Good afternoon all..
First post in this thread and wanted to say hello.. Started working on my DCG3 a week or so ago. Acquired parts and boards from Tea. This is my third DIY audio project and I def consider myself a complete noob with all of this! So far, I've built a whammy headphone amp (configured also for use as pre), and recently completed an Aleph J with the Zen Mod boards. Lots of help from pFarrell and 6L6..
So far, I have finished the DCSTB boards, and will be powering them with dual Antek transformers. Powered them up last night and measured voltages (Unloaded). On the left side I have 17.31 and -17.27. Right side producing 17.22 and -17.34. Close enough I believe.
My listening setup currently is Mac/Tidal --> Schitt Modi Multibit --> Whammy --> Aleph J --> Klipsch Hersey I's, modified with "Super Hersey mod"(Estimating 95db sensitivity). For headphones, I"m using Fostex X-00's.. (25 ohms). At some point, I'd like to add a pair of open back phones and have looked at Beyer DT880's (specs say 250 ohms?).
I'm reading this entire thread before going to far looking for tips and ideas.. On page 280 now, so I have a lot of reading to do. In terms of the guide, I've read through it and based on what I've read I'm thinking 110-120mAh for bias (10R) and 3x gain. I'm wondering however about impedance of a different pair of phones not being ideal?
Planning on Alps 20k pot and I also have a 20k stepped attenuator (China/Ebay) donated by pFarrell to try. Chassis likely Slimline 2U, but not committed on that yet. I'll also be using in-select board, as well as Mark Johnson's power board.
Wanted to run all of this by some much smarter folks, all ears for any suggestions. Thanks for reading!
Cheers,
john
First post in this thread and wanted to say hello.. Started working on my DCG3 a week or so ago. Acquired parts and boards from Tea. This is my third DIY audio project and I def consider myself a complete noob with all of this! So far, I've built a whammy headphone amp (configured also for use as pre), and recently completed an Aleph J with the Zen Mod boards. Lots of help from pFarrell and 6L6..
So far, I have finished the DCSTB boards, and will be powering them with dual Antek transformers. Powered them up last night and measured voltages (Unloaded). On the left side I have 17.31 and -17.27. Right side producing 17.22 and -17.34. Close enough I believe.
My listening setup currently is Mac/Tidal --> Schitt Modi Multibit --> Whammy --> Aleph J --> Klipsch Hersey I's, modified with "Super Hersey mod"(Estimating 95db sensitivity). For headphones, I"m using Fostex X-00's.. (25 ohms). At some point, I'd like to add a pair of open back phones and have looked at Beyer DT880's (specs say 250 ohms?).
I'm reading this entire thread before going to far looking for tips and ideas.. On page 280 now, so I have a lot of reading to do. In terms of the guide, I've read through it and based on what I've read I'm thinking 110-120mAh for bias (10R) and 3x gain. I'm wondering however about impedance of a different pair of phones not being ideal?
Planning on Alps 20k pot and I also have a 20k stepped attenuator (China/Ebay) donated by pFarrell to try. Chassis likely Slimline 2U, but not committed on that yet. I'll also be using in-select board, as well as Mark Johnson's power board.
Wanted to run all of this by some much smarter folks, all ears for any suggestions. Thanks for reading!
Cheers,
john
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Hi, welcome to the thread.
Your DCSTB is running very close rail voltages considering LEDS & JFETS tolerances. DCG3 is a single ended circuit that does not care for exactly symmetrical rail voltages about its DC offset, that is why there are no trimmers on the DCTB PSU. For even more reliability in the long run.
Regarding the output stage bias choice, if to regularly use headphones of less than 80 Ohm nominal impedance, 150mA gives less THD on such loading. On the other hand it produces more heat on all sinks. It calls for better ventilation measures. OTOH if your best and more regularly used set of cans is > 80 Ohm there is no THD difference with 100-120mA and you keep the preamp cooler.
Avoid the ALPS Blue pot on this preamp if you can is the consensus. The Ebay stepper pot is cleaner and more focused already, although still rougher in the HF and mechanically inferior to a TKD conductive pot or to other expensive steppers.
Your DCSTB is running very close rail voltages considering LEDS & JFETS tolerances. DCG3 is a single ended circuit that does not care for exactly symmetrical rail voltages about its DC offset, that is why there are no trimmers on the DCTB PSU. For even more reliability in the long run.
