Hello Konstantinos,
Thanks for your valuable post. This gives food for rethinking the design. Yes, the 12R-LL3 might be difficult to get. The 12AV7 appeares to be a substitute.
I already tried a cascoded ECC88 for the first stage and it worked out nice. Another option here can be the super mu-stage as described on the site of Triodeguy (Richard Sears). This looks like a family of what Ben suggested as a choke loaded mu-stage for the driver position.
Would you mind to send me the schematic that you use (here of as a PM)?
Best, Arjen.
Thanks for your valuable post. This gives food for rethinking the design. Yes, the 12R-LL3 might be difficult to get. The 12AV7 appeares to be a substitute.
I already tried a cascoded ECC88 for the first stage and it worked out nice. Another option here can be the super mu-stage as described on the site of Triodeguy (Richard Sears). This looks like a family of what Ben suggested as a choke loaded mu-stage for the driver position.
Would you mind to send me the schematic that you use (here of as a PM)?
Best, Arjen.
Hi Arjen,
schame on me, but i don't usually make schematics, at least for simple common cathode SE amps. I can draw one, scan it and send it to you. In the current version, the 2 stages 5687/EL34 are going to be used to drive a 805 in A2, hence the lot of current for the EL34 (50mA) that you will see.
Greetings
Konstantinos
schame on me, but i don't usually make schematics, at least for simple common cathode SE amps. I can draw one, scan it and send it to you. In the current version, the 2 stages 5687/EL34 are going to be used to drive a 805 in A2, hence the lot of current for the EL34 (50mA) that you will see.
Greetings
Konstantinos
The Kimmel choke Loaded MU-stage
If you try the choke loaded mu-stage for your driver, be aware of a few small details
about the choke. (1) It should be humbucking and shielded if possible and mounted as far asit can be away from the power tranny and filter choke. (2) the choke should be isolation mounted to the chasis, ie plastic washers.
A choke loaded mu-stage driver feeding interstage transformer should be a great combo.
Good luck
Ben
If you try the choke loaded mu-stage for your driver, be aware of a few small details
about the choke. (1) It should be humbucking and shielded if possible and mounted as far asit can be away from the power tranny and filter choke. (2) the choke should be isolation mounted to the chasis, ie plastic washers.
A choke loaded mu-stage driver feeding interstage transformer should be a great combo.
Good luck
Ben
Hello,
Konstantinos, a schematic is welcome and says more than a thousand words, also for your own file.
Ben, I know the term humbucking from the pickup in my guitar and did not apply it yet to chokes. Is humbucking related to the way the choke is fysically build up? Like the dual EI84a bobbin that Konstantinos speaks about in post 19?
Best Arjen.
Konstantinos, a schematic is welcome and says more than a thousand words, also for your own file.
Ben, I know the term humbucking from the pickup in my guitar and did not apply it yet to chokes. Is humbucking related to the way the choke is fysically build up? Like the dual EI84a bobbin that Konstantinos speaks about in post 19?
Best Arjen.
Hello,
Speaking of pictures, I took one of the ‘standard’ 6336-SE before I started to modify it. I have long hesitated to do this as it sounds fine as is.
In the picture you see the following:
- one of the monoblocks
- the hoods for the iron and for the tubes areas are removed
- modular, three dimensional and open way of building. The classical two dimensional layout did not really fit in the cabinets (30 x 50 cm) that I have made near the speakers. The open structure allows for lots of air flow.
- because driver and output stage are mounted on aluminum, decoupled strips it is really easy to take them out/put them back and modify components
- all iron is decoupled with teflon strips/bitumen and isolated. The big potted mains transformer is a Bartolucci. The open one is for all heater currents. All capacitors and the OPT are below. Driver stage and output stage have their own power supply.
- all tubes have their own AC-heater
- the switch on is delayed: first all heaters are each passed by via a resistor. Without it especially the 6336 would ask over 12A/6,3V at switch-on. After 30 seconds resistors are switched off. After one minute B+ is switched on. First with a bleeding resistor to dampen voltage because of C/L/C loaded supply. Then the bleeder is switched off. The leds in the middle allow monitoring and switching to/from standby.
- all signal and DC wiring is teflon solid core (this requires care to double and tightly secure each wire end).
- right/front are clips to monitor all heater currents.
Best Arjen.
Speaking of pictures, I took one of the ‘standard’ 6336-SE before I started to modify it. I have long hesitated to do this as it sounds fine as is.
In the picture you see the following:
- one of the monoblocks
- the hoods for the iron and for the tubes areas are removed
- modular, three dimensional and open way of building. The classical two dimensional layout did not really fit in the cabinets (30 x 50 cm) that I have made near the speakers. The open structure allows for lots of air flow.
- because driver and output stage are mounted on aluminum, decoupled strips it is really easy to take them out/put them back and modify components
- all iron is decoupled with teflon strips/bitumen and isolated. The big potted mains transformer is a Bartolucci. The open one is for all heater currents. All capacitors and the OPT are below. Driver stage and output stage have their own power supply.
- all tubes have their own AC-heater
- the switch on is delayed: first all heaters are each passed by via a resistor. Without it especially the 6336 would ask over 12A/6,3V at switch-on. After 30 seconds resistors are switched off. After one minute B+ is switched on. First with a bleeding resistor to dampen voltage because of C/L/C loaded supply. Then the bleeder is switched off. The leds in the middle allow monitoring and switching to/from standby.
- all signal and DC wiring is teflon solid core (this requires care to double and tightly secure each wire end).
- right/front are clips to monitor all heater currents.
Best Arjen.
Attachments
Hello,
In a PM the CCS-expert among us Gary Pimm wrote me the folllowing, that he allowed me to post here:
'A CCS is not a device to place in the cathode circuit of a SE amp. The CCS's work great as plate loads in SE amps but for cathode use they are only usefull in differential (PP) amps.
In a SE amp the cathode needs to be "tied down" tightly for the stage to have gain. In a SE stage the only way the circuit will work is to bypass the CCS with a large capacitor.
The only accomplishment you can get with a CCS on the cathode is tight control of the bias current. The cathode bypass cap will still be handling the full signal current.'
Would any of you like to add or comment?
Best Arjen.
In a PM the CCS-expert among us Gary Pimm wrote me the folllowing, that he allowed me to post here:
'A CCS is not a device to place in the cathode circuit of a SE amp. The CCS's work great as plate loads in SE amps but for cathode use they are only usefull in differential (PP) amps.
In a SE amp the cathode needs to be "tied down" tightly for the stage to have gain. In a SE stage the only way the circuit will work is to bypass the CCS with a large capacitor.
The only accomplishment you can get with a CCS on the cathode is tight control of the bias current. The cathode bypass cap will still be handling the full signal current.'
Would any of you like to add or comment?
Best Arjen.
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