I want to start a thread about this kit build process because after some tinkering and adjusting this amplifier sounds much better than stock, in my opinion, and will be far more reliable. So first thing I want to say is that I built this kit exactly to the guide/schematic and then started to make changes. First thing I noticed was how hot the output tubes were running. The schematic suggests running a 300b with 482 volts at the plate with 73ma plate current. In my opinion this will fry any standard 300b pretty quickly. So the first mod I performed was to bring the plate voltage down to 400. Mine was actually running at 495 and 75ma. So to get the voltage down you will need to use the purple b+ tap, not the red, and use a 5u4gb rectifier tube. This will get you to 400v and 60ma which is a more typical operating point for 300b. This is just one of the mods I have done and there are several more to discuss but I’m interested to hear about others experience with this kit before I move on to the other changes. I have attached photos of what my build looks like at this point. So please chime in if you have this kit. Cheers Thomas
Here is the reply from Mr Ohashi (top tube amp designer from Japan)
Dear Mr. Victor Kung
With all respect, Thomas does not seem to understand the difference between fixed bias and self-bias.
I have attached the measured data for the SV-S1616D, which is a self-biased amplifier, so in order to calculate the plate loss
(Ep-Ek)×Ip=Plate Dissipation(W)
Let us apply the actual measured values.
(486V-84V)×84mA=33.8W
Needless to say, the Maximam Plate Dissipation of 300B is 40W, and the maximum plate current in the self-bias circuit is 100mA.
From the above, the operating conditions of SV-S1616D have a margin of more than 15% in terms of plate dissipation, which is perfectly acceptable.
The seller needs to have the knowledge to clearly answer these low level remarks. We should always be stubborn and eloquent when it comes to quality.
Thanks
Makoto
Dear Mr. Victor Kung
With all respect, Thomas does not seem to understand the difference between fixed bias and self-bias.
I have attached the measured data for the SV-S1616D, which is a self-biased amplifier, so in order to calculate the plate loss
(Ep-Ek)×Ip=Plate Dissipation(W)
Let us apply the actual measured values.
(486V-84V)×84mA=33.8W
Needless to say, the Maximam Plate Dissipation of 300B is 40W, and the maximum plate current in the self-bias circuit is 100mA.
From the above, the operating conditions of SV-S1616D have a margin of more than 15% in terms of plate dissipation, which is perfectly acceptable.
The seller needs to have the knowledge to clearly answer these low level remarks. We should always be stubborn and eloquent when it comes to quality.
Thanks
Makoto
Hi Victor
I do understand that the amp is self bias. I am calculating plate current using the voltage drop across the cathode resistor which is 1200 ohms with a voltage drop of 90. Since 300b is a triode the plate current and cathode current are the same, I believe. So my calculations say 75ma and about 30.4 watts total dissipation. That is under the limit of 36-40 watts max and 100ma max. But that is still quite high in my opinion for standard 300b operating at nearly 500 volts on the plate. I’m just stating here that I prefer to run my 300b at lower plate voltage/current. I think they sound much better at 350-400 volts and in the 55-60ma range. The amp will run cooler and the tubes will last a lot longer.
I do understand that the amp is self bias. I am calculating plate current using the voltage drop across the cathode resistor which is 1200 ohms with a voltage drop of 90. Since 300b is a triode the plate current and cathode current are the same, I believe. So my calculations say 75ma and about 30.4 watts total dissipation. That is under the limit of 36-40 watts max and 100ma max. But that is still quite high in my opinion for standard 300b operating at nearly 500 volts on the plate. I’m just stating here that I prefer to run my 300b at lower plate voltage/current. I think they sound much better at 350-400 volts and in the 55-60ma range. The amp will run cooler and the tubes will last a lot longer.
Which should be fine.. I've been building 300B amps for about 25 years now and while mine are all fixed bias the voltage and dissipation are about the same as discussed. (400 - 425V, and 65mA - 75mA) I haven't had a problem with 300B wearing out quickly and have had pairs of JJ 300B last more than 7000 - 8000 hours.
These SV amplifiers have a very good reputation for quality and design.
These SV amplifiers have a very good reputation for quality and design.
Hi Thomas
Here is the reply from Mr Ohashi....
I do not disagree with what he is saying.
