Who can post the schematic of this GRAAFiti preamp?
GRAAFiti WFB ONE Preamplificatore Valvolare
GRAAFiti WFB ONE Preamplificatore Valvolare
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schematic still needed. There are large issues by the phono input particularly with noise.
No difference in noise between open input and closed input in the "MC" mode. Closed input means with present plug-in socket (cynch connector) from lyra cartridge.
Who can upload a schematic diagram?
Graaf and audio excellence in Germany don't release any schematic.
Thank you for your efforts.
No difference in noise between open input and closed input in the "MC" mode. Closed input means with present plug-in socket (cynch connector) from lyra cartridge.
Who can upload a schematic diagram?
Graaf and audio excellence in Germany don't release any schematic.
Thank you for your efforts.
type referencing brings no informations in this case. Go to new thread
PC900/4AH5
http://www.diyaudio.com/forums/tubes-valves/144278-pc900-ec900-curves.html
in context to the circuit description of the input stage in front of the riaa stages
Pre-Amp with Phono needs new tubes (Schaltungsbeschreibung)
PC900/4AH5
http://www.diyaudio.com/forums/tubes-valves/144278-pc900-ec900-curves.html
in context to the circuit description of the input stage in front of the riaa stages
Pre-Amp with Phono needs new tubes (Schaltungsbeschreibung)
Own schematic draw from the Phono Stage now present
Check out the schematic - maybe several errors are present because I haven't access to PCB's solder side. Particularly the connections of the potentiometers for the gain adjust so as C07L (47uF/100V) are unknown, because the copper wires are not reach from component side. The circuit description don't correspondend with the actually circuit because the caims from the circuit description are untrue (first "without Feedback" and secondly "SRPP")
Check out the schematic - maybe several errors are present because I haven't access to PCB's solder side. Particularly the connections of the potentiometers for the gain adjust so as C07L (47uF/100V) are unknown, because the copper wires are not reach from component side. The circuit description don't correspondend with the actually circuit because the caims from the circuit description are untrue (first "without Feedback" and secondly "SRPP")
Attachments
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Now I have access to PCB's solder side. There are two faults in my drawing from first image in my previous post:
1) C07L (47uF/100V) must be in parallel to C06L resp R16L
2) in the connection between R12L/C05L and grid V03L (PIN7 of E88CC/6922) must be introduce a serial resistor of 1K (R15L) and between R12L/C05L and GND must be introduce a resistor of 510K (R14L).
The noise of the MC input is too large - additional there isn't the usual noise reduction in case of shorted input resp. fit in the RCA-plugs from turntable.
1) C07L (47uF/100V) must be in parallel to C06L resp R16L
2) in the connection between R12L/C05L and grid V03L (PIN7 of E88CC/6922) must be introduce a serial resistor of 1K (R15L) and between R12L/C05L and GND must be introduce a resistor of 510K (R14L).
The noise of the MC input is too large - additional there isn't the usual noise reduction in case of shorted input resp. fit in the RCA-plugs from turntable.
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Where have you found the schematic? Can you upload this? Here an URL with images in open condition: Préampli GRAAF WFB Two • LS3/5a le forum Graaf Graafitti WFB Two High-end tube hybrid preamp | Tube | Westlake Village, California 91361 | AudiogoN - The High-end Audio Community HIFI-ANTIQUE (powered by eStore) according the pictures there are only tubes in the line stage - RIAA stages and MC-head amp seems to be equipped with TO-92 plastic transistors. Maybe one of the members have heard both of this two models and can tell us the audible different between both versions - thank you therefore.
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I was referring to the schematic you posted
see #8)
I do not have the schematic. T01L is a switch, as the tube V04L warms up T01L saturates and the grid of V04L sees vce(sat).
V04L is a follower with its grid being at either 143v (250-112) or vce(sat), turning T01L on and off!
MPSA92 is a PNP device.
Art
see #8)I do not have the schematic. T01L is a switch, as the tube V04L warms up T01L saturates and the grid of V04L sees vce(sat).
V04L is a follower with its grid being at either 143v (250-112) or vce(sat), turning T01L on and off!
MPSA92 is a PNP device.
Art
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Setting Phonostage Graaf WFB One
Hi all, i am new to this forum and have a few questions regarding the Graaf WFB One. First: I was wondering what settings would be the best for a medium output MC Cartridge (Benz Micro Ace M). The gain on the WFB One has three steps, i guess the medium gain is best, but i am open for other points of view. Benz recommends a load of more than 200 Ohms. The Graaf has 100, 500 and 47.000. What would be the best choice (and why)? Second: what replacement tubes are recommended for the best performance? Third: where can i find these? Thanks so much.
Regards from The Netherlands,
FG
Hi all, i am new to this forum and have a few questions regarding the Graaf WFB One. First: I was wondering what settings would be the best for a medium output MC Cartridge (Benz Micro Ace M). The gain on the WFB One has three steps, i guess the medium gain is best, but i am open for other points of view. Benz recommends a load of more than 200 Ohms. The Graaf has 100, 500 and 47.000. What would be the best choice (and why)? Second: what replacement tubes are recommended for the best performance? Third: where can i find these? Thanks so much.
Regards from The Netherlands,
FG
The answers you need are related to the way your gear sounds overall and your taste of course. I used a WFB One for years and its phono stage has a nice sound but can be rather noisy. It has to do with the tubes working in it. Tubes silent enough for a phono stage can be quite expensive. I tried once a pair of new production Gold Lion 6922 that were very silent, so you could try them in the phono stage and see if the hiss gets lower. They are rather expensive, so the best would be to find a seller that allows you to try on your preamp, so you can see if they worth the price.
