Tube or SS Preamp?

[apexaudio]

This SS Preamp I was made in 1990, full complementary simetry, selektor with releys. Tube preamp was made 5 years after.

 

[Mooly]

But what is the question 😉

 

[SY]

And, more importantly, what is the tube?

 

[apexaudio]

I sent unfinished post. Tube is ecc88, work without feedback like Counterpoint SA3.1
Part list:
R1,R2-12k 2W
R3,R4-220R
R5,R6-680R
R7,R8-100R
R9,R10,R13-1M
R11,R12-3M9
R14,R15-10k
R16,R17-1k
R18,R19-10R
R20-680k
R21-470R

C1,C2,C3,C4-1uF400V MKP
C5,C6,C8-22uF/350V
C7-47uF/16V
C9,C10,C11,C12-47uF/350V
C13,C14-1000uF/16V
C15-47nF/100V MKS
C16-220nF/150V MKS
C17-100nF/63V MKS

D1,D2-ZF10V
D3,D4,D5-1N4148
D6,D7,D8,D9,D10,D11,D12,D13,D14-1N4007

V1-ECC88

Q1,Q2-BC546
Q3-IRF830

IC1-NE555
IC2-7805

LD1-RED
LD2-GREEN

RE1-5V2X1A

AC1-120VAC 100mA
AC2-9VAC 1A

 

[apexaudio]

Question. Have anyone expirience compering Nelson Pass "Bride of Zen" preamp vs Tube or full symetry SS Preamps? I think to change symetry SS with Nelsons pramp, any sugest?

 

[Nelson Pass]

IMHO, the BOZ is not quite as good as the more symmetric
SOBOZ, aka the balanced line stage. I think this is simply
due to the lower distortion of the push-pull nature of the
circuit.

😎

 

[apexaudio]

What is your opinion about single triode vs single mosfet line preamp ? I dont speak English, but hope you understand me.

 

[tvrgeek]

Nelson may disagree, but the newest crop of, gasp, Op-Amps are so stinking good that it kind of closes the preamp arguments. Of course, the same care must be exercised in the power, ground, and layout as any high performance analog circuit. No tube circuit can be anywhere as clean. My opinion, my ears and my speakers. Your milage may vary. ( I still play with tubes, they are fun, but can't match ss)

 

[Zen Mod]

if I may chip in ..........

that question is .... different horses for courses 😉

off course - you know that stage can be evaluated only in conjunction with his own power supply ;

few thoughts :

your tube line stage have one serious flaw - too much gain , at least if it's intended for use in modern audio chain , where almost every CD player is capable ( at least voltage vise ) to directly feed usual power amp . local degeneration is way to tame excessive gain ...... even if some ppl are against it ......

Papa's BOZ was sort of student's project ; nice example and chance for every young diy-er to make something different and fresh ; but - it's not flawless either - PS is generic , with too much noise for serious biz ...... stage is somewhat prone to easy overdrive with modern sources etc.

so - conclusion - I think that simple ( but well thought ) tube stage , with decent PS is one range better than similar mosfet stage ( also with decent PS) .

if we use some older - so called audio signal mosfets .... 2SK216 for instance , maybe we can gain better results ; there is place for some local degeneration ..... CCS loading ....... choke , or even xformer loading .....

sky is da limit , if we wanna play ..... but - if you want ultimate results , you must reach for some more complicated rabbits from hat

 

[Zen Mod]

Nelson may disagree, but the newest crop of, gasp, Op-Amps are so stinking good that it kind of closes the preamp arguments. Of course, the same care must be exercised in the power, ground, and layout as any high performance analog circuit. No tube circuit can be anywhere as clean. My opinion, my ears and my speakers. Your milage may vary. ( I still play with tubes, they are fun, but can't match ss)

that really depends what you are looking for ;

anyway - give me anything else , but OP no .........

high S inductance loaded tube stage is hard to beat ;

as always - YMMMV

 

[indianajo]

next preamp

well, here I am with invisible quote. tvrGeek said that the next generation of op amps for preamps was wonderful. I wonder if he could post some part numbers and manufacturers? I have a Mixer I'm using as a preamp that has wonderful scratchless volume controls and hideously hissing (40 db) semiconductor's. I have a Dynaco PAS2 tube preamp that has wonderful SN and for the life of me I can't buy a volume pot that will last more than a year without getting scratchy.

 

[Mooly]

well, here I am with invisible quote.

Yep 😉

tvrGeek said that the next generation of op amps for preamps was wonderful. I wonder if he could post some part numbers and manufacturers?

There is nothing with opamps when used correctly. You will find lot's of threads on that here... so I won't add to the debate this time.

I have a Dynaco PAS2 tube preamp that has wonderful SN and for the life of me I can't buy a volume pot that will last more than a year without getting scratchy.

That makes me think you have another problem. Even a few millivolts of DC on a pot causes the wiper to become noisey. You have either been unlucky or the pots weren't up to much, or there is a problem with the circuit. Current leakage from old caps maybe.
Have you tried ALPS pots ?

 

[analog_sa]

No tube circuit can be anywhere as clean.

Wow. Strong statement 🙂


What exactly do you use? Tubes, topologies, power supplies?
Could it be you use poor, non-regulated power supplies and topologies with poor psrr? It's only fair to make comparisons on a level field.

The only advantage i can see with opamps is that you can avoid using coupling caps/transformers.

 

[apexaudio]

To much gain with this preamp without feedback can reduce with resistor atenuator, that is better than use circuit with NFB to reduce gain.

 

[Gordy]

What is your opinion about single triode vs single mosfet line preamp ? I dont speak English, but hope you understand me.

In my (limited) experience, a triode with a constant current anode load, with LED cathode bias, and with output from the anode (into a 47 k Ohms load), can have excellent performance.

The triode needs to be one with very parallel lines on the anode characteristic graph. 6H30 is a very good tube, with about 25 mA / bias -3V / anode 80 V. Gain is a little too high at about x12. Output impedance about 1200 R.

My next change will be to introduce a step-down transformer of ratio 4:1.
So gain will be x3 and output impedance about 75 R. These will be good figures for me.

I have tried a single mosfet stage, but it was not optimised so it is not fair for me to make a comparison or draw a conclusion.

 

[apexaudio]

Ss pre-amp

This is circuit of pre-amp with A-class PSU (shunt regulator).

 

[apexaudio]

Fets on preamp circuit are K470 and J74, sorry for mistake.

 

[apexaudio]

Preamp circuit corrected.

 

[apexaudio]

In my (limited) experience, a triode with a constant current anode load, with LED cathode bias, and with output from the anode (into a 47 k Ohms load), can have excellent performance.

The triode needs to be one with very parallel lines on the anode characteristic graph. 6H30 is a very good tube, with about 25 mA / bias -3V / anode 80 V. Gain is a little too high at about x12. Output impedance about 1200 R.

My next change will be to introduce a step-down transformer of ratio 4:1.
So gain will be x3 and output impedance about 75 R. These will be good figures for me.

I have tried a single mosfet stage, but it was not optimised so it is not fair for me to make a comparison or draw a conclusion.

What kind of transformer U use, is it DIY?
Regards

 

[Gordy]

Hi apexaudio,

I will have a custom transformer from Sowter. Their normal is 3:1 (their type 8940 for AC-coupled line output), however I will order a variant at 4:1.

SOWTER PRE AMP/ LINE AMP TRANSFORMERS