Sugden information and schematics here
http://www.audiomisc.co.uk/JES/Si402/Si402.html
There are many models, click into the rigth arrow down the page.
regards,
Carlos
http://www.audiomisc.co.uk/JES/Si402/Si402.html
There are many models, click into the rigth arrow down the page.
regards,
Carlos
Attachments
sreten said:
Hi,
I doubt it has 48 amps AC running through it and it is a 50W resistor.
If you cannot work out by logic / inspection what the pot does
you really should not be poking around inside your amplifier.
/sreten.
It's a 5w and 1v dc pass across and the pot are used to ajust this voltage and this is exactly what i was thinking about and i poked inside it and now its perfect.
Thanks
Hi,
Out of interest what were your mods or ideas ?
If altering the pot altered your temperature it sounds like it is for adjusting the quiescent current. With no speakers attached measure the DC offset at the speaker terminals. If you tweak the pot and the offset remains the same this would suggest the pot is NOT for DC balance (guessing what things do is no good. you have to be sure ) Are there any low value resistors in the output stage ( like emmiter resistors ) that you could measure the DC voltage across and so calculate and set the current precisely ). Remember it's not the voltage on the pot your altering -- thats immaterial, if the left channel has 1 volt on the pot and the right 1.5 volts and both give (say) the correct quiescent current then those values are correct. It's what the pot actually sets that matters NOT the setting of the pot itself. ( If that makes any sense )
Bonsai --- How to make friends and influence people
I have had the priviledge of auditioning Sugden gear ( recently, about 2.5 years ago ) at the factory. Had the guided tour, watched individual products being constructed, saw in detail products not yet even on sale. You wouldn't believe me if I told you , but I will say this, they care --- really care about the product- about the quality of parts used etc etc. And nearly everything is done on site, even the metalwork (not the anodising).
Out of interest what were your mods or ideas ?
If altering the pot altered your temperature it sounds like it is for adjusting the quiescent current. With no speakers attached measure the DC offset at the speaker terminals. If you tweak the pot and the offset remains the same this would suggest the pot is NOT for DC balance (guessing what things do is no good. you have to be sure ) Are there any low value resistors in the output stage ( like emmiter resistors ) that you could measure the DC voltage across and so calculate and set the current precisely ). Remember it's not the voltage on the pot your altering -- thats immaterial, if the left channel has 1 volt on the pot and the right 1.5 volts and both give (say) the correct quiescent current then those values are correct. It's what the pot actually sets that matters NOT the setting of the pot itself. ( If that makes any sense )
Bonsai --- How to make friends and influence people
I have had the priviledge of auditioning Sugden gear ( recently, about 2.5 years ago ) at the factory. Had the guided tour, watched individual products being constructed, saw in detail products not yet even on sale. You wouldn't believe me if I told you
, but I will say this, they care --- really care about the product- about the quality of parts used etc etc. And nearly everything is done on site, even the metalwork (not the anodising).
Mooly said:
Very simple thing.
First one is to reroute the preamp audio signal to amplifier section, they run too close from power and take noise.
Second one is to remove a 10k resitor on the left negative (chassis ground) speaker output. This clean the left audio signal from noise.
I think the A21SE use an auto biasing circuit. If it's the case i can't adjust the quiescent current right?
Hi,
Final thoughts on the pot. You say altering it has equalised the temperatures which suggests it is altering the power dissipated on the heatsink presumably by reducing the current flowing through the active devices.
Without a circuit I can't say whether the A21 has an auto bias scheme or not. The pot does something though --- question is what. Can you tell whether the amp uses regulated and stabilised supplies. Could it set the rail voltage ? A small increase or decrease here would cause very noticable differences in power dissipation. If it were me I would want to know exactly what I was altering. A few very simple measurements is all it takes
Enjoy the amp, they are one of the best sounding out there.
Edit. Interesting about your thoughts on the mods-- could do with one to have a play with.
Final thoughts on the pot. You say altering it has equalised the temperatures which suggests it is altering the power dissipated on the heatsink presumably by reducing the current flowing through the active devices.
Without a circuit I can't say whether the A21 has an auto bias scheme or not. The pot does something though --- question is what. Can you tell whether the amp uses regulated and stabilised supplies. Could it set the rail voltage ? A small increase or decrease here would cause very noticable differences in power dissipation. If it were me I would want to know exactly what I was altering. A few very simple measurements is all it takes
Enjoy the amp, they are one of the best sounding out there.
Edit. Interesting about your thoughts on the mods-- could do with one to have a play with.
I feel empathy, a very positive feeling about this brand
Reading the hystory of them, how they started....well.... very interesting things about.
My nephew from UK will come to my home in the end of this year, and i love tradition, those things they have.... i will ask nephew to buy an old one to me if not too much expensive.
Well... Japanese knows what are tradition, family companies, passion to the work they do.... i also feel that audio quality is not so important in this case.... the tradition, the name, the history has some importance... a positive example to all of us.
Good..... i feel good to have japanese here.... i know it is ... cheese sonically speaking...but wonderfull thing watching from another angle.
Picture is the Hioki building, their office...i have an old Multimeter, form Hioki, still operating...not so precise as the modern ones....this one is analogical, and they gave me support to this very old equipmente... you see tradition...mine is 32 years , analogical unit, still operating those days, all life it had operated needing only to replace batteries.... not a 1 percent precision instrument, but reliable, there's tradition, there's passion, respect to customers.... the same as Sugden.
regards,
Carlos
Reading the hystory of them, how they started....well.... very interesting things about.
My nephew from UK will come to my home in the end of this year, and i love tradition, those things they have.... i will ask nephew to buy an old one to me if not too much expensive.
Well... Japanese knows what are tradition, family companies, passion to the work they do.... i also feel that audio quality is not so important in this case.... the tradition, the name, the history has some importance... a positive example to all of us.
Good..... i feel good to have japanese here.... i know it is ... cheese sonically speaking...but wonderfull thing watching from another angle.
Picture is the Hioki building, their office...i have an old Multimeter, form Hioki, still operating...not so precise as the modern ones....this one is analogical, and they gave me support to this very old equipmente... you see tradition...mine is 32 years , analogical unit, still operating those days, all life it had operated needing only to replace batteries.... not a 1 percent precision instrument, but reliable, there's tradition, there's passion, respect to customers.... the same as Sugden.
regards,
Carlos
Attachments
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.