Hirtel junior stereo italian tube amp

[mosfet1]

I've a tube amp made by Hirtel in the late 60' . This brand born in Italy under telefunken company in the late 60', and was specialized in the pro-equipments (like noise reduction sistem called compander), solid state amps and tube amps, sold also like kit.
I ask: what do you think about this schematics?

The two ell80 are Siemens, the ez rectifier Mullard, the ecc are Philips miniwatt. The amp sounds really good with my Tannoy Devon.

Thanks walter

[kevinkr]

Looks reasonable to me, but you ought to replace the electrolytic capacitors. (condensatori el.)

Figure out whether your coupling caps are film, ceramic or worse paper. Replace any that are paper. Small ceramics should probably be replaced with polystyrene or polypropylene types.

Sounds good with your speakers, that's the key thing.

ELL80 might be a bit hard to find as well, might want to start looking for spares now.. Good tube complement too.

The disk input is for a ceramic or crystal cartridge incidentally so if you plan to play records you will need an outboard phono stage - and you will need to remove the eq/loading components on the disk input.

I lived in Milan (as a teenager) in the early 1970's and Hirtel is a brand I apparently missed. I remember the old Geloso store pretty well though. Bought some Brimar 6L6G there I would kill to have today..

[mosfet1]

An extra phono stage It's mounted inside, not very audiophile (electronic kit), I think to replace some capacitors as you decribe in your post. 1) I've some problem with volume pot. in fact with volume knob at low position (seven-eight) one channel it's higher than other, and if I increase volume the difference disappear.
2)With my denon cd player (variable output) I must hold the output level very low because of saturation.

I think: the difference (between channels) at low level maybe the effect of 12ax/ecc83 amplification, and the output level result on a bad (or incorrect value) volume pot (can I put two fixed resistor to decrease imput signal or change the pot with a different value?) it's correct?.

thanks
walter

[kevinkr]

Hi Walter,
The volume pot tracking on a lot of old integrated tube amplifiers was not good. My dad had one new from the factory (Realistic Stereolyne) that mis-tracked by several dB over the useful volume range.

Add a simple resistive divider on the input that you connect the cd player to. When this amplifier was built consumer equipment typically had a maximum output of around 700mVrms, now your cd player is about 10dB higher so make a series attenuator with a 20K and 10K resistor at each input and this will reduce the level by 10dB (Source Z into the volume control will be about 6.7K which is fine for good HF (alta frequenza) response - then you can use the fixed outputs on your cd player which usually also sound a bit better.

Possibly with the padding the volume control will now be operating in the region where the channel to channel tracking is good, otherwise I would recommend replacing it with a good quality alps black beauty or similar. (Same value)

edit: fix typos and grammatical errors