CHASSIS.
Hi,
Sorry if I misled you here.
I actually built it in two cases, one for the PSU and another for the preamp proper.
Dimensions: 16" * 11" * 3"
( Just to give you an idea about what you need if you'd add the phono stage as well.If you don't need that half the width should do.)
Starground is for anything PSU related is inside the PSU chassis, everything signal related is starground inside preamp chassis.
Grataku,
Since you prefer measurements:
Specifications Line preamp:
Powerconsumption: 40W.
Weight 2 Kgs. preamp and 3.5 kgs for the PSU.
Sensitivity (IHF 0.5V)
Line: 525mV into 100K.
THD Typically better than 0.05%.
Frequency Response: 10Hz - 200KHz. +/- 0.2dB.
Noise: better than -90dB.
Input overload: Infinite.
Maximum Output level: 45V
Output Impedance: 47 Ohm.
Stereo Separation: better than 100dB at 1KHz.
Feeling better now ?
Peter,
I knew you'd bring that up.
Cheers,
Hi,
Sorry if I misled you here.
I actually built it in two cases, one for the PSU and another for the preamp proper.
Dimensions: 16" * 11" * 3"
( Just to give you an idea about what you need if you'd add the phono stage as well.If you don't need that half the width should do.)
Starground is for anything PSU related is inside the PSU chassis, everything signal related is starground inside preamp chassis.
Grataku,
Since you prefer measurements:
Specifications Line preamp:
Powerconsumption: 40W.
Weight 2 Kgs. preamp and 3.5 kgs for the PSU.
Sensitivity (IHF 0.5V)
Line: 525mV into 100K.
THD Typically better than 0.05%.
Frequency Response: 10Hz - 200KHz. +/- 0.2dB.
Noise: better than -90dB.
Input overload: Infinite.
Maximum Output level: 45V
Output Impedance: 47 Ohm.
Stereo Separation: better than 100dB at 1KHz.
Feeling better now ?
Peter,
I knew you'd bring that up.
Cheers,
Re: A MATCHING PHONOPREAMP.
These ones are pretty good, but if you'd like a set with matching "feel" i'll get at it sooner or later.
I note this uses an ECC83 class tube. I wonder how close it is to the RCA one?
dave
fdegrove said:This uses yet another PSU, both are identical to the line peamp though.
P.S. Dave, redraw to your hearts content...
These ones are pretty good, but if you'd like a set with matching "feel" i'll get at it sooner or later.
I note this uses an ECC83 class tube. I wonder how close it is to the RCA one?
dave
Hi Frank
Interesting phono. One of the few (i only know of the 834) where all the gain comes from the first stage and all the correction - from the second. How would you describe its sound compared to more traditional topologies like fully passive or 2 stage with an overall feedback. Not that i've tried many, but to me the split passive RIAA has always ruled in both vacuum and sand implemetation. I should try something different though
Your pre-pre can certainly benefit from battery plate supply and something better at the heaters too.
cheers
peter
Interesting phono. One of the few (i only know of the 834) where all the gain comes from the first stage and all the correction - from the second. How would you describe its sound compared to more traditional topologies like fully passive or 2 stage with an overall feedback. Not that i've tried many, but to me the split passive RIAA has always ruled in both vacuum and sand implemetation. I should try something different though
Your pre-pre can certainly benefit from battery plate supply and something better at the heaters too.
cheers
peter
Re:Re: Re: A MATCHING PHONOPREAMP.
Hi,
It would be great or I could have a stab at it myself...I've no idea what font you used for it though.
Anyway, I was just teasing you a little.
The RCA diagram you posted should sound very good too, it reminds me of the first phono preamp Jadis made.
Any idea what the number of the RCA manual is? I've two different ones and none sport the cct you posted.
Cheers,
Hi,
It would be great or I could have a stab at it myself...I've no idea what font you used for it though.
Anyway, I was just teasing you a little.
The RCA diagram you posted should sound very good too, it reminds me of the first phono preamp Jadis made.
Any idea what the number of the RCA manual is? I've two different ones and none sport the cct you posted.
Cheers,
Frank,
I was disappointed when you gave your preamp a passive sound character, I would have liked something more active in the vein of _it sooo good it even makes bad CD sounds amazing_
A minumum of good instrumental specs are the lowest common denominator, a minimum standard for me. I think that an amp with 10% distortion, maybe in different respects, will sound just about as bad as an 80s japanese amp with 0.000001%. I think your list of spect more than meets my criterium.
