Hi
New to the forum. I have an old Croft valve pre amp/phono stage which is either in need of refurb/ugrade/mod or i could do to build a phono stage (valve) from scratch, on a budget, to use with leak stereo 20. MM and MC capability wanted.
Anyone out there have any specs or know somewhere/someone on t'net where i might find something.
Yours in hope
Rauza
New to the forum. I have an old Croft valve pre amp/phono stage which is either in need of refurb/ugrade/mod or i could do to build a phono stage (valve) from scratch, on a budget, to use with leak stereo 20. MM and MC capability wanted.
Anyone out there have any specs or know somewhere/someone on t'net where i might find something.
Yours in hope
Rauza
Depends what the "budget" is like.
A pair of ECC85s with plate load CCS set about 7mA and 0.82V Schottky bias (around 135V on the plates if I recall) makes a nice phono gain stage of ~50dB, enough for some of the medium output MCs. For low output MC carts, you'll need a SUT. Suggest the Hashimotos.
Use passive equalization, all in one.
The power supply should be VT rectified. Follow up with at least two stages of LC filtering. The use a single CCS and gas shunt tubes. A 150V and 75V give a nice output of about 225V, that the plate CCS can draw on. Rig for 14-25 or so mA through the gas tubes during normal operation. Don't even think of using the gas tubes without the common CCS upstream, they'll be noisy.
Following the 2nd ECC85, use a follower (I'm partial to the 6SN7/6FQ7 types, but ECC99 and others will work well). Look up Broskie's or Yaniger's servo stages; use those for a DC coupled output.
I expect you'll have it done by the start of the work week. LOL
Oh yeah, the Siemens tubes sound nice, but when you're ready to lay down a bit of cash, find a pair of Telefunkens. Mmmmmmmmmmm.
Stuart
A pair of ECC85s with plate load CCS set about 7mA and 0.82V Schottky bias (around 135V on the plates if I recall) makes a nice phono gain stage of ~50dB, enough for some of the medium output MCs. For low output MC carts, you'll need a SUT. Suggest the Hashimotos.
Use passive equalization, all in one.
The power supply should be VT rectified. Follow up with at least two stages of LC filtering. The use a single CCS and gas shunt tubes. A 150V and 75V give a nice output of about 225V, that the plate CCS can draw on. Rig for 14-25 or so mA through the gas tubes during normal operation. Don't even think of using the gas tubes without the common CCS upstream, they'll be noisy.
Following the 2nd ECC85, use a follower (I'm partial to the 6SN7/6FQ7 types, but ECC99 and others will work well). Look up Broskie's or Yaniger's servo stages; use those for a DC coupled output.
I expect you'll have it done by the start of the work week. LOL
Oh yeah, the Siemens tubes sound nice, but when you're ready to lay down a bit of cash, find a pair of Telefunkens. Mmmmmmmmmmm.
Stuart
LOMC is out, if holding costs down is important.
Undoubtedly, there are better phono preamps available. However, you will be (IMO) hard pressed to better the cost/performance of a tweaked RCA setup. The Sovtek 12AX7LPS is inexpensive and exhibits excellent noise behavior.
Undoubtedly, there are better phono preamps available. However, you will be (IMO) hard pressed to better the cost/performance of a tweaked RCA setup. The Sovtek 12AX7LPS is inexpensive and exhibits excellent noise behavior.
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