Thank you for the information in that post Agaton. The "level" was just right. Nothing in the post was obvious to me, as I'm new to tape, and you described it well.
Is it the Eros Tape Head Preamplifier Kit from Bottlehead that you are using with the Studer A67?
https://bottlehead.com/?product=eros-tape-head-preamplifier-kit
Did you use another set of Studer A80 Reproducer replay electronics for the 1/4 track playback head, or did you, as with the Studer A67, opt for replay electronics from an alternative manufacturer?
Yes an Eros. It was very heavily modified though. Initially it was built with Teflon caps in critical stages and Mundorf gold/silver in oil in others.I think it was also built with special wiring but it is a long time ago and neither myself or my long suffering tech/builder is likely to remember. Later on circuitry was modified : Input valves were changed from EF 86 to EF804 with the circuit adapted. This in the interest of lower noise although the EF804 has a different sound to the EF86 (crisper and cleaner than the warmer but often murky 86/806) . Way back Abbey Road did the same to all their Telefunken eqp. It is said that this change is what gave the Beatles their characteristic sound. True? Dunno. Adjustable pots were also added to the Eros to allow HF linearization.
The Eros was bought as a test bed for the use of outboard electronics. As can be seen it was heavily modified and gain /hum problems was an early frustration only solved by the higher inductance Nortronics heads.
These frustrations led me away from outboard electronics (Cello ,Bottlehead and others and to the adoption of the superb but rare and earlier Mark Levinson electronics that used the Studer on-board architecture. Both the Levinson and later Cello tape electronics were designed by Tom Colangelo,who took over design after John Curl left the company.
Our very own Valve Audio supremo,Schalk Havenga, once in a moment of sublime insanity, took on a project to modify a Whisper for tape use. True perfectionist that he is ,this project quickly became a stunning study in design far removed from the Whisper. Unfortunately for me but fortunately for the world Schalk realised he had a company to run and cannot bankrupt himself in such silly pursuits and the project was killed off with my blessing. Sadly I lost the design study but it was stunning!
This is the Eros: As can be seen it has had a hard life.
DSCN5785 by
jdza, on Flickr
IMG_0525 by
jdza, on Flickr
A80 reproducer:Yes, a second cage was added for the additional replay electronics. Note in the photo neither cages carry any record electronics
DSCN5790 by
jdza, on Flickr