Great idea! Why didn't I think of that myself! 👍 👍
(Will go and do that, right now. 🙂 )
zman01 and X,
Thanks for the hints and suggestions. If I was going to populate a CRC design for the AN39, it would have to be one of the following in the attached pic as I have 2 of each of them, and do not plan to purchase any other's.
Which one would you choose, the red colored Project 16 board (Prasi took this over years ago), the LT4320/CRC board, or the CRCRC board, and why would you make that choice.
I am planning to refurbish the SLB and get it working, so the above is for curiosity and knowledge and as a backup if things go really wrong with the SLB rebuild.
MM
Thanks for the hints and suggestions. If I was going to populate a CRC design for the AN39, it would have to be one of the following in the attached pic as I have 2 of each of them, and do not plan to purchase any other's.
Which one would you choose, the red colored Project 16 board (Prasi took this over years ago), the LT4320/CRC board, or the CRCRC board, and why would you make that choice.
I am planning to refurbish the SLB and get it working, so the above is for curiosity and knowledge and as a backup if things go really wrong with the SLB rebuild.
MM
Myles,
Two more follow up questions for you:
1. Can you please share a pic of the chassis that you are planning to use for the AN39 build?
2. What is the AC voltage of the transformers you have for the project, and what make/model?
Two more follow up questions for you:
1. Can you please share a pic of the chassis that you are planning to use for the AN39 build?
2. What is the AC voltage of the transformers you have for the project, and what make/model?
Hi MM
But if you populate this CRC for AN39 you needed different voltages trafo....
here is my USSA 5 with CRC ...
My litle system 2 x Mimesis 9.2 clone monoblock ,USSA 5, Mirand 4490 dac, Salas dcg3 and 6V6 preamp, Emerald phono and Thorens 280 ...simply and nothing special...also Wolverine and ALPHA NIRVANA amps added ...
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@zman01 ,
Right now my chassis is empty. Check post 3323 for the original chassis design I was planning. I had the 2X SLB's with heatsinks bolted together positioned between the CPU heatsinks which made it very tight quarters.
I have now redesigned the layout and will be moving the CPU heatsinks and fans to the rear of the chassis and the SLB's w/heatsinks will be moved to wood side panels. I do not have it all set up yet, as I have some metal work to do. Since this will be my amp, I do not care if there are extra holes in the chassis base due to remodeling and moving modules. Once I have it set up, I will post a pic. Basically it will be: the rear panel w/ fan cut outs, inputs, outputs, > fans/cpu vertically mounted , speaker protect boards > amplifier > SLB's on the wood side panels > 2 Antek 400VA trans /dual 24V secondaries > SFP soft start board on the front wood panel. The wood panels are 3/4" teak wood that I have reconditioned.
@ Nikos, you may be right about the different transformer's due to no CapMx, so may run hotter. I also have 2CapMx boards from xrk that I may be able to use. Hopefully will not have to modify much.
MM
Right now my chassis is empty. Check post 3323 for the original chassis design I was planning. I had the 2X SLB's with heatsinks bolted together positioned between the CPU heatsinks which made it very tight quarters.
I have now redesigned the layout and will be moving the CPU heatsinks and fans to the rear of the chassis and the SLB's w/heatsinks will be moved to wood side panels. I do not have it all set up yet, as I have some metal work to do. Since this will be my amp, I do not care if there are extra holes in the chassis base due to remodeling and moving modules. Once I have it set up, I will post a pic. Basically it will be: the rear panel w/ fan cut outs, inputs, outputs, > fans/cpu vertically mounted , speaker protect boards > amplifier > SLB's on the wood side panels > 2 Antek 400VA trans /dual 24V secondaries > SFP soft start board on the front wood panel. The wood panels are 3/4" teak wood that I have reconditioned.
@ Nikos, you may be right about the different transformer's due to no CapMx, so may run hotter. I also have 2CapMx boards from xrk that I may be able to use. Hopefully will not have to modify much.
MM
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MM,
With a standard CRC power supply and 2 x 24V AC secondary transformers, the DC voltage after rectification is likely to be a bit higher (31-32.5 V DC) than what is the recommended value for the AN amplifier. A higher rail voltage will result in more heat dissipation from the output devices.
If you need to use a CapMx to reduce the voltage from the CRC power supply, that ends up defeating some of the KISS (Keep It Simple Stupid) approach that we were trying to get using a simple CRC PSU.
Would you be able to measure how much is the voltage from your transformer secondaries?
With a standard CRC power supply and 2 x 24V AC secondary transformers, the DC voltage after rectification is likely to be a bit higher (31-32.5 V DC) than what is the recommended value for the AN amplifier. A higher rail voltage will result in more heat dissipation from the output devices.
If you need to use a CapMx to reduce the voltage from the CRC power supply, that ends up defeating some of the KISS (Keep It Simple Stupid) approach that we were trying to get using a simple CRC PSU.
Would you be able to measure how much is the voltage from your transformer secondaries?
zman01 , I measured 25.2 V from the secondaries. See post 3346 for schematics and some voltages measured.
