Hi Guys!
First time post, not an expert but know a little bit about this amp.
I had a pair and wish I had kept them - they were superb. I replaced all the caps with new (an easy job - it's all hard wired) and the resistors with equivalent 2W types to keep thermal noise down. I found a great improvement in the sound quality by removing the feedback resistor bypass capacitor - these things really sang! I didn't experience and problems with oscillation as a result but that was just my experience and I am no expert. I sold them to a friend to bring him into the valve community and he has enjoyed them ever since!
Very Best to All,
Graham (aka That Radio Thing)
First time post, not an expert but know a little bit about this amp.
I had a pair and wish I had kept them - they were superb. I replaced all the caps with new (an easy job - it's all hard wired) and the resistors with equivalent 2W types to keep thermal noise down. I found a great improvement in the sound quality by removing the feedback resistor bypass capacitor - these things really sang! I didn't experience and problems with oscillation as a result but that was just my experience and I am no expert. I sold them to a friend to bring him into the valve community and he has enjoyed them ever since!
Very Best to All,
Graham (aka That Radio Thing)
Hi Graham
Nice tip on removing the feedback cap, thanks.
Is it the MA-12's you had ?
I just caught up on the thread, having started to look at mine again.
Issues with the chassis' resolved...
...simply need a bigger chassis / s.
Has anyone tried dropping in a few motor-run caps, here & there ?
Any good tips from peoples, on any aspect of refurbing MA-12's / Mullards, most welcome...
...the refurb. cometh !!!
Cheers.
Si.
Nice builds Wide Range Sound...
...coooool !
Leaks are great Kevin...
...especialy with gravy !
wink...
Nice tip on removing the feedback cap, thanks.
Is it the MA-12's you had ?
I just caught up on the thread, having started to look at mine again.
Issues with the chassis' resolved...
...simply need a bigger chassis / s.
Has anyone tried dropping in a few motor-run caps, here & there ?
Any good tips from peoples, on any aspect of refurbing MA-12's / Mullards, most welcome...
...the refurb. cometh !!!
Cheers.
Si.
Nice builds Wide Range Sound...
...coooool !
Leaks are great Kevin...
...especialy with gravy !
wink...
MA-12 Schematic...again...+ PICS !!!!
Hi Vacuum heads !
( there's no air, in there ! )
Just thought I'd bung the schematic up again, as it was a few pages back.
4mm test-points near the valves...?
Mmmm...?
Si.
Slightly concerned that if I add regulated heater supplies, the transformer might be a bit pushed.
When they were last 'fired-up' it did get rather warm.
Maybe a small extra transformer for the 'teeny-toob' driver heaters could be good ?
Mmmmmmmm..............?
Hi Vacuum heads !
( there's no air, in there ! )
Just thought I'd bung the schematic up again, as it was a few pages back.
4mm test-points near the valves...?
Mmmm...?
Si.
Slightly concerned that if I add regulated heater supplies, the transformer might be a bit pushed.
When they were last 'fired-up' it did get rather warm.
Maybe a small extra transformer for the 'teeny-toob' driver heaters could be good ?
Mmmmmmmm..............?
Attachments
*ahem* Noob here!
I have a full MA12 instruction manual (including a full sheet schematic I think)
I'll need to scan it - only if there is enough interest!
However, I'm looking for a replacement output transformers for my MA12 pair (and TBH the mains tx too) Any ideas if there is an "off the shelf" - the OP tx is marked as as a RADFORD and not a mullard.
Now, back to reading...
CR
I have a full MA12 instruction manual (including a full sheet schematic I think)
I'll need to scan it - only if there is enough interest!
However, I'm looking for a replacement output transformers for my MA12 pair (and TBH the mains tx too) Any ideas if there is an "off the shelf" - the OP tx is marked as as a RADFORD and not a mullard.
Now, back to reading...
CR
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