Author Topic: Transistor select for QSXM2  (Read 6327 times)

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Offline horvlas

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Transistor select for QSXM2
« on: July 28, 2012, 04:20:24 PM »
heaveno P-A!
I downloaded the schematics in the past years, I didn' have time to build due to child born. Now I plan to build this preamplifier again, I have some questions:
1. Has the schematic changed since then? I have the revision 1 schem. modified at 2001-12-03, it is indicated at the right left corner.
2. What is your recommendation for transistor select to best sounding and lowest noise combination nowdays? I use MM Ortofon VMS30mkII and MC Denon DL-103 low output cartidge. I think the more interesting version is the low output MC, because of the noise. SSM2210/20 MAT02/03 are no longer available, AD website advise MAT12, but it has horrorific price. What about the 2sC2240 and 2sa970 combination? They has better audio spec and lowest noise than BC550/560. Are they good choice?
3. Which are the critical positions in the circuit where I have to buy ultra low or/and noise transistors?  Maybe I can explore some genuine source for SSM2210/20 but due to high price I can't afford to buy them for all transistor position.
4. What about the Jfet input stage mod? Has anyone tried it? Is it better than the original transistor input stage? It is mentioned in the original web thread.

Regards,

Leslie.

Offline peranders

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Re: Transistor select for QSXM2
« Reply #1 on: July 28, 2012, 07:35:39 PM »
1. I haven't changed the design but the latest issue can be downloaded.

2. One pair of SSM2210/20 is needed. I have those for sale.

3. The critical position is only the input transistors and only in the first stage. The correction amp won't need any low noise transistors.

4. JFET is good but requires development. Don't know if anyone has tried that.
/Per-Anders Sjöström, owner of this forum

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Offline horvlas

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Re: Transistor select for QSXM2
« Reply #2 on: July 28, 2012, 08:01:21 PM »
heaveno P-A!
Thanks for quick answer.
In the past I could download the projects, but now I can't login. Please give me a new usename and password for downloads.
1. Only one pair is needed? Only theese first pair of transistors determine the main noise even with MC mode? I see in the input stage the transistors are paralelled. Other three pairs doesn't need  SSM2210/20?
2. What do you think about 2sc2240BL/2sa970BL combination? Are they better than Bc550c/560c for this project for other positions?
3. What type of SSM2210/20 do you have for sale? DIP? SSM2210/SSM2220 B or P or S? Please give me a price offer for a pair of 2210/2220

Offline peranders

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Re: Transistor select for QSXM2
« Reply #3 on: July 28, 2012, 08:14:43 PM »
I'll come back tomorrow afternoon
/Per-Anders Sjöström, owner of this forum

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Offline horvlas

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Re: Transistor select for QSXM2
« Reply #4 on: July 28, 2012, 09:43:38 PM »
Ok, I am waiting for your answer.

Offline horvlas

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Re: Transistor select for QSXM2
« Reply #5 on: August 04, 2012, 08:01:22 PM »
I'm still waiting for your reply!

Offline peranders

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Re: Transistor select for QSXM2
« Reply #6 on: August 09, 2012, 06:36:17 PM »
heaveno P-A!
Thanks for quick answer.
In the past I could download the projects, but now I can't login. Please give me a new usename and password for downloads.
1. Only one pair is needed? Only theese first pair of transistors determine the main noise even with MC mode? I see in the input stage the transistors are paralelled. Other three pairs doesn't need  SSM2210/20?
2. What do you think about 2sc2240BL/2sa970BL combination? Are they better than Bc550c/560c for this project for other positions?
3. What type of SSM2210/20 do you have for sale? DIP? SSM2210/SSM2220 B or P or S? Please give me a price offer for a pair of 2210/2220
1 Yes, one pair of ultra low noise transistors are needed. Extra transistors won't improve the noise level much.
2 I'll doubt it, don't know.
3 DIP, the P version. Price according to the price list.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff