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In Reply to: RE: Here's the chart you ask for posted by sony6060 on July 23, 2023 at 00:38:36
I was commenting on the correctness of TRE's
reasoning. It is perfectly sound, provable and reasonable.
It's all academic if you're building for a
definite set of purposes to get a better overall product.
Then, you adjust the rules only as needed, but
you don't deny the accuracy of TRE's work.
-Dennis-
Follow Ups:
Dennis, I did not adjust any rules. Show me a maximum capacitance chart for a 5U4GB based upon peak current and I will stand corrected. Problem is there is no chart. So, again use 40uF as recommended by the manufacture.
If you find charts to be confusing or not as explicit as you would like, just use PSUD to model a supply. If you design a supply that violates the limits of a particular rectifier tube type it will tell you.Earlier, Tre posted two PSUD sims of power supplies using a 5AR4 whose data sheet lists 60uf as an input cap.
The first PS used a 20uf cap and PSUD warned that the 20uf was too large. This was due to the particular specs of that design - specifically the combination of very low PT resistance and a relatively large current load. The second PS he posted had different design specs and used a 220uf cap and PSUD indicated that this was OK - when used under those conditions.
So the cap value listed in the data sheet is neither the maximum you can use under all conditions nor is it safe to use under all conditions.
If you set PSUD up to simulate a particular PS you can easily play with cap values and find out what the maximum cap value is for that particular supply. You may not want to use the maximum value, for a variety of reasons, but it will tell you exactly how far you can go without violating the data sheet specs and damaging the tube.
Edits: 07/23/23
I've seldom seen posts from anyone so dedicated to remaining uninformed.
Wrong, I am very informed and especially so about tubes. You refuse to admit no manufacture recommends a value capacitor based upon peak repetitive current. However, manufactures do recommend maximum capacitor value.
State whatever you want, but you are wrong about this subject and capacitor value.
No they don't. Here's a GE 5U4GB data sheet. Cap value is not listed under Maximum Ratings. It's listed under "Typical Operation".
A 40uf cap isn't the maximum that can be used just as a 10H Choke isn't the maximum value that can be used in a choke input filter.
Note that it does list Transient Peak Plate Current Per Plate under Maximum Ratings. That is determined by a combination of operating factors, only one of which is the cap value.
The factors involved in the combination interact with each other and NO SINGLE FACTOR DETERMINES SAFE USE.
That's why one of the two PSUD sims Tre posted warns that one combination (with a 20uf cap) is unacceptable and the other (with a 220uf cap) is safe.
Here's the RCA data sheet for the 5U4GB. The note at the bottom clearly indicates that 40uf in NOT the maximum.
It says "WHEN capacitance values higher than 40uf ARE USED" . . . one of the other factors (plate supply impedance) must be adjusted. If you do so you can use a cap value larger than 40uf. This is about as plain as it gets.
Exactly as I been stating with many posts. 40uF. No chart with repetitive peak current to capacitor value as I been stating all along.
Frankly, I do not completely trust PSU2. However, I did state Cary Audio used 470uF on a 5U4GB and no one has complained of reduced rectifier life. If reduced from 50K hours to 25K hours, who would care.
All of you defending Tre's comment. I am glad you are Tre's friend, but it has absolutely zero to do with what I have been posting. And, I easily admitted I do not have Tre's talents. What more do all of you want?
"Frankly, I do not completely trust PSU2."
Apparently, you don't trust RCA either. The footnote on the data sheet very clearly indicates that 40uf is not the maximum.
There are ways to calculate what the peak plate current will be (the Radiotron Desinger's Handbook has the math) and ways to reduce that current to keep it below the max rating without lowering the cap value but as you say, there is no chart.
Such is life.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Calculating is beyond most of us. However, Cary Audio uses 470uF and his amp been out or 15 years without any complaints.
they must have a large amount of DCR in the secondary of their power transformer and/or the current supplied must be comparatively small.
"Calculating is beyond most of us."
As I said, designing power supplies for audio circuits should be left to the engineers.
