Hi Everyone, this is a Final wiring of a SRPP 6SL7; 6AS7 Power amplifier that needs a going over, to see if I have everything hooked up right. I realize terminal strips have a ground to them as the center tap of them goes to the screw, but, my chassis bottom is all wood! I would like a floating ground amplifier, with only the Power transformer and all AC to ground at the EIC Socket if possible...What do you think? I have a gold colored floating bus bars as shown! This could be a great sounding amplifier indeed! Pianolydia
P.s. thanks for your input will be utmost appreciated!!
P.s. thanks for your input will be utmost appreciated!!
i am testing my tube amp now, however I will build a board for it.
I would do the following:
1. Mark the underside of the chassis (black Marker) Pin 1 on each tube
2. Twist and connect all the heaters
3. connect the anode resistors and bypass capacitors neg to ground
4. Connect the grid bias resistors
5. Connect coupling capacitors
6. connect main B+ capacitors (neg to ground) and resistors
7. Connect Output transformer primaries to plates and UL tap to grid if used
8. Connect plates and output transformer centertap to appropriate B+ points
I would use different colour wire for each of inputs / outputs / B+ taps
Check each step of the way
power up and test
I would do the following:
1. Mark the underside of the chassis (black Marker) Pin 1 on each tube
2. Twist and connect all the heaters
3. connect the anode resistors and bypass capacitors neg to ground
4. Connect the grid bias resistors
5. Connect coupling capacitors
6. connect main B+ capacitors (neg to ground) and resistors
7. Connect Output transformer primaries to plates and UL tap to grid if used
8. Connect plates and output transformer centertap to appropriate B+ points
I would use different colour wire for each of inputs / outputs / B+ taps
Check each step of the way
power up and test
This is my SRPP 6SL7 ; 6AS7 Schematic
Enjoy, as I designed this myself, with TubeCad, and SECad from John Broskie! This is a simple Cathode Bias SRPP Awesome design centered around the best curves, I could get with keeping in mind, IMD, PSRR, and Distortion figures as well as tube life! This corresponds to the wiring drawing below in this thread.
Enjoy, as I designed this myself, with TubeCad, and SECad from John Broskie! This is a simple Cathode Bias SRPP Awesome design centered around the best curves, I could get with keeping in mind, IMD, PSRR, and Distortion figures as well as tube life! This corresponds to the wiring drawing below in this thread.
.33uf working into 200k seems very low.
Will the 6SL7 drive the 6AS7 with such low voltages?
Phil
Will the 6SL7 drive the 6AS7 with such low voltages?
Phil
Yes, this will work well!
Yes, it will at 22% Imax, Voltage, at 57% wattage at 48% as per 43.6mA
I based the fact that input voltage will be about 31vdc which is low, but for 1000 ohms drops 100 volts. I ran the SECAD and input voltage and same grid resistor and grid stopper at 1k got good readings. Notice though that it all is based upon the bias resistor and primary impedence of the output transformer! I had to go to a low Primary to get this to work, but the Distortion figures are very good! However, you are right, too low of bias and positive grid will happen! The only problem with these programs is they base there readings at idle. 200k is shunt resistor will not affect as much as the 1k in line voltage drop! thats the one we have to worry about
Yes, it will at 22% Imax, Voltage, at 57% wattage at 48% as per 43.6mA
I based the fact that input voltage will be about 31vdc which is low, but for 1000 ohms drops 100 volts. I ran the SECAD and input voltage and same grid resistor and grid stopper at 1k got good readings. Notice though that it all is based upon the bias resistor and primary impedence of the output transformer! I had to go to a low Primary to get this to work, but the Distortion figures are very good! However, you are right, too low of bias and positive grid will happen! The only problem with these programs is they base there readings at idle. 200k is shunt resistor will not affect as much as the 1k in line voltage drop! thats the one we have to worry about
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My apologies this is correct!
My apologies, I left out the 6SL7 readings shown in TubeCad, at b+265 in at .33uF coupling cap, and 200k Rl grid resistor, and 100 Ohm Ra=Rk and this set the bias at 3.0mA with 5mA Max. this gave a reading of PSRR -7.96. Readings were 60% IMAX, 53% Voltage, and 40% Wattage. Now, the 6AS7 readings was the correct figures below, 22% IMAX, 57% Voltage and 48% wattage dissipation. PSRR -2.0 which is excellent! Yielding 4.6% 2nd. 0% 3rd. the 1.5k bias resistor set the bias for 43.6mA current. That should do it!
My apologies, I left out the 6SL7 readings shown in TubeCad, at b+265 in at .33uF coupling cap, and 200k Rl grid resistor, and 100 Ohm Ra=Rk and this set the bias at 3.0mA with 5mA Max. this gave a reading of PSRR -7.96. Readings were 60% IMAX, 53% Voltage, and 40% Wattage. Now, the 6AS7 readings was the correct figures below, 22% IMAX, 57% Voltage and 48% wattage dissipation. PSRR -2.0 which is excellent! Yielding 4.6% 2nd. 0% 3rd. the 1.5k bias resistor set the bias for 43.6mA current. That should do it!
