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Old 27th February 2004, 11:28 AM   #11
fscarpa58 is offline fscarpa58  Italy
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hi

the ECC88 has a 0 Volts bias. is it intentional?

Federico
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Old 27th February 2004, 11:46 AM   #12
fdegrove is offline fdegrove  Europe
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Hi,

Quote:
the ECC88 has a 0 Volts bias. is it intentional?
No, it doesn't.
Look at the 10M gridleak resistor.

Cheers,
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Old 27th February 2004, 02:08 PM   #13
GAK is offline GAK
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Frank: The volume control is at the input of the amp

Kuei:
Thanks for the suggestion.Nice-attractive schem.

My problem is that I read somewhere that ECC83 and ECC88 doesn't sound nice in a phono stage.I think Danielak suggests it too.Frank also avoid to use ECC at his phono stage and uses 7025.I haven't any experience upon this.Until now I had SS phono stages.This is my first tube phono and I'd like to build sth really good.
So,I'd like the opinion of other experts ,too.

For me Kuei,it's a very nice schem.Without decoupling caps,gain at 42db is what I need and also, 2 stages!!I don't like cathode followers ,too.

How much is the Zout ?
Half valve for each channel right?I was always wondering if this effects the separation of two channels (L-R).
Why you are using 51K1 input R and not the classic 47K?

One more question:what about SRPP, u-follower and Kimmel circuits?For SRPP I heard that doesn't sound nice and they need very good PSU.I don't know anything for the other two topologies.
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Old 27th February 2004, 02:49 PM   #14
fdegrove is offline fdegrove  Europe
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Hi,

Quote:
Frank: The volume control is at the input of the amp
Thanks. In which case I presume you have the amp close to your listening position?

Either way, placing the phono preamp in such a way that you can quickly adjust the volume to make up for loudness differences of various records isn't going to be easy, I think.

Quote:
My problem is that I read somewhere that ECC83 and ECC88 doesn't sound nice in a phono stage.I
Don't believe everything you read.
Sure a good 6SL7 and 6SN7 is a great sounding valve but so are dozens of others regardless of them being octal, noval, pico 7 or whatever socket and bulb size.
What they don't tell you is that most small octal twin triodes from this range tend to be far more prone to microphony than their, say, noval counterparts.
Oh, and I've heard 6SN7s and 6SL7s from reputed manufacturers that sounded far worse than any humble nine pinner....Go figure.

Quote:
Frank also avoid to use ECC at his phono stage and uses 7025.
Not really, the 7025 is a special quality low noise ECC83.
Some ECCs I like, others I don't like at all.
One particular brand of ECC83s I never had decent recsults with is the folded plate RFTs and some older Shuguang ECCs.

Those could probably made to sound O.K. with some tweeking but I just don't bother.

Quote:
For SRPP I heard that doesn't sound nice and they need very good PSU.
Most circuits benefit from a stiff well regulated PS, the SRPP and most other half-assed PP circuits really need them.
Some of the better amps I know use SRPP stages extensively, it is a very linear and good sounding topology for as long as you have it working with a fixed load.
IOW, don't get fooled by the lowish Zo and think about driving a mile of capacitive cable so to speak, it won't work.

Same goes for cathode followers, some are very good in all respects, others are pretty useless.

At the end of the day it's just "horses for courses" as usual.

Cheers,

P.S. Whether octal or noval or whatever, use the best sockets you can lay your hands on.
This alone will have a great impact on the final soundquality.
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Old 27th February 2004, 08:50 PM   #15
ThorstenL is offline ThorstenL  Germany
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Konnichiwa,

Quote:
Originally posted by GAK
My problem is that I read somewhere that ECC83 and ECC88 doesn't sound nice in a phono stage.
Depends. In some ways ECC83 & ECC88 have complementary sonic traits, many modern and NOS options exist, it's just basically a nice and easy to get combo, especially considering that you need only one of each, so you can buy singles.....

