Hi,
The difference is modest. from around 75uS to 78uS, one might slightly the RIAA series resistor marked 48k7 on the schematic.
47K there should bring things back into line.
Ciao T
The difference is modest. from around 75uS to 78uS, one might slightly the RIAA series resistor marked 48k7 on the schematic.
47K there should bring things back into line.
Ciao T
ecc83 anode B+ too high?
Hi
I built this amp a couple of years ago. The line stage sounds really good. In fact, i love it. I would love to have a little more gain tho. However, I noticed that the ECC 88 (6dj8) was running really hot. The plate voltage running at 230V. Isn't that too high for ECC83? Would 100k instead of 12k remedy this? I am pretty new to this. So I was looking for a solution. I am glad that i came back to this thread.
Thanks Kuei!
Thanks
Yaho!
Hi
I built this amp a couple of years ago. The line stage sounds really good. In fact, i love it. I would love to have a little more gain tho. However, I noticed that the ECC 88 (6dj8) was running really hot. The plate voltage running at 230V. Isn't that too high for ECC83? Would 100k instead of 12k remedy this? I am pretty new to this. So I was looking for a solution. I am glad that i came back to this thread.
Thanks Kuei!
Thanks
Yaho!
Hi,
There is no ECC83 mod. The second stage is designed for a ECC88/6DJ8/6922.
Please fit the correct valve and wire the heaters correctly and everything will work.
As it stands the second stage will have very low gain and high distortion/output impedance. Changing the Anode load to something like 100K would create too much gain and an even higher output impedance.
Ciao T
There is no ECC83 mod. The second stage is designed for a ECC88/6DJ8/6922.
Please fit the correct valve and wire the heaters correctly and everything will work.
As it stands the second stage will have very low gain and high distortion/output impedance. Changing the Anode load to something like 100K would create too much gain and an even higher output impedance.
Ciao T
Thanks for the reply
Hi
Thanks for the reply Thorsten. Very kind of you to do so. I read some of your posts and learned a lot. Anyways, I really suck at explaining myself. Let me try this again please.
However, I was just checking the plate voltage on
6dj8 and it read 230v. I was wondering if that was too high for 6dj8. If so I may have messed this up. But the phonostage works and it sounds very clean. My field is far from engineering so my questions may bore many people here.
Thanks
Hi
Thanks for the reply Thorsten. Very kind of you to do so. I read some of your posts and learned a lot. Anyways, I really suck at explaining myself. Let me try this again please.
Yes. I got it!
I built this amp exactly to the design. It is really working fine.
Got it. Anode load stays at 12k.
However, I was just checking the plate voltage on
6dj8 and it read 230v. I was wondering if that was too high for 6dj8. If so I may have messed this up. But the phonostage works and it sounds very clean. My field is far from engineering so my questions may bore many people here.
Thanks
Last edited:
Nobody's answered, so maybe I can help.
Is that 230V on both pin 1 and pin 6 on the 6DJ8? Or does pin 1 measure differently from pin 6?
230V on either pin 1 or pin 6 means that part of the tube isn't drawing any current at all. I think something must be wrong. What is the voltage on the other side of the plate resistor (the lead that goes to the power supply, not to pin 1 or pin 6)?
Have you tried a different 6DJ8 in there, and if so, did it measure the same?
I assume the heaters are lighting up. Did you check the voltage at pins 4 and 5 (heaters)?
--
Hi,
230V seems high if you have a real 6922 or related in there.
As rongon said, try a different one you can also try reducing the gridleak resistor, you can go as low as 3.3MOhm The Anode pin voltage with a 6922 etc. should be around 90V (can vary a fair bit).
Also, double-check the value of the resistor in the cathode, it really is 10 Ohm (or a direct short), the bias for the tube comes from the grid circuit.
Ciao T
230V seems high if you have a real 6922 or related in there.
As rongon said, try a different one you can also try reducing the gridleak resistor, you can go as low as 3.3MOhm The Anode pin voltage with a 6922 etc. should be around 90V (can vary a fair bit).
Also, double-check the value of the resistor in the cathode, it really is 10 Ohm (or a direct short), the bias for the tube comes from the grid circuit.
Ciao T
Problem solved
Rongon and Thorsten
Thanks for your help. My problem is solved. I put a new 6922 and the anode voltage is read at 67-68V. Looking good.
I learned something important as well. At the power on, the 6922 receives 230V until the heater is warmed up. Therefore, i need to find a solution to slow start the amp.
I would treasure any help on this matter. But I will research as well.
Thanks again
Yaho
Rongon and Thorsten
Thanks for your help. My problem is solved. I put a new 6922 and the anode voltage is read at 67-68V. Looking good.
I learned something important as well. At the power on, the 6922 receives 230V until the heater is warmed up. Therefore, i need to find a solution to slow start the amp.
I would treasure any help on this matter. But I will research as well.
Thanks again
Yaho
Hi All,
I have built Thorsten’s Phono Pre according to specification with the PSU and the RIAA amplifier housed in separate boxes. It is very good sounding (with Brimar CV4004 together with Telefunken PCC88 that sounds as good on 6V as on 7V heater supply). However, although SQ was good it wasn’t quite in level with my cics Memory Player (computer sound) after I had paid great concern filtering the computer PSU voltages from high frequency noise by use of pi-filters (CLC). As I always search ways to further improve SQ I tested to insert a LC-filter to suppress potential high frequency noise on incoming B+ in the amplifier box. Actually it became a T-filter (LCL) as I happened to have 3.3mH - 150uF/400V - 3.3mH in my junk box. Although the chain of 4 RC smoothing filters in the PSU box takes good care of low frequency ripple, the LC-filter was an immediately heard SQ improvement. It raised the SQ to be well in level with the very good computer sound I had already achieved. Blacker background, tighter bass and cleaner sound allover. It was quite a remarkable lift. I can only speculate about why the added filter was so effective. It may be that it takes care of the high frequency distortion on my 230V power line (I have observed flat tops on my 230V AC), it may be that the DC power cord between the boxes becomes an antenna for radio frequencies, or it may be HF noise from the rectifier diodes, although I use fast diodes. Anyway, I thought I should tell about this potential possibility to further improve SQ for those interested. Many thanks to Thorsten for his very good sounding and elegant Phono Pre.