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10 W EDCOR is very, very small for 6AS7, IMO.
You see that OT is cheep and current is enough for primary coil, but it isn't first important condition. It iron is far for providing good sound.
In Your place I will use 25 W EDCOR / If I need 3 w output power, I multiply 3 to 10-15 to receive wattage of OT/.....
You see that OT is cheep and current is enough for primary coil, but it isn't first important condition. It iron is far for providing good sound.
In Your place I will use 25 W EDCOR / If I need 3 w output power, I multiply 3 to 10-15 to receive wattage of OT/.....
Yes, I will do that!
Good point, The more headroom the better! outout transformers, people say is where one should spend most of their $$$, Thanks! Pianolydia
Good point, The more headroom the better! outout transformers, people say is where one should spend most of their $$$, Thanks! Pianolydia
Would like Eli Duttman to look at this!
Hi Everyone, I would like a person who knows how to wire up a Tube amp such as this, and tell me if I have everything wired up correctly! Thanks Pianolydia
Hi Everyone, I would like a person who knows how to wire up a Tube amp such as this, and tell me if I have everything wired up correctly! Thanks Pianolydia
I'm sorry, when i red the thread title i was thinking SRPP was related to output stage...not the front end 😀
Anyway i don't get why use only a side of 6AS7...and then use 2 6AS7 for stereo , i would use only one 6AS7 for stereo . Am I missing something ?
I know 🙂 my fault , i was thinking the OP was using the 6AS7 in SRPP , this would be intresting for me while the use of SRPP as driver is common.
Anyway i still don.t get the use of half 6AS7.
Okay! here is an answer
There is a possibility that one can Parallel SE the same tube but be prepared to either have higher distortion and that will have to be dealt with and lower impedance output trans primary of 600ohms or less, and Most twin Triodes do not match each others plates and there could be some differences in tonality between stereo speakers because of that! Now, using biasing pots may be a way to match up the closer sections and dial everything in, But with these 6AS7's I am not sure it would be worth the extra 3-4 watts..... I am guessing and only guessing, that the Cost would be way more expensive to run as the Output trans will be a lot more expensive. Might as well go to a 300B output stage, you could get about 12-watts per channel SE with such and the Cost of the Output trans your already going to Spend $$$, So if I am wrong someone tell me!. There is another possibility, Run two 6AS7's in PP using one Output transformer, Only problem: You will lose some of that mid range magic the SE Triode gives you! Two totally different Topologies, But, with PP You would have more Dynamic Power and clarity in the lower bass region I believe! Just my two cents worth. I like to keep everything that is SE Triode AS FEW PARTS AS I CAN! AND HI QUALITY! pianolydia P.s. reason for only one half a 6AS7 is, it is easier to find (2) halves that match up than all in one tuibe! as each channel can be matched together easier especially if using used tubes....
There is a possibility that one can Parallel SE the same tube but be prepared to either have higher distortion and that will have to be dealt with and lower impedance output trans primary of 600ohms or less, and Most twin Triodes do not match each others plates and there could be some differences in tonality between stereo speakers because of that! Now, using biasing pots may be a way to match up the closer sections and dial everything in, But with these 6AS7's I am not sure it would be worth the extra 3-4 watts..... I am guessing and only guessing, that the Cost would be way more expensive to run as the Output trans will be a lot more expensive. Might as well go to a 300B output stage, you could get about 12-watts per channel SE with such and the Cost of the Output trans your already going to Spend $$$, So if I am wrong someone tell me!. There is another possibility, Run two 6AS7's in PP using one Output transformer, Only problem: You will lose some of that mid range magic the SE Triode gives you! Two totally different Topologies, But, with PP You would have more Dynamic Power and clarity in the lower bass region I believe! Just my two cents worth. I like to keep everything that is SE Triode AS FEW PARTS AS I CAN! AND HI QUALITY! pianolydia P.s. reason for only one half a 6AS7 is, it is easier to find (2) halves that match up than all in one tuibe! as each channel can be matched together easier especially if using used tubes....
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Myth busting....
Hi,
First of all these are NOT twin triodes but are dual triodes.
This mean that a single envelope contains two triodes of the same type but these are not matched.
Putting these in // essentially means that you now have a new single triode tube with half the internal resistance, twice as much dissipation, twice the gm and slightly less noise (3dB).
Any PSE or PPP stage operates in much the same way. Even current manufacture 2A3 tubes are essentially two tubes in a single envelope and there must be other examples for sure.
Bottom line is, matching half a 6AS7 two another half one or matching a //ed one to another //ed one amounts to the same job really.
Using one half a 6AS7 means also using the other whether you take advantage of it or not, the unused half will still wear out.
Also, the paralleled tube presenting only half of the load to the OTP means higher output and less distortion for the same load.
