By accident I bought fifty years old german tube amplifier Braun CSV-13. It is 12W EL84 push-pull. All the goodies are closed into metal case, the frontpanel is made of alluminium, the cover is heavy, made of perforated steel. At the rear panel we have archaic terminals in german DIN standard. Even mains terminal is strange and it's impossible to buy suitable plug.
I replaced it first, and connected the amplifier by DIN terminals....and the sound was horrible. Slow, fat bass, no shape, no space, no details, and many distortions at higher sound levels. So I replaced all the tubes. And nothing was better. I started to search schematic, and I found it. After short inspection I decided to bypass preamp and tone control, and... bingo! It plays quite well. But after few days of playing electrolytics started to leak. No way out, there's need to solder. I made new power supply, I replaced old selenium rectifier, and I rebuilt driver section to omit electrolytics in the signal path. In the end I replaced old flimsy plastic rear panel with DIN terminals by new panel made of solid aluminium and equipped with modern Monacor speaker terminals and RCA signal terminals. Unfortunately OPT's haven't ultralinear taps, but the sound is very good anyway.
I replaced it first, and connected the amplifier by DIN terminals....and the sound was horrible. Slow, fat bass, no shape, no space, no details, and many distortions at higher sound levels. So I replaced all the tubes. And nothing was better. I started to search schematic, and I found it. After short inspection I decided to bypass preamp and tone control, and... bingo! It plays quite well. But after few days of playing electrolytics started to leak. No way out, there's need to solder. I made new power supply, I replaced old selenium rectifier, and I rebuilt driver section to omit electrolytics in the signal path. In the end I replaced old flimsy plastic rear panel with DIN terminals by new panel made of solid aluminium and equipped with modern Monacor speaker terminals and RCA signal terminals. Unfortunately OPT's haven't ultralinear taps, but the sound is very good anyway.
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It will sound better if you triode-strap the EL-84s!
Hi.
Yes, it is a very good approach to bypass the entire tone-control stages as they surely render the sound "horrible". Likewise, I bypassed the entire line+tone-control stages of my 50-year young stock Dynaco PS-2 preamp.
You have done everything right. But you can still make it sound better by converting the PP powerstage from pentode to triode by simply connect the G2 of each EL-84 to its plate with a 100R resistor. I guarantee you will find it sound more transparent, more airy & more musical.
This is what I have done with my 50-year young stock Dynaco ST-70 which sounded "horrible", "fat" & "slow" like what you just described. Like you, I hate vintage sounds.
I triode-strapped the EL-34 Ultra-Linear PP with a more complex Vg2 level shifter, switchable from triode-UL. Yet I've left it triode-strapped mode for ever since day one of its upgrade. I've also reduced the 20dB global loop NFB to 10dB. This offsets somewhat the reduced O/P power after triode convertion.
Listening is believing. Triode sounds so much more musical than pe tode.
c-J
McGyver said:
Hi.
Yes, it is a very good approach to bypass the entire tone-control stages as they surely render the sound "horrible". Likewise, I bypassed the entire line+tone-control stages of my 50-year young stock Dynaco PS-2 preamp.
You have done everything right. But you can still make it sound better by converting the PP powerstage from pentode to triode by simply connect the G2 of each EL-84 to its plate with a 100R resistor. I guarantee you will find it sound more transparent, more airy & more musical.
This is what I have done with my 50-year young stock Dynaco ST-70 which sounded "horrible", "fat" & "slow" like what you just described. Like you, I hate vintage sounds.
I triode-strapped the EL-34 Ultra-Linear PP with a more complex Vg2 level shifter, switchable from triode-UL. Yet I've left it triode-strapped mode for ever since day one of its upgrade. I've also reduced the 20dB global loop NFB to 10dB. This offsets somewhat the reduced O/P power after triode convertion.
Listening is believing. Triode sounds so much more musical than pe tode.
c-J
Yes, I LOVE triode sound. But REAL triode, and not triode-strapped pentode. Especially direct heated triodes are magical. I'm using upgraded ukrainian monoblocks based on 6B4G DHT in PSE, and I love it. And Braun amplifier goes to one of my friends. Maybe I'll install triode-pentode switch. No need to drill, becaude there are 3 unused switches on the frontpanel.
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