The best setting for gain could be the one that gives the lower hiss at the volume position you listen usually. I know the Benz Ace as well and would suggest you to start with the 100 ohms position and see what happens. If you need more brilliance on top end you try 500. 47000 is for MM carts, but sometimes could be useful with MC as well, when you listen to very closed in records. Don't know what to say for PC900's apart that if you have Telefunkens on board keep them, but remember that they could give heavy noise issues sometimes, as it happened with one of the quartet that was in my preamp.
I tried many tubes in the line stage of my WFB, but always ended up back to russian tubes. This could be an effect of the designer choices, as the preamp was originally equipped with Sovtek's 6922. 6n23, produced by Voskhod (rocket logo) Reflektor and Saratov, is a 6922 equivalent, works fine and is much less expensive than the european NOS that could give a rather screamy sound, maybe impressive at first but tiring after some time. I find 6n23 better than the usual EH 6922 and is available in the higher spec version EV, usually more silent.
Another way to improve the sound performance of the preamp can be the substitution of the output capacitors, the ones placed closer to the output sockets, and maybe the one behind them, that are part of the power supply but well worth the same. You can try some of the so called audiophile capacitors, like Audyn Cap or Jantzen. For the WFB One the Audyn Cap Plus can be a very good choice, not too expensive.
The best setting for gain could be the one that gives the lower hiss at the volume position you listen usually. I know the Benz Ace as well and would suggest you to start with the 100 ohms position and see what happens. If you need more brilliance on top end you try 500. 47000 is for MM carts, but sometimes could be useful with MC as well, when you listen to very closed in records. Don't know what to say for PC900's apart that if you have Telefunkens on board keep them, but remember that they could give heavy noise issues sometimes, as it happened with one of the quartet that was in my preamp.
I tried many tubes in the line stage of my WFB, but always ended up back to russian tubes. This could be an effect of the designer choices, as the preamp was originally equipped with Sovtek's 6922. 6n23, produced by Voskhod (rocket logo) Reflektor and Saratov, is a 6922 equivalent, works fine and is much less expensive than the european NOS that could give a rather screamy sound, maybe impressive at first but tiring after some time. I find 6n23 better than the usual EH 6922 and is available in the higher spec version EV, usually more silent.
Another way to improve the sound performance of the preamp can be the substitution of the output capacitors, the ones placed closer to the output sockets, and maybe the one behind them, that are part of the power supply but well worth the same. You can try some of the so called audiophile capacitors, like Audyn Cap or Jantzen. For the WFB One the Audyn Cap Plus can be a very good choice, not too expensive.
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Graaf WFB one tubes
Hello Clack, Thank you so much for your reply and sharing your experience. I recently bought this pre amp as a companion for my beloved Graaf GM20 power amp. The tubes present in the WFB one are four matched Siemens NOS PC900, one pair of EEC88 JJ and one pair of 6922 Electro Harmonix. The former owner replaced the tubes in 2013 and played about 300 hours since then. At that time he paid €30,- a piece for the PC900 and €25,- a piece for the other tubes. That implies for me its not an option to buy many variants just to trie
But when i need replacement, its good to have your input. Next weekend it is time to finally connect my turntable and play my records once again. I will follow your advice and start with medium gain and 100 ohms load and find out what gives the best results. Wont get much sleep i'm afraid The pre amp runs quite hot. Have you got any thoughts about life length for the tubes in the WFB one?
Regards,
FG
Hello Clack, Thank you so much for your reply and sharing your experience. I recently bought this pre amp as a companion for my beloved Graaf GM20 power amp. The tubes present in the WFB one are four matched Siemens NOS PC900, one pair of EEC88 JJ and one pair of 6922 Electro Harmonix. The former owner replaced the tubes in 2013 and played about 300 hours since then. At that time he paid €30,- a piece for the PC900 and €25,- a piece for the other tubes. That implies for me its not an option to buy many variants just to trie
But when i need replacement, its good to have your input. Next weekend it is time to finally connect my turntable and play my records once again. I will follow your advice and start with medium gain and 100 ohms load and find out what gives the best results. Wont get much sleep i'm afraid
The pre amp runs quite hot. Have you got any thoughts about life length for the tubes in the WFB one? Regards,
FG
The Gm 20 is an excellent amp. Maybe WFB One is not quite at its height. Anyway I too used it with the same amp with nice results. Temperature is not an issue for the WFB. So tubes will last long. Tou should have E88CC or 6922 tubes in your preamp. The ones you have in it maybe are not the best. So, you could try to find a good 6n23 quartet, they are not expensive, and have a remarkable improvement.
About the GM 20, an improvement is to change the four 1 uF capacitors that are near the output tubes. Because the amp runs quite hot, capacitors have to bear a great effort. Audyn caps QS 6 will do, they are not expensive and will give you a better sound. You can think about changing the other PP capacitors too, as high temperature cause their aging. The same for the Kendeil electrolythics placed near the power transoformer. I blew one a couple of years ago.
About the GM 20, an improvement is to change the four 1 uF capacitors that are near the output tubes. Because the amp runs quite hot, capacitors have to bear a great effort. Audyn caps QS 6 will do, they are not expensive and will give you a better sound. You can think about changing the other PP capacitors too, as high temperature cause their aging. The same for the Kendeil electrolythics placed near the power transoformer. I blew one a couple of years ago.
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