Ingvar
I have built Thorsten’s Phono Pre according to specification with the PSU and the RIAA amplifier housed in separate boxes. It is very good sounding (with Brimar CV4004 together with Telefunken PCC88 that sounds as good on 6V as on 7V heater supply). However, although SQ was good it wasn’t quite in level with my cics Memory Player (computer sound) after I had paid great concern filtering the computer PSU voltages from high frequency noise by use of pi-filters (CLC). As I always search ways to further improve SQ I tested to insert a LC-filter to suppress potential high frequency noise on incoming B+ in the amplifier box. Actually it became a T-filter (LCL) as I happened to have 3.3mH - 150uF/400V - 3.3mH in my junk box. Although the chain of 4 RC smoothing filters in the PSU box takes good care of low frequency ripple, the LC-filter was an immediately heard SQ improvement. It raised the SQ to be well in level with the very good computer sound I had already achieved. Blacker background, tighter bass and cleaner sound allover. It was quite a remarkable lift. I can only speculate about why the added filter was so effective. It may be that it takes care of the high frequency distortion on my 230V power line (I have observed flat tops on my 230V AC), it may be that the DC power cord between the boxes becomes an antenna for radio frequencies, or it may be HF noise from the rectifier diodes, although I use fast diodes. Anyway, I thought I should tell about this potential possibility to further improve SQ for those interested. Many thanks to Thorsten for his very good sounding and elegant Phono Pre.
Ingvar
Hi,
I'm very happy with Thorsten's Phono Pre and PSU.
I have the opportunity to modify HV stage using 120uF MKP or 150uF MKP (actually HV stage it is built up using 5 x 100uF/450V electrolytic and 5 x 1K 2W resistors). It is necessary to modifiy the resistor value in order to keep same filtering, please ?
Thank you very much!
I'm very happy with Thorsten's Phono Pre and PSU.
I have the opportunity to modify HV stage using 120uF MKP or 150uF MKP (actually HV stage it is built up using 5 x 100uF/450V electrolytic and 5 x 1K 2W resistors). It is necessary to modifiy the resistor value in order to keep same filtering, please ?
Thank you very much!
You can simply replace the 100uF electrolytics with those 120uF MKP caps, as long as the film caps have a high enough DC voltage rating. The 1k 2W decoupling resistors can remain the same. Adding slightly more capacitance should not be a problem.
Let us know if you hear a night and day difference in sound.
PS -- According to many, you only really need to put a film cap in the position closest to the load. The rest can be electrolytics, and supposedly you'll never hear the difference. But hey, if you can change all the PSU caps to film, why not? De luxe!
--
Let us know if you hear a night and day difference in sound.
PS -- According to many, you only really need to put a film cap in the position closest to the load. The rest can be electrolytics, and supposedly you'll never hear the difference. But hey, if you can change all the PSU caps to film, why not? De luxe!
--
Hello,
i would like to use a 5751 in the first stage...just because I have a few...they are similar to ECC83 just with a little less gain (70). Could anybody give me advice how to bias that tube in this circuit.
I think I will have about 3 dB less gain (~39dB) with this tube. Will this be enough? I think I'll need a lil bit more. Also I'll have to set the first R (215k) of the equalization network a lil bit higher due to changes in Ra'?
Best regards,
Falk
i would like to use a 5751 in the first stage...just because I have a few...they are similar to ECC83 just with a little less gain (70). Could anybody give me advice how to bias that tube in this circuit.
I think I will have about 3 dB less gain (~39dB) with this tube. Will this be enough? I think I'll need a lil bit more. Also I'll have to set the first R (215k) of the equalization network a lil bit higher due to changes in Ra'?
Best regards,
Falk
Hi Falk,
Not much action since June on this thread so I try to give you an answer. I use 5751 in my pre with very good result. No need to adjust bias. Optimal bias point for 5751 is the same as for ECC83/12AX7, so no need to re-bias. Less gain doesn't affect the RIAA correction so neither any change of the equalization network is needed.
If you llike, try also to add cathode bypass caps shunting the 619 ohm cathode bias resistors. I use Elna Silmic II 100 uF/6.3 V with very good result. These caps should have low voltage rating for best result (there is only about 0.4 V across the cathode resistors). To my ears they make a substantial sonic improvement to the already very good Thorsten's phono pre. I think they may compensate for a problem with signal degeneration and compression over the cathode bias resistor, restoring the original signal.
Ingvar
Not much action since June on this thread so I try to give you an answer. I use 5751 in my pre with very good result. No need to adjust bias. Optimal bias point for 5751 is the same as for ECC83/12AX7, so no need to re-bias. Less gain doesn't affect the RIAA correction so neither any change of the equalization network is needed.
If you llike, try also to add cathode bypass caps shunting the 619 ohm cathode bias resistors. I use Elna Silmic II 100 uF/6.3 V with very good result. These caps should have low voltage rating for best result (there is only about 0.4 V across the cathode resistors). To my ears they make a substantial sonic improvement to the already very good Thorsten's phono pre. I think they may compensate for a problem with signal degeneration and compression over the cathode bias resistor, restoring the original signal.
Ingvar