Hello
I am going to make the Stan curtis 60w class a amplifier. I tried this amp many years ago when in my early twenties and the project failed. Now I have more experience I wold like to try again. I have all the parts but need the PCB artwork. I thing the original project was published in ETI winter audio edition in the mod 1980's.
I have just heard this amp made with the original PCBS and I was very impressed with the sound. Does any one out there have the mag for sale or a copy of the pcb artwork so I can get some PCBs made. I would like to keep to the original artwork
regards
Nick
I am going to make the Stan curtis 60w class a amplifier. I tried this amp many years ago when in my early twenties and the project failed. Now I have more experience I wold like to try again. I have all the parts but need the PCB artwork. I thing the original project was published in ETI winter audio edition in the mod 1980's.
I have just heard this amp made with the original PCBS and I was very impressed with the sound. Does any one out there have the mag for sale or a copy of the pcb artwork so I can get some PCBs made. I would like to keep to the original artwork
regards
Nick
Nick
I have the original magazine with the full article for the pre and power amps including the pcb artwork. I will also add the updates that Stan Curtis published a year later.
I made the pre and power amps and they do sound very good. I like the design. Not unlike the Krell in sound. I have swapped out the output devices for later faster ones and that helped. I built the amps as monoblocks and added a 4" fan to each monoblock to keep them running at reasonable temperatures. The amps do run at 60 watt class A and give off a lot of heat. The pre amp also sounds good.
The overall article plus pcb plus updates is very long and I only have hard copies. If you give me your address I will post you a photo copy.
Don
I have the original magazine with the full article for the pre and power amps including the pcb artwork. I will also add the updates that Stan Curtis published a year later.
I made the pre and power amps and they do sound very good. I like the design. Not unlike the Krell in sound. I have swapped out the output devices for later faster ones and that helped. I built the amps as monoblocks and added a 4" fan to each monoblock to keep them running at reasonable temperatures. The amps do run at 60 watt class A and give off a lot of heat. The pre amp also sounds good.
The overall article plus pcb plus updates is very long and I only have hard copies. If you give me your address I will post you a photo copy.
Don
Many thanks for the quick reply
My address is 18
the chase rayleigh Essex
SS6 8QL
Can I purchase the originals? if yes I can purchase through ebay as a buy it now item?
regards
Nick
My address is 18
the chase rayleigh Essex
SS6 8QL
Can I purchase the originals? if yes I can purchase through ebay as a buy it now item?
regards
Nick
Ok
Thanks again for your help, are you still using you amps today? and what output transistors did you use?
best regards
Nick
Thanks again for your help, are you still using you amps today? and what output transistors did you use?
best regards
Nick
Stan Curtis 60W class A
Nick,
The article and schematics can be found at the excellent class A amplifier site, run by Geooff Moss:
http://www.tcaas.btinternet.co.uk/curtis60w.pdf
http://www.tcaas.btinternet.co.uk/curtis60w.gif
Not 100% sure about the update article, as I don't recall seeing this, but there is an "update" section at the end of the article, so I assume this is the same thing.
PaulF
Nick,
The article and schematics can be found at the excellent class A amplifier site, run by Geooff Moss:
http://www.tcaas.btinternet.co.uk/curtis60w.pdf
http://www.tcaas.btinternet.co.uk/curtis60w.gif
Not 100% sure about the update article, as I don't recall seeing this, but there is an "update" section at the end of the article, so I assume this is the same thing.
PaulF
Hi,
is this a ClassA push pull amp?
If so, then why is the output bias set to 3A, when the specification claims 60W of ClassA into 8r0?
is this a ClassA push pull amp?
If so, then why is the output bias set to 3A, when the specification claims 60W of ClassA into 8r0?
Hi Don/Nick
Could I beg a favour and ask that you share the preamp article with me? I built it years ago, and remember it being very good.
If this amp had an active current source for half the output, you would be correct.
3A bias is higher than need be for push-pull class A.
Only enough bias to keep the un-driven half of the output stage from cutting off when the oher half is driven to peak is required. This is typically one half of the peak current required. 2A is probably all that is needed.
3A bias is higher than need be for push-pull class A.
Only enough bias to keep the un-driven half of the output stage from cutting off when the oher half is driven to peak is required. This is typically one half of the peak current required. 2A is probably all that is needed.
That's the problem.
It either needs 4A bias for a single ended ClassA or 2A bias for push pull.
Stan Curtiss would not have got it wrong so why 3A of bias?
