6C33C SE-OTL Project

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Wolfgang
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Re: 6C33C SE-OTL Project

Post by Wolfgang » Thu Nov 14, 2019 2:06 pm

Maybe a test with the IXCY10M45 as we have already the Maida regulator which improves the SQ so much that I wouldn't want to gamble and lose anything.
Compared to the RCR which I used originally it sounds like a 100% upgrade. Choke loading the input stage I consider rather as difficult mostly from my own practical experience with this. I did tests with buffers and different chokes and it was quite revealing how it can affect the sound and frequency response despite good looking calculations. For the #26 buffer I used a tube anode choke from K&K which worked actually pretty satisfying.
P. Millet made an interesting comparison.Maybe someone has built a circuit like this already and could chime in?
http://www.pmillett.com/current_source.htm
Lower distortion and higher gain is what could be achieved. The lower distortion part would of course be interesting although the 6C33 with the maida reg. sounds already incredibly clean.

brommermartin
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Re: 6C33C SE-OTL Project

Post by brommermartin » Thu Nov 14, 2019 8:22 pm

The test with the SSHV2 regulator faild due to problems with current setpoint :?
Next plan was to try CCS units as load for the 6sn7 driver tubes ( I have very good experience with the CCS work of Ale Moglia )
from Bartola valves
Today I have tested one channel and ik looks great :mrgreen: hopefully it will sound great also .
This is what I have build ,design from Ale Moglia !
Image

brommermartin
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Re: 6C33C SE-OTL Project

Post by brommermartin » Thu Nov 14, 2019 8:27 pm

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Ray P
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Re: 6C33C SE-OTL Project

Post by Ray P » Thu Nov 14, 2019 9:24 pm

Wolfgang wrote:
Thu Nov 14, 2019 2:06 pm
Maybe a test with the IXCY10M45
As these CCS modules just slot in place of the load resistors it should be easy enough to experiment. I think I'll order a pair of the K&K kits so I can (eventually) try them on one channel vs a resistor loaded channel.

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Ray P
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Re: 6C33C SE-OTL Project

Post by Ray P » Thu Nov 14, 2019 9:26 pm

brommermartin wrote:
Thu Nov 14, 2019 8:22 pm
...hopefully it will sound great also .
Watching with interest.

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Ray P
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Re: 6C33C SE-OTL Project

Post by Ray P » Fri Nov 15, 2019 6:42 am

I've done a little reading on using current sources and it seems the Maida reg will deliver many of the benefits of using current sources but they still offer advantages with respect to increasing the gain and linearity of the triode sections of the 6SN7s. WIll increased gain and linearity result in improved SQ or will some sort of interaction between the reg and current sources compromise things? I guess there's only one way to find out.

Wolfgang
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Re: 6C33C SE-OTL Project

Post by Wolfgang » Fri Nov 15, 2019 3:28 pm

WIll increased gain and linearity result in improved SQ or will some sort of interaction between the reg and current sources compromise things?
This depends also on the rest of the circuit. Increasing linearity is the most important benefit we are looking for when using CCS in this context. But how much better it will be also depends on our original operating point and B+. If we decide to adjust parameters regarding the load line we can get pretty good results already with typical resistor anode loads especially if we consider that the ideal looking "flat" load line which we get with CCS will be watered down again when connected to the next stage (300k/50k grid leak resistors).

The most important part to consider is the "sound" we are aiming for. Sometimes it can get clinical and emotionally uninvolving if we do too much. Many high end solid state amps (and some tube amps)sound like this but have incredible low distortion and flat frequency response almost into the MHz range. But we listen to music and not to low distortion and flat frequency curves. So all this needs to be considered and practically tested.
My feeling is that - for the input/ driver stage - either the Maida regulator with a very good operating point of the tube (enough B+, symmetric swing) or CCS would be the right thing to do. Choke loading is somehow in-between but needs very high quality anode inductors or it can backfire especially with big amounts of NFB. I cannot see any benefit of using a combination of both here but would like of course to listen how it sounds if we combine them.

For the output stage it looks a little different again. That's why I want to try a combo of both although I was skeptical from the beginning. CCS is necessary but the psu should be cleaned up and less capacitance could sound better. The SLB psu with the InvOTL was a real eye opener for me and is the main reason why I want to try this. Will be interesting how we can make things work (or not) choosing the right settings for the Maida regulator. I have some ideas that need to be tested practically.

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Ray P
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Re: 6C33C SE-OTL Project

Post by Ray P » Fri Nov 15, 2019 5:49 pm

Talking with Kevin at K&K he tells me that small CCS boards are designed to be mounted onto a typical through hole resistor footprint using some solid copper wire - no other fixing required. It should be very simple to arrange some header pins to be able to switch between CCS and resistors. They're not expensive so I'll get some and experiment.

Wolfgang
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Re: 6C33C SE-OTL Project

Post by Wolfgang » Sat Nov 16, 2019 4:07 pm

Talking with Kevin at K&K he tells me that small CCS boards are designed to be mounted onto a typical through hole resistor footprint using some solid copper wire - no other fixing required. It should be very simple to arrange some header pins to be able to switch between CCS and resistors. They're not expensive so I'll get some and experiment.
So you will get this one:
CCS.jpg
CCS.jpg (16.62 KiB) Viewed 576 times
The 2W max is very borderline for the first triode if you don't plan to reduce B+. Did you discuss this with Kevin and he said it's ok?

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Ray P
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Re: 6C33C SE-OTL Project

Post by Ray P » Sat Nov 16, 2019 5:08 pm

Wolfgang wrote:
Sat Nov 16, 2019 4:07 pm
The 2W max is very borderline for the first triode if you don't plan to reduce B+. Did you discuss this with Kevin and he said it's ok?
Yes, that's the one I've discussed with Kevin; just needs a slightly larger heatsink.

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