burnedfingers said:
Joe, it's a simple circuit, and since the volume control is in front of the gain tube, you can use anything. Some will just need more signal grounded out than others.
Changes would of course be in the plate resistor and cathode resistor of the 1st tube. Use the values contained in the "Resistance Coupled Amplifier" chart in the back of any tube manual.
As far as "older looking" goes... you have limited options in an ST shape or a metal preamp tube. 6F5, 6SF5, 6C8-G, 6K5 (good luck), 6C5, 6J5, 6F8-G were about all you had to work with prior to WWII. High gain broadcast type preamps in the 30's used 6F5's a lot.
PREAMP.
Hi,
If you allow me, don't forget the 12AY7A/6072 is a low noise tube.
All octal based tubes I know of aren't designed with this in mind.
Since this is a preamp and you both have highly effecient speakers this may be an issue.🙄
Cheers,😉
Hi,
If you allow me, don't forget the 12AY7A/6072 is a low noise tube.
All octal based tubes I know of aren't designed with this in mind.
Since this is a preamp and you both have highly effecient speakers this may be an issue.🙄
Cheers,😉
Re: PREAMP.
As I stated a few posts back, yes Frank, it definitely is an issue. But it bears repeating, so thanks for mentioning it.
I don't recommend using octals for the gain stage in this design - but Joe specifically asked about old tubes.
fdegrove said:
As I stated a few posts back, yes Frank, it definitely is an issue. But it bears repeating, so thanks for mentioning it.
I don't recommend using octals for the gain stage in this design - but Joe specifically asked about old tubes.
Hi guys,
One question about the power supply circuit.
could someone please clarify what spec the transformer needs to be ?
Cheers,
Fbleagh
One question about the power supply circuit.
could someone please clarify what spec the transformer needs to be ?
Cheers,
Fbleagh
SPECCIES.
Hi,
In the PC bizz we say (between the teeth) RTFM, here we politely point you to page #1 post # 2.
Cheers,
Hi,
In the PC bizz we say (between the teeth) RTFM, here we politely point you to page #1 post # 2.
Cheers,
Fred,
Sorry should have worded my query a bit better.
I understand that the transformer needs a
300 -0- 300 primary @ 100ma
btu im unsure as to the 2 secondaries.
IE. sec1 = 5V @ ??
and Sec2 = ?? @ ??
Cheers,
Fbleagh
Sorry should have worded my query a bit better.
I understand that the transformer needs a
300 -0- 300 primary @ 100ma
btu im unsure as to the 2 secondaries.
IE. sec1 = 5V @ ??
and Sec2 = ?? @ ??
Cheers,
Fbleagh
ERRRRR...IT'S FRANK...I SWEAR IT IS.
Hi,
These are heater requirements, so all you need to do is specify a voltage + heater current requirement for the rectifier (5Y3GT-5V) and whatever tube(s) you want to use (6.3 V in this case).
To help you out:
The heater of the 5Y3 needs 2.0 A.
A single twin triode 6SN7 would consume 600 mA.
Cheers,😉
Hi,
These are heater requirements, so all you need to do is specify a voltage + heater current requirement for the rectifier (5Y3GT-5V) and whatever tube(s) you want to use (6.3 V in this case).
To help you out:
The heater of the 5Y3 needs 2.0 A.
A single twin triode 6SN7 would consume 600 mA.
Cheers,😉
I just found out the following from Hammond Manufacturing
Model 272BX
95VA
Primary 115 60 Hz
Secondary 300-0-300V 100mA
Secondary 5 V@2 A
Secondary 6.3 V@3 A
73$ canadian from Digikey
hope this helps 🙂
Model 272BX
95VA
Primary 115 60 Hz
Secondary 300-0-300V 100mA
Secondary 5 V@2 A
Secondary 6.3 V@3 A
73$ canadian from Digikey
hope this helps 🙂
Excellent.
I found the 372BX for use here in australia.
Same specs but universal primary.
One other question , would there be any probs using a 6SN7GT is this circuit instead of the 6SN7 ?
The pinouts and numbers look like they match. Am I correct ?
I found the 372BX for use here in australia.
Same specs but universal primary.
One other question , would there be any probs using a 6SN7GT is this circuit instead of the 6SN7 ?
The pinouts and numbers look like they match. Am I correct ?
6SN7
Hi,
No problem whatsoever.
The pinout is indeed the same for all these 6SN7 equivalents.
Cheers,😉
Hi,
No problem whatsoever.
The pinout is indeed the same for all these 6SN7 equivalents.
Cheers,😉
FBLEAGH
It will be interesting to see if your finished product works as good as mine does🙄
If you have followed this thread you will notice that I didn't get the same bias voltages as stated by another party. I was accused of not using the correct values, incorrect placement of parts, using the wrong tap for heaters, and about anything else you could imagine. There is an error in the design, it didn't take into account the grid resistance of the tube which would change the calculations for the resistances.
I hope that you don't have a problem with hum like I do. Dispite the usage of star grounding, floating the input and output jacks above ground as well as the volume control. There are no ground loops that I can find on mine. Feel free to email me for my changes to the circuit.
Joe
It will be interesting to see if your finished product works as good as mine does🙄
If you have followed this thread you will notice that I didn't get the same bias voltages as stated by another party. I was accused of not using the correct values, incorrect placement of parts, using the wrong tap for heaters, and about anything else you could imagine. There is an error in the design, it didn't take into account the grid resistance of the tube which would change the calculations for the resistances.
