The Tale of Two Preamplifiers - Part 2

Hi!

In part 1 the story of these two preamplifier was already introduced. In this post I will reveal which tubes got tested and which were the favourites in terms of sound.

The test set up which was used for evaluation was already shown in part 1. An adjustable power supply provided all the necessary voltages for the different tubes.

Operating points are chosen with a couple of switches which selected from an array of resistors for cathode or filament bias.

Pretty much all directly heated triodes with an UX4 base are usable, for example: UX201A, UX112A, 26, 30, 31, 45, 50, 183/483 and 71A. But even indirectly heated triodes like the 27, 37, 56 or 76 could be used with  socket adaptor.

Also the 46 was tested with a socket adaptor which tied grid 2 to the plate.

And in addition two european DHTs. A Siemens Da:

Again to be plugged in via an adaptor:

And the Telefunken RE074:

Also with an adaptor:

The 10Y or 801A were not included since I have separate preamps with these tubes which could be used for comparison. Hopes were very high for the european tubes and also the 45 and 50. But surprisingly none of them turned out to excel in this set up. To be fair, none of the tubes sounded really bad and the differences are rather subtle. After all the overall sound is largely determined by the circuit topology and its execution. One of the winners was not much of a surprise since I was already familiar with it:

The 26 which I already used in a 26 line stage before. It has a very gentle and smooth sound and applies a touch of 'dark chocolate' or 'caramel' flavour to the sound which can be very pleasing. This description is of course an exaggeration for illustration. The effect is rather subtle. The other tube which came out as a favourite and turned out to be even better than the 26 was the 31. A directly heated battery triode.

Shown above as UX231 in tubular shape. The 31 offered a very refined and high resolution sound in this set up. A runner ups in this competition were the 71A and 183/483 which also provided a very clean and impressive sound. Also not bad was the 27. It does not exhibit it the certain magic of indirectly heated triode but is very interesting nonetheless. More about this in an upcoming post.

Since the originator of the project could note decide between the 26 and 31, he commissioned two preamps.

Since both tubes run at similar plate voltages, the two preamps can be used with the same power supply. Both tubes run in filament bias. Additional bypass resistors are used in the 31 unit so it can work with the same power supply as the 26 without any switches.

The powert supply uses a full ave bridge with 4 half wave tube rectifiers. But not with 6AX4 TV dampers as usual but this time with a different tube, the 1V. More about this tube in an upcoming post.

Shown above both preamps with the PSU. The back sides:

An interesting project which gave some valuable insights. Thanks again to the originator of this. It has been an interesting journey. I'll ask for some sound descriptions from the owner of these preamps for another part of this story. Stay tuned!

Best regards

Thomas

Custom 300B Amplifiers

Hi!

Pretty much all my amplifiers are built to order and can be tailored to specific requirements. These latest amps are an example how far customisation can go.

In this case the customer provided the interstage and output transformers and also participated in the chassis layout. The transformers are made by Monolith Magnetics in Belgium. The layout and chassis is based on my portrait style but adapted to fit the different output transformers.

The circuit is based on my earlier 300B/300B amps but with some circuit modifications requested by the customer. Shown above one channel of the amp equipped with EML tubes.

The power supply uses a classic rectifier instead of my favourite full wave bridge with TV damper tubes. Switches are placed on top which allow adaption of the filament voltage to different brands of 300B tubes which draw different filament current. The power transformer was also provided by the customer.

One channel, amplifier and power supply.

The amplifier chassis with Electro Harmonix tubes:

With Elrog ER300B:

The full amplifier set:

Best regards

Thomas

The Tale of Two Preamplifiers - Part 1

Hi!

In the previous post I already mentioned the project which evaluated the sound qualities and usefulness of a variety of tubes in line preamplifiers. Two preamplifiers resulted from this evaluation and I will present them in a few separate posts.

Although I am very fond of the 10Y in line stages, and also as driver tube for DHT power amps, I occasionally get asked for alternatives. Also some people prefer to not use the same tube twice in a system. So if the 10Y is already in use as driver this means to look at some other tubes.