Myles,
With Prasi's supply with 25Vac secondaries you will finish up with around 35Vdc. To run the 8R AN39 you will need to drop (35 -27) volts. Even if you have a 3V drop at the trafo under load you need to drop 5V and you are forced to use the SLB and each reg will dissipate 5V X 1.7A = 8.5W.
You need to get those SLBs working to complete your amplifier. The only option is to ditch your present trafos for two new ones with 22Vac secondaries.
HD
With Prasi's supply with 25Vac secondaries you will finish up with around 35Vdc. To run the 8R AN39 you will need to drop (35 -27) volts. Even if you have a 3V drop at the trafo under load you need to drop 5V and you are forced to use the SLB and each reg will dissipate 5V X 1.7A = 8.5W.
You need to get those SLBs working to complete your amplifier. The only option is to ditch your present trafos for two new ones with 22Vac secondaries.
HD
If your transformer secondaries is the outside winding, which is normal unwind say 5 windings and test the voltage, unwind until you get the exact voltage you want and do the same to the other transformer. Cost you nothing. If the transformer is dual secondaries then you are stuffed. An expensive way is use an autotransformer at the input and dial in any voltage to you amp's transformers you want (also a great addition to your test equipment). Finally, something that may sound stupid but connect a 12V vehicle globe in series with the secondary, it serves as a great soft clipping device as well. Just looked on AliExpress for pricing and a 1 KVA auto transformer costs around $32
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Sure, but all the toroids I've ever bought have clear film wrapping round the outside ... so you'd have to remove that first.
As I presume it was put there for a good reason - removing it may not be a good idea?
As the AN39 requires '+' and '-' DC rails ... the traffos need to have dual secondary windings???
What a weird idea! If you're after great sound - which, after all, is the reason why you would want to build this quite expensive DIY amp ... why on earth would you want to put another transformer in front of the amp's power traffos?
I don’t think another transformer (or variac) will affect sound unless it limits current. The audio path is clear of this. As long as it doesn’t add noise or mess up the sine wave shape too badly.
Can we use the IXTQ36P15P in place of FQA36P15 which is not available from any reliable source? If yes any other part replacements should I be looking at?
Thanks
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Thanks for all the input about possible ways to fix my problems with the Nirvana amplifier and SLB's.
I agree with you Hugh, the SLB's must work, and that is what I will be working towards. I have already removed the BJT's, the lt4320's, the bd139,140 transistors, which really just leaves me with resistor's and capacitors to check. Once I have checked everything I will begin to assemble the SLB....again.
I agree with you Hugh, the SLB's must work, and that is what I will be working towards. I have already removed the BJT's, the lt4320's, the bd139,140 transistors, which really just leaves me with resistor's and capacitors to check. Once I have checked everything I will begin to assemble the SLB....again.
Yes, Manniraj, the IXYS mosfet is very suitable in this role and can replace the FQA36P15 Fairchild.
HD
HD
Sure, the variac is not in the signal path. And if it somehow added noise or deformed the mains sine wave - then it would be an absolute no-no.
But even so ... I suggest the Zout of the mains, after the variac is higher than it is from the wall - and this is not optimal.
Obviously you will have to buy new transformers and when they arrive you can test the amps, no need for any workarounds to se if you have any faults.
Hello Hugh,
Just for clarification, " you are stating that with the 25V secondaries, it is OK to use the SLB's." I bought the Antek 4224's for the AN amp based on the following guide ( from xrk971 post #35 on the SLB power supply GB thread).
How to size the trafo? Depends on the brand a bit. I would size the VA rating at 3x nominal requirement to reduce sag and saturation. So for +/-24v at 1.25A that’s 48v x 1.25A that’s about 200VA and voltage at required rails plus 3v for the cap Mx and probably 4-5v more for sag. So 24v +3v + 4v = 31v. Now divide by 1.4 and you get 22v. So for the typical 25w Class A amp, use dual 200VA 22v trafos one per channel. Note that some brands like Antek sag more than others so step up one more notch to 24v. But maybe a Talema or Toroidy is fine at 22V. Yes, dual secondaries not center tapped. One more thing, it never hurts to go up one more notch in VA rating either so dual 300VA would assure you of even better performance.
Also, I have removed most parts from one of my dual rail SLB's. Question:
" Is it possible to test the n channel MFet's (STP110N8F6) on board with DMM or should one desolder the MFet's and test them." I am assuming that a normal resistance test can be performed to see if MFets are OK.
Thanks for the clarification's before I begin to rebuild the SLB's.
MM
Nikos, we await with interest on your subjective comparisons of those great amps 🙏 . . . .
Myles,
My head is spinning!
22 or 24 Vac x 2 is fine and I would go with 200VA or 225VA.
If a MOSFET is blown the gate to source measures usually 0-100 ohms.
No need to remove them when testing
Hugh
My head is spinning!
22 or 24 Vac x 2 is fine and I would go with 200VA or 225VA.
If a MOSFET is blown the gate to source measures usually 0-100 ohms.
No need to remove them when testing
Hugh