneer amplifier case for mine. All the valves are inside and I didn't have to buy any phono or power sockets. I would guess that would probably have saved me about €50.00
I personally don't much like having the valves out on show as they are more vunerable and also it makes it much harder to accommodate the finished unit.
I would point out that mine hasn't got a phono amplifier section or the superregs. Also mine only uses 3 PCC88's where as the original uses 5. Compared to many other high end kit out there I would say that the original was still good value for money.
Going back to the power supply. I tried using a bipolar transistor capacitance multiplier in my power supply. It definately sounded worse than a simple CRCRCRC power supply. I cannot comment on the power supply asked about before, as it uses FETs. Still it may not sound better than a simpler version.
Shoog
Shoog
I never heard of the Pareto principle before, but it perfectly sums up my philosphy to most things. I think I am probably sacrificing about 20% of the performance of any given project but saving 80% of the cost. To me that is a fair trade. I do have a stock of quality components as well and they get used in critical places. It bores me rigid when I see a thread springing up on caps and resistors.
Shoog
Shoog
Hello Shoog, others,
Thanks for sharing the results of your quest.
Some years ago I’ve build the FVP5 (rev. 1 of 30-11-98).
The result is more than satisfying in it’s original design.
In the meantime the shunt super regulation is ready and can be added.
There are some differences between your schematic and mine.
- In my version the lower tube of the second stage is a mosfet –ccs. The power supply is 200 volts, while in your case it is 156 volts. Did you deliberately settle on 156 volts?
- The plate resistor of the first tube is 25k (yours 19k). This might be related to the lower supply voltage?
- I wonder why R8 in your schematic (it is not in mine) is so critical in value (you mention 1k and 660 ohm, and the need to tweak this value). How can this be of influence on the sounds anyway. Can someone explain this? Is this related to interaction between the two stages?
- the resistor R4 in your schematic is 47k, while my schematic says 470k.
- the value of R5 in your schematic is split up in mine in 1m5 (with 0.22 uF in parallel) and 47k
- Can you tell what is the voltage at the cathode of the first stage with supplementary current circuit?
- I would like to learn if the supplementary current to bias up the LED into a more linear range in the first stage could also be applied to the led in the second stage in your schematic and if it would benefit the sound. Did you consider this?
Best regards, Arjen.
Thanks for sharing the results of your quest.
Some years ago I’ve build the FVP5 (rev. 1 of 30-11-98).
The result is more than satisfying in it’s original design.
In the meantime the shunt super regulation is ready and can be added.
There are some differences between your schematic and mine.
- In my version the lower tube of the second stage is a mosfet –ccs. The power supply is 200 volts, while in your case it is 156 volts. Did you deliberately settle on 156 volts?
- The plate resistor of the first tube is 25k (yours 19k). This might be related to the lower supply voltage?
- I wonder why R8 in your schematic (it is not in mine) is so critical in value (you mention 1k and 660 ohm, and the need to tweak this value). How can this be of influence on the sounds anyway. Can someone explain this? Is this related to interaction between the two stages?
- the resistor R4 in your schematic is 47k, while my schematic says 470k.
- the value of R5 in your schematic is split up in mine in 1m5 (with 0.22 uF in parallel) and 47k
- Can you tell what is the voltage at the cathode of the first stage with supplementary current circuit?
- I would like to learn if the supplementary current to bias up the LED into a more linear range in the first stage could also be applied to the led in the second stage in your schematic and if it would benefit the sound. Did you consider this?
Best regards, Arjen.
Lots of good questions.
"- In my version the lower tube of the second stage is a mosfet -ccs. The power supply is 200 volts, while in your case it is 156 volts. Did you deliberately settle on 156 volts?"
A mosfet CCS will probably perform better, but might not sound better. I said this before that the triode CCS seems to work well enough. My original inspiration came from the Gainclone buffer circuit which Vacuum State use, on this there is a bipolar transistor on the top and a triode on the bottom. The designer must have made the decision to stack them in this order for a good reason. Also to substitute a mosfet CCS would require re-jigging all other components.
The 156V was the power supply I had and which I designed the rest of the circuit around. Other voltages would work but would need component adjustments.
"- The plate resistor of the first tube is 25k (yours 19k). This might be related to the lower supply voltage? "
The choice of the first plate resistor was made to place the plate at about 100V. This is a critical point as it sets the bias point of the second stage. I found through experimentation that this gave a nice balance between an overly full sound or an overly thin sound.
"- I wonder why R8 in your schematic (it is not in mine) is so critical in value (you mention 1k and 660 ohm, and the need to tweak this value). How can this be of influence on the sounds anyway. Can someone explain this? Is this related to interaction between the two stages?"
This follows on from my previous answer. It is a fine tuning mechanism to set the bias point of the second stage and hence the tonal characture of the whole preamp. This is why I strongly suggest using a 1K5 variable resistor so that you can adjust the tone of the circuit to your own taste.
"- the resistor R4 in your schematic is 47k, while my schematic says 470k."
