when a RCA 5U4G slipped from my hand, it was slow motion (to mee it seem) as i watched helplessly until it hits a concrete floor, then bursts into pieces 🙁 i can only mutter s**t! 
Frankfdegrove said:
Pardon my ignorance it slipped my mind, what do you mean by this.
arnoldc said:when a RCA 5U4G slipped from my hand, it was slow motion (to mee it seem) as i watched helplessly until it hits a concrete floor, then bursts into pieces 🙁 i can only mutter s**t!
arnoldc
I think I've said more than that, huhuhuhuhu
Hi,
It just means that the 6SN7 and 6CG7/6FQ7 are electrically identical tubes, they just use a different type of socket.
With heater variants I meant that the 12CG7/12FQ7 is the same electrically as the 12SN7, the 8CG7/8FQ7 is the same as the 8SN7.
That's where it ends for those two...
The only difference between the CG and FQ, as far as I know, is that the CG series sport an internal shield between the two sections of the tube which causes the inter-electrode capacitances to be slightly different.
Nothing to be concerned about in this kind of application.
Cheers, 😉
It just means that the 6SN7 and 6CG7/6FQ7 are electrically identical tubes, they just use a different type of socket.
With heater variants I meant that the 12CG7/12FQ7 is the same electrically as the 12SN7, the 8CG7/8FQ7 is the same as the 8SN7.
That's where it ends for those two...
The only difference between the CG and FQ, as far as I know, is that the CG series sport an internal shield between the two sections of the tube which causes the inter-electrode capacitances to be slightly different.
Nothing to be concerned about in this kind of application.
Cheers, 😉
Frank, I am new to this board and thread. Does your preamp have any gain? I read you prefer the sonic signature of the tube regulated power supply. I would probably use a high capacitance SS regulated supply. Thanks for sharing your efforts.
Hi,
Badge,
First of all welcome.
The linelevel section is a buffer, no gain, preceded by a volumecontrol.
If you think you need gain there are several possibilities to integrate it within this design. Just ask.
I do, to me it sounds more natural.
Cheers,😉
Badge,
First of all welcome.
The linelevel section is a buffer, no gain, preceded by a volumecontrol.
If you think you need gain there are several possibilities to integrate it within this design. Just ask.
I do, to me it sounds more natural.
Cheers,😉
Thank you for the welcome Frank. I will need about 10 dB of gain. I modded my SACD player by going off the dac directly to a pair of Lundahl transformers. I used the two times gain taps but the output is still not up to line level standards. Can you help me with the need for this amount of gain? Perhaps another transformer output with gain?
Hi,
I can try...😉
Note that I used a 350VDC regulated supply for this one iso of the 300VDC.
This requires some biasing of the heaters for the top triodes of around 80VDC to keep within limits of heater to cathode insulation.
The easiest way to go about this is to use two dedicated heater supplies and use one tube envelope for the bottom triodes, another one for the top triodes.
Only the top needs biasing of the heaters; this can be done by a resistive divider taken from the B+.
If you feel the need for more gain the bottom cathode of the first triode can be bypassed with a high quality cap such as the excellent Black Gate.
A value of 470µF/100V should be more than ample for subsonic bass.
Should the preamp have to drive low impedances such as 10K, I recommend increasing the last coupling cap (currently 2µF) to about 10µF.
Cheers,😉
I can try...😉
Note that I used a 350VDC regulated supply for this one iso of the 300VDC.
This requires some biasing of the heaters for the top triodes of around 80VDC to keep within limits of heater to cathode insulation.
The easiest way to go about this is to use two dedicated heater supplies and use one tube envelope for the bottom triodes, another one for the top triodes.
Only the top needs biasing of the heaters; this can be done by a resistive divider taken from the B+.
If you feel the need for more gain the bottom cathode of the first triode can be bypassed with a high quality cap such as the excellent Black Gate.
A value of 470µF/100V should be more than ample for subsonic bass.
Should the preamp have to drive low impedances such as 10K, I recommend increasing the last coupling cap (currently 2µF) to about 10µF.
Cheers,😉
Attachments
Hi,
A suitable PS.
I used one for each channel.
The 4K7 trimpot allows to set the output of the regulator to output 350VDC.
The heater and biasing scheme isn't included in the drawing.
Basically I'd use 2*15VAC, each of which bridge rectified, filtered and regulated using 7812s of sufficient current rating.
Cheers,😉
A suitable PS.
I used one for each channel.
The 4K7 trimpot allows to set the output of the regulator to output 350VDC.
The heater and biasing scheme isn't included in the drawing.
Basically I'd use 2*15VAC, each of which bridge rectified, filtered and regulated using 7812s of sufficient current rating.
Cheers,😉
Attachments
HEY-Hey!!!,
Here is the current "Ultimate". shunt regulated, choke input behemoth. Even the filament's DC is choke input. Hg vapour rectifiers, and a 2C50 amplifier tube. Z-o on order of a few hundred Ohms.
regards,
Douglas
see it here, file is just a wee bit larger than allowed...
http://img.AudioAsylum.com/cgi/i.pl?u=users/12633&f=Hg_linestage.JPG
Here is the current "Ultimate". shunt regulated, choke input behemoth. Even the filament's DC is choke input. Hg vapour rectifiers, and a 2C50 amplifier tube. Z-o on order of a few hundred Ohms.
regards,
Douglas
see it here, file is just a wee bit larger than allowed...
http://img.AudioAsylum.com/cgi/i.pl?u=users/12633&f=Hg_linestage.JPG
Gday Frank
I seem to have missed it but if you would be so kind , what is/are the current requirements for the Line/Buffer stage ,in case I want to use RC filtering only ?
thanx
keith
I seem to have missed it but if you would be so kind , what is/are the current requirements for the Line/Buffer stage ,in case I want to use RC filtering only ?
thanx
keith
Greetings
Frank
Thats all inclusive right ? MC+Phono+Buffer ?
I want the last stage only
regards
keith
Frank
Thats all inclusive right ? MC+Phono+Buffer ?
I want the last stage only
regards
keith
Hi,
Morning, Keith
Disregarding the valve regulators, yes.
I suggested this figure as the spare power may be useful later on and it won't hurt anyway.
Cheers,😉
Morning, Keith
Disregarding the valve regulators, yes.
I suggested this figure as the spare power may be useful later on and it won't hurt anyway.
Cheers,😉
Hullo Frank
You wouldn’t recommend a substitute for that 6FR7 in that Shunt. Or would you??
BTW the Monsoon is hitting us early this year. 🙂
Thanks
You wouldn’t recommend a substitute for that 6FR7 in that Shunt. Or would you??
BTW the Monsoon is hitting us early this year. 🙂
Thanks
Hi Ashok,
Similar to the 6FR7 are:
6FD7 6EW7 6FD7 6DE7, probably a few others if you're willing to go for a different socket type.
Monsoon most of the year around here but this year it looks fine so far...😉
Ciao,😉
Similar to the 6FR7 are:
6FD7 6EW7 6FD7 6DE7, probably a few others if you're willing to go for a different socket type.
Monsoon most of the year around here but this year it looks fine so far...😉
Ciao,😉
Hi Frank
Any thoughts/tips on valve spacing . I'm doing single chassis dual supply for the first attempt. (have to convince myself first that I'm going in the right direction i.e. valves) MC stage also dual psu.
Using PSUD II for obtaining R values (RC filtering)without knowing actual current requirement is a bit of a pain. e.g. calculate for 40 ma on the 12bh7a stage and only use say 20 ma throws the values out ,or am I doing something wrong. I realise that consumption will vary from brand to brand.
regards
keith
Any thoughts/tips on valve spacing . I'm doing single chassis dual supply for the first attempt. (have to convince myself first that I'm going in the right direction i.e. valves) MC stage also dual psu.
Using PSUD II for obtaining R values (RC filtering)without knowing actual current requirement is a bit of a pain. e.g. calculate for 40 ma on the 12bh7a stage and only use say 20 ma throws the values out ,or am I doing something wrong. I realise that consumption will vary from brand to brand.
regards
keith
Hi,
Keith,
Usually about an inch apart but it depends on what kind of valve, component size (Cs, Rs etc.).
That's where a breadboarded prototype comes in handy.
So, basically dual mono in a single box, correct?
Ditto.
I was under the impression you were interested in the linestage only?
Or maybe you want MC stage and phonostage in a single box as well?