For this project I built a test set up which can operate a variety of directly heated tubes with UX4 base:

Tubes with other bases can be plugged in via a socket adaptor as seen on the left in the photo above. The test set up has two pairs of different line output transformers, selectable via switch. One is for tubes with lower plate resistance and the other for those with higher rp. The biasing can be switched between conventional cathode bias and filament bias. Different bias resistors can be selected via a set of switches. Filament and plate voltages can be monitored via jacks at the top plate. Plate and filament voltages were taken from an adjustable supply which was shown in a post about a 300B amp. This way suitable operating conditions can be selected for a wide variety of tubes. When used with a passive transformer volume control this set up is a fully functional line preamplifier.

Stay tuned for part 2 in which I will mention all the tubes tested.

Best regards

Thomas

Happy New Year!

Hi!

It is Sylvester and time again to recap what was going on during 2015 and what is planned for 2016.

2015 was the best year for VinylSavor so far. Many exciting projects and some significant improvements in sound quality.

First there was the new generation of LCR phono stages with a new improved biasing scheme introduced in a EC8020 phono stage and later also used in new builds of D3a phono stages in both landscape and portrait chassis styles.

The 211 had a significant come back for me with 4 newly build amplifiers. A new incarnation of the 6HS5/211 amps, two new versions of the 801A/211 concept with Tango transformers. Both in square chassis, one of them with less height and more floorspace and the other introducing the new tower style chassis.

While the former were commissioned by a customer, I built the tower style version as demo amps which I plan to show at next years High End fair. And then there were the totally over the top 211/211 amps with all silver transformers.

Silver was a big topic this year, even more than 2014. Besides the silver 211/211 amps there were the all silver 300B amps with power supplies using mercury vapour tubes. Those two amps represent the best sounding power amplifiers I have built so far.

On the preamp side there was also another build of the single ended 10Y line stage with silver finemet OPTVCs.

And then there was the silver version of the differential line stage. This project was the biggest surprise for me in 2015 and held the biggest step in sound quality I achieved in a component so far. It deserves the title 'ultimate line preamplifier'. A special thanks to those who commissioned these over the top projects and helped to push the envelope!

Although the 10Y and especially it's specially selected variant 1602 remain my favourite line stage tube, there are other interesting candidates as well. For example the 26 as used in a 26 line stage built this year. There was an interesting project going on this year about which I have not written anything yet. This involved building a test setup which enabled the use of a whole variety of different tubes in a line stage and culminated in the build of two new preamps. The tale of these two preamps will be told in 2016. Thanks a lot to the originator of this project which enabled new insights into different sound worlds.

So what is planned for 2016? The ultimate line preamplifier definitely needs a companion phono stage. I finally need to proceed with the all differential EC8020 phono which I already mentioned in last years Sylvester post.  Initially as a copper version and hopefully there will also be a chance to build it all silver in similar fashion to the ultimate line preamp.

The topic of push pull power amps is also not forgotten yet and maybe 2016 will be the time for a VinylSavor PP amp.

And finally I decided to look into digital playback. Although vinyl will remain my preferred source, I understand that there are a lot of people who simply prefer the convenience of digital and the possibility of downloading music. And finally not everything is available on vinyl.

All the best for 2016 for all of you and your families!

Thomas

Music : Freddy Quinn, Auf hoher See

Hi!

At events like the ETF or the High End fair I occasionally like to play some fun records. It is interesting to watch the reactions. While some seem to take things too serious, others really enjoy them. This is one of those records. 'Auf hoher See' by Freddy Quinn.

Freddy Quinn was very popular in Germany during the 50ies and 60ies and produced a lot of records during that time and also played in some movies.

Most of his songs are about the sea and sailors. This is also the theme of this record as is evident from the title and cover. The album was released in 1962 on Polydor. Like most of the Polydor albums of this era, the recording quality is exceptional. Also the vinyl quality of these early Polydor discs leaves nothing to wish for. They can be recognised by the orange label with the stars at the top. Later releases have a red label and are of lesser quality but still mostly very good. The first song on the album is probably the best and also the one which often leaves people with their mouths open if they haven't heard such a record before. It starts with water waves which almost give the feeling as if the water is splashing over your feet. Then a choir slowly sets in which is unbelievably realistic. And finally Freddy starts to sing. His particular accent and the way he rolls the 'rrrrr' together with the hilarious lyrics is really funny. Freddy Quinn probably didn't take himself too serious when he recorded this.

And this is how to listen to such a record. Don't expect anything serious or artistically challenging. Just have fun listening to it and be amazed by the truly exceptional recording quality.

Best regards

Thomas