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Most Exotic SE Interstage Transformers
Most Exotic SE Interstage Transformers
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Old 21st September 2014, 09:57 PM   #1
petavgeris is offline petavgeris  Greece
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Default Most Exotic 5kOhms Output Transformers

After a rather long time of inactivity, I am going to present you my latest project that I have been working on. After the exotic power amplifier with 211 output tube and the exotic phono preamplifier, I am going to show you the most exotic output transformers.

They are rated at 5kOhms of nominal load, proposed for tubes like 300B, 2A3, type 45, type 50 tubes, and the Telefunken AD-1 and RE604 tubes. These are cost-no-object creations only for the perfectionist music aficionado that wants to have the very best possible in terms of sound quality. Just for verification, they have been extensively compared to almost any other product available in the international market.

They are manufactured out of the most 'extreme', custom ordered ferromagnetic material that exists today, proposed for most accurate reproduction of musical signals. They are Double C Core shaped and the alloy ribbon is 20-24 microns (0.020-0.024 mm) thick for superior performance in High Frequencies. They are able to possess the minimum distortion to sound.

The coil formers are hand built, made of carton pieces, precision cut at a laser jet machine with tolerance of 0.05mm. The same holds true for the mounting brackets, made of baltic birch plywood. The mounting/securing strap is absolytely non magnetic and the bolts and nuts are all stainless steel 316 grade for lack of ferromagnetic properties.

The primary coil is wound at an unusually high number of turns, providing superior performance in low frequencies that no other transformer in the market is able to provide! For the technically inclined, the c cores have been tuned to a very high initial permeability level when DC biased, for maximum fidelity (low level detail, stellar clarity and unparalleled impact, authority and dynamics). The structure of the secondary coil is very complicated in order to have trully superior performance in high frequencies. 24 wires are coming out of the secondary coil and all must be used for proper performance. There exist no secondary coil output taps here, every time the user replaces the loudspeaker, he must make adjustments in order to achieve proper/ideal connection.

Due to the fact that the securing band can be taken off, the user has access to the gapping spacers, so he can find tune the performance of these transformers according to his taste (more power at low frequencies vs. more clarity, finesse and dynamics). This feature is offered for the first time to the end user!


Specifications:

Nominal load: 5kOhms
Primary inductance: 45 Henries without DC biasing, at 1V rms
Frequency response (with 2A3 tube): -1dB @ below 10Hz to 56 kHz, -3dB @ below 10Hz up to 85 kHz.
Secondary coil arrangement capability: 4 - 6 - 8 - 16 ohms

The pictures with the square wave response were taken with cables of high capacitance, so there is a small resonance already in the signal coming out of the generator.
Attached Images
File Type: jpg opt001.jpg (298.1 KB, 505 views)
File Type: jpg opt002.jpg (231.8 KB, 492 views)
File Type: jpg opt003.jpg (248.6 KB, 486 views)
File Type: jpg opt004.jpg (286.9 KB, 478 views)
File Type: jpg opt005.jpg (218.7 KB, 475 views)
File Type: jpg opt006.jpg (282.8 KB, 154 views)
File Type: jpg opt007.jpg (200.2 KB, 150 views)
File Type: jpg r_1kHz-sw-gen.jpg (198.2 KB, 179 views)
File Type: jpg r_1kHz-sw-trans.jpg (211.7 KB, 163 views)

Last edited by petavgeris; 21st September 2014 at 10:00 PM.
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Old 21st September 2014, 10:31 PM   #2
petavgeris is offline petavgeris  Greece
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Default Most Exotic SE Interstage Transformers

Now I am going to present you the most exotic interstage transformers for Single Ended vacuum tube amplifiers. They are proposed for the creme de la creme of Directly Heated Triodes (DHT) that usually have internal impedances between 5 and 10 kOhms. But more conventional tubes can equally be used here.

These are cost-no-object creations only for the perfectionist music aficionado that wants to have the very best possible in terms of sound quality. Just for verification, they have been extensively compared to almost any other product available in the international market.

They are manufactured out of the most 'extreme', custom ordered ferromagnetic material that exists today, proposed for most accurate reproduction of musical signals. They are Double C Core shaped and the alloy ribbon is 20-24 microns (0.020-0.024 mm) thick for superior performance in High Frequencies. They are able to possess the minimum distortion to sound.

The four-chamber coil formers are hand built, made of carton pieces, precision cut at a laser jet machine with tolerance of 0.05mm. The same holds true for the mounting brackets, made of baltic birch plywood. The mounting/securing strap is absolytely non magnetic and the bolts and nuts are all stainless steel 316 grade for lack of ferromagnetic properties.

The primary coil is wound at an unusually high number of turns, providing superior performance in low frequencies that no other transformer in the market is able to provide! For the technically inclined, the c cores have been tuned to a very high initial permeability level when DC biased, for maximum fidelity (low level detail, stellar clarity and unparalleled impact, authority and dynamics).

