maplin 4-20
I have an amp which I think is a version of the Maplin 4-20.
I know these are not highly regarded but since it works ok, I thought I might try one or two basic upgrades.
Obviously I'm not going to throw a lot of money at this, but a few component changes might be interesting.
I believe it might be based on the Mullard amps but i'm not sure how closely.
Problem is I don't have a schematic nor can i find one. Can anyone help?
I have an amp which I think is a version of the Maplin 4-20.
I know these are not highly regarded but since it works ok, I thought I might try one or two basic upgrades.
Obviously I'm not going to throw a lot of money at this, but a few component changes might be interesting.
I believe it might be based on the Mullard amps but i'm not sure how closely.
Problem is I don't have a schematic nor can i find one. Can anyone help?
HI Al, now that you have the shematic, let see what you can do.
1-Change the tubes for better quality ones (some brands are better than others in specific fonctions)
2_Change resistors and capacitors (in the signal path at least) for higher grade.
3-Change the transfos for better ones (this is the weakest piont in this amp, no real bass, strident highs and lack of dynamics) Could be costly but you'll get the greatest improvement.
4- Change the SS rectifier for a tube rectifier (could be complicated!)
Good luck !
Andre
1-Change the tubes for better quality ones (some brands are better than others in specific fonctions)
2_Change resistors and capacitors (in the signal path at least) for higher grade.
3-Change the transfos for better ones (this is the weakest piont in this amp, no real bass, strident highs and lack of dynamics) Could be costly but you'll get the greatest improvement.
4- Change the SS rectifier for a tube rectifier (could be complicated!)
Good luck !
Andre
Sorry...
I've commented on these OP transformers before.....
The grid leaks of the EL34's are a bit too high at the anode voltage used.
It goes on....
The chassis is a bit cramped, so it gets rather too hotEC8010 said:What will be left of the original amplifier after all these changes? The chassis?
I've commented on these OP transformers before.....
The grid leaks of the EL34's are a bit too high at the anode voltage used.
It goes on....
What will be left of the original amplifier after all these changes? The chassis?
Thats about all. Mind you the sockets on the back are pretty good!
I know the trafos are the weakest link, but i'll only change these if i find something secondhand.
I've already fitted a new quad of EH tubes which was money well spent.
As for the rest of it ......
Cap changes etc, no problem.
Who designed the ruddy thing in the first place ??????
I don't think anyone's going to admit to that are they?
The Millenium 4/20 was designed by Mike Holmes.I have a pair of these and I've just fitted upgraded O/P transformers, bought directly from him.They are type VT1041 and cost £80.45 inclusive. That included postage as well.I also have KT66's installed but you need to move one valve base out by an inch. The VT1041's will allow the use of KT88's if you upgrade the mains trannies.
I like the sound of mine and they drive a large pair of TDL Monitors no problem. Mikes web address is www.livinginthepast.demon.co.uk and his email address is mikech@livinginthepast.demon.co.uk
Hope this helps. Si.
I like the sound of mine and they drive a large pair of TDL Monitors no problem. Mikes web address is www.livinginthepast.demon.co.uk and his email address is mikech@livinginthepast.demon.co.uk
Hope this helps. Si.
Hello Trebla, Yes it definitely was worth the effort.As well as gains in the bass it opened up the sound considerably.I actually like these amps (mine are mono blocks, not the design with one mains tx for both amps.)I bought them because they are close to the Leak in terms of circuit design and valves used. You must accept that Mike was commissioned by Maplin to design these so was probrably held by price constraints i.e. the cheap O/P trannies.Maplin don't supply this kit anymore but Mike still has parts available and he'll talk to you, unlike some people. I think the KT66's made a real improvement and I fitted those before I did the O/P/Ts. I also have all the original assembly instructions etc if you're interested. I could send them to your own email address if you wish. Regards, Si.
Thanks Si.
It sounds as though an extra mains trafo may be needed as well, to get the results you have heard.
It's getting more expensive by the day. I'll give it some thought. This amp already has some reasonable quality caps/resistors inside and I think sounds clearer than the Leak I used to have a few years ago. Just needs the top and bottom ends sorting.
The build instructions might be useful in any case so I would be very grateful if you could email these.
It sounds as though an extra mains trafo may be needed as well, to get the results you have heard.
It's getting more expensive by the day. I'll give it some thought. This amp already has some reasonable quality caps/resistors inside and I think sounds clearer than the Leak I used to have a few years ago. Just needs the top and bottom ends sorting.
The build instructions might be useful in any case so I would be very grateful if you could email these.
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