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Krell KSA 50 pcb
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Old 4th December 2017, 10:38 PM   #8891
grimberg is offline grimberg  United States
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Since 2008 I have been using fans made by Noctua (Fans - Products) to cool off my computers. They now have a 200mm fan which runs at 800 RPM and has a claimed noise level of 18.1 dB/A. Looks like a good candidate for cooling an amplifier.
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Old 4th December 2017, 10:40 PM   #8892
grimberg is offline grimberg  United States
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David,

Do you have access to metalworking equipment or did you order the front panel and cover?
Also, I would like to make a small Krell badge for my clones. How did you make yours?
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Old 4th December 2017, 10:50 PM   #8893
Ricren is offline Ricren
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Good suggestion on the Noctua NF20.Excelent product. Two models: PWM $50 and FLEX $30.
In addition, Antec have a good 3 velocity 200mm fan for $18.

From Antec files:
3 Speed Fan- Current: 0.08A, 0.17A, 0.3A- Speed: 400 rpm, 600 rpm, 800 rpm- Airflow: 83 cfm, 108 cfm, 134 cfm- Noise: 24 dBA, 27 dBA, 30 dBA
Rated Voltage -- 12V DC
Operating Voltage -- 10.8V ~ 13.2V
3-Speed switch lets you balance quiet performance with maximum cooling

Last edited by Ricren; 4th December 2017 at 10:55 PM.
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Old 5th December 2017, 12:16 AM   #8894
AVWERK is offline AVWERK  United States
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The badges were made by a member in Europe back in that time period and he offered them one time only. It wasn,t a group buy, just everyone responding to a couple of posts he made while he was building his clone. They were CNC,d out of brushed metal clad Formica material. Back lighting was my design though.

The machining is nothing fancy and the handles are made of acrylic and painted. Just made a jig with a long laminate trim router held on with 5/16"-28 bolts.
The front panel was cut on a table saw , sanded, acid etched and clear coated.

The big fans that are now avaible are the best bet and were not around 10 years ago. I might even remake the 50 water to accept a couple of them. That air path design is still not optimum ,but bigger fans would lower noise contributions.

I am currently going to use them in an OTL /6c33 in the works.
They have the low speed torque to provide that low speed and super low noise.
The key to low noise is keeping the inlet clear , some distance from any objects in the path and a clear open area exiting and yes those big slow fans.

A pic of the downward blowing fan 100 mono build. 2 speed and no noise.
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Old 6th December 2017, 03:38 AM   #8895
batte spl is offline batte spl  Italy
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hi all, I find myself in the house two transformers from 500va one, 28.5 v for rail , 8 capacitors 22000 uf 63 v, and two audio delta cards clone ksa 50, now my problem is this I can not find official sellers the tr 2sa970 and 2sc2240, you confirm that I can replace them with ksa992 and ksc1845? do they sound the same way? I saw that there are those who use mje differences?
what tr power do you recommend in the case to-264, mjl21194 / 3 is the best? or which one? thank you all
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Old 1st January 2018, 01:50 AM   #8896
konst is offline konst  United States
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Just amazing the quality of stuff you guys are doing.......
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Old 2nd January 2018, 04:23 PM   #8897
spurlte is offline spurlte  United States
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Default Pinkmouse KSA-50 PCBs

I have a pair of pinkmouse KSA-50 boards available. What would they be worth now? Add shipping and they're yours. I have a wonderful KSA-100 still kicking ash which I never push bias pass .365mv and never have to raise volume one quarter turn-don't want to blow out the windows. I use 1KVA transfos, so I have two sets of speaker. One with 12" woofers and the other with 15" woofers.
I built this amp because I lost my hearing in the Army so I have to ---FEEL--- the music. If these boards are too old and outdated I understand.
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Old 15th March 2018, 05:19 AM   #8898
lgreen is offline lgreen  United States
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Quote:
Originally Posted by Ricren View Post
Good suggestion on the Noctua NF20.Excelent product. Two models: PWM $50 and FLEX $30.
In addition, Antec have a good 3 velocity 200mm fan for $18.

From Antec files:
3 Speed Fan- Current: 0.08A, 0.17A, 0.3A- Speed: 400 rpm, 600 rpm, 800 rpm- Airflow: 83 cfm, 108 cfm, 134 cfm- Noise: 24 dBA, 27 dBA, 30 dBA
Rated Voltage -- 12V DC
Operating Voltage -- 10.8V ~ 13.2V
3-Speed switch lets you balance quiet performance with maximum cooling
I tried the Noctua NF-P12 and NF-S12 FLX. You have to consider how dense your fins are and how close the fan is to the array of heat sink fins in order to get the best fan type to match -static pressure fan (heatsink has high density of fins, fan is close) or normal PWM fan. I Did some experiments and found the normal one worked better for me. Also these fans are very quiet but the system will run about 5 or 10 C higher than with and old school noisy fast fan. And you really need a nice grill to not impede the airflow or you will add another 2-5 C to the system.

These fancy Noctua fans are not the cure all everyone holds them out to be, temps did rise as compared with my older, noiser, 'Aspire' fan. If you hold your hand over the Noctua, all the airflow seems to be going out by the edges, very little in the center, interesting...maybe this is how they keep the turbulence noise down.

You can see the latest here- Krell Clone 12 years later

Krell KSA 50 pcb


Krell KSA 50 pcb


Krell KSA 50 pcb


I recently looked at the data sheet for the MJL21193/94 to check what temps they can work at with the associated heat de-rating. I am no expert but after doing the math for temp derating, current, voltage, and thermal resistance to junction/case and case/heatsink, I concluded that 3 pairs per channel should be able to do the job at over 120 C 50W class A. I have 4 pairs per channel so the quiet Noctua fans running on a hot day at heatskink temp of 75C or even 80C should not bother me too much, but I would not use this amp on a hot day like that anyway. Think of the heatsinks as accepting tiny little blow torches at every transistor- like a creme brulee torch. The data sheet shows these devices operating at 150C which is pretty toasty.

Quote:
Originally Posted by spurlte View Post
I have a pair of pinkmouse KSA-50 boards available. What would they be worth now? Add shipping and they're yours. I have a wonderful KSA-100 still kicking ash which I never push bias pass .365mv and never have to raise volume one quarter turn-don't want to blow out the windows. I use 1KVA transfos, so I have two sets of speaker. One with 12" woofers and the other with 15" woofers.
I built this amp because I lost my hearing in the Army so I have to ---FEEL--- the music. If these boards are too old and outdated I understand.
Not sure what those would be worth but at this point one who wants to divest of the boards should figure out what errors are on there and point to the solution... identified and buried in this thread... I think there were a couple of issues with those?
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Last edited by lgreen; 15th March 2018 at 05:31 AM.
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Old 21st March 2018, 01:30 AM   #8899
AVWERK is offline AVWERK  United States
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Can you recall what issues with these boards as I can,t remember anything significant

Regards
David
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Old 21st March 2018, 01:41 AM   #8900
troystg is offline troystg  United States
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Quote:
Originally Posted by AVWERK View Post
Can you recall what issues with these boards as I can,t remember anything significant

Regards
David
To my knowledge there was no issues with the pink mouse boards ordered by Mark. The Jan boards had a unique potentiometer that was unobtainable so they needed to be modified slightly.
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