These interstage transformers are proposed for the best Directly Heated Triode tubes that have ever been made. All interstage transformers suffer from poor high frequency extention, but here this is not the case at all! They can be loaded at unusually high loads, well exceeding 47 kOhms, ideal loading conditions are 47 - 68 kOhms, according to application. This way the user can drive his favorite tubes that provide spectacular sound at ideal loading conditions. The very best DHTs have internal impedance around 5-10 kOhms and these transformers are their ideal match at 1:1 turns ratio (bifilar wound). Due to their design, primary voltage must not exceed 350 Volts DC.

Due to the fact that the securing band can be taken off, the user has access to the gapping spacers, so he can find tune the performance of these transformers according to his taste. This feature is offered for the first time to the end user!


Specifications:

Nominal load: 47-68 kOhms (the transformers pictured here are tuned at 56kOhms, for Telefunken RE134 tube with an Rp of ~5 kOhms)
Primary and Secondary DC resistance: 740 ohms
Primary inductance: 440-530 Henries depending on which tube will be used, without DC biasing, at 1V rms, .
Frequency response (with Telefunken RE084 tube with Rp ~10 kOhms) loaded @ 68kOhms: -3dB @ below 10 Hz to 195 kHz.
Frequency response (with Telefunken AD-1 tube with Rp ~600 Ohms) loaded @ 68 kOhms: -3dB @ below 10 Hz to ~2 MHz.

1st graph picture: 1 kHz square wave response, input impedance: 10 kOhms, loading impedance: 68 kOhms
2nd graph picture: 10 kHz square wave response, input impedance: 10 kOhms, loading impedance: 68 kOhms
3rd graph picture: 10 kHz square wave response, input impedance: 600 Ohms, loading impedance: 68 kOhms
4th graph picture: 100 kHz square wave response, input impedance: 600 Ohms, loading impedance: 68 kOhms
Attached Images
File Type: jpg se001.jpg (301.8 KB, 285 views)
File Type: jpg se002.jpg (188.0 KB, 253 views)
File Type: jpg se003.jpg (233.4 KB, 235 views)
File Type: jpg se004.jpg (279.8 KB, 242 views)
File Type: jpg se005.jpg (297.1 KB, 245 views)
File Type: jpg se006.jpg (231.4 KB, 118 views)
File Type: jpg z_1kHz_10kohms.jpg (237.8 KB, 129 views)
File Type: jpg z_10kHz_10kohms.jpg (292.1 KB, 103 views)
File Type: jpg z_10kHz_700ohms.jpg (216.1 KB, 78 views)
File Type: jpg z_100kHz_700ohms.jpg (313.2 KB, 100 views)
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Old 22nd September 2014, 07:33 AM   #3
Alkis is offline Alkis  Greece
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Finally square wave response! Nice job Pet!
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Old 22nd September 2014, 09:24 AM   #4
trobbins is offline trobbins  Australia
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What's the inductance variation as DC bias moves from 0 bias to twice DC bias for a likely nominal max design DC bias level?
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Old 22nd September 2014, 09:43 AM   #5
AmadeusMozart is offline AmadeusMozart  New Zealand
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Quote:
Originally Posted by petavgeris View Post
The pictures with the square wave response were taken with cables of high capacitance, so there is a small resonance already in the signal coming out of the generator.
Show the square wave pictures at 10 and 20 Khz and at 50 and 100 Hz. 1 Khz is meaningless.
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Old 22nd September 2014, 10:02 AM   #6
petavgeris is offline petavgeris  Greece
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Quote:
Originally Posted by trobbins View Post
What's the inductance variation as DC bias moves from 0 bias to twice DC bias for a likely nominal max design DC bias level?
Hello!
On these c cores t/f the initial permeability is around half the incremental permeability. A little of DC bias is enough to reach maximum permeability and the cores email perfectly linear till saturation behins to unfold.
Permeability remains almost dead flat in regards to both signal amplitude and frequency. Permeability linearization is a achieved through the application of magnetic gap but these cores impose extremely linear permeability as an inherent property, thus they are amazingly good for Push Pull applications and not only Single Ended.
Thank you for your comment.
Greetings from Athens, Greece!
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Old 22nd September 2014, 03:06 PM   #7
kevinkr is offline kevinkr  United States
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Most Exotic SE Interstage Transformers
Performance looks exceptionally good based on square wave behavior.
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Old 22nd September 2014, 03:58 PM   #8
TheGimp is offline TheGimp  United States
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Would you please show a 100Hz square wave response?
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Old 22nd September 2014, 06:05 PM   #9
aroS3 is offline aroS3  Greece
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Excellent freq response. Well done Peter once again.
Good luck to all your upcoming projects.

Best regards,

George
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Old 23rd September 2014, 01:18 AM   #10
TonyTecson is offline TonyTecson  Philippines
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Most Exotic SE Interstage Transformers
merged two threads and moved to vendors forum, one thread per user applies...
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