I just scored a turntable. Pretty nice Pioneer belt-drive, I had one in the hippie daze; lapped the platter and arm bearings, balanced everything out, and it was the envy of stoned Honolulu with a high-end Shure for the tooth.
Gonna do it again, but I need a killer phonostage. Not nice; not BFB, not anything else; S O A!
Thankew,
Poinz
Gonna do it again, but I need a killer phonostage. Not nice; not BFB, not anything else; S O A!
Thankew,
Poinz
I need to build a phono stage as well so will be following this keenly. One of my ideas was to start with an LT1028 op amp to get the initial gain quietly, then hand over to an ECC40. I could then finish off with a DHT stage in push pull into an OPT like LL1540.
I'd like a DHT in there, and I certainly like the ECC40 better than the usual 9 pin suspects, plus I've always liked the sound of diff. pairs with CCS under into an OPT - no caps.
Don't know in this case whether to put the passive RIAA equalisation before or after the ECC40
How does that sound?
Andy
I'd like a DHT in there, and I certainly like the ECC40 better than the usual 9 pin suspects, plus I've always liked the sound of diff. pairs with CCS under into an OPT - no caps.
Don't know in this case whether to put the passive RIAA equalisation before or after the ECC40
How does that sound?
Andy
andyjevans said:
For many of us here, yes. I do use them in digital electronics to a limited extent but prefer the THS4131 in all digital applications. (OT: My digital stuff is all balanced internally and I use transformers to go from balanced to unbalanced output.) Tubes absolutely everywhere else..
I can highly recommend the D3A (triode connected) or 5842, depending on required gain. Both in carefully designed circuits are capable of significantly better than 2nVrtHz with 1kHz noise bandwidth in a properly designed and implemented circuit. Quiet in the same sense that your op-amp is quiet and no sand in the signal path.
show me your fave phonostage circuits
Poinz,
For all kinds of reasons this may provoke the Purity Police, but, if you know someone with a Scott integrated/receiver, check out the phono pre. Charles Hansen has an updated version of it in the July '06 AX. I don't remember if Hansen mentions it, but lifted dc on the heaters helps.
Poinz,
For all kinds of reasons this may provoke the Purity Police, but, if you know someone with a Scott integrated/receiver, check out the phono pre. Charles Hansen has an updated version of it in the July '06 AX. I don't remember if Hansen mentions it, but lifted dc on the heaters helps.
I can highly recommend the D3A (triode connected) or 5842, depending on required gain. Both in carefully designed circuits are capable of significantly better than 2nVrtHz with 1kHz noise bandwidth in a properly designed and implemented circuit. Quiet in the same sense that your op-amp is quiet and no sand in the signal path.>>>
Kevin (or anyone else) - can you point me in the direction of some schematics with the 5842/D3A? I have both in my collection.
Andy
Kevin (or anyone else) - can you point me in the direction of some schematics with the 5842/D3A? I have both in my collection.
Andy
OK, I'm gonna get it for this one. I had been using the phono stage in a Scott "Laboratory Reference Amplifier" (I don't remember the number and I am 1200 miles away) while working on something better. Something in the power amp section (not currently used) started smoking, so I gathered up some sand and built a chip phono stage. It uses a National LME49720. The circuit is on the first page of the data sheet. It works quite well, and is mounted inside the turntable so there is no hum and noise pickup. I have been experimenting with tube phono stages, but haven't bettered the sand preamp yet.
Another member sent me the circuit for his "top secret phono pre". It uses the D3A which is scarce in the US. I have finally gathered all of the parts (like a year ago), but haven't had the time to build it. It will be the next one to challenge the sand!
andyjevans said:
Actually, no. I have a fairly nice opamp phono stage and it does some things pretty well. Most importantly it deals with the biggest problem of low level tube circuits - microphony.
What i meant was that the first stage will pretty much set the sound character. If noise is an issue, and it will be with a MC cart, i find a FET front end being much less distracting in a tube circuit than opamps. For several years i couldn't find a good enough step-up transformer and used a battery powered K170 first stage with very satisfiying results. In a split riaa it's also possible to postion the first network following the fet.
