12AX7 MM/MC Phono Preamplifier PCB ref VTL - Page 3

SY · 22nd October 2011, 10:28 AM

Poor conformance to RIAA with tube age or variation (open loop gain is marginal), high input C, inadequate overload margins, mediocre linearity, mediocre noise. Other than that...

kevinkr · 22nd October 2011, 10:52 PM

Quote:

Originally Posted by SY

Poor conformance to RIAA with tube age or variation (open loop gain is marginal), high input C, inadequate overload margins, mediocre linearity, mediocre noise. Other than that...

And it doesn't sound nearly as good as the CAT SL-1 or any number of other more modern designs.

SY · 22nd October 2011, 11:20 PM

Or the Allen Wright designs, or yours, the Arthur Loesch design, the Morgan Jones Practical Preamp, or even mine. Tossing that old Marantz?ARC topology and going in another direction ca. 1978 was the single best improvement in my phono system. I probably built/modified 15 or 20 more of that circuit type (for other people) and learned first-hand the deficiencies.

gzaudiophile · 23rd October 2011, 07:21 PM

I tried this board. There is hums. I am not new to tube stuff. I built a preamp copying Jadis-JP200, but wire to wire. If you want use PCB board, use Lite version from any eBay story. Just stay away from this guy who is a business man rather a music fan.

gabrielbecheanu · 27th October 2011, 09:11 PM

Hi
I have this preamplifier, i hope to finish him soon and hope to be good. If there are some modification to do i would like to know also
Best regards.

Stratos858 · 10th February 2012, 12:13 PM

I Try this pcb myself this period. I had many hums in the begining. I almost stable those with star grounds etc. I use tungsol tubes and the standar solen caps of the kit. I am in test right now. The sound is ok with an mc ortofon samba with little hums. (in MM is totaly silent). Is wellcome any ideas to improve it (i am at the end and is impossible to change schematics. I have to deliver to my customer).

I try to upload some pics

Stratos858 · 10th February 2012, 12:19 PM

View image: DSC00559

View image: DSC00614

Stratos858 · 10th February 2012, 12:26 PM

...I have very poor bass. Any ideas? Maybe the silver i use (in and out)???

Sorry for many post
Thanks

quadzilla · 17th February 2012, 12:22 PM

Quote:

Originally Posted by SY

Poor conformance to RIAA with tube age or variation (open loop gain is marginal), high input C, inadequate overload margins, mediocre linearity, mediocre noise. Other than that...

Is this in reference to the Marantz clones, or the VTL clones?

I'm asking because I have a phono stage based on the VTL schematic, but the guy that built it used a 2.2 uf cap in the C9 position, and I'm wondering what that would have done to the values in the RIAA filter. I don't know that he corrected for that, assuming it makes a difference.

Stratos858 · 17th February 2012, 12:42 PM

I think is VTL ref

22nd October 2011, 10:28 AM	#21
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	Poor conformance to RIAA with tube age or variation (open loop gain is marginal), high input C, inadequate overload margins, mediocre linearity, mediocre noise. Other than that... __________________ If there's a sucker born every minute, where do the rest of them come from?

22nd October 2011, 11:20 PM	#23
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	Or the Allen Wright designs, or yours, the Arthur Loesch design, the Morgan Jones Practical Preamp, or even mine. Tossing that old Marantz?ARC topology and going in another direction ca. 1978 was the single best improvement in my phono system. I probably built/modified 15 or 20 more of that circuit type (for other people) and learned first-hand the deficiencies. __________________ If there's a sucker born every minute, where do the rest of them come from?

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23rd October 2011, 07:21 PM	#24
gzaudiophile diyAudio Member Join Date: Jan 2008	I tried this board. There is hums. I am not new to tube stuff. I built a preamp copying Jadis-JP200, but wire to wire. If you want use PCB board, use Lite version from any eBay story. Just stay away from this guy who is a business man rather a music fan.

27th October 2011, 09:11 PM	#25
gabrielbecheanu diyAudio Member Join Date: Jun 2006 Location: Constanta	Hi I have this preamplifier, i hope to finish him soon and hope to be good. If there are some modification to do i would like to know also Best regards.

10th February 2012, 12:13 PM	#26
Stratos858 diyAudio Member Join Date: Nov 2011 Location: Athens, Greece	I Try this pcb myself this period. I had many hums in the begining. I almost stable those with star grounds etc. I use tungsol tubes and the standar solen caps of the kit. I am in test right now. The sound is ok with an mc ortofon samba with little hums. (in MM is totaly silent). Is wellcome any ideas to improve it (i am at the end and is impossible to change schematics. I have to deliver to my customer). I try to upload some pics

10th February 2012, 12:19 PM	#27
Stratos858 diyAudio Member Join Date: Nov 2011 Location: Athens, Greece	View image: DSC00559 View image: DSC00614

10th February 2012, 12:26 PM	#28
Stratos858 diyAudio Member Join Date: Nov 2011 Location: Athens, Greece	...I have very poor bass. Any ideas? Maybe the silver i use (in and out)??? Sorry for many post Thanks

17th February 2012, 12:42 PM	#30
Stratos858 diyAudio Member Join Date: Nov 2011 Location: Athens, Greece	I think is VTL ref