In the low cost version :
Why not use the BUZ 900D/905D or 20n16/20P16 (250Watt) types instead of two 125 Watt types?
Then you do not have to pair the output devices and you could use only one set of drivers . Would be easier to make a good and stable PCB too.
Isn´t the MJE340/350 too slow compared to the very fast ones used in the earlier clones (BSS71/74)?
Koldby
Why not use the BUZ 900D/905D or 20n16/20P16 (250Watt) types instead of two 125 Watt types?
Then you do not have to pair the output devices and you could use only one set of drivers . Would be easier to make a good and stable PCB too.
Isn´t the MJE340/350 too slow compared to the very fast ones used in the earlier clones (BSS71/74)?
Koldby
I was talking about the Ft not the turn on time. They are not turned off at all (exept when the amp is turned off).
High Ft normally results in better slewrate , but at the same time makes the amp more prone to instability.
I was under the impression, that one of the things , that makes the GM sound good and transparent, was the use of very fast devices???
Why else should GM go for the BSS71/73?
Please correct me if I am wrong.
Koldby
High Ft normally results in better slewrate , but at the same time makes the amp more prone to instability.
I was under the impression, that one of the things , that makes the GM sound good and transparent, was the use of very fast devices???
Why else should GM go for the BSS71/73?
Please correct me if I am wrong.
Koldby
Kodby
In another thread on this forum(http://www.diyaudio.com/forums/solid-state/174468-very-best-amplifier-i-have-ever-heard.html) you will find schema for both Goldmund Memesis 9 and 3 in which it is used BSS71/74 (one couple) as drivers. As mentioned in #95 Jacco Vemeulen has explained that to to use MJE 340/350 as drivers in this context, will affect the slew rate negatively. I chose to listen to his advice and use BSS 71/74 in my last Golmund Memesis 9 clone. In my first clone, a variant of Memesis 3, I use MJE 340/50. It works okay, but they will be replaced withw BSS71/74 later on.
In # 87 in this thread MJE 340/50 is used as a driver for each MOSFET as Tommy describes.
Is this schema (#87) originally from Goldmund? If it is, it confirms Tommy
claims that this is a way to go in order to both maintain a high slew rate and avoid oscillation???. A high slewrwte is one of Goldmunds "trademarks".
In my Memesis I have cured this istability problems by using different values on the gate resistors: 680 ohm for N channel and 470 ohm for P channel.
This also affect slew rate negatively, I know.
If you have intentions to build a Goldmund clone according to the schema in #87 (Q2,3,9 and 10) or the orginale Memesis 9 (T7,8,9 and 10), I strongly recommend you to use a common heatsink for those transitors.
Eivind Stillingen
In another thread on this forum(http://www.diyaudio.com/forums/solid-state/174468-very-best-amplifier-i-have-ever-heard.html) you will find schema for both Goldmund Memesis 9 and 3 in which it is used BSS71/74 (one couple) as drivers. As mentioned in #95 Jacco Vemeulen has explained that to to use MJE 340/350 as drivers in this context, will affect the slew rate negatively. I chose to listen to his advice and use BSS 71/74 in my last Golmund Memesis 9 clone. In my first clone, a variant of Memesis 3, I use MJE 340/50. It works okay, but they will be replaced withw BSS71/74 later on.
In # 87 in this thread MJE 340/50 is used as a driver for each MOSFET as Tommy describes.
Is this schema (#87) originally from Goldmund? If it is, it confirms Tommy
claims that this is a way to go in order to both maintain a high slew rate and avoid oscillation???. A high slewrwte is one of Goldmunds "trademarks".
In my Memesis I have cured this istability problems by using different values on the gate resistors: 680 ohm for N channel and 470 ohm for P channel.
This also affect slew rate negatively, I know.
If you have intentions to build a Goldmund clone according to the schema in #87 (Q2,3,9 and 10) or the orginale Memesis 9 (T7,8,9 and 10), I strongly recommend you to use a common heatsink for those transitors.
Eivind Stillingen
In the schematic original Goldmund(M390,T600,T5000,...) BJT for Vas used FZT857,FZT957.
In the cheap version myclone I used MJEs,I do not see any difference in the measurements or listening test.
Drive current use MJEs set at 4mA(#200mW/1 driver).original Goldmund M390 also use them.
T5000 used Driver : KSC2690 + KSA1220
Output stage set at 115mA/1latetal mosfet with B+/-= +/-60V.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.