Author Topic: "To Pre or not to Pre" Question is driving me nuts!!  (Read 15554 times)

Offline audiophool

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #20 on: August 12, 2011, 11:55:00 AM »
Your elaboration of the half baked theory I had gleaned from reading and asking the odd question is welcomed for the clarification and extension of understanding it brings me and hopefully others.
Thank you for taking the time.

Offline gthicm

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Ladder versus series shunt attenuators
« Reply #21 on: August 15, 2011, 10:42:33 AM »
I quite believe that the shunted arrangement you have there would be optimal, the signal effectively passes only through the Shinkoh which is only 1, very high quality, resistor.
I recall a discussion with AndyR from SNA about this some years back, it might have been in relation to an AKSA preamp and involved a TKD pot shunted with Vishay Z-foils.
I know what you mean about the Dales, my previous stepper was a ladder type with Dales and it did lean to the pale and washed out side of things.
My present arrangement is similar to your arrangement in that the signal passes through only 1 resistor on the way in.
You will need a clearance from DCA before you fire up those OTLs  :o

Audiophool,

A point of clarification in regard the shunt style arrangement being discussed.
The leg to ground (the pot) as actually a very significant, and probably the most significant 'flavouring' component in this setup.  The current path is from source thru the series resistor acting as a voltage divider thru the pot to ground.  The voltage seen at the grid (which is a high input impedance) is the resultant I*R across the pot.  Thus the signal that the grid is seeing is actually the vlotage appearing across the the pot from the current flow thru it.

I noted that GAMVE commented that the pot seemed to be paralleled across the tantalum resistor which suggests that the shunt arrangement drawn earlier is probably not how it is aranged. 
Assuming that the pot is indeed parallelled across the tantalum, it is possible that the tantalum itself is the 'shunt' leg as you discussed above and there is another fixed series resistor, in which case the pot will act to vary the shunt leg to ground in a continuous manner.  In this arrangement the sonic influence of the pot increases as volume increases.

Option B is that the series resistor is the tant and the pot is paralled across it using a fixed shunt to ground ie also a variable voltage divider.  This is a less likely setup because it creates a greater variation in the input resistance.  BUT the sonic flavour is more consistent with volume because the leg to ground is unchanging.


Stepped attenuators will provide lower noise injection than a carbon film pot.  That is an additional attraction to the greater channel balance that you mention.
One also then has a defined sonic flavour from a particular style of resistor and have the ability to play.
A series shunt (switching both series and shunt) is the best way as there are only ever 2 resistors in the pathway at this position. 


Food for contemplation,

Cheers

Rawl
Right on the money, Rawl.  This is a very good explanation of the issues with series shunt attenuators, not to mention the varying input impedance with this arrangement.  The ladder type, or L Pad atenuator overcomes these problems as there are only ever two resistors in the circuit.  The downside is cost and complexity, as one needs double the resistors, but there are some reasonably priced kits to make them.  Michael Percy has some good ones for very reasonable prices.  The only thing is that you need good soldering skills and lots of patience.

Offline gamve

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #22 on: December 14, 2011, 06:17:44 PM »
Tripped over an interesting possible modification for this preamp while browsing yesterday. I noticed there are adaptor plugs available to change from a 5687 9 pin tube to an octal ECC32  :o
Steven and I had a bit of a discussion on the possibility of adding another gain stage to the killeramp while I was visiting in
Sydney and I guess this was still in the back of my mind. I guess that it would be possible to get this but from the preamp out instead of an extra stage in the killeramp?
Questions for the technically advanced (your there Zen? Rawl?)
1. How close are the 5687 and the ECC32 electrically in there characteristics, power supply requirements? heater voltage, current draw etc.
2. Hoping that they are similar, what needs to be done/changed to give this a try
I love the sound of the ECC32 and would dearly love to try one in my pre.....
Cheers
Graham
« Last Edit: December 14, 2011, 06:55:17 PM by gamve »

Offline kajak12

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still discovering the link between electronics and audio reproduction.so much to learn and so little time


Offline zenelectro

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #25 on: December 15, 2011, 03:18:51 PM »
Tripped over an interesting possible modification for this preamp while browsing yesterday. I noticed there are adaptor plugs available to change from a 5687 9 pin tube to an octal ECC32  :o
Steven and I had a bit of a discussion on the possibility of adding another gain stage to the killeramp while I was visiting in
Sydney and I guess this was still in the back of my mind. I guess that it would be possible to get this but from the preamp out instead of an extra stage in the killeramp?
Questions for the technically advanced (your there Zen? Rawl?)
1. How close are the 5687 and the ECC32 electrically in there characteristics, power supply requirements? heater voltage, current draw etc.
2. Hoping that they are similar, what needs to be done/changed to give this a try
I love the sound of the ECC32 and would dearly love to try one in my pre.....
Cheers
Graham

Hi guys

Adding a gain stage is not a bad idea because it can give a lot of advantages in one swoop

The trouble with 1 stage (tube) to drive OP tube is you need a lot of voltage gain, or a high u, so tube choice get
thin, hence ECC32 and equivalents. Also generally tubes with high u, don't have a lot of current drive.

