Ultra-high performance, yet rather simple - hybrid and more!

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#421
As for my tubsumo ips. I adjusted the vas current down using r29. I still have something wrong. Even with the current reduced to 2.15mA the bias on the output stage can't be adjusted low enough. I did have the amp running at 100ma bias per output device and something is definitely not right. I was afraid to run it long enough to do any measuring.
I think I need to build an output stage to use for testing. Pulling an amp from my system each time is a pia.

Wishing everyone the best for the new year,
Evan
 
#424
#425
The Semelab BUZ900Ps are 'double die' devices. They are essentially two of the Renesas devices in a single package. Years ago I built a pair of Randy Slone Opti MOS amplifiers and successfully substituted BUZ900P/BUZ950Ps devices for the prescribed 2Sk1058/2SJ162. I no longer remember the details tho. Mr Slone suggested and supported the upgrade in an email exchange at the time. Unfortunately Mr Slone is no longer with us.
 
#428
evanc said:
As for my tubsumo ips. I adjusted the vas current down using r29. I still have something wrong. Even with the current reduced to 2.15mA the bias on the output stage can't be adjusted low enough. I did have the amp running at 100ma bias per output device and something is definitely not right. I was afraid to run it long enough to do any measuring.
I think I need to build an output stage to use for testing. Pulling an amp from my system each time is a pia.

Wishing everyone the best for the new year,
Evan
Click to expand...

This is kind of strange. I have tested this IPS with Slewmaster OPS , but with IRFP240/9240 output devices - OPS quiescent current could be adjusted in a wide range, starting from zero.
 
#430
vzaichenko said:
Need a good holiday after a challenging year 🙂
Happy New Year! :xmasman:
Click to expand...
I too look forward to a "better" or at least easier year.

Yes something strange. Before I hooked the tubsumo ips up I had turned the OPS quiescent current to zero. Even with the ips set to output very low current the OPS still showed a lot of bias.
I am going to build your output stage to use as a tester and after some playing and listening I could use them to drive my midranges/tweeters.
I used buz 901/906 devices in two amps, a moskido hybrid and an f4 style amp Both amps sounded great but were room heating monsters. I used different gate resistors as well as small added caps to make the pairs a better compliment. I believe that thermal runaway is not an issue with these devices.
I would use the renasis devices (they are a lot cheaper then the semilab parts) but am somewhat afraid of buying ebay parts...any thoughts?
Evan
 
#431
evanc said:
I too look forward to a "better" or at least easier year.

Yes something strange. Before I hooked the tubsumo ips up I had turned the OPS quiescent current to zero. Even with the ips set to output very low current the OPS still showed a lot of bias.
I am going to build your output stage to use as a tester and after some playing and listening I could use them to drive my midranges/tweeters.
I used buz 901/906 devices in two amps, a moskido hybrid and an f4 style amp Both amps sounded great but were room heating monsters. I used different gate resistors as well as small added caps to make the pairs a better compliment. I believe that thermal runaway is not an issue with these devices.
I would use the renasis devices (they are a lot cheaper then the semilab parts) but am somewhat afraid of buying ebay parts...any thoughts?
Evan
Click to expand...

Tayda Electronics is a safe supplier to deal with. They have an eBay store as well as their own webstore
 
Last edited:
#435
evanc said:
I too look forward to a "better" or at least easier year.

Yes something strange. Before I hooked the tubsumo ips up I had turned the OPS quiescent current to zero. Even with the ips set to output very low current the OPS still showed a lot of bias.
I am going to build your output stage to use as a tester and after some playing and listening I could use them to drive my midranges/tweeters.
I used buz 901/906 devices in two amps, a moskido hybrid and an f4 style amp Both amps sounded great but were room heating monsters. I used different gate resistors as well as small added caps to make the pairs a better compliment. I believe that thermal runaway is not an issue with these devices.
I would use the renasis devices (they are a lot cheaper then the semilab parts) but am somewhat afraid of buying ebay parts...any thoughts?
Evan
Click to expand...

Evan , the super-pair with EF3 BJT's could be unstable - Val used a EF2 FET
arrangement.
My original Kypton V had issues except with large Cdom around the super-pair
stage. The same IPS without the baxandall was fine. CFA baxandall IPS
was also fine with the EF3.
I think both Thimios and Terry had these issues. 😱
Your bias should be 10ma centered trimmer @ 5.2ma VAS I (all 4 of mine were).

OS
 
#437
"Evan , the super-pair with EF3 BJT's could be unstable - Val used a EF2 FET"

I have a pair of the EF2 MOSFET output stages built but they are getting daily use. I'm going to put a pair of val's output stages together to play with. They should make plent of power for my midranges and tweeters. This would allow me to use all four of the 5 pair slewmonsters to drive woofers One amp for each 15" driver (insert evil laughter).
Jwilhelm I hope you have good results. The more I see people working things out the more I learn.
 
#438
evanc said:
"Evan , the super-pair with EF3 BJT's could be unstable - Val used a EF2 FET"

I have a pair of the EF2 MOSFET output stages built but they are getting daily use. I'm going to put a pair of val's output stages together to play with. They should make plent of power for my midranges and tweeters. This would allow me to use all four of the 5 pair slewmonsters to drive woofers One amp for each 15" driver (insert evil laughter).
Jwilhelm I hope you have good results. The more I see people working things out the more I learn.
Click to expand...

Subwoofers for a mansion ? Just one "monster" on my 10" will shake my house.
Bolt yer china down .... 😀

OS
 
#439
evanc said:
"Evan , the super-pair with EF3 BJT's could be unstable - Val used a EF2 FET"

I have a pair of the EF2 MOSFET output stages built but they are getting daily use. I'm going to put a pair of val's output stages together to play with. They should make plent of power for my midranges and tweeters. This would allow me to use all four of the 5 pair slewmonsters to drive woofers One amp for each 15" driver (insert evil laughter).
Jwilhelm I hope you have good results. The more I see people working things out the more I learn.
Click to expand...

I'm hoping I have good results too. I've got two hybrids on the go and neither are working out well. These are my first experience with tubes.
 
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