Hirtel junior stereo italian tube amp - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 17th January 2007, 08:57 AM   #1
mosfet1 is offline mosfet1  Italy
diyAudio Member
 
Join Date: Nov 2006
Default Hirtel junior stereo italian tube amp

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
Attached Images
File Type: jpg hirtel-juniorstereo.jpg (82.6 KB, 312 views)
  Reply With Quote
Old 17th January 2007, 03:11 PM   #2
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
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..
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 18th January 2007, 07:36 AM   #3
mosfet1 is offline mosfet1  Italy
diyAudio Member
 
Join Date: Nov 2006
Default hirtel junior amp

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
  Reply With Quote
Old 18th January 2007, 03:27 PM   #4
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
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
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Apex Junior amp? cyberspyder Subwoofers 30 26th March 2010 03:50 AM
Sunfire True Sub Junior Problem sjdemark Subwoofers 2 15th July 2009 04:31 PM
italian style Stee Solid State 90 10th February 2009 06:44 PM
blues junior complaints and 6G15 question layt Tubes / Valves 4 2nd July 2006 12:38 AM
New diy Forum in Italian plovati Everything Else 3 15th October 2005 05:25 PM


New To Site? Need Help?

All times are GMT. The time now is 03:07 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2