Once you go to a 2 stage IP, you only need a gain of 20 per stage to get total of 400.
This opens up many more possibilities, especially some nice high current high drive tubes.


5687 and ECC32 are very different tubes. 5687 is like a 6DJ8 on steroids but with a bit lower gain.
Used in a lot of Audio Note stuff.

If you sub 5687 for ECC32 with same configuration it wont work. Less voltage gain, but will want to
run at much higher current. 5687 should work well in a 2 stage cascaded circuit. IOW 1 stage following
the next.
 
Another option is to try a cascode. This means one half of the tube on top of the other but different to
SRPP. This will give high voltage gain and still only 1 coupling cap. I don't know of any cascode
1 driver stage amps but 5687 should be suitable for cascode. Something like an ECC32 wouldn't work
very well as a cascode.

How much voltage have you got available at the HT? From memory it was 350 or so?

I'll do a bit of poking around the net and see what I can find but as you can see it's a can of worms.

PS cascade and cascode are 2 different things, cascade = 1 after the other, cascode = one on top of the other.

PSS I think I'm going to cascode the missus :)

cheers

T


Offline zenelectro

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #26 on: December 15, 2011, 03:54:18 PM »
OK I had a bit of a look and before you know it I'm reading an article by John Broskie
on a circuit that he called 'ultra path'.

Its funny, this is exactly the same circuit I modded with Steven on his amplifier's OP stage.

In the Broskie article he ties a cascoded front end tube to the utrapath OP stage for a
2 stage high gain SE amp.

The only thing that worries me is cascodes sound different and it may take some tweaking
to get even close to original amp sound.

T



 

Offline kajak12

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #27 on: December 15, 2011, 10:43:28 PM »
Tripped over an interesting possible modification for this preamp while browsing yesterday. I noticed there are adaptor plugs available to change from a 5687 9 pin tube to an octal ECC32  :o
Steven and I had a bit of a discussion on the possibility of adding another gain stage to the killeramp while I was visiting in
Sydney and I guess this was still in the back of my mind. I guess that it would be possible to get this but from the preamp out instead of an extra stage in the killeramp?
Questions for the technically advanced (your there Zen? Rawl?)
1. How close are the 5687 and the ECC32 electrically in there characteristics, power supply requirements? heater voltage, current draw etc.
2. Hoping that they are similar, what needs to be done/changed to give this a try
I love the sound of the ECC32 and would dearly love to try one in my pre.....
Cheers
Graham

Hi guys

Adding a gain stage is not a bad idea because it can give a lot of advantages in one swoop

The trouble with 1 stage (tube) to drive OP tube is you need a lot of voltage gain, or a high u, so tube choice get
thin, hence ECC32 and equivalents. Also generally tubes with high u, don't have a lot of current drive.

Once you go to a 2 stage IP, you only need a gain of 20 per stage to get total of 400.
This opens up many more possibilities, especially some nice high current high drive tubes.


5687 and ECC32 are very different tubes. 5687 is like a 6DJ8 on steroids but with a bit lower gain.
Used in a lot of Audio Note stuff.

If you sub 5687 for ECC32 with same configuration it wont work. Less voltage gain, but will want to
run at much higher current. 5687 should work well in a 2 stage cascaded circuit. IOW 1 stage following
the next.
 
Another option is to try a cascode. This means one half of the tube on top of the other but different to
SRPP. This will give high voltage gain and still only 1 coupling cap. I don't know of any cascode
1 driver stage amps but 5687 should be suitable for cascode. Something like an ECC32 wouldn't work
very well as a cascode.

How much voltage have you got available at the HT? From memory it was 350 or so?

I'll do a bit of poking around the net and see what I can find but as you can see it's a can of worms.

PS cascade and cascode are 2 different things, cascade = 1 after the other, cascode = one on top of the other.

PSS I think I'm going to cascode the missus :)

cheers

T


Terry you should try push and pull on your missus :P
still discovering the link between electronics and audio reproduction.so much to learn and so little time

Offline vitavoxdude

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Pushing and pulling
« Reply #28 on: December 15, 2011, 11:45:18 PM »
Could not resist..............
Most of the fairer sex (who made that statement!) tend to push you into decisions that leave you pennyless, then they pull all your resources until sucked dry and then they discard you for a richer model..................ho hum and the laws are there to protect them, not us.  Go figure.  Of course there are some worth hanging onto but they are rear indeed.

Sorry for hijacking the thread.
V
We all like different things so lets all agree to disagree and if any common ground is found then worship it.  Mine is the KD hence being present on this forum.

Offline gamve

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #29 on: December 17, 2011, 01:38:30 PM »
Thanks for your replies Terry. Looks like it is not a simple exercise to change from the 5687 to a ECC32. I would not bugger about going to a cascode stage with the 5687 tube cause it already sounds very good and works well with my other gear. I was basically just curious to see if a ECC32 could be swapped with a few basic changes in the same circuit.
Cheers
Graham

Offline Jehuty

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #30 on: June 22, 2014, 01:47:10 AM »
I'm quite keen to get this one: http://www.transcendentsound.com/Transcendent/Velvetizer.html

His Groundid Grid Preamp (http://www.transcendentsound.com/Transcendent/Transcendent_Sound_Grounded_Grid_Preamp.html) seems popular and look at the cost compared to other preamps in the lists below:
Quote
For CD playback
1. Vacuum State RTP-3D
2. AcousticPlan Sarod
3. Silvaweld SWC 1000
4. Kondo KSL M7
5. Vacuum State FVP 5a
6. Wyetech labs Pearl
7. Silvaweld SWC 450
8. Transcendent Sound Grounded Grid
9. Sphinx Project 4 MkIII
10. Audible Illusions Modulus 3a
11. Sonic Euphoria PLC
12. Jolida JD 1000a

For LP Playback
1. Vacuum State RTP-3D
2. Kondo KSL M7 + KSL SFz transformer
3. Silvaweld SWC 1000 + Silva SWH 650
4. Vacuum State FVP 5a
5. Wyetech labs Pearl + Silva SWH 650
6. AcousticPlan Sarod
7. Silvaweld SWC 450 + PS Audio
8. Transcendent Sound Grounded Grid
9. Sphinx Project 4 MkIII
10. Audible Illusions Modulus M3a
11. Sonic Euphoria PLC
12. Jolida JD 1000a
Link: http://www.positive-feedback.com/Issue26/preamps.htm

Hmmm I wonder where the CAT preamp would be on that listing?

Price for the Velvetizer: http://tubehifi.websitetoolbox.com/post/show_single_post?pid=1282056157&postcount=1

Anyone got experience with his Groundid Grid preamp?
Not all that matters can be measured, not all that can be measured matters.

Offline Tuyen

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #31 on: June 22, 2014, 01:42:09 PM »
A pair of 'good' sounding 300b tubes not cheap though?  $1500 and over?? Unless think of using chinese or russian (eletroharmonics)?

The GG ive heard before. Very clean clear detailed and dynamic. Doesn't have richness or valve 'bloom'.  Was only a stock unit though.  Maybe with mods could of been different story!

Falls Audio maybe able to build a nice DHT pre using a less common tube thus making price vs sq  better overall?

Offline gamve

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #32 on: June 22, 2014, 01:43:09 PM »
I'm quite keen to get this one: http://www.transcendentsound.com/Transcendent/Velvetizer.html

His Groundid Grid Preamp (http://www.transcendentsound.com/Transcendent/Transcendent_Sound_Grounded_Grid_Preamp.html) seems popular and look at the cost compared to other preamps in the lists below:Link: http://www.positive-feedback.com/Issue26/preamps.htm

Hmmm I wonder where the CAT preamp would be on that listing?

Price for the Velvetizer: http://tubehifi.websitetoolbox.com/post/show_single_post?pid=1282056157&postcount=1

Anyone got experience with his Groundid Grid preamp?



William, Talk to Mark OTL. You have heard his grounded grid pre-amp

Offline Tuyen

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #33 on: June 22, 2014, 01:47:02 PM »
How about a used Tram2 pre?

Bryan and rab seem to love theirs. Can use 45/2a3 tubes which are sometimes cheaper than 300b?

Offline Jehuty

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #34 on: June 22, 2014, 10:00:06 PM »
A pair of 'good' sounding 300b tubes not cheap though?  $1500 and over?? Unless think of using chinese or russian (eletroharmonics)?

The GG ive heard before. Very clean clear detailed and dynamic. Doesn't have richness or valve 'bloom'.  Was only a stock unit though.  Maybe with mods could of been different story!

Falls Audio maybe able to build a nice DHT pre using a less common tube thus making price vs sq  better overall?
Thanks for sharing Tuyen. Paul Baker preamp is my dream preamp, but to build one is just too expensive for me. I am keen on Transcendent new 300B preamp because it's affordable, yes very true a great pair of 300B would be expensive but they are still more affordable than Western Electric 205D.

William, Talk to Mark OTL. You have heard his grounded grid pre-amp
Hi Graham, yes we heard them together at his place and I actually have a fond memory about his system. Fast, clean, neutral without sounding overly clinical. Perhaps with 300B, it would add texture, body, weight and liquidity? That's what I hope.

How about a used Tram2 pre?

Bryan and rab seem to love theirs. Can use 45/2a3 tubes which are sometimes cheaper than 300b?
I read people got so many problems with the Tram2 so that's why I'm not that keen. Plus, I've already got single ended parallel 45 amp so I think I would gain more by adding 300B sound? Not sure, but I guess I just have to buy and try it.
Not all that matters can be measured, not all that can be measured matters.

Offline Tuyen

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #35 on: June 23, 2014, 03:09:36 AM »
Interesting idea of wanting to add the some of that '300b sound' to your system.    I would of just thought that the price of a good pair of 300b tubes + price of the preamp, total will be over $2k?  Then mods (at least Jensen/solen caps in power supply, Shinkoh resistors, duelund/mundorf coupling and output caps), $3-4k ?     If just keep it stock with average parts/tubes, wouldn't it just bottleneck the rest of the system? All the beauty and magic of the killerdac and 45 amp will be washed away?   

I thought the killerdac works best direct into the 45 amp with a volume pot?  If not, couldn't Paul advise how make them work best together?   After, then just tune the system (ie. just change parts on the Kdac/45amp) to give the system more of an overall '300b sound' that you are after?

Or am I missing something?

Offline ozmillsy

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #36 on: June 23, 2014, 07:52:00 AM »
I thought the killerdac works best direct into the 45 amp with a volume pot?  If not, couldn't Paul advise how make them work best together?   After, then just tune the system (ie. just change parts on the Kdac/45amp) to give the system more of an overall '300b sound' that you are after?

Or am I missing something?
Well, I have decided that the best thing in my case, was to run the system that way. 
Ie: killerdac->pot->amp

I came to the conclusion that my tannoy system with Radford amp and killer front end had soo much engagement and beauty,  that I didn't need my M3 preamp adding more colours to the mix.  It was just in the way.

 But that doesn't mean this is the right way for everyone. 

Sometimes our gut tells us we need something extra.
It's all about the music,, not the equipment.

Offline zenelectro

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #37 on: June 23, 2014, 09:48:59 AM »
Well, I have decided that the best thing in my case, was to run the system that way. 
Ie: killerdac->pot->amp

I came to the conclusion that my tannoy system with Radford amp and killer front end had soo much engagement and beauty,  that I didn't need my M3 preamp adding more colours to the mix.  It was just in the way.

 But that doesn't mean this is the right way for everyone. 

Sometimes our gut tells us we need something extra.

That is generally the best option IMO.

To run no pre amp there are 2 options:

a) Use a passive volume after the DAC
b) Use a volume control inside the DAC and connect the DAC directly to power amp.

There are advantages / disadvantages to both.

With a) the passive volume control loads the DAC down
With b) you can run the DAC 'open' or no load into the power amp, the power amp but the volume control must be inserted 'inside' the DAC
which will have it's own effect.

IMO, either is a better option than a pre amp, especially given the extra cost.
I already have a bunch of custom special low impedance volume controls for this very purpose but haven't yet tried it.

Z

Offline ozmillsy

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #38 on: June 23, 2014, 10:20:37 AM »
Hey Zen,  the problem with a) is that it doesn't always work well.   It's hit and miss,  depending on the source(s) and connecting amp.

I totally understand why active preamps are preferred by many.
It's all about the music,, not the equipment.

Offline zenelectro

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Re: "To Pre or not to Pre" Question is driving me nuts!!
« Reply #39 on: June 23, 2014, 04:45:16 PM »
Hey Zen,  the problem with a) is that it doesn't always work well.   It's hit and miss,  depending on the source(s) and connecting amp.

I totally understand why active preamps are preferred by many.

If you understand the impedances and how they interact it's not a problem. The volume pot however, should ideally be inside  amp or very close to it
otherwise you can easily pick up unwanted noise. Also a passive pot will not drive the interconnect that well.
 
But IMO, option B/ is the best way to go, coupled with a very high impedance input R in the amps valve #1. You can easily go to 470k or 1Meg, this will unload the
DAC beautifully and allow for the best dynamics and lowest bass. I am surprised no one has asked me to install one - it's a very cheap high performance
replacement for a pre amp.   

When I get out of Hospital I'll install one in the Enterprise and see how it goes.

Z