I am glad we are down to two enclosure, much better.
Next item on the list, the PS. How did you arrive to such circuit? Why not just do the usual pi filter with the big 10H inductor instead?
I was disappointed when you gave your preamp a passive sound character, I would have liked something more active in the vein of _it sooo good it even makes bad CD sounds amazing_
A minumum of good instrumental specs are the lowest common denominator, a minimum standard for me. I think that an amp with 10% distortion, maybe in different respects, will sound just about as bad as an 80s japanese amp with 0.000001%. I think your list of spect more than meets my criterium.
I am glad we are down to two enclosure, much better.
Next item on the list, the PS. How did you arrive to such circuit? Why not just do the usual pi filter with the big 10H inductor instead?
REHONOSTAGE.
Hi,
Thanks for your comments, Peter.
Where preamps are concerned I firmly believe in gainscaling.
I'm well aware of the fact that this odd RIAA correction isn't widely spread but the results speak for themselves.
The main disadvantage of passive RIAA correction is its inherently high insertion loss.
If you look at the phono pre Dave presented you'll notice they had to reduce the gain of the second stage to avoid excessive hiss.
Every time I tried designing a passive RIAA pre I ended up with an inverting preamp with three stages.
I heard some good ones, one was an SRPP the other a Klimo preamp.
As for the sound, what can I say?
The only way I think I can better it is by using LCR RIAA correction, which would require a complete redesign, or maybe going for a balanced design.
In the near future I plan to replace the electrolytes after the regulator with BGs and some MKPs.
Other than that all passive components are the best I could lay my hands on as it is.
Where this preamp excels is in dynamic range and signal to noise ratio, it makes most CDPs sound rather dull in comparison...granted, my heavyweight, suspensionless TT helps a lot in that department too.
Comparing identical CDs and vinyl I find more in favour of vinyl than CDs.
Also, we compared this preamp with high-end gear from ARC,C-J and some flagship preamps from VTL and it embarassed their loaded owners time and time again.
Do I sound like a good salesman?
As for the pre-pre, most of your suggestions I tried already, except for the battery supply, with good results.
I'll definetely try the battery supply one of these days for, with a 2mA powerconsumption per channel, this should be easy enough.
For the technical minded amongst us: the B+ is only 24VDC, it's derived from a voltage doubler, filtered and regulated.
It than goes to a capacitance multiplier and finally a J-FET rewired as a CCD is acting as a CCS.
For all its apparent simplicity it does sound very fine and is absolutely dead quiet, which it should be with four triodes paralelled.
I've still to hear a stepup xformer that betters it although I haven't tried them all.
I'll need to win the lottery for that first.
One final remark for anyone wanting to build the pre-pre: layout is critical if you don't want radio breakthrough.
I have it fed straight from the tonearm wires where I feel it does the best job.
Cheers,
HONOSTAGE.Hi,
Thanks for your comments, Peter.
Where preamps are concerned I firmly believe in gainscaling.
I'm well aware of the fact that this odd RIAA correction isn't widely spread but the results speak for themselves.
The main disadvantage of passive RIAA correction is its inherently high insertion loss.
If you look at the phono pre Dave presented you'll notice they had to reduce the gain of the second stage to avoid excessive hiss.
Every time I tried designing a passive RIAA pre I ended up with an inverting preamp with three stages.
I heard some good ones, one was an SRPP the other a Klimo preamp.
As for the sound, what can I say?
The only way I think I can better it is by using LCR RIAA correction, which would require a complete redesign, or maybe going for a balanced design.
In the near future I plan to replace the electrolytes after the regulator with BGs and some MKPs.
Other than that all passive components are the best I could lay my hands on as it is.
Where this preamp excels is in dynamic range and signal to noise ratio, it makes most CDPs sound rather dull in comparison...granted, my heavyweight, suspensionless TT helps a lot in that department too.
Comparing identical CDs and vinyl I find more in favour of vinyl than CDs.
Also, we compared this preamp with high-end gear from ARC,C-J and some flagship preamps from VTL and it embarassed their loaded owners time and time again.
Do I sound like a good salesman?
As for the pre-pre, most of your suggestions I tried already, except for the battery supply, with good results.
I'll definetely try the battery supply one of these days for, with a 2mA powerconsumption per channel, this should be easy enough.
For the technical minded amongst us: the B+ is only 24VDC, it's derived from a voltage doubler, filtered and regulated.