Now, a single 1/2 6AS7G exists and there also exist others that are pretty close to it. Just as there are tubes that are more less the same as a //ed 6AS7G as well.
All in all the fear of losing said "midrange clarity" may be justified but then I'd look at something like a superbly linear DHT and suffer the price hit plus all other consequences rather than fretting over the effect of //ing a humble 6AS7G.
In fact, IMHO, there's more to win than to loose by paralleling them in most cases.
Ciao, 😉
Hi,
First of all these are NOT twin triodes but are dual triodes.
This mean that a single envelope contains two triodes of the same type but these are not matched.
Putting these in // essentially means that you now have a new single triode tube with half the internal resistance, twice as much dissipation, twice the gm and slightly less noise (3dB).
Any PSE or PPP stage operates in much the same way. Even current manufacture 2A3 tubes are essentially two tubes in a single envelope and there must be other examples for sure.
Bottom line is, matching half a 6AS7 two another half one or matching a //ed one to another //ed one amounts to the same job really.
Using one half a 6AS7 means also using the other whether you take advantage of it or not, the unused half will still wear out.
Also, the paralleled tube presenting only half of the load to the OTP means higher output and less distortion for the same load.
Now, a single 1/2 6AS7G exists and there also exist others that are pretty close to it. Just as there are tubes that are more less the same as a //ed 6AS7G as well.
All in all the fear of losing said "midrange clarity" may be justified but then I'd look at something like a superbly linear DHT and suffer the price hit plus all other consequences rather than fretting over the effect of //ing a humble 6AS7G.
In fact, IMHO, there's more to win than to loose by paralleling them in most cases.
Ciao, 😉
does this mean
Yes, sorry, I termed that wrong; I meant dual triode. Yes Dual triode is two Triodes in one envelope. If I were to use a 850 ohm primary which would be halfed 1.7k in primary impedence, into the same load of 4-ohms, would the Power supply have to be re-designed? could we keep the same component values, we would just have higher tube dissipation, and more power output as a result? Would we have to have a different bias resistor to change the current flowing at idle? this is a concern, what do you think, since I like the EDCOR 15-4-1.7K? I would have to step up to the CXSE 25-4-600 to get the simulations in SECAD software to say that everything is OK! in terms of operating conditions.... I already Own the 6AS7's NOS and want to keep them....pianolydia
Yes, sorry, I termed that wrong; I meant dual triode. Yes Dual triode is two Triodes in one envelope. If I were to use a 850 ohm primary which would be halfed 1.7k in primary impedence, into the same load of 4-ohms, would the Power supply have to be re-designed? could we keep the same component values, we would just have higher tube dissipation, and more power output as a result? Would we have to have a different bias resistor to change the current flowing at idle? this is a concern, what do you think, since I like the EDCOR 15-4-1.7K? I would have to step up to the CXSE 25-4-600 to get the simulations in SECAD software to say that everything is OK! in terms of operating conditions.... I already Own the 6AS7's NOS and want to keep them....pianolydia
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Hi,
You also have the option of using only one 6AS7G where each half amplifies one channel.
It's not clear to me if you're going to build this as a stereo unit with one PS or if these are going to be mono blocks with their PS on board.
Ciao, 😉
You also have the option of using only one 6AS7G where each half amplifies one channel.
It's not clear to me if you're going to build this as a stereo unit with one PS or if these are going to be mono blocks with their PS on board.
Ciao, 😉
Yes, this is a Stereo one PSU amplifier
Yes, this is a Stereo; one PSU amplifier! One thought I had, was to get a 50-watt Power resistor and parallel that OPT Primary to lower the value the OPT sees as plate Impedance will be too high with 1.7k In PSE tube output topolgy! What are your thoughts, as It would be nice to PSE Each 6AS7 per channel giving 8-9watts per channel! ~ Pianolydia
Yes, this is a Stereo; one PSU amplifier! One thought I had, was to get a 50-watt Power resistor and parallel that OPT Primary to lower the value the OPT sees as plate Impedance will be too high with 1.7k In PSE tube output topolgy! What are your thoughts, as It would be nice to PSE Each 6AS7 per channel giving 8-9watts per channel! ~ Pianolydia
Hi,
It does not work that way.
If you keep the same OPT you'll end up loosing some power due to the mismatch anyhow.
BTW, I can understand why one would like the Edcor OPTs but why does it have to be the one with the 1K7 primary?
You'll also need to change some part values when the 6AS7Gs are //ed but we can see about that later.
Hopefully the 8SL7 stage has enough clout to drive the output properly.
Ciao, 😉
It does not work that way.
If you keep the same OPT you'll end up loosing some power due to the mismatch anyhow.
BTW, I can understand why one would like the Edcor OPTs but why does it have to be the one with the 1K7 primary?
You'll also need to change some part values when the 6AS7Gs are //ed but we can see about that later.
Hopefully the 8SL7 stage has enough clout to drive the output properly.
Ciao, 😉
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