Quote:
Originally posted by GAK
Frank also avoid to use ECC at his phono stage and uses 7025.
The 7025 is listed as pin and electrical equivalent of the ECC83. If I write ECC83 I really mean any of the following:

12AX7, 12AX7R, CV10319, CV492, 12AX7A, 12AX7S, 12AX7WA, 5721, 5751, 5751WA, 6057, 6681, 6L13, 7025, 7382, 7494, 7729, B339, CK5751, CV3970, CV4004, CV4017, CV8156, CV8222, CV8312, E2164, E83CC, ECC803, ECC803S, ECC863, M8137, QB339

And when I write ECC88 I mean any of the following:

6922WA, CCA, CV10320, CV2492, CV2493, CV8065, E88CC, E88CC01, ECC868, 6DJ8, 6N23P, CV5358, ECC88, 7DJ8, CV10403, PCC88, UCC88, 6N1P, E188CC,7308, CV5231, CV5354, E288CC, 8223

Using the standard russian 6N23 (aka 6922) and the EHX 12AX7 makes for a nice sounding phonostage, using NOS Mullaed Box Anode CV4004 and Siemens 7308 sounds notably better of course.

Quote:
Originally posted by GAK
How much is the Zout ?
Around 2500 Ohm, dependiong upon the ECC88 type valve used.

Quote:
Originally posted by GAK
Half valve for each channel right?
Yup.

Quote:
Originally posted by GAK
I was always wondering if this effects the separation of two channels (L-R).
Hmmm. It is hard to make a LP Pickup with > 30db channel separation. Sharing valves between channels will couple a little at high frequencies, but a lot less (at least 20db++ less) than any Pickup. I'd not loose much sleep. On the plus side, the halves within one valve envelope are usually assebled by the same person from the same tray of parts and hence chances are good for very close match, sonically and elecitically.

Quote:
Originally posted by GAK
Why you are using 51K1 input R and not the classic 47K?
Because it's closer to the nominal 50K and because I like people asking "why do you use 51k1" instead of enquiring into the intricacies of the design.... ;-)

Quote:
Originally posted by GAK
One more question:what about SRPP, u-follower and Kimmel circuits?
What about them? Implemented correctly and applied well they work okay, but I don't like to work so hard and prefer a much more KISS approach. Why use halve a dozend parts where one good one will do?

Sayonara
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Old 27th February 2004, 09:51 PM   #16
ThorstenL is offline ThorstenL  Germany
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Konnichiwa,

Quote:
Originally posted by fscarpa58
the ECC88 has a 0 Volts bias. is it intentional?
Actually, it has what is normally called Gridleak biasing. It is not ideal for Amplifier driver stages, but with stages working at a fairly low level this works fine.

The advantage of very small value coupling cap's and no cathode RC combo have too much a lure for me to resist. Sonically it works great, as evidenced also by Kurt Strains Phonostage (who converted his second stage to gridleak bias on my suggestion and gary Piumm's Phonostage who in turn took the gridleak bias from Kurt.

Reading them old valve books has many cool ideas rarely seen in modern commercial gear.

BTW, the first stage has an unbypassed Cathode resistor to stabilise the gain and output impedance (which impacts on the RIAA EQ accuracy) and also helps to reduce the classic "ECC83" sound a little.

For implementation, this was meant to be fed 250V from a simple, solid state regulated supply, All cap's in the main audio Circuit MKP (PSU) and Silver Mica, all resistors good quality metal film, PTFE Valve sockets should really be considered mandatory for a Phonostage.

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Old 1st March 2004, 01:27 PM   #17
GAK is offline GAK
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I'm going to order the parts this week.Thanks again Kuei for the schem.Hope to be satisfied!

Some questions:
- silver/mica or polysterene?
- Any suggestion for the signal resistors (215K , 48K7 , 100R) ?
I'm thinking to use 0,1% but what brand?Or to use simple metal film?
The other resistors will be 0,1% metal film .
- What is PTFE valve sockets?Those with the can that covers the valve?
- In the future I'm planning to use an MC cartridge.Step-up with xformers or active?I'm asking this now 'cause if I'll use xformers I'd like to put them in the same chassis with this project.

Any comments-suggestions for the following PSU?
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Old 1st March 2004, 01:30 PM   #18
GAK is offline GAK
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Sorry for the bad quality of the schem.If there's any problem to understand it ,tell me to post a new one.
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Old 1st March 2004, 01:40 PM   #19
fscarpa58 is offline fscarpa58  Italy
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hi

as I know PTFE = Teflon

federico
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Old 1st March 2004, 01:57 PM   #20
GAK is offline GAK
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Teflon?

Kuei: Do you believe that PTFE sockets are better for phonostage?
What about other projects like amps , preamps?
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