Regarding the output stage bias choice, if to regularly use headphones of less than 80 Ohm nominal impedance, 150mA gives less THD on such loading. On the other hand it produces more heat on all sinks. It calls for better ventilation measures. OTOH if your best and more regularly used set of cans is > 80 Ohm there is no THD difference with 100-120mA and you keep the preamp cooler.
Avoid the ALPS Blue pot on this preamp if you can is the consensus. The Ebay stepper pot is cleaner and more focused already, although still rougher in the HF and mechanically inferior to a TKD conductive pot or to other expensive steppers.
Salas,
Thank you for the great design and all of the work and support you have put into this.. You've been on here daily for 5 years now? Amazing..
I"m planning on using a piece of aluminum bar stock for heat sink. The dimensions are 180mm x 30mm x 10mm. Without some sort of airflow would this be sufficient to run 150mAh? Same aluminum sink that Patrick used, which is running 120mAh I believe..
Will start with Ebay pot.. Thanks for the suggestion!
j
Thank you for the great design and all of the work and support you have put into this.. You've been on here daily for 5 years now? Amazing..
I"m planning on using a piece of aluminum bar stock for heat sink. The dimensions are 180mm x 30mm x 10mm. Without some sort of airflow would this be sufficient to run 150mAh? Same aluminum sink that Patrick used, which is running 120mAh I believe..
Will start with Ebay pot.. Thanks for the suggestion!
j
Ok.. Thank you Salas.. I'll make sure my chassis has enough ventilation holes above and below the heat sinks. I'm envisioning myself listening to speakers more than headphones. I'll keep reading and chewing on that before making a decision on bias. Thanks for your thoughts! I'm certain I'll have more questions as this unfolds, looking forward to hearing how this sounds compared to my whammy as a pre!
That is very good option, but i want less audio cases, not more.
The UBIB's are connected to the case, so that is one big heatsink, with hopefully enough cooling capacity.
separate chassis gives more advantages, i know, but i'm going ahead with my one chassis.
regards,
John
Hi savvas,
There are 7 transformers:
2x 100VA 18V for the DCG3 (balanced)-> 4x UBIB
2x 65VA 9V for the DAM 1941 -> 3x UBIB
1x 65VA 15V for the neurochrome -> 2x SSLV 1.1
1x 65VA 6V for the ian canada stuff -> 2x LinearPi
1x 65va 12V for the elma lin motor -> LT1083 generic ps
If i could get rid of 1 transformer, that would save me maybe 1 kilo.
On 37 kilo's 1 kilo is not a lot.
If i would get a transformer with more secondaries it would have to be bigger in size and weight.
When finished it will be in a audio rack, i'm not gonna travel with it.
I did find enough room to fit everything now, smaller margins, it is just a tight squeeze.
regards,
John
There are 7 transformers:
2x 100VA 18V for the DCG3 (balanced)-> 4x UBIB
2x 65VA 9V for the DAM 1941 -> 3x UBIB
1x 65VA 15V for the neurochrome -> 2x SSLV 1.1
1x 65VA 6V for the ian canada stuff -> 2x LinearPi
1x 65va 12V for the elma lin motor -> LT1083 generic ps
If i could get rid of 1 transformer, that would save me maybe 1 kilo.
On 37 kilo's 1 kilo is not a lot.
If i would get a transformer with more secondaries it would have to be bigger in size and weight.
When finished it will be in a audio rack, i'm not gonna travel with it.
I did find enough room to fit everything now, smaller margins, it is just a tight squeeze.
regards,
John
Are you saying the DCG3 is not worth investing in? ouch.
If i am gonna build something, i will build it no compromise. The cost saving of 1 transformer less (example) is 38 euro.
In my business those calculations are necessary, but in our hobby?
Hobbies cost money.
regards,
John
I knew i had to put a smiley in my last message, i do appreciate comments. 
Ok, what would you suggest to leave out?
my approach is that i want less boxes, 1 device for pre amp and dac and streamer.
When i build my salas FSP everybody said the transformers should be in a seperate chassis for less noise. I put the transformers in the same chassis and there is zero noise.
regards,
John
Ok, what would you suggest to leave out?
my approach is that i want less boxes, 1 device for pre amp and dac and streamer.
When i build my salas FSP everybody said the transformers should be in a seperate chassis for less noise. I put the transformers in the same chassis and there is zero noise.
regards,
John