It either needs 4A bias for a single ended ClassA or 2A bias for push pull.
Stan Curtiss would not have got it wrong so why 3A of bias?
Hi
The article on the uk site is only part of the original and does not include the pre amp or updates.
Don
The article on the uk site is only part of the original and does not include the pre amp or updates.
Don
Andrew
When you read the article Sran Curtis talks about the output transistor (a) always being turned on (b) operating in true class a (c) always operating in its linear region. And the general tone is that the amplifier is full class A. I set the bias to 4 amp and not 3 amp. This means that each output transistor dissiipates 53 watt and not 40 watt as discussed in the article.
Don
When you read the article Sran Curtis talks about the output transistor (a) always being turned on (b) operating in true class a (c) always operating in its linear region. And the general tone is that the amplifier is full class A. I set the bias to 4 amp and not 3 amp. This means that each output transistor dissiipates 53 watt and not 40 watt as discussed in the article.
Don
Hello Don
Thanks again for the photo copies of the article, If I owe you any money, just let me know and I can send you a cheque for the copying costs
thanks
Nick
Thanks again for the photo copies of the article, If I owe you any money, just let me know and I can send you a cheque for the copying costs
thanks
Nick
stan curtis class a
Hello
I received the copies today, many thanks for this. So you have 2 mono blocks actually working? any tips before I start construction? are they still used today?
best regards
Nick
Hello
I received the copies today, many thanks for this. So you have 2 mono blocks actually working? any tips before I start construction? are they still used today?
best regards
Nick
AndrewT said:
Hi,
I think you've answered your own question as it is not single ended.
Its push pull and will enter class B into lower impedance loads.
So presumably class A is maintained into < 8R, seems to be ~ 6R.
Enough current for 8R is not enough for an 8 ohm speaker .......
🙂/sreten.
Hi Sreten,
you are thinking along the lines I adopted for the Krell Klone I built.
If we are right, then it looks like Stan designed for 60W into 8r0 in full ClassA and when driving real 8ohm speakers discovered that it sounded better by increasing the bias by a further 50% to make it stay in ClassA for virtually any 8ohm reactive load upto the same 31Vpk of output voltage.
This implies 93W into 5r2 in ClassA, seems he missed, or deliberately avoided, the traditional trick of claiming the most it can do.
you are thinking along the lines I adopted for the Krell Klone I built.
If we are right, then it looks like Stan designed for 60W into 8r0 in full ClassA and when driving real 8ohm speakers discovered that it sounded better by increasing the bias by a further 50% to make it stay in ClassA for virtually any 8ohm reactive load upto the same 31Vpk of output voltage.
This implies 93W into 5r2 in ClassA, seems he missed, or deliberately avoided, the traditional trick of claiming the most it can do.
jamesfeline
I do still have the stan curtis 60 watt power amps.
the power amps I normally use alternate between;
Kelvin labs 60 watt monoblocks
Electrocompaniet 25 watt amps
Forte 4/5
Musical Fidelity M270
jlh 30 watt amps
I recommend also trying the Stan curtis pre amp which I also enjoyed.
As I mentioned earlier I used more modern power output transistors in the stan curtis 60 watt power amps that I built. Sometime in the future I will try different devices at the input. I have modified the electrocompaniet and put jfets at the input. This seems to me to give more detail and resolution. It may be worth considering in the stan curtis amp.
I did not find the stan curtis amp difficult to build or set up. Please remember however that it does need large heatsinks. I hope you build it and enjoy it.
Don
I do still have the stan curtis 60 watt power amps.
the power amps I normally use alternate between;
Kelvin labs 60 watt monoblocks
Electrocompaniet 25 watt amps
Forte 4/5
Musical Fidelity M270
jlh 30 watt amps
I recommend also trying the Stan curtis pre amp which I also enjoyed.
As I mentioned earlier I used more modern power output transistors in the stan curtis 60 watt power amps that I built. Sometime in the future I will try different devices at the input. I have modified the electrocompaniet and put jfets at the input. This seems to me to give more detail and resolution. It may be worth considering in the stan curtis amp.
I did not find the stan curtis amp difficult to build or set up. Please remember however that it does need large heatsinks. I hope you build it and enjoy it.
Don
Hello .. new post
I have started the construction for this amplifier .. now that I have listened to one, well impressed
so the 1st thing to do is make the original PCB with the appropriate gerber files
regards
I have started the construction for this amplifier .. now that I have listened to one, well impressed
so the 1st thing to do is make the original PCB with the appropriate gerber files
regards
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