I have a hybrid Bada ph12 headphone amp with blown MOSFET, which I want to rebuil/mod. I don't want to deal with MOSFET any more. I am going to rebuilt it as all tubes.
The ph12 has three 6SN7 mounte on PCB. B+ power supply is 230v. Heater are from 3 7806 regulators.
I want to re-use as much as possible what is on the PCB. Any suggestions?
The ph12 has three 6SN7 mounte on PCB. B+ power supply is 230v. Heater are from 3 7806 regulators.
I want to re-use as much as possible what is on the PCB. Any suggestions?
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OK, I did a quick test today to connect my HT600 headphone dirctly to the 2.2uf cathode follower output capacitor, and I got loud enough volume - about 11:00 o'clock for normal listening.
So if I replace the 2.2uf CF output cap with a larger one, it should be OK for my high impedence headphone.
To get more amp to headphone. I am thinking to put a small output transformer between the CF and headphone. Anyone has a schematic for a parafeed tranny?
So if I replace the 2.2uf CF output cap with a larger one, it should be OK for my high impedence headphone.
To get more amp to headphone. I am thinking to put a small output transformer between the CF and headphone. Anyone has a schematic for a parafeed tranny?
If you want to increase output power with 100% tubes, two ways can be studied:
The first solution: add grid coupling capacitor betweem u7 and u8, convert ub8 into a commun-cathod amplifier, add a transformer in the anode to adapt any headphone impedance.
The second solution: don't touch the three present tubes, just add one extra tube as last stage amplifer with transformer. The impedance of the transformer will be defined by the added tube.
The first solution: add grid coupling capacitor betweem u7 and u8, convert ub8 into a commun-cathod amplifier, add a transformer in the anode to adapt any headphone impedance.
The second solution: don't touch the three present tubes, just add one extra tube as last stage amplifer with transformer. The impedance of the transformer will be defined by the added tube.
I have a Bada PH12, which I find with a few mods to be excellant, however as I will be moving to somewhere that I won´t have neighbours to molest with my sound system, a h/amp is not something i will require in the future, so this is what I propose to do - turn it into a power amp.
My only experience up to now is with all valve amps, so what I am proposing maybe a non-starter.
As I understand it - the output of the mosfets (rated at 125W each) are dictated by the paralleled resistors in front of them.
These presently total 200 Ohms per side - if I want to have an output of 20-25W per channel what value do I need to change these resistors to?
I also intend to use Welwyn W23/9W wirewounds so they will total 36W per channel. I will fix PC coolers to the aluminium top plate, to which the mosfets are already screwed and as I already use a Papst fan for cooling, which is very effective, I forsee no problems there apart from fitting speaker binding posts - what other changes do I need to make.
I also intend to use some exotic caps, which will later be used in the Moskido that I shall build. This project I think is a good way for me to get to understand hybrid amps.
Looking forward to answers as if the Bada sounds as good as a power amp as it does as a h/amp then it will mean no more all valve amps for me.
My only experience up to now is with all valve amps, so what I am proposing maybe a non-starter.
As I understand it - the output of the mosfets (rated at 125W each) are dictated by the paralleled resistors in front of them.
These presently total 200 Ohms per side - if I want to have an output of 20-25W per channel what value do I need to change these resistors to?
I also intend to use Welwyn W23/9W wirewounds so they will total 36W per channel. I will fix PC coolers to the aluminium top plate, to which the mosfets are already screwed and as I already use a Papst fan for cooling, which is very effective, I forsee no problems there apart from fitting speaker binding posts - what other changes do I need to make.
I also intend to use some exotic caps, which will later be used in the Moskido that I shall build. This project I think is a good way for me to get to understand hybrid amps.
Looking forward to answers as if the Bada sounds as good as a power amp as it does as a h/amp then it will mean no more all valve amps for me.
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