You shouldn't really see any obvious changes in circuit performance going from one to the other... differences will be very very small, perhaps a slightly better noise figure using the 2SA's.
It is a very small difference though.
Any basic audio circuit should should cope with massive differences in hFE whether it is 50 or 500, that is the beauty of negative feedback... it irons all those differences out.
It is a very small difference though.
Any basic audio circuit should should cope with massive differences in hFE whether it is 50 or 500, that is the beauty of negative feedback... it irons all those differences out.
thanks for calming down ... I thought I had already ordered a970 bl on the left I put 2 robots I chose from the cheat a841 .... and on the right I put 2 970 ... and I have one pair 5401 ..... I have them removed from the right channel ... I thought 970 would be better ... but now I don’t know myself ... maybe 5401 should have been ordered even so ...
there are changes in sound with the a970 bl the sound is worse ... the frequencies are cut and the sound quality is no longer so high .. it is necessary to go at least to 5401 or can you advise some more?
The 2SA970 should not affect the frequencies. The only way to know for sure is to look at the response with an oscilloscope and signal generator and see if all is well.
Maybe you are expecting to much 🙂 you change the transistors hoping for some dramatic change when in reality it is still exactly the same... and then your perceptions kick in and you feel it is worse.
It is a very common observation 🙂
Maybe you are expecting to much 🙂 you change the transistors hoping for some dramatic change when in reality it is still exactly the same... and then your perceptions kick in and you feel it is worse.
It is a very common observation 🙂
no, I still didn’t have an elephant) I ordered transistors from alik, maybe they have poor quality hfe from 300 to 330 I will switch to 5401 unambiguously ...
I'm going to give you an honest answer... transistors don't 'sound' at all 🙂 All things being equal you should not hear any differences if you substitute a transistor with a dozen different types as long as they are suitable for the application. They do not have a 'sound'.
If you really can hear a difference then something else is going on... either the circuit is super critical on devices (which for audio circuitry would be bad design) or your substitution is causing some unexpected behaviour such as instability or oscillation.
Another possibility is that your expectations are skewing the result... you want it to sound different in some way and it doesn't. That happens a lot.
If you really can hear a difference then something else is going on... either the circuit is super critical on devices (which for audio circuitry would be bad design) or your substitution is causing some unexpected behaviour such as instability or oscillation.
Another possibility is that your expectations are skewing the result... you want it to sound different in some way and it doesn't. That happens a lot.
thanks for the answer, but I can hear the difference .. eio is not heard except perhaps deaf ... and I don’t know why the variety of transistors affects this way ...
Could you have bought a fake transistor and that may be causing problems? Did you buy from eBay or a reputable dealer?
I bought where it is cheaper and express ... maybe they do not correspond to the current of 100 hertz ... therefore they sit down with low frequencies, removing high
I wouldn't buy transistors or anything important like that from China myself especially with the amount of copy items from there.
This repair has been carried out by a few people on here and others from other forums have done the same as described here and nobody else has reported what you say you hear. It is this that's leading me to believe you may have faulty transistors or even fake ones.
Also don't go for the cheapest option if you're looking for quality results my friend it never works out.
This repair has been carried out by a few people on here and others from other forums have done the same as described here and nobody else has reported what you say you hear. It is this that's leading me to believe you may have faulty transistors or even fake ones.
Also don't go for the cheapest option if you're looking for quality results my friend it never works out.
Hi Mooly,
Hope you're well.
I had a question I was hoping you could help me with.
The chap I sold my system to has called and said the amp is cracking and popping on the left channel. My question is as per your post I quoted would I need to replace Tr1 and Tr2 only or Tr3 & Tr4 also?
I've got 4 a970 GR transistors here to do the job that I bought from cricklewood. If I was to replace all 4 would the same a970 gr transistor work in place of the 4 that I will be replacing?
Thank you
Regards
Taz
The odd numbered parts are for one channel and the even numbered the other, so its either TR1 and TR3 or TR2 and TR4 depending which channel it is.
The image in post #42 is supposed to show which channel is which but tbh both look almost the same to me on the scan.
The 2SA970's should be fine as replacement but always double check the pin outs to be sure they match the originals.
The image in post #42 is supposed to show which channel is which but tbh both look almost the same to me on the scan.
The 2SA970's should be fine as replacement but always double check the pin outs to be sure they match the originals.
Attachments
Thank you for your reply Mooly.
Sorry I wasn't clear in the previous post. I am going to replace both channels and wanted to know if I would need to replace all 4 transistors or just the ones in TR1 & TR2?
Replacing both channels while I'm in there seems the logical thing to do, wouldn't want the other channel blowing out and having to do it all over again in 6 months time.
Good thing I had the transistors already, otherwise the delay for them could have been few weeks.
From the reference sheet they look the same but will double check in the morning before I give it a go. I will then be following your other posts about setting DC offset and bias.
Want to thank you for your replies in helping us keep these oldies on the road.
Kind regards
Taz
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I always say to make both channels the same when changing parts but remember... although these are a known failure item it doesn't automatically follow that they are the cause of your fault.
The VAS stage that runs hot would also be a possible suspect, as would dries around that stage.
The VAS stage that runs hot would also be a possible suspect, as would dries around that stage.
Thank you.
I will change the transistors and hope it fixes the problem. Will look for weak solder joints around the VAS and re-solder any that need it.
Appreciate your help Mooly
I will change the transistors and hope it fixes the problem. Will look for weak solder joints around the VAS and re-solder any that need it.
Appreciate your help Mooly
P10308-174508.jpg — Яндекс.Диск
hi, advise where to dig? some kind of rephasing ... maybe the wires from the transformer are incorrectly soldered?
hi, advise where to dig? some kind of rephasing ... maybe the wires from the transformer are incorrectly soldered?