I wouldn't do it that way...I even doubt it would work properly.
Not optimal anyway, best to put the MC stage in a dedicated box and have it close to the tonearm base.
If you're using a valve regulated supply it doesn't really matter for as long as you have at least about 50VDC difference between input and output of the reg. it will work just fine.
PSUD will of course come up with different values for the R in the pi filter for different current draw...It is not aware of the reg, you see?
Hardly.
If you give me a clear explanation of what your plans are, I may be able to give more "on target" answers.
Best,😉
Keith,
Usually about an inch apart but it depends on what kind of valve, component size (Cs, Rs etc.).
That's where a breadboarded prototype comes in handy.
So, basically dual mono in a single box, correct?
Ditto.
I was under the impression you were interested in the linestage only?
Or maybe you want MC stage and phonostage in a single box as well?
I wouldn't do it that way...I even doubt it would work properly.
Not optimal anyway, best to put the MC stage in a dedicated box and have it close to the tonearm base.
If you're using a valve regulated supply it doesn't really matter for as long as you have at least about 50VDC difference between input and output of the reg. it will work just fine.
PSUD will of course come up with different values for the R in the pi filter for different current draw...It is not aware of the reg, you see?
Hardly.
If you give me a clear explanation of what your plans are, I may be able to give more "on target" answers.
Best,😉
Hi Frank
thanks for reply and advice.
1.The idea was to have it all in 1 box yes (dual mono single box , limited resources) as the whole unit is about 30 cm away from TT.
(exc. psu)
2. What if I seperate the MC stage and leave the phono/buffer in one box ?.
I also had plans to try a dac output(before I/V R) from a cdp via MC stage to buffer hence my previous question to you about hf filtering.
regards
keith
thanks for reply and advice.
1.The idea was to have it all in 1 box yes (dual mono single box , limited resources) as the whole unit is about 30 cm away from TT.
(exc. psu)
2. What if I seperate the MC stage and leave the phono/buffer in one box ?.
I also had plans to try a dac output(before I/V R) from a cdp via MC stage to buffer hence my previous question to you about hf filtering.
regards
keith
Hi,
O.K. but just don't make any mistake, no matter what this is not going to be an el cheapo preamp.
There just aren't that much corners left that can be cut....
Given a single box you're going to have to be creative here and have the iron exposed on top together with some PS caps and maybe the regulator valves as well.
If the box is big enough you may be able to include the MC stage if you can fit it so it won't pick up any radiation from the other stages' xfmrs.
Beware I never tried the MC stage as a DAC I/V, as the cathode is at groundlevel the negative grid voltage is basically at 0V, given the low output from a MC cart that's fine as the ECC88 is linear at that part of the loadline with low current (about 0.5mA/triode IIRC).
A DAC output however may well overload it and ggenrate some gridcurrent...maybe this idea deserves a dedicated thread to gather some more diverse input.
The concept is quite appealing though and I admit it's been float in my head for ages too...Just never got around to trying it out.
As for HF filtering, if the output of the DAC is clean_ assuming this scheme actually works_ then there shouldn't be any problem.
The headamp doesn't have any RF filter at the input as I use it but it can be easily added.
Cheers, 😉
O.K. but just don't make any mistake, no matter what this is not going to be an el cheapo preamp.
There just aren't that much corners left that can be cut....
Given a single box you're going to have to be creative here and have the iron exposed on top together with some PS caps and maybe the regulator valves as well.
If the box is big enough you may be able to include the MC stage if you can fit it so it won't pick up any radiation from the other stages' xfmrs.
Beware I never tried the MC stage as a DAC I/V, as the cathode is at groundlevel the negative grid voltage is basically at 0V, given the low output from a MC cart that's fine as the ECC88 is linear at that part of the loadline with low current (about 0.5mA/triode IIRC).
A DAC output however may well overload it and ggenrate some gridcurrent...maybe this idea deserves a dedicated thread to gather some more diverse input.
The concept is quite appealing though and I admit it's been float in my head for ages too...Just never got around to trying it out.
As for HF filtering, if the output of the DAC is clean_ assuming this scheme actually works_ then there shouldn't be any problem.
The headamp doesn't have any RF filter at the input as I use it but it can be easily added.
Cheers, 😉