On the other hand, we sample all of the plate currents of the approximately 200 pairs we have purchased from Western Electric 300B remanufactured since 2021, and determine the average
in a fixed bias circuit
Plate Voltage=300V
Grid Bias=-58V
The average value is 68.9mA, which is an extremely high efficiency under the operating conditions of the data clearly shows that this is probably due to the graphene coating on the plates, which has improved the efficiency by more than 15% compared to lots made before 2006.
In other words, it is the designer's opinion that there is no risk in operating conditions with an effective plate voltage of approximately 400 V and a plate current of 80 mA.
The SV-S1616D has shipped approximately 1000 sets since 2015. The majority of them are equipped with 300B made by Shuguang of China, and we have not experienced any trouble caused by the 300B operating conditions.
On the other hand, if longevity is more important than sound quality, the 300B can be easily changed by simply increasing the resistance value for bias voltage generation, but we believe that the goodness of the 300B cannot be achieved at 65mA or less in terms of operation.
Audio amplifier design is similar to seasoning of a curry rice restaurant. Some restaurants are sweet, some are spicy. The customer has the right to choose it.
Victor curry are spicy but very tasty.
I have nothing to say further.
thank you Mr Ohashi's feedback to Thomas's concerns.
Here is the reply from Mr Ohashi....
I do not disagree with what he is saying.
On the other hand, we sample all of the plate currents of the approximately 200 pairs we have purchased from Western Electric 300B remanufactured since 2021, and determine the average
in a fixed bias circuit
Plate Voltage=300V
Grid Bias=-58V
The average value is 68.9mA, which is an extremely high efficiency under the operating conditions of the data clearly shows that this is probably due to the graphene coating on the plates, which has improved the efficiency by more than 15% compared to lots made before 2006.
In other words, it is the designer's opinion that there is no risk in operating conditions with an effective plate voltage of approximately 400 V and a plate current of 80 mA.
The SV-S1616D has shipped approximately 1000 sets since 2015. The majority of them are equipped with 300B made by Shuguang of China, and we have not experienced any trouble caused by the 300B operating conditions.
On the other hand, if longevity is more important than sound quality, the 300B can be easily changed by simply increasing the resistance value for bias voltage generation, but we believe that the goodness of the 300B cannot be achieved at 65mA or less in terms of operation.
Audio amplifier design is similar to seasoning of a curry rice restaurant. Some restaurants are sweet, some are spicy. The customer has the right to choose it.
Victor curry are spicy but very tasty.
I have nothing to say further.
thank you Mr Ohashi's feedback to Thomas's concerns.
Hi Victor
Thank you for the info and help. Also I want to thank Mr. Ohashi for his response.
So I want to be clear that all the changes I’ve made here are easily reverse able and are just resistor value changes in a few places and a change to the purple b+ wires.
If anyone here looking at this thread wants to tinker/experiment with a different sound from this amp and would like to chat about the various ways to go about it then speak up. Otherwise I will just let it be. Cheers Thomas
Thank you for the info and help. Also I want to thank Mr. Ohashi for his response.
So I want to be clear that all the changes I’ve made here are easily reverse able and are just resistor value changes in a few places and a change to the purple b+ wires.
If anyone here looking at this thread wants to tinker/experiment with a different sound from this amp and would like to chat about the various ways to go about it then speak up. Otherwise I will just let it be. Cheers Thomas
Hello Hifihunter,
I've been a member of this forum for quite awhile but only confirmed my email address today and now cannot start a convedrsation with you since I'm under moderation.
However, I built the Sunvalley 300B amp from Victor and don't like the sound quality using the higher voltages that Sunvalley uses (their GZ34, 5.6K dropping resistor, and too high a voltage for really good 300B tubes even though you've had Sunvalley respond to what you did.
I've tried the GZ34, GZ37, RCA5U4GB, and RCA5u4G and like the RCA5U4GB the best with my dropping resistor value of 7.5K. However, I sense I need to get the voltage down to 360 volts and by using your purple wire approach, this would be a better method.
I've changed the dropping resistor from 5.6K to 6.5K in the power supply and that now brings my net cathode biased voltage to around 380Volts. I've been listening and would like to drop the voltage even further to maybe 360 volts (would probably sound even better) and now look at the purple wires that you used (320V instead of the typical 380V that Sunvalley uses for this build) and think that maybe going back to the original 5.6K dropping resistor and using the purple wires instead would get me closer to what I'm trying to do rather than adjusting the dropping resistor value.
Could you share what resistors you changed when you used the purple 320V wires instead of the 380V wires.