Because the Mosfet only needs a small amount of voltage to operate compared to a valve, the 47K sets a lower voltage drop across the Mosfet.
The choice of values of R4 and R5 are relatively arbitary, its is the ratio that is important.
" Can you tell what is the voltage at the cathode of the first stage with supplementary current circuit? "
About 2.1V. This voltage will be relatively static with different currents. Without the supplemantart bias the sound is muddy. I did not consider it neccissary to apply supplementary current to the Red LED because it is passing about 7mA and is hence already in its linear range. I also think that because the bottom triode is somewhat isolated from the signal it is less critical. Adding supplementary current may bring improvements, I did not feel it was warrented.
I would say that it may be a good idea to substitute a lower gain triode for the voltage gain stage. This is because the gain is excessive and will probably overload the second stage. All that would be required would be to choose a low gain triode with a good operating point that places the plate at 100V. This may also bring sonic benefits as the ECC88 is not the best sounding triode and will add its sonic signiture to the preamp in a way that the SLCF not.
I did not design my preamp to better the original. I did it as an intellectual exercise. It may or may not come close to the original - I cannot say. All I can say is that it is very neutral in itself.
I would be very interested in what benefits are derived from adding the superreg.
Shoog
"- In my version the lower tube of the second stage is a mosfet -ccs. The power supply is 200 volts, while in your case it is 156 volts. Did you deliberately settle on 156 volts?"
A mosfet CCS will probably perform better, but might not sound better. I said this before that the triode CCS seems to work well enough. My original inspiration came from the Gainclone buffer circuit which Vacuum State use, on this there is a bipolar transistor on the top and a triode on the bottom. The designer must have made the decision to stack them in this order for a good reason. Also to substitute a mosfet CCS would require re-jigging all other components.
The 156V was the power supply I had and which I designed the rest of the circuit around. Other voltages would work but would need component adjustments.
"- The plate resistor of the first tube is 25k (yours 19k). This might be related to the lower supply voltage? "
The choice of the first plate resistor was made to place the plate at about 100V. This is a critical point as it sets the bias point of the second stage. I found through experimentation that this gave a nice balance between an overly full sound or an overly thin sound.
"- I wonder why R8 in your schematic (it is not in mine) is so critical in value (you mention 1k and 660 ohm, and the need to tweak this value). How can this be of influence on the sounds anyway. Can someone explain this? Is this related to interaction between the two stages?"
This follows on from my previous answer. It is a fine tuning mechanism to set the bias point of the second stage and hence the tonal characture of the whole preamp. This is why I strongly suggest using a 1K5 variable resistor so that you can adjust the tone of the circuit to your own taste.
"- the resistor R4 in your schematic is 47k, while my schematic says 470k."
Because the Mosfet only needs a small amount of voltage to operate compared to a valve, the 47K sets a lower voltage drop across the Mosfet.
The choice of values of R4 and R5 are relatively arbitary, its is the ratio that is important.
" Can you tell what is the voltage at the cathode of the first stage with supplementary current circuit? "
About 2.1V. This voltage will be relatively static with different currents. Without the supplemantart bias the sound is muddy. I did not consider it neccissary to apply supplementary current to the Red LED because it is passing about 7mA and is hence already in its linear range. I also think that because the bottom triode is somewhat isolated from the signal it is less critical. Adding supplementary current may bring improvements, I did not feel it was warrented.
I would say that it may be a good idea to substitute a lower gain triode for the voltage gain stage. This is because the gain is excessive and will probably overload the second stage. All that would be required would be to choose a low gain triode with a good operating point that places the plate at 100V. This may also bring sonic benefits as the ECC88 is not the best sounding triode and will add its sonic signiture to the preamp in a way that the SLCF not.
I did not design my preamp to better the original. I did it as an intellectual exercise. It may or may not come close to the original - I cannot say. All I can say is that it is very neutral in itself.
I would be very interested in what benefits are derived from adding the superreg.
Shoog
Hello Shoog, others,
Thanks for your clear reply.
This would be an interesting experiment.
* I would say that it may be a good idea to substitute a lower gain triode for the voltage gain stage. This is because the gain is excessive and will probably overload the second stage. All that would be required would be to choose a low gain triode with a good operating point that places the plate at 100V.
Yes, other tubes might be better. I did not try other tubes yet.
Does anyone have a suggestion for a tube that would be a drop-in replacement so one does not need to recalculate all values?
* This may also bring sonic benefits as the ECC88 is not the best sounding triode and will add its sonic signiture to the preamp in a way that the SLCF not.
First I'll try to add the shuntreg in the next months. That already is quite time consuming.
Best regards, Arjen.
Thanks for your clear reply.
This would be an interesting experiment.
* I would say that it may be a good idea to substitute a lower gain triode for the voltage gain stage. This is because the gain is excessive and will probably overload the second stage. All that would be required would be to choose a low gain triode with a good operating point that places the plate at 100V.
Yes, other tubes might be better. I did not try other tubes yet.
Does anyone have a suggestion for a tube that would be a drop-in replacement so one does not need to recalculate all values?
