My second phonostage now up for grabs. This is one that I built as a lockdown project. As an audio engineer, my brief was simple...look at a building a high accuracy RIAA valve powered phonostage for MM and MC cartridges which had low distortion and could be compatible with most phono cartridges on the market. After lots of research, I settled on the "BB3" circuit design, a collaborative effort by many bright bods over at DIY Audio which promised great things. It is a cascaded passive design (very little feedback needed) using low noise high gain valves for the first 40dB of gain (MM) and a secondary circuit using very low noise FETs for the additional MC gain with input loading easily changed for the MC side by swapping out a couple of resistors, if needed (and for most, it won't be needed). I bought the part populated PCB direct from the project's promotor, and set about designing improvements to the circuit after much testing and analysing the results.
I also designed the off board power supply and had a massively oversize high quality E&I power transformer (the best where absolute sound quality is concerned) and had that custom built in the UK before assembling the circuits and wiring them up in custom aircraft grade CNC's aluminium enclosures. Amongst the improvements and upgrades to the original circuit, I introduced the concept to the designer team of modifying their design along the following lines:
Both chassis are robustly earthed to mains earth, separated from the audio signal ground (although the circuit is also grounded) and safety continuity was assured. All internal wiring was rated to 600V and everything done to comply with current CE Regs even though this was for my own personal use (why wouldn't you?).
Below is a photo of the phonostage part way thrugh construction. I will have some more to post once I remove it from my system to provide additional external shots.
The improved circuit ideas were adopted by the team who released the improvements as their "BB3" Mk2 version, originally on sale to custom order BUT they didn't adopt the twin chassis idea and sold the end product with a small toroidal in the same case for around £1500 as it was a cheaper and more convenient way to make them. I didn't make this compromise with my version.
This was the result which I've left the lids off to give you an idea of the work I put into it:
I am selling this and my high end TRON valve stages to help fund a new project for my business needs. The new owner will be delighted with the sound quality from either of thse phono stages. The uplift to build one this way compared with the single box solution would have had to sell at £2K minimum. I am after just £850 ono for this one which is bargain basement pricing and can throw in a spare set of valves. These are highly regarded phonostages in audio circles and there's loads of information on line about them (just google "BB3 phonostage").
It is fully compatible with any turntable set up and will hugely better your amplifier's built down to a price on-board phonostage. The outputs plug straight into any line level RCA input (ie "AUX, Tuner or CD inputs).
I also designed the off board power supply and had a massively oversize high quality E&I power transformer (the best where absolute sound quality is concerned) and had that custom built in the UK before assembling the circuits and wiring them up in custom aircraft grade CNC's aluminium enclosures. Amongst the improvements and upgrades to the original circuit, I introduced the concept to the designer team of modifying their design along the following lines:
- Instead of s single JFET per channel for MC gain, I searched for and found optimal JFET and op-amp types which had a good degree of overload tolerance combined with class leading low noise operation, and tripled up the JFETs so there were now three per channel in parallel, further reducing noise floor
- Introduction of a new soft start/stop circuit to ensure voltage spikes at start up and shut down were not transmitted to the speakers (the "whump" sound you get at start up and shut down)
- Measuring and testing microphonics and low noise of valves for positions V1-V3, I found the optimum combination for gain and RIAA and recommended the use of top spec Telsa PCC88 valves for gain (lowest microphonics due to rugged plate, heater and envelope design) and a reliable low noise, low microphonic ruggedised military spec 6N2P Russian twin triode valve for the RIAA. Thhis has a 6.5V heater and the circuit adapts to this or the standard 12ax7 tube using a 12.6v heater (JJ803s recommended for that).
- Power supply removed from main circuit enclosure to ensure separation of the transformer from sensitive low current signal circuit reducing the effects of EMI from the magnetic field that transformers emit.
Both chassis are robustly earthed to mains earth, separated from the audio signal ground (although the circuit is also grounded) and safety continuity was assured. All internal wiring was rated to 600V and everything done to comply with current CE Regs even though this was for my own personal use (why wouldn't you?).
Below is a photo of the phonostage part way thrugh construction. I will have some more to post once I remove it from my system to provide additional external shots.
The improved circuit ideas were adopted by the team who released the improvements as their "BB3" Mk2 version, originally on sale to custom order BUT they didn't adopt the twin chassis idea and sold the end product with a small toroidal in the same case for around £1500 as it was a cheaper and more convenient way to make them. I didn't make this compromise with my version.
This was the result which I've left the lids off to give you an idea of the work I put into it:
I am selling this and my high end TRON valve stages to help fund a new project for my business needs. The new owner will be delighted with the sound quality from either of thse phono stages. The uplift to build one this way compared with the single box solution would have had to sell at £2K minimum. I am after just £850 ono for this one which is bargain basement pricing and can throw in a spare set of valves. These are highly regarded phonostages in audio circles and there's loads of information on line about them (just google "BB3 phonostage").
It is fully compatible with any turntable set up and will hugely better your amplifier's built down to a price on-board phonostage. The outputs plug straight into any line level RCA input (ie "AUX, Tuner or CD inputs).
