Hello,
So I had this Adcom 5802 from which I got the enclosure, the transformer, the big caps in the ps filter(which were recently replaced and measure 4miliohm and 22000u) and the small power supply that controls the big toroid.
So I decided to use the enclosure to build a nice 20w/8r and 27w/4r.
The amp uses the Stasis Fe as a front end, accepts rca and xlr inputs and has a voltage gain of 10x.
The output stage is similar to the one in Sit 5 and uses same working principle.
Here how the pcbs look. There is the main pcb with the output stage and a slave pcb with the front end.
The amp looks like this
From outside(good shape cosmetically, can send more photos using direct messaging)
And here the inside
A few more photos with the amp
You will notice that I used the small 12v power supply to control the big toroid from the front switch.
I installed some temperature sensors connected directly to each sit capsule to monitor the temp meanwhile testing. If needed I can leave these in place else they can be removed though it won’t change a thing soundwise.
The sensors will help if you use the amp with improper cooling because once the capsule reaches 75C they will turn off the main trafo.
Here are a few thd graphs
1w/4r
1w/8r
27w/4r
20w/8r
The power supply is dual mono, each channel is powered from its own winding from the trafo.
Initially the Adcom trafo gave too much output voltage which I had to lower a bit so I took the trafo at a trafo winding factory near my town so they rewinded completely the secondaries. When I got the transformer back it made a bit of noise so I have to return it back for a 2nd attempt. Now the noise got lower but there still is some. I will askthem to make another attempt.
I didn`t get a new trafo because I wanted to be able to use the amp at 120/240v like it iniatially was designed and still can be used.
In the meantime that the trafo was at the factory I used smps power supplies with great success and practically no noise and very low cost(320w meanwell)
Because I want to go ahead with my projects I need to pull some funds from somewhere and this amp will save me this time. So don`t have other funds to put a new trafo inside.
I was thinking at the following..
I was planning to ask 1300e for the amp it the trafo would have worked as expected.
A trafo for this amp is around 250e at Toroidiy so what about 1000e for the amp as it is?
I will send it with the actual trafo.
The amp weights a bit more than 25kg. I can ship it in the UK and some countries in the EU(Austria, Italy, Germany, Belgium and probably others) at 1.2 pounds/euros. For the UK no custom taxes will be implied. So in these cases the shipping will be quite cheap.
If you have a pair of field coil drivers that that you want to trade I am all eyes and ears 🙂
As for the sound.. what I can tell is that it`s explosive! I built a few sit amps but none sounded so powerful like this one.
Edit:
Somebody asked how h2 looks so here we go
10w/8r
10w/4r
So I had this Adcom 5802 from which I got the enclosure, the transformer, the big caps in the ps filter(which were recently replaced and measure 4miliohm and 22000u) and the small power supply that controls the big toroid.
So I decided to use the enclosure to build a nice 20w/8r and 27w/4r.
The amp uses the Stasis Fe as a front end, accepts rca and xlr inputs and has a voltage gain of 10x.
The output stage is similar to the one in Sit 5 and uses same working principle.
Here how the pcbs look. There is the main pcb with the output stage and a slave pcb with the front end.
The amp looks like this
From outside(good shape cosmetically, can send more photos using direct messaging)
And here the inside
A few more photos with the amp
You will notice that I used the small 12v power supply to control the big toroid from the front switch.
I installed some temperature sensors connected directly to each sit capsule to monitor the temp meanwhile testing. If needed I can leave these in place else they can be removed though it won’t change a thing soundwise.
The sensors will help if you use the amp with improper cooling because once the capsule reaches 75C they will turn off the main trafo.
Here are a few thd graphs
1w/4r
1w/8r
27w/4r
20w/8r
The power supply is dual mono, each channel is powered from its own winding from the trafo.
Initially the Adcom trafo gave too much output voltage which I had to lower a bit so I took the trafo at a trafo winding factory near my town so they rewinded completely the secondaries. When I got the transformer back it made a bit of noise so I have to return it back for a 2nd attempt. Now the noise got lower but there still is some. I will askthem to make another attempt.
I didn`t get a new trafo because I wanted to be able to use the amp at 120/240v like it iniatially was designed and still can be used.
In the meantime that the trafo was at the factory I used smps power supplies with great success and practically no noise and very low cost(320w meanwell)
Because I want to go ahead with my projects I need to pull some funds from somewhere and this amp will save me this time. So don`t have other funds to put a new trafo inside.
I was thinking at the following..
I was planning to ask 1300e for the amp it the trafo would have worked as expected.
A trafo for this amp is around 250e at Toroidiy so what about 1000e for the amp as it is?
I will send it with the actual trafo.
The amp weights a bit more than 25kg. I can ship it in the UK and some countries in the EU(Austria, Italy, Germany, Belgium and probably others) at 1.2 pounds/euros. For the UK no custom taxes will be implied. So in these cases the shipping will be quite cheap.
If you have a pair of field coil drivers that that you want to trade I am all eyes and ears 🙂
As for the sound.. what I can tell is that it`s explosive! I built a few sit amps but none sounded so powerful like this one.
Edit:
Somebody asked how h2 looks so here we go
10w/8r
10w/4r
Last edited:
Very nice work!
Are you using the N type IXFN280N085 ?
I believe Ben is using P type.
Thanks
Eric
Are you using the N type IXFN280N085 ?
I believe Ben is using P type.
Thanks
Eric
Thanks.
No, I have the pch sot227 puck mosfet that Pa uses in his, because of this I said it is working the same.
It has less output power than a Sit 5 because the Adcom enclosure is much smaller than what is needed so a compromise had to be made somewhere and it was done with the output power.
I got it set for up to 80w/8r but then the sound wasn’t exactly what I was looking for so had to find the right balance for this enclosure.
I am attaching the diagram for the os.
If we are speaking about same Ben(Mah) then I think he has a previous version.
No, I have the pch sot227 puck mosfet that Pa uses in his, because of this I said it is working the same.
It has less output power than a Sit 5 because the Adcom enclosure is much smaller than what is needed so a compromise had to be made somewhere and it was done with the output power.
I got it set for up to 80w/8r but then the sound wasn’t exactly what I was looking for so had to find the right balance for this enclosure.
I am attaching the diagram for the os.
If we are speaking about same Ben(Mah) then I think he has a previous version.
Attachments
Damn...... If I didn´t have this XA160.5 "clone" in the closet.... This would be mine, but my wife would kill me
This one doesn’t have global feedback so the sound is a bit different, I can say with more shape.
You know the thd is there (from the thd measurements) but it sounds in such a way that gives you a pleasant listening experience.
You know the thd is there (from the thd measurements) but it sounds in such a way that gives you a pleasant listening experience.
Awesome work on this 'rare' amplifier Schultzsch!
Someone is going to get a special power amp, Good luck with your sale.
Someone is going to get a special power amp, Good luck with your sale.