I also purchased the HV board kit fro DIY webstore (their HV Delay V4) and might use that to "slow start" the RCA5U4GB. It doesn't heat slowly like the GZ34 and I'm using Western Electric 300B power tubes and all NOS Brimar 9 pin tubes so want to extend their life.
Thanks in advance for any help.
Richard
I've been a member of this forum for quite awhile but only confirmed my email address today and now cannot start a convedrsation with you since I'm under moderation.
However, I built the Sunvalley 300B amp from Victor and don't like the sound quality using the higher voltages that Sunvalley uses (their GZ34, 5.6K dropping resistor, and too high a voltage for really good 300B tubes even though you've had Sunvalley respond to what you did.
I've tried the GZ34, GZ37, RCA5U4GB, and RCA5u4G and like the RCA5U4GB the best with my dropping resistor value of 7.5K. However, I sense I need to get the voltage down to 360 volts and by using your purple wire approach, this would be a better method.
I've changed the dropping resistor from 5.6K to 6.5K in the power supply and that now brings my net cathode biased voltage to around 380Volts. I've been listening and would like to drop the voltage even further to maybe 360 volts (would probably sound even better) and now look at the purple wires that you used (320V instead of the typical 380V that Sunvalley uses for this build) and think that maybe going back to the original 5.6K dropping resistor and using the purple wires instead would get me closer to what I'm trying to do rather than adjusting the dropping resistor value.
Could you share what resistors you changed when you used the purple 320V wires instead of the 380V wires.
I also purchased the HV board kit fro DIY webstore (their HV Delay V4) and might use that to "slow start" the RCA5U4GB. It doesn't heat slowly like the GZ34 and I'm using Western Electric 300B power tubes and all NOS Brimar 9 pin tubes so want to extend their life.
Thanks in advance for any help.
Richard
Hi Richard,
So recently I have been thinking about this thread even though it seemed like no one was interested in it. I was planning to post a photo of the innards as it is now. I have made some more changes to the circuit since my last post. When I get home I will upload a new picture.
Can I ask you a question first?
Are you using a 12at7 as the input tube?
Changes to the bias of this input tube make a big difference in the sound. I am not using a 12at7 anymore. I’m wondering if you’ve tried a 5751 or a 12ax7? I’m presently using a 12av7/5965 with higher plate current flowing.
So recently I have been thinking about this thread even though it seemed like no one was interested in it. I was planning to post a photo of the innards as it is now. I have made some more changes to the circuit since my last post. When I get home I will upload a new picture.
Can I ask you a question first?
Are you using a 12at7 as the input tube?
Changes to the bias of this input tube make a big difference in the sound. I am not using a 12at7 anymore. I’m wondering if you’ve tried a 5751 or a 12ax7? I’m presently using a 12av7/5965 with higher plate current flowing.
Thanks for your reply.
Yes, I'm using the single 12AT7 (NOS Mullard). I haven't tried any other tube in that position and really like it. Even though my voltages have dropped, I like the sound quality better than the stock kit.
I'm still wondering if my dropping resistor approach (going from 5.6K to 6.5K) would keep things pretty much "as is" regarding the heater and filament supply wires. The B+ is lowered, and the heater current and filament wire voltages stay the same as Sunvalley designed. If I increase the dropping resistor, the cathode bias net will go from around 380 volts on the 300B tubes to a bit lower than my current 380 volts. That might be good enough. I also have a Dennis Had 300B amp, and that is set for the WE300B tubes that I also use in this amp and supposedly does 360 volts, but I haven't measured it. I like the Sunvalley Amp sound quality better(particularly using the upgraded parts that I have), but I want to get as close to the Had amp as I can in voltages to find out if it makes sense to stay around 360 volts. 380 volts isn't much higher, and I'm now trying to lower that if it sounds better. He uses an RCA 5U4GB rectifier, and I like that sound quality better than the stock kit sound quality. It's good but not good enough for me.
My dropping resistor change only affects the B+ voltage and doesn't change the heater or filament wire voltages. By using your 320-volt purple wires, I might have to increase the 12AT7 to something with a higher gain since that approach will also affect the heater wires. Currently, I don't, so I am wondering what might be best - the way I'm using the dropping resistor change or yours using 320V instead of the 380V that is recommended. The 320V wires are for using a pentode tube instead of the 300B, and I like the 300B and am going in that direction. Your 320V wires create a different heater voltage, which might be why you need to use a different tube than the 12AT7 and then change a few resistors.
I'm attaching my voltage readings using the 5U4GB and the 7.5K dropping resistor to this message.
I have ordered a Mills resistor for the dropping resistor that is 9.1 K instead of my current dropping resistor, which is 7.5 K. If that is too much, I can always purchase a dropping resistor in between. I don't think that the voltages on the 9-pin tubes would support using anything higher than 9.1 K. I'm going to try that value, hear the result, and then make my decision.
I am concerned about the 5U4GB not having a slow start, and I have purchased the slow start PCB from DIY Hi-Fi. If I decide that's how I'll go (permanent use of 5U4GB rectifier), I'll purchase the remaining parts, build the PCB, and install it. So far, this amp sounds good and hopefully I can increase the sound quality a bit more. Time will tell.
Using the 5U4GB and a dropping resistor of 7.5K creates a B+ net on my 300B tube to 380 volts. That sounds much better than the GZ34 and the 5.6K resistor used in the kit. That voltage net is around
That sound quality is much too hard and not delicate enough. I'm using a Bricasti M12 DAC and have really refined my source. The speakers I'm using are extremely transparent (Voxativ A2.6 in Hagen cabinets bi-amped) and I'm listening for the best I can create using this upgraded kit. I'm also using a really large 12W Mills for that power supply dropping resistor position instead of something smaller, and it's probably overkill. I could easily use something smaller, but why not? It can't hurt and maybe affects sound quality.
Richard
Yes, I'm using the single 12AT7 (NOS Mullard). I haven't tried any other tube in that position and really like it. Even though my voltages have dropped, I like the sound quality better than the stock kit.
I'm still wondering if my dropping resistor approach (going from 5.6K to 6.5K) would keep things pretty much "as is" regarding the heater and filament supply wires. The B+ is lowered, and the heater current and filament wire voltages stay the same as Sunvalley designed. If I increase the dropping resistor, the cathode bias net will go from around 380 volts on the 300B tubes to a bit lower than my current 380 volts. That might be good enough. I also have a Dennis Had 300B amp, and that is set for the WE300B tubes that I also use in this amp and supposedly does 360 volts, but I haven't measured it. I like the Sunvalley Amp sound quality better(particularly using the upgraded parts that I have), but I want to get as close to the Had amp as I can in voltages to find out if it makes sense to stay around 360 volts. 380 volts isn't much higher, and I'm now trying to lower that if it sounds better. He uses an RCA 5U4GB rectifier, and I like that sound quality better than the stock kit sound quality. It's good but not good enough for me.
My dropping resistor change only affects the B+ voltage and doesn't change the heater or filament wire voltages. By using your 320-volt purple wires, I might have to increase the 12AT7 to something with a higher gain since that approach will also affect the heater wires. Currently, I don't, so I am wondering what might be best - the way I'm using the dropping resistor change or yours using 320V instead of the 380V that is recommended. The 320V wires are for using a pentode tube instead of the 300B, and I like the 300B and am going in that direction. Your 320V wires create a different heater voltage, which might be why you need to use a different tube than the 12AT7 and then change a few resistors.
I'm attaching my voltage readings using the 5U4GB and the 7.5K dropping resistor to this message.
I have ordered a Mills resistor for the dropping resistor that is 9.1 K instead of my current dropping resistor, which is 7.5 K. If that is too much, I can always purchase a dropping resistor in between. I don't think that the voltages on the 9-pin tubes would support using anything higher than 9.1 K. I'm going to try that value, hear the result, and then make my decision.
I am concerned about the 5U4GB not having a slow start, and I have purchased the slow start PCB from DIY Hi-Fi. If I decide that's how I'll go (permanent use of 5U4GB rectifier), I'll purchase the remaining parts, build the PCB, and install it. So far, this amp sounds good and hopefully I can increase the sound quality a bit more. Time will tell.
Using the 5U4GB and a dropping resistor of 7.5K creates a B+ net on my 300B tube to 380 volts. That sounds much better than the GZ34 and the 5.6K resistor used in the kit. That voltage net is around
That sound quality is much too hard and not delicate enough. I'm using a Bricasti M12 DAC and have really refined my source. The speakers I'm using are extremely transparent (Voxativ A2.6 in Hagen cabinets bi-amped) and I'm listening for the best I can create using this upgraded kit. I'm also using a really large 12W Mills for that power supply dropping resistor position instead of something smaller, and it's probably overkill. I could easily use something smaller, but why not? It can't hurt and maybe affects sound quality.
Richard