“Shiny Eyes” SE 45

This is a gem and I could confidently say: a reference amplifier. I’ve built it to compare with my PSE 4P1L and the results are amazing. If one has the appropriate speakers for SE tube amps and low power ( the 1st watt is all that matters), than this amp is a must to experience. I’ve spent many hours to experiment with different driver tubes. My goal was to make a 2 stage amplifier where the driver has minimum distortions with a dominant 2nd harmonic. This way the amplifier as a whole will get a predominant 2nd harmonic and will reveal the gorgeous sound of the 45. I also desired to make it less complex in comparison with my PSE 4P1L.

main-side-front

The result of this brainstorming was an amp with lower input sensitivity. I used type 76 triode to drive the 45. The 45 has a Miller capacitance of about 40 pF ( including some stray) and it is easy to drive in class A by using a low  current driver such as the 76 at 5 mA, without introducing slewing distortions.

The power supply was built in a separate enclosure for a hum free DHT amp. It uses all Hammond transformers and chokes. Hammond 272Hx is used to provide the high voltage using a 5V4G rectifier and a CLCLC filter with 4.7uF-8H-47uF-8H(Hammond 193D)-47uf. The last capacitor is Clarity TC600, 4 pin Kelvin terminations for decoupling high frequency power supply noise from the signal path. A gorgeous Simpson 600V panel meter is showing the high voltage. The same transformer is used to provide 6.3DC to the 76 filaments, using a DC power supply based on LT1085 regulator. There are 2 Hammond  167Q6 used to provide raw DC supply to the Coleman filament regulators for the 45s. The high voltage comes delayed 25-30 seconds to allow the 45 filament to reach a quasi-steady state and extend their life. The delay timer is based on the 555 IC. The power supply has a 12 pin connector where the umbilical cord is plugged in. The umbilical cord is permanently attached to the main amp case and carries only DC. Here are some pictures of the power supply:

psu-inside

 

The main amplifier case is built out of American cherry solid hardwood stained with light oil urethane, 4 coats. The top plate is gold anodized aluminum made by Front Panel Express. The main amplifier is provided with Neutrik RCAs and Cardas binding posts. A nice Shurite 3V panel meter can be switched to measure each of the 45 filament and allow precise adjustment to 2.5V. There are separate 10 turns 2W pots top panel accessible for this adjustment. The output transformers are James 6115HS. I’ve provided a switch to choose between 5K and 7K load. On the 7K load the sound is more pleasant as the distortions are reduced. Here is the schematics and some pictures:

schematics-45-76-js6115hs

topmain-frontside-bothmain-backback-1fpe-topmain-inside

 

I’ve always measured my amps and in majority of cases the measurements tell the truth about the sound of the device. In this case, as you can see from the distribution of the harmonics, there is a 2nd harmonic dominant SE amp that sound better than it measures. ( as always with early DHTs ).

Input sensitivity:

1 Vrms for 0.25W output, 2.2 Vrms for 1W output,  3 Vrms for 1.75W output max

Frequency response: 20Hz-30kHz @ -1dB

THD  5K load : 1.66% @ 0.5W, 2.5% @ 1W, 3.47% @ 1.5W and 4.9% @ 1.75W

THD  7K load: 1.24% @ 0.5W, 1.77% @ 1W, 2.8% @ 1.5W and 4.08% @ 1.75W

thd-5-and-7k-load-45-amp

fft-1w-7kfft-1w-5kthd-and-harmonics-45-ampfr-at-0-25w

I’ve needed a bit of gain to drive this amp to max power. I found that my 18dB 01A preamp is a great fit. I’ve also tried 26 pre and 10Y pre and they all sound excellent combined with this SE 45.

“Shiny Eyes” 01A DHT line stage

Here is another built of my favorite 01A DHT,  Thoriated Tungsten filament.

IMG_4365

It uses the Lundahl LL2745 in a 5.6:1 step down configuration. A separate enclosure power supply is providing low ripple high and low voltage. A 7 wire umbilical cord brings the power to the main preamp chassis. This preamp is solid state assisted on both high voltage and low voltage side. The 01A is filament biased using Coleman regulators.

There is no capacitor in the signal path besides the power supply ones. There are minimal parts in the signal path carefully chosen for reliability and sound quality.

01A is a superb sounding tube and can often improve the listening experience when combined with solid state amplifiers, digital recordings. There are still plenty of 01As available outthere. Just be patient to find the less microphonic ones. As usual, I dealt with reducing the effect of microphony by starving filaments and suspending the sockets on neoprene mounting dampers.