I hope that you don't have a problem with hum like I do. Dispite the usage of star grounding, floating the input and output jacks above ground as well as the volume control. There are no ground loops that I can find on mine. Feel free to email me for my changes to the circuit.
Joe
If by chance you do get it running without any hum problem you might want to lower the B+ to 250volts and use a pair of 5692 red base RCA tubes in place of the 6SN7/6SN7GT. There is supposed to be a great difference in the sound of them.
Joe
Joe
This "design" is not unique, or even particularly interesting. It is a simple resistance coupled amplifier, capacitor coupled to a cathode follower. Anybody who owns a tube manual can find the driver stage in the back verbatum, and the values are taken from the "resistance coupled amplifier chart", and the cathode follower design principles are contained in the front of the RCA manual.
I have not ever had any hum problems with it, and find it quite nice to listen to.
I have not ever had any hum problems with it, and find it quite nice to listen to.
your pre-amo circuit is very good. I test another circuit which use half 6sn7 or 26,56,76 to push one pre-amp ourtput trans, if the output had quality bandwidth,
its very good.
thanks
Thomas
its very good.
thanks
Thomas
Humming problem finally solved.
While accusations have flown in the past about my grounding techniques and my possible wiring mistakes and me not building this little jewel per the schematic, I have finally resolved my humming "basturds" problem. The fault lies in the transformer. When the transformer is remoted the hum goes away. Now being dubbed by some as uninformed and sadly mistaken the conclusion that I seem to draw is that the lack of shielding is the hum problem. Even with the DC taken off the heaters it seems to be 100 percent quiet.
While trying not to start WW3 here....
My suggestion to anyone wanting to try this line amp would be to read the suggestions posted in earlier threads. The addition of the 100Ohm resistors on the grids seemed to help the stability. There are other modifications that I have done, some on my own and some on the suggestion of others on the board. I would gladly post the modifications complete with resistor and cap values but I doubt that my hand Cad would be appreciated.
While finally setting the plate voltage at 250volts I popped in the more expensive Red Base 5692 RCA tubes in place of the dime store 6sn7 variety I had been using. I noticed a marked difference in the response of the unit. This seems to support my earlier remarks "you get what you pay for" The cheaper tubes sounded good but there was a marked improvement when going to the more expensive "Red October" tubes.
The cheap coupling caps were discarded in favor of the more expensive oil/paper variety and this lended a smoother fuller sound. The cheap .30 a piece resistors were discarded in favor of a more pleasing variety that retail for $3.00 a piece. While some "more informed" on this board would dub this as BS I still maintain the proof is in the listening.
This project while taking too long due to my "uninformed status" has produced usable results. The line amp is certainly nothing special but it will maintain a position of high honor in my garage workshop.
"Uninformed Joe"
While accusations have flown in the past about my grounding techniques and my possible wiring mistakes and me not building this little jewel per the schematic, I have finally resolved my humming "basturds" problem. The fault lies in the transformer. When the transformer is remoted the hum goes away. Now being dubbed by some as uninformed and sadly mistaken the conclusion that I seem to draw is that the lack of shielding is the hum problem. Even with the DC taken off the heaters it seems to be 100 percent quiet.
While trying not to start WW3 here....
My suggestion to anyone wanting to try this line amp would be to read the suggestions posted in earlier threads. The addition of the 100Ohm resistors on the grids seemed to help the stability. There are other modifications that I have done, some on my own and some on the suggestion of others on the board. I would gladly post the modifications complete with resistor and cap values but I doubt that my hand Cad would be appreciated.
While finally setting the plate voltage at 250volts I popped in the more expensive Red Base 5692 RCA tubes in place of the dime store 6sn7 variety I had been using. I noticed a marked difference in the response of the unit. This seems to support my earlier remarks "you get what you pay for" The cheaper tubes sounded good but there was a marked improvement when going to the more expensive "Red October" tubes.
The cheap coupling caps were discarded in favor of the more expensive oil/paper variety and this lended a smoother fuller sound. The cheap .30 a piece resistors were discarded in favor of a more pleasing variety that retail for $3.00 a piece. While some "more informed" on this board would dub this as BS I still maintain the proof is in the listening.
This project while taking too long due to my "uninformed status" has produced usable results. The line amp is certainly nothing special but it will maintain a position of high honor in my garage workshop.
"Uninformed Joe"
hi burnedfingers,
will 6sn7 U only use one plate had cause more noise than 76 tubes.
The hum noise look 76 & 56 was lower.
can U tell me which method to low down the hum?
thanks
Thomas
will 6sn7 U only use one plate had cause more noise than 76 tubes.
The hum noise look 76 & 56 was lower.
can U tell me which method to low down the hum?
thanks
Thomas
Back from the dead, I found this post while searching EZ preamp circuits. I wondered what any follow-up might be 3 years on? Anyone still using this design? Any tweaks that yielded nice improvements? Any sound comparos with a Foreplay or similar? Just curious.
speaker
(I do think this thread would be well worth the read from start to finish for any beginner too. Much good data covered in a practical way.)
speaker
(I do think this thread would be well worth the read from start to finish for any beginner too. Much good data covered in a practical way.)
burnedfingers said:
