DIY RIAA Preamplifier with PCL86 Lamps: MM Insert, Anodic Power Supply +300V, 50W Transformer

I have the opportunity to buy a DIY preamplifier (infinite - no housing) on PCL86 lamps.
Description of the amplifier:
"amateur-made and well-functioning stereo preamplifier with RIAA correction characteristics for turntables with MM insert, made on PCl86 tubes." Preamplifier without casing and mechanical construction components Component set Complete and efficient Riaa preamplifier board with PCL86 elements and lamps Anodic power supply board + 300V. Power supply lamp board with 300mA current stabilizer Power transformer about 50W 220 / 250V-125mA, 28V-0.4A For this design is documentation of connections and schemes according to which this preamplifier was made. Pre-amplifier made on these lamps It is possible to mount this preamplifier inside the power amplifier, and mount it in an interesting housing. The PCB with the preamplifier and the power supply made by printing (hand-drawn), correction elements on the universal board, glow plug board on the universal board. with behavior m safety rules (it has one carcase corner removed, which has no effect on the parameters and use goes). General dimensions: 13 / 8cm / high pre-amplifier plates with 5.6cm elements. With 13cm tubes. 6.3cm lamp spacing. Mounting holes 11.8 / 6.8cm.fi.5.5. Anode power supply plates 8.7 / 5.1cm / height 3.5cm. Set open montaz.8 / 4,5cm.fi.3mm. Glowing plates 6,7 / 2,3cm / height 4cm. Transformatory outline marker 8.5 / 7cm / height.8cm. "
Description, description, but I asked a few questions of the seller, below the questions and answers:
1- what was the preamplifier modeled on?
Ad.1 - on the German construction, I found a diagram on the net. Elektor magazine. The board adopted from EDW 01-2005.
2- steaming lamps?
Ad. 2- no, but the voltages on the anodes vary in the order of 2V.
3- lamp operation adjusted?
Ad. 3- no, but the values of the elements resistors in accordance with the diagram. Electrolytes in the order of capacity wolfness. the power supply is also compatible.

And here is my question: how do you view such a construction?
Is it right to play well? I do not have the opportunity to listen before buying ...

Why is this powerful lamp (PCL86) for the preamplifier? Besides, it's also a power eater. There are many proven, classic designs on the internet. As for me it's a mess, but someone can find the justification for using the final tube as a preamplifier.

It does not matter if it's RIAA?

fafikdog wrote:

It does not matter if it's RIAA?

RIAA is the name of the curve that describes the frequency characteristics of the preamplifier.

fafikdog wrote:

And here is my question: how do you view such a construction?
Is it right to play well? I have no way to listen before I buy ...

It sounds like sound, but it can roar.
I have never made such an experiment (there are many other lamps much better suited for this purpose), but I would not expect a revelation.

In amps of a similar type, lamps with very low noise are usually used, because its sensitivity should be quite high. Frequently, EF86 or special triodes are used in the first stage. Simply, for the experiment, you can use the indicated lamp, the practice will show that it came out.

aksakal wrote:

EF86 or special triodes

most often used in the first stage
ECC808 (not to be confused with ECC88 or E88CC which have parameters and purpose completely different). They have static parameters identical to ECC83, but they are equipped with an inter-system screen and prevents interference from the incandescence to the lamp electrodes. similarly to the EF86 and EF83 pentodes dedicated for audio applications.
Here, however, someone apparently to use garbage for non-standard purposes. This is also evidenced by the in the form of inserting a second pentode unblocked with a resistor capacity of a significant value into the net. It may be right only in for which one of the normal states is overloading of the final stage, here it causes a harmful increase in the end stage input capacity (due to the capacity between the first and second mesh multiplied by the Miller effect), which heavily loads the degree triode working on a high 220k? anode resistance. In correctly constructed voltage stages with pentodes, the second mesh connects through the capacitor to the mass (sometimes to the cathode, if a CVT signal is sent to it).
C3 and C7 capacitors in the cathode and triode grid are unnecessary. Their absence would not cause a significant shift of the lamp's working point, whereas the fewer elements in such sensitive places, the smaller capacitances dispersed through which interference could penetrate. The fact that this full improvisation also testified by the marked polarity of electrolytic capacitor C3: apparently the author was not able to decide how it should be. In the meantime, if you already use it - it would be enough to swap the R2 and R3 resistors, and then a 47nF film capacitor would suffice.

Dear, ??m??! I read the topic many times, but I did not find the ECC808 lamp in my friend's posts. And one more reminder, why so many theories, it may be better to propose a specific scheme, there will be more benefits for the author of the topic. I think that not everyone who creates a subject wants to become an expert in radio technology, he needs help in a specific situation http: //www.radiolamp.ru/shem/vinil/ There are 14 patterns on this website.