 

Another DHT switchable preamp

Built for my audiophile pal Paul, this is a one enclosure preamp  using 101D or 26 vacuum tubes.

IMG_4225

This is an all DHT( direct heated tubes) preamplifier/ line stage.  It has one stage and is built within the same enclosure. This a very good option for anyone who want to try and compare the sound of the 101D  DHT triode and the 26 DHT triode.

The power supply uses Lundahl LL1683 for main HV in a choke input 0.47uF(Obbligato gold film)-10H Lundahl LL1638-68uF(Obbligato Film-Oil)- 10H Lundahl LL1638-68uF(Obbligato Film-Oil). The rectifier used is the 274B and can be replaced by any rectifier in the 5U4G family. HV is supplied with a low ripple which is perfectly adequate considering that the shunt regulator SSHV1 will add at least 80dB PSSR bringing the ripple at extremely low levels ( I could not measure it with my equipment).  The raw power supply for the filament biases are using Hammond 167 series transformers at 12.6Vac, followed by a rectifier bridge with 1N5822 and 10mF-2×0.33ohms-10mF-0.1uF-220pF. The two raw filament supplies are delivering up to 1 Amp to the Coleman regulator.  The Coleman regulator is adjusted at 1A which is perfect for the 101D tube and slightly starved for the 26.

 

The preamplifier  uses either the 101D or the 26 tube in a filament bias configuration. In order to switch between 101D and 26 tubes, there are 2 sets of DTDP high quality Carling switches. The anode load of the DHTs is Lundahl  LL1660/10mA connected step down Alt. Q 4.5:1 ratio. This allows to deliver a 20 times lower output impedance compared to the plate resistance of the DHT . The input of the preamplifier is DC connected, therefore care must be taken when connect to other audio equipment to make sure that there is no DC to feed this preamplifier. The preamp is provided with a stereo remote volume control by Khozmo in 64 steps, shunt stepped attenuator having only two resistors in the signal path at a time. All components and wires are high end audio such as Vishay nude, silver gold wire, NEOTECH – Solid Core Copper, *PTFE Jacket
(99.9999% UP-OCC Mono-Crystal design).

Specifications

The following measurements are only to give you a sense  of the approximate performance. I used a computer software and interface and this comes with some artifacts and noise that are not present when the amp is connected in a audio path. One, if owns high quality audio analyzer, can take more precise measurements

  • Frequency response: better than 30Hz-30kHz @ -1dB
  • Distortions better than 0.2% at 3Vrms output, for most tubes if carefully selected for low distorsion
  • Gain using the 26: about 5.5dB
  • Gain using the 101D: about 4.8dB
  • Input impedance: 50 kohms, unbalanced
  • Output impedance under 400 ohms for the 26 and under 300 ohms for the 101D

More pictures: Top plate from Front Panel Express with a very nice powder coated finish…

 

Switchable 01A-26 DHT preamplifier

night viewThis is an all DHT( direct heated tubes) preamplifier/ line stage.  It has one stage and is built within the same enclosure. This a very good option for anyone who want to try and compare the sound of the early 01A  triode and the 26 triode.

The power supply uses Hammond 269AX for main HV in a quasi choke input 0.47uF(film)-30H(40mA)-47uF(Obbligato Film-Oil)-500ohms-47uF(Obbligato Film-Oil). The rectifier used is the 6BY5GA. HV is supplied with a low ripple which is perfectly adequate considering that the shunt regulator SSHV1 will add at least 80dB PSSR bringing the ripple at extremely low levels ( I could not measure it with my equipment).  The raw power supply for the filament biases are using the Hammond167L12 transformers, 1N5822 and 10mF-2×0.33ohms-10mF-0.1uF-220pF. The two raw filament supplies are delivering up to 1 Amp to the Coleman regulator.  The sense resistor of the Coleman regulator is switched between 1 ohms and 3.9ohms, to supply either 0.91A to the 26 filaments or 0.233A to the 01As.

The preamplifier  uses either 01A or 26 tube. In order to switch between 01A and 26 tubes, there are 2 sets of DTDP high quality mini Carling switches. One of the switches is used to switch between the Rsense of the Coleman regulators, and the second switch is switching the bias resistors placed between one of the filament pins and signal ground ( a permanently connected 30 ohms Mills MRA12 is used to bias the 01A and when switching to the 26 tube there are 2 more 30 ohms Mills MRA12 added in parallel to the 30 ohms( equivalent bias resistor for the 26 will consequently be 10 ohms)), and the anode voltage adjustments of 120V for the 01A and of 155V for the 26.

