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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

The Analogue Addicts Phono Preamplifier 2006 Edition
The Analogue Addicts Phono Preamplifier 2006 Edition
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Old 19th June 2006, 07:45 AM   #11
ThorstenL is offline ThorstenL  Germany
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Konichiwa,

Quote:
Originally posted by Robert F
This phono stage is direct coupled, offset is fairly low so no problem in his particular system. Is there any reason we couldn't apply some offset nulling here (noise maybe)?
Yes, noise may become an issue, the other reason I never went for that is that you would really need a servo and I don't "like" Servos. Wrapping the capacitor into the feedback loop should do equally well.

Quote:
Originally posted by Robert F
I am interested in your subjective take on the improvements with the new version.
There are nearly 10 years between this one and my earlier version, which has long passed on to a friend, so - no idea, honestly. Sounds very nice though.

Ciao T
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Old 19th June 2006, 05:06 PM   #12
Marinos is offline Marinos  Greece
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Hi kuei,

Choosing 78xx/79xx regulators instead of the 317/337 has been done for simplicity and cost efectiveness or there are technical reasons for this ?

The 100 u BG at the output could be a cerafine ?

Did you build the whole circuit in one box ?

Do you feel that the 1 u decoupling Wimas are enough for the 637 in this circuit ? Could the "blue" MKP Siemens bricks used instead ?

What about your preference of Micas in the RIAA circuit ? is it still valid ?

Thanks for the excellent write up and for sharing (once more),
Marinos
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Old 19th June 2006, 05:26 PM   #13
ThorstenL is offline ThorstenL  Germany
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Konnichiwa,

Quote:
Originally posted by Marinos
Choosing 78xx/79xx regulators instead of the 317/337 has been done for simplicity and cost efectiveness or there are technical reasons for this ?
Yes, there was a serious technical reason for this. I wanted to use one of the Preamp PCB's from the Shanling Amplifiers (I have a box full of these around from modding the Amp's - the best mod is to just pull these rotten unneccesary things out ) and they feature a pair of 78/7915 regs and another pair of 78/7905 regs with various decoupling caps etc.

Just leaving the 7X15's in place, soldering some cap's below and adding the RC filtering (which would still have been needed for the 317/337 anyway) reusing the already present decoupling capacitors made the job of sorting this out very quick and easy.

There is no reason not to use better regulators if you have them, but equally there is no real reason to do so. Use whatever is in the project box and takes your fancy.

Quote:
Originally posted by Marinos
The 100 u BG at the output could be a cerafine ?
Or silmic or anything you fancy. With 1K in series it's sonic signature will be minimised. My reason for the BG was that it is very small.

Quote:
Originally posted by Marinos
Did you build the whole circuit in one box ?
On the shanling PCB shown earlier on. The two seperate Op-Amp positions alread provisioned for OPA627, so that was the Op-Amp's taken care off, where there used to be the PGA2311 Volume control IC I had two rows of 8 positions "veroboard" after cutting/peeling some traces which is ideal to wire up the headamp.

Quote:
Originally posted by Marinos
Do you feel that the 1 u decoupling Wimas are enough for the 637 in this circuit ?
These are the ones local to the Op-Amp, remember there is also a shared 470u per rail within an inch or so of PCB trace.

Quote:
Originally posted by Marinos
Could the "blue" MKP Siemens bricks used instead ?
I selected the Wima's based on size/resonance frequency. Larger size capacitors are a bad idea IMHO and need then again further bypassing. I wanted to keep it simple. I'd suggest any physically small 1uF Film Cap.

Quote:
Originally posted by Marinos
What about your preference of Micas in the RIAA circuit ? is it still valid ?
Yes, in fact I might try mix some Mica's back in to add a little more bite to the Circuit. For now I literally used "what I had around".

My ideal preference for RIAA Circuit capacitors has long been non-magnetic NOS Silver/Mica for the HF portion (75uS/3.18uS) with a Tinfoil & Polystyrene for the LF portion (3180uS/318uS).

All Polystyrene sounds a little warmer and laid back, all Mica can be a little etched and "High End HiFi" sounding, it depends on the circuit. Valve circuits generally seem to prefer all Mica RIAA EQ's (exceptions apply).

Sayonara
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Old 20th June 2006, 09:18 AM   #14
fred76 is offline fred76  Philippines
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Quote:
If we have a Denon DL-103R (I do)
Hi KYW,

What R load do you prefer for the DL-103R? Thanks.

regards,
fred
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Old 20th June 2006, 10:14 AM   #15
ThorstenL is offline ThorstenL  Germany
Previously: Kuei Yang Wang
 
Join Date: Nov 2002
Konnichiwa,

Quote:
Originally posted by fred76
What R load do you prefer for the DL-103R? Thanks.
For now I selected 1K based on recommendations by people I trust (the needed 1nF or so are nearly supplied by the J-Fet), but I'll try some more.

Easiest thing to do is to get a pair of "Y" adapters and to solder some selection of components into some cheap RCA Plugs and to listen.

Sayonara
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Old 20th June 2006, 10:27 AM   #16
Onvinyl is offline Onvinyl
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note that in the datasheet the load for the DL103 is specified with 1k, and for the DL103-R its 47k!
Rüdiger
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Old 20th June 2006, 04:27 PM   #17
fred76 is offline fred76  Philippines
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Quote:
For now I selected 1K based on recommendations by people I trust (the needed 1nF or so are nearly supplied by the J-Fet), but I'll try some more.

Easiest thing to do is to get a pair of "Y" adapters and to solder some selection of components into some cheap RCA Plugs and to listen.
Thanks. I'd try 1k for the active MC section in my ss phono. There are binding posts in the MC section for R loading. However in my particular phonostage, the MC output signal would also pass through the MM stage’s 100pF input cap, unlike the AA's MC stage which bypasses this since its MM cap load seem to be directly terminated at the rca input jacks not on the pcb...

A bit OT: I use Y-adapters for a Valve phono for some time now (R rolling). What Rload/s do you recommend for the 103R when used with step-up trannies?? For now I use 12k-12.5k to get an Rload of ~100 Ohms using 1:10 stepups for an MM phono input of 51.1k//100pF.

Quote:
I selected the Wima's based on size/resonance frequency. Larger size capacitors are a bad idea IMHO and need then again further bypassing. I wanted to keep it simple. I'd suggest any physically small 1uF Film Cap.
Does this also hold true for coupling caps in phono sections not just decouplers? Thanks.



regards,
fred
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Old 20th June 2006, 06:02 PM   #18
jackinnj is offline jackinnj  United States
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The Analogue Addicts Phono Preamplifier 2006 Edition
fwiw - here's what I get when the AA Phono Preamp is simmed. The transfer function block A1 sets the time constants and gain so that the error only is shown in the bode plot (+/- 0.5dB)

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Old 20th June 2006, 06:17 PM   #19
jackinnj is offline jackinnj  United States
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The Analogue Addicts Phono Preamplifier 2006 Edition
this is a sim of the El Cheapo -- notice that the scaling factor is a bit different -- same scale on the Bode Plotter (+/- 0.5dB)

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Old 20th June 2006, 09:09 PM   #20
federico moreno is offline federico moreno  Argentina
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Default thanks...

Thorsten, I enjoy a lot your hieratic, concise and controversial posts.

I have played a lot with the ¨vintage¨ El Cheapo, surprising with it even the most obscene and rustic vinyl detractors.
From time to time I was wondering about a suitable ac power supply to go with it, and now here it comes, with the added benefit of a newly developed version of the original preamp...

Thank you very much for your effort.

Cheers

Federico
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