* This may also bring sonic benefits as the ECC88 is not the best sounding triode and will add its sonic signiture to the preamp in a way that the SLCF not.
First I'll try to add the shuntreg in the next months. That already is quite time consuming.
Best regards, Arjen.
Hi Shoog
I am building this crossover by John Broskie http://www.glass-ware.com/tubecircuits/18 db.gif
Instead of the ECC88 cathode followers I am using a PCF80/ECF80 (I have a lot - who doesn't) with the triode as buffer and the pentode as CCS. The supply is a bipolar one, with rails at +100V/-100V. I am building it in a quiet modular version, that makes it easy to test other buffer circuits.
Now I see your FVP5 version and I thought of using it as the buffer, see how it sounds. As I already have the bipolar supply and want to keep the grid at ground potential, I copy pasted your schematic in paint and redraw it somewhat to adapt to my situation. What do you think, shall it work? Is it worth the trouble to build it? Other question, as I am like you, always trying to salvage parts (and I am noob on mosfets). I have some of these mosfets MOS-N-FET BS107 200V, 0.12A, 0.5W http://easymeasure.nl/bs107.pdf Can they be used instead of the IRF510 (first impression is that the rating are ok, N channel as the IRF, but the bs107 is a depletion one, whatever that means, mosfet).
Many thanks for the attention
Erik
I am building this crossover by John Broskie http://www.glass-ware.com/tubecircuits/18 db.gif
Instead of the ECC88 cathode followers I am using a PCF80/ECF80 (I have a lot - who doesn't) with the triode as buffer and the pentode as CCS. The supply is a bipolar one, with rails at +100V/-100V. I am building it in a quiet modular version, that makes it easy to test other buffer circuits.
Now I see your FVP5 version and I thought of using it as the buffer, see how it sounds. As I already have the bipolar supply and want to keep the grid at ground potential, I copy pasted your schematic in paint and redraw it somewhat to adapt to my situation. What do you think, shall it work? Is it worth the trouble to build it? Other question, as I am like you, always trying to salvage parts (and I am noob on mosfets). I have some of these mosfets MOS-N-FET BS107 200V, 0.12A, 0.5W http://easymeasure.nl/bs107.pdf Can they be used instead of the IRF510 (first impression is that the rating are ok, N channel as the IRF, but the bs107 is a depletion one, whatever that means, mosfet).
Many thanks for the attention
Erik
Attachments
I designed and built a buffer circuit for a Gainclone. If you search the forum under my name and buffer you should pull it up. It uses split rails of +/-80V and has all the components worked out.
I cannot honestly answer your question on the substitution of mosfets. The N type is fine, but I don't know about the depletion mode.
Shoog
I cannot honestly answer your question on the substitution of mosfets. The N type is fine, but I don't know about the depletion mode.
Shoog
Hi Shoog
Many thanks for the reply. I searched in the chipamp forum, but could not find the thread.
The main reason why I ask if your version of the FVP5 could be adapted is your comment that this circuit does cut the feedback, but still provides a low output impedance. (I can't find it right now, maybe I dreamed about it). Not that I am againt feedback, but for me it would not be hard to just give it a try, see what happens and how it sounds. Although not hard to implement, it can take some time
, but I will let you know about the results
Erik
Many thanks for the reply. I searched in the chipamp forum, but could not find the thread.
The main reason why I ask if your version of the FVP5 could be adapted is your comment that this circuit does cut the feedback, but still provides a low output impedance. (I can't find it right now, maybe I dreamed about it). Not that I am againt feedback, but for me it would not be hard to just give it a try, see what happens and how it sounds. Although not hard to implement, it can take some time
, but I will let you know about the resultsErik
The circuit as you showed it should work without modification even with higher voltages. The only thing that might need adjustment would be the 47K resistor. Just don't forget to add a resistor to ground on the input.
If you do any comparisons I'am certain that there would be interest in your results.
Shoog
If you do any comparisons I'am certain that there would be interest in your results.
Shoog
ErikdeBest said:
Try these http://cgi.ebay.de/10-x-IRFD220-Power-MOSFET_W0QQitemZ9732893937QQcategoryZ31336QQrdZ1QQcmdZViewItem
not the same as you thought but dirt cheap and more than suitable for the job
Cheers
Andrea
av-trouvaille said:
av-trouvaille said:
Hi Arjen,
which circuit did you use for the shunt super-regulator?
As for the questions,
R5 is split to isolate the cathode of the tube from the non-linear capacitance of the Mosfet, since the 0u22 shunts the larger resistor for AC signals
Using a different tube needs some calculations to be done, but the operating point can be quite easily deducted from the curves of the tube.
Pin-to-pin-compatible tubes with lower mu than E88CC (that I know of
) are 6H30, 6N6, 6GU7, all in the ballpark of mu close to 20.Gain is probably too high even with these.
I'm seroiusly thinking to use the SLCF as unity gain preamp, maybe after a trafo (that might add some boost if needed) .....
Cheers
Andrea
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