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Old 23rd December 2008, 09:01 AM   #541
AndrewT is offline AndrewT  Scotland
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Default Re: Shunt up and running

Quote:
Originally posted by kstlfido
..........Shunt notes- seems to pull appx 120 mA. I'm getting 36.7 volts out- so all seems to be working fine. I had to use 1/2W resistors on the 220 ohms and an old 1W carbon comp on the 5.6 ohm. The sink gets VERY hot- it's a 45mm x 45mm finned job and I can barely keep my hand on it for more than 15 seconds!
it is a transformer + CCS + Shunt + load.
Try reducing the current passing the CCS. Even a 10% reduction in CCS current could make a big difference to the shunt temperature.
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Old 23rd December 2008, 09:05 AM   #542
Salas is offline Salas  Greece
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Very nice work! I like the construction style. Since I have listened to the Riaa in many systems, and in various constructions, based on your subjective comparisons I think that you must substitute that 82k//82k combination with 43k, and see about an extra buffer stage. Especially with the shunt PSU, the bass is a particularly strong area by experience. Have compared to some ultra $ commercial gear too. The general characteristic of this phono stage is nearer tube than transistor but with resolution and ease. Tune it up, buffer it, listen again. In the mean time, happy Christmas holidays!
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Old 23rd December 2008, 09:10 AM   #543
Salas is offline Salas  Greece
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Default Re: Re: Shunt up and running

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Originally posted by AndrewT
it is a transformer + CCS + Shunt + load.
Try reducing the current passing the CCS. Even a 10% reduction in CCS current could make a big difference to the shunt temperature.
Sound advice. Use a 6R8 for R1 Kent. That will save you 20mA off. Its a nice construction and the current is plenty, why modify with new big heat sinks? Better reduce Iccs.
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Old 23rd December 2008, 09:28 AM   #544
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OK- will do the R1 change to 6k8 on shunt and to 43k from 41k first- easy to do.

Buffer- like this one from your other design? I have some spare 2sk170...
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Old 23rd December 2008, 09:29 AM   #545
Salas is offline Salas  Greece
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P.S. See if your MC needs more electrical damping, you may listen to a 500R or lower Rload at the input. That detail thing is usually hinting at not best loading or a need for a better Riaa filter tuning. Or both. We have seen you need a slightly bigger Riaa series resistor earlier, given your final capacitor values.
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Old 23rd December 2008, 09:30 AM   #546
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Um, like this one? Sorry pic didnt attach b4.
Attached Images
File Type: jpg picture-1.jpg (9.0 KB, 638 views)
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Old 23rd December 2008, 09:31 AM   #547
Salas is offline Salas  Greece
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Quote:
Originally posted by kstlfido
OK- will do the R1 change to 6k8 on shunt and to 43k from 41k first- easy to do.

Buffer- like this one from your other design? I have some spare 2sk170...
6R8 not K8! For buffer, do it like Jonners, he has exactly the same circuit as yours. Look back in pages.
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Old 23rd December 2008, 09:39 AM   #548
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sorry I meant 6r8... I have cold and sleepy. Will play with the damping too, thanks.

RIAA accuracy- I've got some Russian green PS caps on the way- hope to stack 3 up then trim with silver mica to get exactly 15 nF. Some say stacking more than 2-3 is not a good idea...I wonder why?

I think this previous pic I found was from Jonners. Will check, thanks!
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Old 23rd December 2008, 09:42 AM   #549
Salas is offline Salas  Greece
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Yes, either R20 1.6k 1W & R19 680R for a higher running current, or R20 2.2k & R19 1.2k for an about Idss current one. Listen to both if you like.
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Old 23rd December 2008, 09:51 AM   #550
Salas is offline Salas  Greece
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Quote:
Originally posted by kstlfido

Some say stacking more than 2-3 is not a good idea...I wonder why?
They talk about resonating with each other. Don't know if its just a theory, but sometimes too many start sounding smeared in practice indeed. Some go along well with each other, some not. One is best if its value is right. For space and expenditure too.
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