Question, which Cary Audio amp uses 470uf as an input cap in the power supply? Thanks.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I forget the model Cary Amp, just remember the advertising bragging about the large cap 15 years ago. Iy is not a high resistance transformer. 1940 thru 1960 transformers hv secondaries were wound with high resistance. New transformers are much lower secondary resistance. I bet the Cary Audio transformer was less than 30 ohms HV secondary.
Using PSU2, higher capacitance capacitors actually add little additional peak to average current.
Just because the ad said there was 470uf of capacitance in the power supply that doesn't mean it was in the C1 (input cap) position.In a CLC or a CRC filter, the second capacitor can be much larger without causing problems because it is "hidden" from the rectifier by the L or the R.
It is just the first C (the cap directly following the rectifier tube, C1) that we are concerned about.
To know for sure you would have to look at the schematic.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 07/24/23
The schematic shows 470uF directly connected to the 5U4GB. Tre, why are you constantly trying to discredit all of my posts?
Wait just a minute here. You said "I forget the model Cary Amp, just remember the advertising bragging about the large cap 15 years ago." and now you are saying you have seen the schematic.
I'm not sure I believe you. are you just talking through your teeth?
Maybe your posts need to be discredited. Show me the schematic or I call BS.
Don't be making up shit.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
You are a jerk. I saw schematic in a review 15 yeasr ago. Who knows where the review is. Go away.
Here it is Cary Audio SLI-80 as t came up on a search Cary Audio 5U4GB. It has two 5U4GB. Now, you will still say I am a liar without the schematic, but spec is below with PS caps.
Edits: 07/24/23
Found this, shows 1200uF @ 450 volt capacitors in power supply as stated below. The original has two 1000uF @ 450 volt caps in series. See below:
SLI-80 INTEGRATED AMPLIFIER
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SLI-80 Integrated Amplifier
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ABOUT THE SLI-80 INTEGRATED AMPLIFIER
This item is replaced by SLI-80 Heritage Series (HS) tube amp and is no longer in production.The following section describes the SLI-80 basic specifications. The specifications are subject to change without notice or obligation.
Circuit Type Push-Pull Ultra-Linear Pure Class AB-1
Power Output 40 Watts - Triode
80 Watts - Ultra-Linear
Input Sensitivity .45 Volt for full output
Noise and Hum -82 dB below full output
Frequency Response 19 Hz to 23 KHz +/- .5 dB
Inputs CD, AUX1, AUX2, Headphone jack
Tubes 2 ea - 6922 Input Buffer Preamp
2 ea - 6SN7 Pre Driver/Phase Inverter
4 ea - KT88 Output Tubes
2 ea - 5U4 Rectifiers
Speaker Posts 5 way, gold-plated
Tube Sockets Ceramic w/ silver pins
Power Transformer 1 ea. - EI Laminate, Silicon Impregnated
Output Transformer(s) 2 ea. - EI Laminate, Silicon Impregnated
Resistors 1% Metal Film
Capacitors Oil filled coupling, (copper optional)
Power Supply Capacitors 2 ea - 1200µF @ 450 VDC
6 ea - 10µF @ 400 VDC Film & Foil
AC Cord 3 Conductor Shielded, Detachable
AC Power Requirements 117/234 VAC @ 50/60 Hz
Consumption 166 watts - Operation
Warm-Up Time 3 Minutes
Break-In Time 100 hours of playing time
Finish Textured black steel chassis with machined, black anodized aluminum front panel
Weight 42 lbs
Dimensions 7″ H x 17″ W x 16″ DNow, stop calling me a liar Tre. I am sick of it.
Edits: 07/24/23 07/24/23
Your you next BS towards me, the input choke. No Tre, there is no input choke on chassis as seen in picture. Where is your apology?
Edits: 07/24/23 07/24/23
I can only imagine how badly those rectifier tubes are being tortured.
I would still love to see a schematic, there must be some kind a compensating measures being taken.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
To all friends of Tre stating I was full of BS, no apology from Tre. He still is defending the high capacitance with as he states a compensation network. There is no compensating network in this amp and Dennis Had the designer did make mistakes.
Go away Tre.
Sorry, but I believe you might need to go away. Clearly, you can't supply any schematic or any other data to support this over the top back and forth.
-Rod
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