Pete Millett LR phono preamp

[Thermionic Idler]

With all the positive sentiments expressed for inductive phono stages, I've just ordered a PCB for Pete Millett's LR phono design. After much research, this seems like a good way to try out the concept without cost or build complexity getting hideously out of control.

I'll probably use Lundahl SUT's as I've been very pleased with the Lundahl input transformers I used in the 300B amps.

Power supply will likely be the same AMB regulated affair that I use in the linestage to very good effect.

[izzy wizzy]

This will be a fascinating watch from the sidelines which is the only audio hobby thing I can do for the next 3 to 4 months. A great project technically and I bet your build will be fab. Good luck!

[pre65]

This will be a fascinating watch from the sidelines which is the only audio hobby thing I can do for the next 3 to 4 months.

Is all your kit on the high sea ?

[Thermionic Idler]

Actually I think I'm going to power this - and possibly also the Twisted Pear DAC project that I bought off Ray (need to investigate that further) - with a Silentswitcher, rather than a traditional power supply.

Having researched the Silentswitcher, I'm exceedingly intrigued. I'm all up for not having to deal with mains voltages and being able to ground the chassis to signal ground without risking life and limb.

It should mean I can make each chassis about half the size they'd otherwise be, and they'd probably fit together on a single shelf, saving rack space and machining costs.

[Thermionic Idler]

Pinged Cinemag to see if they'll ship the inductors to me directly - there is a supplier for them in Europe but the price they're charging is double that listed on Pete M's bill of materials! Not spending an extra 100 quid if I don't have to....

[izzy wizzy]

Is all your kit on the high sea ?

Don't think it's left the motherland yet and the first lot is in the Pacific somewhere. Covid makes ships go slower than they used to.

[Ray P]

Actually I think I'm going to power this - and possibly also the Twisted Pear DAC project that I bought off Ray (need to investigate that further) - with a Silentswitcher, rather than a traditional power supply.

Having researched the Silentswitcher, I'm exceedingly intrigued. I'm all up for not having to deal with mains voltages and being able to ground the chassis to signal ground without risking life and limb.

It should mean I can make each chassis about half the size they'd otherwise be, and they'd probably fit together on a single shelf, saving rack space and machining costs.

Good shout Dave. I'm using one of Jan Didden's SilentSwitchers on my buffered passive preamp - it's powering the Muses volume attenuator and the BUF-03 buffer stages - it's an excellent power supply and Jan is a very supportive designer They're sold in the DIY Audio store but I purchased mine direct from Jan,

[Thermionic Idler]

Of course having modelled the circuit in Spice to get an idea of the gain structure, and me being me, I'm now pondering whether the opamps could be replaced with valve stages... so much for making life easy for myself...

No that's a daft idea Idler. Stop it.

[izzy wizzy]

Of course having modelled the circuit in Spice to get an idea of the gain structure, and me being me, I'm now pondering whether the opamps could be replaced with valve stages... so much for making life easy for myself...

No that's a daft idea Idler. Stop it.

Then you might go Stephie Bench's LR phono. You'd be on safer ground with Pete's though.

http://www.intactaudio.com/forum/viewto ... 2693775edc

[Thermionic Idler]

Of course having modelled the circuit in Spice to get an idea of the gain structure, and me being me, I'm now pondering whether the opamps could be replaced with valve stages... so much for making life easy for myself...

No that's a daft idea Idler. Stop it.

Then you might go Stephie Bench's LR phono. You'd be on safer ground with Pete's though.

http://www.intactaudio.com/forum/viewto ... 2693775edc

Oh I say. Now that looks interesting. I expect the boards are unobtanium now but with the schematic available, should be able to re-create using KiCad or something, the layouts are all right there.

Think I'll stick with Pete's for now though, I'm a bit concerned at the requirement for 4 x D3a's, which I don't think are being made any more (?) and thus are only going in one direction in terms of price. And then we're back to the whole power supply complexity, probably requiring separate chassis and umbilicals and a link to the preamp to power everything up and down - whereas all the Millett needs is a cheap USB wall wart which can be left on all the time, job done.

I'll file all the relevant info away though, just in case I'm feeling ambitious in the future...

[IslandPink]

I'm a bit concerned at the requirement for 4 x D3a's, which I don't think are being made any more (?) and thus are only going in one direction in terms of price.

D3's have always been old stock ( like a lot of other stuff ) , but yes, the prices are climbing. You just reminded me to look for a few more
When I first started buying a few they were about £6, last time I looked they were £25.

[IslandPink]

Just checked - now £30 to £35.
and.. why are Colomor selling this crap ? -
https://www.ebay.co.uk/itm/373576211476 ... 56fae09c14
That should be thrown in the bin.

[Thermionic Idler]

PCB arrived today from Pete Millett - looks pretty decent quality. There's going to be a 3 month wait for the inductors but I have plenty to do in the meantime.

[Thermionic Idler]

Finally the LR phono has a proper power supply, instead of a lash-up in a cardboard box.

Rather pleasant chrome finish on the top-end Toroidy transformers, seems a shame to enclose them in a box.

[Paul Barker]

Of course having modelled the circuit in Spice to get an idea of the gain structure, and me being me, I'm now pondering whether the opamps could be replaced with valve stages... so much for making life easy for myself...

No that's a daft idea Idler. Stop it.

Then you might go Stephie Bench's LR phono. You'd be on safer ground with Pete's though.

http://www.intactaudio.com/forum/viewto ... 2693775edc

Think I'll stick with Pete's for now though, I'm a bit concerned at the requirement for 4 x D3a's, which I don't think are being made any more (?) and thus are only going in one direction in terms of price.

I had no trouble buying d3a’s that Im using in the 801a amp, I dont think enough people are into valves any more to force d3a’s into scarcity. They may have been all the rage in our past, but people haved moved in other directions since. That bandwaggon is almost empty.