Moved away from hybrids in the meantime.
This is 12au7 gain stage then 12au7 phase splitter into 2 EL84's.
Transformers are mains to 6VAC and heaters.
6VAC to 150VAC transformer for valve B+.
Reverse main s transformer for output transformer.
All with latest JLCPCB purple solder resist.
Transformer middle lower is mains transformers.
One to the lower right is 6VAC to 150VAC.
Top right transformer is output transformer (waiting for it to come.)
This is 12au7 gain stage then 12au7 phase splitter into 2 EL84's.
Transformers are mains to 6VAC and heaters.
6VAC to 150VAC transformer for valve B+.
Reverse main s transformer for output transformer.
All with latest JLCPCB purple solder resist.
Transformer middle lower is mains transformers.
One to the lower right is 6VAC to 150VAC.
Top right transformer is output transformer (waiting for it to come.)
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Yes its an audio amplifier.
Jack sockets are for guitar input. Might need a pre amp.
On a previous design the frequency response wasn't that high.
Its just a cheap design.
Jack sockets are for guitar input. Might need a pre amp.
On a previous design the frequency response wasn't that high.
Its just a cheap design.
nigelwright7557,
Looks good!
Easy to build, too.
Please post a schematic of the amp and power supply, if you get the time to draw one out.
Thanks!
Looks good!
Easy to build, too.
Please post a schematic of the amp and power supply, if you get the time to draw one out.
Thanks!
Since the only input jack I see is the guitar jack, I assume that this is a guitar amp. In that case just about anything will work for the OPT.....unless you are playing bass, which is what I think that I see in your avatar.
Two stages of 12AU7 may not get you into compression or distortion with average guitar pickups. A 12AT7 will get you more gain, and a 12AX7 even more. All have the same pinout, but will need some resistor value tweaking in order to work.
Finally got it built up.
B+ was 60 volts due to grossly underestimating current EL84's take. Sound was very distorted.
So removed reversed transformer and replaced it with a 9VAC 25VA transformer.
Sounds very good now.
Shame about wrong transformer but can get a new pcb made in with the next batch of pcb's I buy.
B+ was 60 volts due to grossly underestimating current EL84's take. Sound was very distorted.
So removed reversed transformer and replaced it with a 9VAC 25VA transformer.
Sounds very good now.
Shame about wrong transformer but can get a new pcb made in with the next batch of pcb's I buy.
So a 150 volt transformer would make a bit over 200 with light load but you dropped to *60* under load? I don’t think it would be that bad unless you were using a half wave rectifier and a cap that really needs replacement. That trafo must be *really* undersized. Even when they are, it usually won’t drop much more than what it would with a choke-input filter.
The first transformer was only 6va which when I looked at el84 current is woefully inadequate !
I have replaced it with a 25va transformer and B+ holds up now.
Sadly the transformer doesnt fit in same holes so have had to invert it and glue it to the pcb which looks pretty naff.
Will try to off load it on ebay as a cheapie.
I quite often get batches of pcb's made so will slip the next revision in with those to save on postage.
The previous distortion is gone now and it sounds sweet.
The bottom end is very strong, maybe lacks a little top end if anything.
I have replaced it with a 25va transformer and B+ holds up now.
Sadly the transformer doesnt fit in same holes so have had to invert it and glue it to the pcb which looks pretty naff.
Will try to off load it on ebay as a cheapie.
I quite often get batches of pcb's made so will slip the next revision in with those to save on postage.
The previous distortion is gone now and it sounds sweet.
The bottom end is very strong, maybe lacks a little top end if anything.