It than goes to a capacitance multiplier and finally a J-FET rewired as a CCD is acting as a CCS.
For all its apparent simplicity it does sound very fine and is absolutely dead quiet, which it should be with four triodes paralelled.
I've still to hear a stepup xformer that betters it although I haven't tried them all.
I'll need to win the lottery for that first.
One final remark for anyone wanting to build the pre-pre: layout is critical if you don't want radio breakthrough.
I have it fed straight from the tonearm wires where I feel it does the best job.
Cheers,
Re:ReREAMP.
Hi,
Grataku,
Mostly it will depend on the content of that distortion spectrum but you definetely have a point there.
Glad to meet your standards...
He,he...you should have seen my first prototype: full wave tube rectified, LC filtered followed by an even stiffer tube regulator...
Granted it may seem over the top but it works extremely well and not for all the obvious reason reasons:
When you see the caps behind the regulators it will become clear that the function of the reg is one of completely isolating the preamp proper from the mains, presenting a ripple free B+ to the tubes behind it.
I tested this supply rigourously and I never saw it sag, not even a few milivolts.
One day I put it to the test and removed all bleeder Rs, listened for a while, than pulled the mains plug while I still had a record spinning...it went on as if nothing had happened for more than 2 minutes, after that the voltage dropped and it distorted as can be expected of course.
With a self and PI filter you can't come close to that kind of isolation and the chokes I tried didn't like such high capacitance behind them, they went into core saturation at power on.
Anyway, if you want to try out both versions for comparison, be my guest.
Cheers,
REAMP.Hi,
Grataku,
Mostly it will depend on the content of that distortion spectrum but you definetely have a point there.
Glad to meet your standards...
He,he...you should have seen my first prototype: full wave tube rectified, LC filtered followed by an even stiffer tube regulator...
Granted it may seem over the top but it works extremely well and not for all the obvious reason reasons:
When you see the caps behind the regulators it will become clear that the function of the reg is one of completely isolating the preamp proper from the mains, presenting a ripple free B+ to the tubes behind it.
I tested this supply rigourously and I never saw it sag, not even a few milivolts.
One day I put it to the test and removed all bleeder Rs, listened for a while, than pulled the mains plug while I still had a record spinning...it went on as if nothing had happened for more than 2 minutes, after that the voltage dropped and it distorted as can be expected of course.
With a self and PI filter you can't come close to that kind of isolation and the chokes I tried didn't like such high capacitance behind them, they went into core saturation at power on.
Anyway, if you want to try out both versions for comparison, be my guest.
Cheers,
Re:Rehono Preamp.
Hi,
Thank you, I'm flattered.
I do:
For MM:
Sensitivity 2 mV into 47K with 100pF in //
Input overload: better than 20dB at 1KHz.
RIAA accuracy: better than +/- 0.2 dB from 20-20KHz.
Signal to noise ratio on phono only: better than -70dB.
Stereo separation phono stage: better than 80dB at 1KHz.
I am surprised but here goes: it's the low noise audio version of the ubiquitous ECC83/12AX7A.
My favourites where the ECC803S from TFK but the E83CC from Tesla is every bit as good.
Other than that any good ECC83 like the box anode Mullards, most Philips sound great too.
If you want reduced gain the 5751 (u 70) is perfect for that as are some Sovteks (u can vary from section to section and tube to tube, they usually do not make a u of 100, 90 is closer).
I usually select those for low noise and pick the ones I like best for sonic balance, respect for timbre...in short, the usual suspects.
Cheers,
hono Preamp.Hi,
Thank you, I'm flattered.
I do:
For MM:
Sensitivity 2 mV into 47K with 100pF in //
Input overload: better than 20dB at 1KHz.
RIAA accuracy: better than +/- 0.2 dB from 20-20KHz.
Signal to noise ratio on phono only: better than -70dB.
Stereo separation phono stage: better than 80dB at 1KHz.
I am surprised but here goes: it's the low noise audio version of the ubiquitous ECC83/12AX7A.
My favourites where the ECC803S from TFK but the E83CC from Tesla is every bit as good.
Other than that any good ECC83 like the box anode Mullards, most Philips sound great too.
If you want reduced gain the 5751 (u 70) is perfect for that as are some Sovteks (u can vary from section to section and tube to tube, they usually do not make a u of 100, 90 is closer).
I usually select those for low noise and pick the ones I like best for sonic balance, respect for timbre...in short, the usual suspects.
Cheers,