I also like the D3A, EF280, 6S45 and 3GK5 for the input stage. It's certainly worth investugating the Oz-Loesch version of the famous phono stage as it offers low noise and compatibility with low output MCs.
tubelab.com said:
http://cache.national.com/ds/LM/LME49720.pdf
Is that a 47nF and a 33nF cap in series? Is that what the notation 47nF/33nF means? Similarly, are there resistors in series?
Hello ,
here is my preamp with 2 x D3a for phono and with E288CC parallel as line - stage . It works now without problems for three years and I enjoy the sound every day .
...and here is the circuit :
Regards , Alexander .
P.S.: More pictures are here :
http://www.ak-tubes.de/Vorverstaerker/D3a RIAA/riaa.htm
here is my preamp with 2 x D3a for phono and with E288CC parallel as line - stage . It works now without problems for three years and I enjoy the sound every day .
An externally hosted image should be here but it was not working when we last tested it.
...and here is the circuit :
An externally hosted image should be here but it was not working when we last tested it.
Regards , Alexander .
P.S.: More pictures are here :
http://www.ak-tubes.de/Vorverstaerker/D3a RIAA/riaa.htm
Hello Sy ,
triode connected , g2 on a , g3 on k .
This time I experimented with gain - blocks for the next ETF
.
The tube is a 18046 from Valvo ( or with 6,3 volt heaters E81L or EL861 from RFT ) and I use them to drive my LCR - network . This tube is very similar to the C3g , which is my second projekt , you can change the modules .
Regards , Alexander .
triode connected , g2 on a , g3 on k .
This time I experimented with gain - blocks for the next ETF
.An externally hosted image should be here but it was not working when we last tested it.
The tube is a 18046 from Valvo ( or with 6,3 volt heaters E81L or EL861 from RFT ) and I use them to drive my LCR - network . This tube is very similar to the C3g , which is my second projekt , you can change the modules .
Regards , Alexander .
show me your fave phonostage circuits
Poinz,
Alexander's post reminded me I had been thinking about pentode phono possibilities - I like pentode drivers, but I couldn't figure out the first R - and also reminded me I built one about four years ago - an EF86 12AX7 passive EQ from a Heath AA100. It wasn't stand alone so it had been sitting neglected on a shelf. I stole juice from a 12B4A amp I built recently and fired it up. This thing had me dancing - not well and in the garage where nobody could see me, but dancing. I think you'll probably find the interaction with the rest of your system sets your final choice, but a pentode/pentode trioded first stage is worth checking out. The Heath SP 2 uses an EF86 at very low voltages passive EQed to a 12AU7. The 12AU7 offers the possibility of other tubes with lower output impedances. Let us know which way you jump with this.
Poinz,
Alexander's post reminded me I had been thinking about pentode phono possibilities - I like pentode drivers, but I couldn't figure out the first R - and also reminded me I built one about four years ago - an EF86 12AX7 passive EQ from a Heath AA100. It wasn't stand alone so it had been sitting neglected on a shelf. I stole juice from a 12B4A amp I built recently and fired it up. This thing had me dancing - not well and in the garage where nobody could see me, but dancing. I think you'll probably find the interaction with the rest of your system sets your final choice, but a pentode/pentode trioded first stage is worth checking out. The Heath SP 2 uses an EF86 at very low voltages passive EQed to a 12AU7. The 12AU7 offers the possibility of other tubes with lower output impedances. Let us know which way you jump with this.
show me your fave phonostage circuits
Try http://tdsl.duncanamps.com/sheets/aa100sm.jpg and http://www.tech-systems-labs.com/schematic/SP-2-SCH.pdf. I could try to draw up something more specific, if you'd like.
Try http://tdsl.duncanamps.com/sheets/aa100sm.jpg and http://www.tech-systems-labs.com/schematic/SP-2-SCH.pdf. I could try to draw up something more specific, if you'd like.
what about this circuits - particularly for low impedance MC cartridges?
Teflon coupling capacitors & More No-Gain—No-Pain Tube Buffer Circuits
Teflon coupling capacitors & More No-Gain—No-Pain Tube Buffer Circuits
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