Remember, that post was for a CD output stage. I said it could be ADAPTED for line stage use. You wouldn't use the resistor divider and LCR filter before the grid in a line stage. Did you put all those parts in? You would just connect the grid to a volume control wiper (I'd add a 1MEG safety resistor from grid to ground and maybe a grid stopper of 100 ohms).
You should measure gain of 5X to 6X (around 15 dB). And yes, a 10 W resistor will be very hot with 5 watts dissipated in it. That's normal. I would make sure that it has plenty of air flow and is not right next to other components that it could cook.
You should measure gain of 5X to 6X (around 15 dB). And yes, a 10 W resistor will be very hot with 5 watts dissipated in it. That's normal. I would make sure that it has plenty of air flow and is not right next to other components that it could cook.
If it's not too much hassle, may I suggest you try this- http://www.diyaudio.com/forums/showthread.php?postid=821678#post821678
That's what I use and sounds just right and gain just right for my 45, 2A3 and 300B amps.
That's what I use and sounds just right and gain just right for my 45, 2A3 and 300B amps.
Thanks for the replies guys.
Brian, I did remove all of the filtering components, I have connected a 220k resistor from grid to ground, thats it nothing more.
arnoldc, if I use the schematic that you showed, how would I incorporate the CCS?
BTW what is the ouput impedance of the linestage?
This just hit me, I am presently using headphones (Senn HD 580) with the circuit, is that why I have low gain?
Thanks
Lawrence
Brian, I did remove all of the filtering components, I have connected a 220k resistor from grid to ground, thats it nothing more.
arnoldc, if I use the schematic that you showed, how would I incorporate the CCS?
BTW what is the ouput impedance of the linestage?
This just hit me, I am presently using headphones (Senn HD 580) with the circuit, is that why I have low gain?
Thanks
Lawrence
As Arnold said, that would be your problem! IIRC, those phones have an impedance of about 300 ohms. Most linestages will not drive them at all. The output Z of my circuit will be about 900 ohms. That makes a divider ratio of 300/(300+900) or about 1/4. That would eliminate most of the gain of the tube, increase distortion enormously, and cause a bass roll-off because the coupling cap isn't sized for 300 ohms. You need a headphone amp, many of which are described in this forum.
OK, I finally have a power supply combination that works unbelievably well and sounds great! I had been running my 12B4 on an Eico tube regulated bench supply all these months and there was always a small hint of hum and noise in the speakers if you put your ears right up to them. Recently LuckyLyndy and found an interesting H-V regulator board thats made in GErmany by Thel Audio World Audio in Staufenerg Germany. Cost of the board was about 80.00 US Dollars delivered. It comes fully assembl;ed. This regulator board uses an IRFPG50 as the pass device. Its driven by a pretty conventional driver transistor/zener type circuit. Voltage is set with a 10 turn pot. The nice part about this board is that it will accept either DC 100 to 400 volts input, or AC 80 to 320 volts. Its rated at 100ma maximum and I am drawing about 60 ma through it and it gets just a tad bit warm after several hours opaeration. While I won't post the schematic here I might be inclined to scan it and e-mail it to anyone interested.
At any rate it got rid of every last bit of noise form my 12B4 line stage and the stage seems to have improved in many aspects to boot. The S/N has got to be around 90db plus now! The bottom end does seem a tad bit deeper and more refinedl. The midrange is still glorious and the highs seem cleaner and even more refined than they were without it. Needless to say adding this solid state regulator did not change the overall character of the sound, it improved it without doubt!
It wold be easy tio breadboard this circuit.... but even so the assembled version is even a good deal!!
Thanks to Promethius for getting and mailing these regulator boards to us!!
Mark
At any rate it got rid of every last bit of noise form my 12B4 line stage and the stage seems to have improved in many aspects to boot. The S/N has got to be around 90db plus now! The bottom end does seem a tad bit deeper and more refinedl. The midrange is still glorious and the highs seem cleaner and even more refined than they were without it. Needless to say adding this solid state regulator did not change the overall character of the sound, it improved it without doubt!
It wold be easy tio breadboard this circuit.... but even so the assembled version is even a good deal!!
Thanks to Promethius for getting and mailing these regulator boards to us!!
Mark
Attachments
Powering my 12B4 line stage for now...... An Eico Adjustable regulated H-V bench supply, Thel RNT-400 regulator board, a Power One 40 amp regulated adjustable supply for the filaments. there is also an adjustable chip type regulator inside the line stage to set the filamant voltage and provide further regulation. LIke I originally predicted the power supplies will cost far more than the line stage itself.
Mark
Thel Audio World
Mark
Thel Audio World
Attachments
Well, I think you'd have to hear it before you could really judge.... If one of you two want to send me a shunt regulator card I will be happy to make a comparison for you. If its noticably better I will buy it from you!
I have considered a shunt regulator but too many have said that shunt regulators generate alot more noise that the pass type do. And noise riding on the DC is a big factor in this line stage. There is no measurable noise comming out of the Thel regulator that I could measure on my Tektronix 7904A scope. I would have to be set up in a screen room to be able to see what little is there since all I see is residual RF the scope picks up from the air.
Don't forget that the DC comming into the Thel card is ALREADY regulated! The tube H-V supply was just not as clean as this sort of line stage requires. As good as this thing now sounds it would be dificult to imagine it getting very much better than it is.
Mark
I have considered a shunt regulator but too many have said that shunt regulators generate alot more noise that the pass type do. And noise riding on the DC is a big factor in this line stage. There is no measurable noise comming out of the Thel regulator that I could measure on my Tektronix 7904A scope. I would have to be set up in a screen room to be able to see what little is there since all I see is residual RF the scope picks up from the air.
Don't forget that the DC comming into the Thel card is ALREADY regulated! The tube H-V supply was just not as clean as this sort of line stage requires. As good as this thing now sounds it would be dificult to imagine it getting very much better than it is.
Mark
Mark A. Gulbrandsen said:
I don't judge anything; I just urge you to try.
you probably have few gas stab tubes just layin' around ?
besides-mentioning those "too many" .....they probably don't know how to make decent shunt reg with gas tubes as reg element (only,assisted or co-existed)...
anyway-it's not nuclear science
one of good old plain gas shunt regs is good enough for phono stage,and entire chain is linked to pair of KHs........hiss or hum are nowhere, and OA2+OC3 combo is directly above first 12AX7's anode
if you insist-I can send you these tubes
full blast electronic shunt reg must not be better overall .........
series reg and shunt reg.......think in B class versus A class domen.
...
Mark A. Gulbrandsen said:
give me link to post with your stage actual schmtc (or give me current/per channel and Ub) ,confirm what you have of gas stabs (OB2 and OD3, 2pcs each ?) and I'll calculate what I can.....I'm sure that someone else here will find some mistake....
but forum is for this ..........0B2 is 105V
0D3 is for 150V
just short data..........
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