Hi guys, a newbie here
I have just built one of Grant Wills 6CM5 Stereo amp using the M1120 transformers (my only other build was Grant's Lamington). Grant was a great help when I was stumped by something. On first power up I got a horrible shriek but had read somewhere to reverse the OPT secondary leads. All was good and its sounds fantastic!. but
I'm trying to get a better bass response and have just ordered some EDCOR CXPP25-MS-8K OPT's with a EDCOR XPWR039-120/240 mains tranny which outputs 110V x 2 @250mA and 6.3v x 2@4A. I will use Grant's original design for B+ with a voltage doubler. I have also discovered that the 6N2P valves are almost identical to the 12AX7 apart from slightly lower gain and only 6V heaters. I have just ordered 8 from Russia (only $20!) and was wondering if any of you guru's can forsee any problems I may encounter i.e using 6N2P for PI, 250mA not enough to run everything etc . Why isn't everybody using these cheaper valves?
Any advise would be greatly appreciated !
I have just built one of Grant Wills 6CM5 Stereo amp using the M1120 transformers (my only other build was Grant's Lamington). Grant was a great help when I was stumped by something. On first power up I got a horrible shriek but had read somewhere to reverse the OPT secondary leads. All was good and its sounds fantastic!. but
I'm trying to get a better bass response and have just ordered some EDCOR CXPP25-MS-8K OPT's with a EDCOR XPWR039-120/240 mains tranny which outputs 110V x 2 @250mA and 6.3v x 2@4A. I will use Grant's original design for B+ with a voltage doubler. I have also discovered that the 6N2P valves are almost identical to the 12AX7 apart from slightly lower gain and only 6V heaters. I have just ordered 8 from Russia (only $20!) and was wondering if any of you guru's can forsee any problems I may encounter i.e using 6N2P for PI, 250mA not enough to run everything etc . Why isn't everybody using these cheaper valves?
Any advise would be greatly appreciated !
Attachments
The valves are not commonly used because their not plug and play compatible whit the 12AX7.
However. if you where to use a toggle switch it would be possible to build an amplifier that will accept both the tube types.
A problem you might encounter, is that the 6n2p heater consumes 300mA more current.
Take care.
V4lve.
However. if you where to use a toggle switch it would be possible to build an amplifier that will accept both the tube types.
A problem you might encounter, is that the 6n2p heater consumes 300mA more current.
Take care.
V4lve.
Last edited:
Hi guys,
If anyone's interested I have just about finished the amp with EDCOR transformers instead of the M1120's I used the 6N2P valves for pre-amp and phase inverter. (The mains transformer has 2 x 4A @ 6.3V to cope with the load.
I have wired 4 separate pots for adjusting the bias so I can balance mismatched valves(I'm using 6BQ6's).
My problem is, the bass response isn't that much better than using the M1120 100v line trannys.
When I play James Taylor its perfect but when I play RUSH I'm not getting that punching bass.
I have increased the values of the coupling caps, increased and decreased C2 and C6, changed NFB resistor from 10K to 5K to 20K.
I am playing it through 15in PA speakers. I have tried an old sansui amp to make sure its not the speakers fault and the bass is great.
Hope someone can help !
I have included the tagboard layout a friend did for me (beware there are some errors!)
If anyone's interested I have just about finished the amp with EDCOR transformers instead of the M1120's I used the 6N2P valves for pre-amp and phase inverter. (The mains transformer has 2 x 4A @ 6.3V to cope with the load.
I have wired 4 separate pots for adjusting the bias so I can balance mismatched valves(I'm using 6BQ6's).
My problem is, the bass response isn't that much better than using the M1120 100v line trannys.
When I play James Taylor its perfect but when I play RUSH I'm not getting that punching bass.
I have increased the values of the coupling caps, increased and decreased C2 and C6, changed NFB resistor from 10K to 5K to 20K.
I am playing it through 15in PA speakers. I have tried an old sansui amp to make sure its not the speakers fault and the bass is great.
Hope someone can help !
I have included the tagboard layout a friend did for me (beware there are some errors!)
Attachments
No punching bass means crap frequency response. The only way to be sure is to measure with a tone generator and scope across a dummy load. I had a similar problem with my Chinese Dynaclone VAA-70MKii. But the values of your coupling caps seem OK.
Incidentally, I did spot two errors: no top caps connected and ECC81 input tube. The missing anode connections are pretty fatal...
Incidentally, I did spot two errors: no top caps connected and ECC81 input tube. The missing anode connections are pretty fatal...
Thanks for the response.
The drawing doesn't show the op transformer wiring, I should add that!
I do have a tone gen, do I need to connect a dummy load or can I just use the speakers?, what am I looking for on the cro? When I put a 20hz tone into the speakers I can see the wave but can only just hear a faint rumble (plus lots of other noises possibly due to the power supply driving the T gen). I don't start to get any real tone till about 40hz?
Thanks in advance
The drawing doesn't show the op transformer wiring, I should add that!
I do have a tone gen, do I need to connect a dummy load or can I just use the speakers?, what am I looking for on the cro? When I put a 20hz tone into the speakers I can see the wave but can only just hear a faint rumble (plus lots of other noises possibly due to the power supply driving the T gen). I don't start to get any real tone till about 40hz?
Thanks in advance
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