Hi all,
I own a Dared DV-6C that i have done extensive tube rolling on the 12ax7 family, I was looking to experiment with 12hb7/ 6N6P / ECC99but don't know if i will run into problems because of the higher heater current draw.
In annex is the schematics for the circuit if someone can take a look and give an opnion.
The Dared DV-6C review with more schematics
6moons audio reviews: Dared DV-6C
6moons audio reviews: Dared DV-6C
Thanks
I own a Dared DV-6C that i have done extensive tube rolling on the 12ax7 family, I was looking to experiment with 12hb7/ 6N6P / ECC99but don't know if i will run into problems because of the higher heater current draw.
In annex is the schematics for the circuit if someone can take a look and give an opnion.
The Dared DV-6C review with more schematics
6moons audio reviews: Dared DV-6C
6moons audio reviews: Dared DV-6C
Thanks
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If you are unsatisfied with your dared then using wrong tubes won't help.
It's like mounting wrong dimension tyres on the car in hope for better performance.
It's like mounting wrong dimension tyres on the car in hope for better performance.
Strange schematic.
Why are the 5 connections to the control grids of the 12AX7's called "Outputs"? And why are the 5 connections to the cathodes called "Inputs"? Except maybe for grid current, there will not be coming anything out of the control grids.
Why are the 5 connections to the control grids of the 12AX7's called "Outputs"? And why are the 5 connections to the cathodes called "Inputs"? Except maybe for grid current, there will not be coming anything out of the control grids.
You'll run into problems because the circuit is designed for the 12AX7, not the 12BH7. You would need to change a whole bunch of resistors to get a 12BH7 to run properly.
Sound will probably come out if you plug in a 12BH7, and it will sound different, but it will perform horribly.
Those "tube stages" are totally pointless, given that they are just whimpy cathode followers. They're here just to improve the sales, not the sound.
There're no reason for tube rolling, changing, experimenting, etc. Just bypass the whole damn thing.
There're no reason for tube rolling, changing, experimenting, etc. Just bypass the whole damn thing.
I own it for 10 years and very satisfied, i think it's unbeatable for the price $500, I am only driven by curiosity.
For $500 you will get a real (used) dynaco/scott or similar that has real tube
power.
The triode sections are being run with about 1.2 mA each; the grid voltage is about -2V. The anode voltage is somewhere just under 250V (looking at the maximum voltages of the electrolytics in the anode power supply).
The value of the cathode resistors (10K) is very low for a triode section of a 12AX7 but it will (and does) work anyway.
If you would use tube types which draw (way) more current with the same values of the cathode resistor, than the B+ will drop, because of the 10K resistor in the anode power supply. With the 5 triode sections, so with 6 mA in total, the voltage drop over this 10K resistor will be 60V. With 5 triodes drawing 2 mA each, it will be 100V, etc.. Most of them will settle in a cathode-follower topology, but at working points which will be inferior in most cases.
I hope the manufacturer pays more attention on the quality control of the produced equipment than on their schematics. Funny that non of the reviewers noticed the mistake in the schematic...
The value of the cathode resistors (10K) is very low for a triode section of a 12AX7 but it will (and does) work anyway.
If you would use tube types which draw (way) more current with the same values of the cathode resistor, than the B+ will drop, because of the 10K resistor in the anode power supply. With the 5 triode sections, so with 6 mA in total, the voltage drop over this 10K resistor will be 60V. With 5 triodes drawing 2 mA each, it will be 100V, etc.. Most of them will settle in a cathode-follower topology, but at working points which will be inferior in most cases.
I hope the manufacturer pays more attention on the quality control of the produced equipment than on their schematics. Funny that non of the reviewers noticed the mistake in the schematic...
Before modding anything, you might wanna try the 12AY7. Lower gain but guaranteed different sound.
Many years ago I swapped 12AX7 in a Project Tube box-S riaa with Sylvania´s 12AY7, and loved the sound so much, that the 12AX7 never made it back. Also tried different brands of 5751, but the 12AY7 was always the winner 🙂
Many years ago I swapped 12AX7 in a Project Tube box-S riaa with Sylvania´s 12AY7, and loved the sound so much, that the 12AX7 never made it back. Also tried different brands of 5751, but the 12AY7 was always the winner 🙂
The 'gain' of the triode sections is a little bit less than 1 (one), because of the cathode-follower topology. The difference in 'gain' with other tubes than 12AX7's will be close to 0 (zero).
Don't know about gain but I already tried these tubes:
- TAD 7025-S / 12AX7
- Tung-Sol 12AX7 / ECC803-S Gold
- JAN-Philips 5751
(TAD and Tung-sol make around 3db diference to the Philips that as 70 gain vs 100)
and the amp gets completely diferent with each.
Maybe i will go with the 12au7 that i know works well, only that i read that the 12bh7 is normally better than the 12au7 even in circuits designed natively to the 12au7.
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Sorry 🙂
Didn´t realize it was cathode-follower. Strange to use 12AX7. I guess then, that besides the opt for better current drive/lower output impedance, the change in sound would be minimal.
Didn´t realize it was cathode-follower. Strange to use 12AX7. I guess then, that besides the opt for better current drive/lower output impedance, the change in sound would be minimal.
You mean the "in/out" 😀
Problem with the tubes you want is, that they draw double or more current from the heater. If it was me (but I´m stupid 🙂 ) I would redesign the heater-circuit and go with 6N6P-EV. Put all 3 tube heaters in series, and use an 1.5A 18v regulator on a heatsink. Lower impedance, and then as PCL200 points out, redesign it for at anode current draw in the area of 10-15 mA pr. tube.
While in Stereo mode I have the option to take the other two tubes and only one remains, don't know if in this circuit will help to take the stress out from the power supply from the extra heater current draw.