Sjöström Audio DIY forum

Projects => Headphone amplifiers => Topic started by: goldkenn on July 31, 2010, 08:03:32 PM

Title: QRV01 output stage
Post by: goldkenn on July 31, 2010, 08:03:32 PM
Not sure I should use both T19/20/21/22 along with T24/25/26/27 or either one set?
Title: Re: QRV01 output stage
Post by: peranders on July 31, 2010, 09:46:48 PM
I can help you next weekend with this.
Title: Re: QRV01 output stage
Post by: goldkenn on August 01, 2010, 08:26:35 AM
If possible, please advise a working configuration, since from QSXM2 phono, due to too many opttions, I wasted too much time and money upon SMD configuration (finally not working using SMD transisitors, I know more calculations and testing upon something like resistor value could make it work but I did spent too much on it, so finally simply swapping back to all BC550C/560C configuration), and as QRV01 have almost the same many options as QSXM2, I am tried for possible configurations, thanks peranders :-)
Title: Re: QRV01 output stage
Post by: peranders on August 01, 2010, 09:05:23 AM
The reason for having footprints for SOT23 was that it's easier to find good parts and harder in TO92. They have the same performance if they have the same data.
Title: Re: QRV01 output stage
Post by: goldkenn on August 01, 2010, 01:01:22 PM
Bt the way, other then the output stage:
1) Can I use SSM-2210/SSM-2220 for MT1/2/3/4? If okay then what resistor value should I use for current supply?

2)  The "class A temperature regulation circuit " you mnetioned to forget is which part? Am I need to omit some parts or do some jumper wiring for modifications?

3) Any easy find replacement (possible to buy from RS or Farnell) of BF471/BF472? Nothing could find here in Hong Kong, and I am not sure which replcement no need for any re-calculation of components value.

Thanks!
Title: Re: QRV01 output stage
Post by: goldkenn on August 09, 2010, 11:21:32 AM
Any news?
Title: Re: QRV01 output stage
Post by: peranders on August 09, 2010, 12:49:12 PM
1 You don't have to change anything.

2 Omit R47, OC1, IC10 and all parts around. The same goes for the other channel in corresponding locations.

3 Use BC5xx transisitors if you can't find any similar types with low capacitances.
Title: Re: QRV01 output stage
Post by: peranders on August 09, 2010, 12:51:29 PM
Quote from: goldkenn on July 31, 2010, 08:03:32 PM
Not sure I should use both T19/20/21/22 along with T24/25/26/27 or either one set?

T19-T22 or T24-T25 or T26-T27
Title: Re: QRV01 output stage
Post by: goldkenn on August 10, 2010, 12:44:46 PM
Thanks P-A :-)

By the way, did this transformer match the PCB pin layout?
http://hk.farnell.com/block/fl14-15/transformer-14va-2-x-15v/dp/1131496
Title: Re: QRV01 output stage
Post by: peranders on August 11, 2010, 08:47:15 AM
The suggested type will almost fit but not entirely.
Title: Re: QRV01 output stage
Post by: goldkenn on August 12, 2010, 08:01:10 AM
Which from farnell could entirely fit? Since some pdf not in English, I can't make sure the measurement.
Title: Re: QRV01 output stage
Post by: peranders on August 13, 2010, 12:23:08 PM
I'm not sure you can find any flat transformer that will fit.

https://www.elfa.se/elfa3~se_en/elfa/init.do?shop=ELFA_SE-EN#toc=18744;item=56-172-12;
http://www.hahn-trafo.com/english/flat-type-transformators-ui39.php
Title: Re: QRV01 output stage
Post by: goldkenn on August 21, 2010, 08:09:12 PM
Did MJE345/350 replace BF471/472 perfect in QRV01? I found serveral pairs MJE340/350 from my drawer, and I serach did found many examples they do replace each others and work great, however, the pdf of MJE340/350 have not shown the capacitance, since you have mentioned low capacitance is needed, will MJE340/350 work?
Title: Re: QRV01 output stage
Post by: peranders on August 22, 2010, 08:44:32 AM
MJE340 is a small power transistor with for me unknown HF properties. I would use the BC transistors in this position.
Title: Re: QRV01 output stage
Post by: goldkenn on August 28, 2010, 08:04:34 AM
How to tune P1 and P3? Can't find any info since you have not yet finishe the instrcution section yet......
Title: Re: QRV01 output stage
Post by: peranders on August 28, 2010, 09:48:52 AM
I'll get back to you tomorrow evening.
Title: Re: QRV01 output stage
Post by: goldkenn on August 29, 2010, 09:39:26 AM
THANKS
Title: Re: QRV01 output stage
Post by: peranders on August 29, 2010, 08:44:07 PM
Those pots are for trimming the bias of the output stage.
Title: Re: QRV01 output stage
Post by: goldkenn on August 30, 2010, 04:00:53 AM
Quote from: peranders on August 29, 2010, 08:44:07 PM
Those pots are for trimming the bias of the output stage.

Of course! This is a servo amp and I can guess the trimmer is for bias, but how? Please advise.
Title: Re: QRV01 output stage
Post by: peranders on August 30, 2010, 08:14:23 AM
Trim for decent temperature, "not too hot" and hot may be 50-60 deg C.