The measurements were taken at the speaker terminals. The load was 8-ohm non-inductive resistor dummy speaker loads.
Thanks,
Scott
SE Input/Output Measurements
I have attached a chart with input/output voltage readings taken for this amplifier. I took readings for both 8 ohm & 5 ohm loads in both the triode & UL modes. The input and corresponding output voltage readings were taken at the level right before clipping of the output waveform. The volume control was set for minimum resistance, fully clockwise. The input signal level was adjusted on the function generator. The output readings were taken across the speaker terminals. Resistive dummy loads were used on the amplifier output.
I have attached a chart with input/output voltage readings taken for this amplifier. I took readings for both 8 ohm & 5 ohm loads in both the triode & UL modes. The input and corresponding output voltage readings were taken at the level right before clipping of the output waveform. The volume control was set for minimum resistance, fully clockwise. The input signal level was adjusted on the function generator. The output readings were taken across the speaker terminals. Resistive dummy loads were used on the amplifier output.
The actual measured inductance across the custom output transformer primary is 58H.
I have extracted pages out of the manual and attached them here.
A disclaimer: Due to auto-numbering of the complete document, the step numbers and page numbers are not correct on the attached PDF document. The resolution of the photos has been greatly reduced so I can post it here. The actual document is 41 pages with high resolution photos and is about 40MB. This will however give you an idea of the format of the document.
I noted the comment about the 6mm shaft on the Alps pot.
As mentioned a knob with a 1/4' bore will be sloppy.
You can get high quality knobs with the correct 6mm bore here:
chassis_knobs
They are pricey, but fit well and are excellent quality. Why spoil a nice project with a lousy part?
(BTW...Great instruction manual. It would be hard not to have good results).
As mentioned a knob with a 1/4' bore will be sloppy.
You can get high quality knobs with the correct 6mm bore here:
chassis_knobs
They are pricey, but fit well and are excellent quality. Why spoil a nice project with a lousy part?
(BTW...Great instruction manual. It would be hard not to have good results).
The volume knob included with the kit is not a lousy part. It looks and works just fine. It just doesn't cost $16.00. I can find plenty of that type, but it adds about another $20.00 to the kit price. Like I point out in the manual, if you build up the shaft, it is not sloppy when tightened. Anyone however is welcome to supply and install any knob that they wish.
There is a seller on EBAY who has prepunched and painted chassis for stereo SE amp. They run about $160 or so shipping and all. The chassis has all of the features that are listed above. I went thru a phase where I was running SE KT-88s; I was not too impressed with the sound tho. I then built a 300B amp, and finally reached by SE Nirvana when I built a Cathode Follower 6S33S amp. But that is on another thread...
Power for the KT-88 SE will be on the order of 15-20 Watts in Pentode or Ultralinear, and about half that in Triode. You will need to run feedback from the KT88 plate to the drive tube plate and cathode, in order to get sufficient damping factor.
Power for the KT-88 SE will be on the order of 15-20 Watts in Pentode or Ultralinear, and about half that in Triode. You will need to run feedback from the KT88 plate to the drive tube plate and cathode, in order to get sufficient damping factor.
Can you give me a link to the seller on Ebay? I don't know how that is possible considering that I personally designed the chassis shown above and it is configured for custom transformers that were also designed by me.
This amplifier does not use or require feedback. I have tried implementing feedback in this design and all it does is muffle the supreme clarity that this circuit offers. This circuit does not provide optimum sound when run in the pentode mode.
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Thanks for sending parts of the manual to view, the only problem was the resolution of the pictures was very poor but like you said it might give me an idea.
I have been studying the design to help myself understand and have a few questions:
1. With the 5u4gb there seems to be no softstart with this DHR, is there one provided or is the use of 5ar4 IDHR possible.
2. Could we use a thermistor CL80 or CL90 in the +power line to stop the inrush before it goes into the PT and on into the rectifier this could also act as a softstart?.
3. What would the shipping cost be to Toronto, On, Canada.
At this moment I do not have a paypal account is there any other method of payment possible.
I have been studying the design to help myself understand and have a few questions:
1. With the 5u4gb there seems to be no softstart with this DHR, is there one provided or is the use of 5ar4 IDHR possible.
2. Could we use a thermistor CL80 or CL90 in the +power line to stop the inrush before it goes into the PT and on into the rectifier this could also act as a softstart?.
3. What would the shipping cost be to Toronto, On, Canada.
At this moment I do not have a paypal account is there any other method of payment possible.
1. There is no need for a soft-start in this design. The power supply capacitors are rated very conservatively and will more than handle the startup voltage. The 5AR4 has different series resistance requirements and would also yield a much higher B+ that would require a complete redesign of the power supply circuit.
2. No need.
3. Box #1 $45.70 w/insurance. Box #2 $32.45 w/insurance. Box #3 $32.45 w/insurance. Total shipping/insurance = $110.60
3A. Or, you could make a day trip and pick it up for free at my office near the JFK airport.
For payment you could send a postal money order. Send me a PM if you would like to go that route and I will send you the mailing address.
Cheers!
Scott
The 5U4G delivers 50mA less current than than the 5U4GB, 225mA vs. 275mA. The total current draw for this amp is about 150mA, so the 5U4G will be OK. Running a simulation for the 5U4G using PSUD II indicates that the B+ will be a few volts higher than with the 5U4GB. No problem though.
Yes. Check out the thread that is my signature. Some have posted photos that are towards the end of the thread. Thanks.
Regarding safety earthing; what if a fault develop across the 10ohm resistor? Will it last enough to blow the fuse?
Or it will not, so the chassis will hot at 220vac or 400vdc?
Regards,
The chassis is at earth ground. Bonded to AC ground at the IEC entry. You must use a power cord with AC ground. A high voltage fault to the chassis will open the fuse. The RC ground breaker from signal ground to the chassis is for ground loop noise reduction.
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