The anode load of the DHTs is a Mosfet-Jfet inductance simulator which has the advantage to lower the distortion to minimum and higher the amplification to maximum. The input of the preamplifier is DC connected, therefore care must be taken when connect to other audio equipment to make sure that there is no DC to feed this preamplifier. The output is capacitor coupled, using a quality capacitor: the Mundorf  Supreme.

The preamp is provided with volume control using Alps RK27 potentiometers, one per channel. The advantage of using separate volume control per channel is to be able to balance the sound. Tubes can’t be perfectly paired and they also drift differently in time.

 

Specifications

The following measurements are only to give you a sense  of the approximate performance. I used a computer software and interface and this comes with some artifacts and noise that are not present when the amp is connected in a audio path. One, if owns high quality audio analyzer, can take more precise measurements

  • Frequency response: better than 10Hz-30kHz @ -1dB
  • Distortions better than 0.1% at 8Vrms output ( as low as 0.02% depending on the specific vacuum tube)
  • Gain : about 19dB(x8)
  • Input impedance: 82 kohms, unbalanced
  • Output impedance under 300 ohms for the 26 and under 500 ohms for the 01A

“Shiny Eyes” Parallel Push-Pull EL34B

“Shiny Eyes” Parallel Push-Pull EL34B is my first medium power push-pull monoblock . It was sponsored by my audiophile friend Rocky.

First, I want to thank  Kevin Carter from K&K Audio for his technical support and his awesome sounding push-pull driver, an all balanced driver using the Russian pentode 6J49P in triode mode and very good Lundahl transformers.

It uses six EL34B per channel delivering a maximum of 50Wrms into 4 or 8 ohms. The output audio transformer is a 120W Hammond 1650TA. The driver stage is full balanced push-pull input stage kit from K&K Audio using all Lundahl transformers LL1544A for input and LL1692A for output. Driver tubes are 6J49P carefully selected by Kevin Carter.

The power supply consists of a 375VA potted Plitron toroidal transfomer with secondaries at 340V/0.8A and 6.3V/ 12.8A. HT is SiC diodes rectifed and CLCLC filtered, using Hammond 159V chokes and MKP 50uF 900V capacitors. The driver has its own shunt regulator. The high voltage is delivered with a 30 seconds time delay based on IC555.

The enclosure that holds together the mono-blocks was delivered by Modushop in Italy, model Pesante 5U 400.   On the back panel one can observe the IEC main power jack and the fuse holder on the left, the RCA input jack in the center, and on the right the Cardas speaker binding posts and two switches, one for 4 and 8 ohms and one for speaker on/mute. On the front panel there are two meters: the center one is a VU meter, and the right side mA meter shows the total anode current of the six EL34Bs. This mA meter should show not more than 420mA ( typically between 350 and 400mA). On the right of the front panel one can notice the main power switch and light indicator.

The case of the mono-block amplifier is running hot in few spots that are close to the group of the six EL34Bs power vacuum tubes. It is not recommended to touch the top of the case above the power tubes where the temperature can reach values that are not safe for touching. For this reason this amp should not be left unsupervised. Each monoblock weights about 60-70 lbs .

This a medium power amplifier ( 2x50W max), providing a transparent, detailed, good dynamics sound. The EL34Bs are running self-biased, class A triode mode.

Here are some measurements:

Input Voltage (Vrms) Output Voltage (Vrms) on 8.3 ohms Power(W) THD (%)
0.5 6.23 4.67 0.3
0.73 8.8 9.3 0.53
1 12.5 18.8 0.95
1.45 18 39 1.87
1.55 19.2 44 1.76
1.66 20.5 50 2.29

Specifications

  • FR : 20Hz-22kHz =/- 1dB
  • Input sensitivity for 50W output: 1.66 Vrms
  • THD at 1kHz, 40W on 8Ohms output is better than : 2%

Max power: 50W

Mains Voltage: 120V at 60Hz

The schematics ( exception the driver):

 

More pictures:

Shiny Eyes SE 300B

front closeuptopThis amp was born because I wanted to re-purpose the awesome output transformers Monoliths Etude -1 used in the PSE 4P1L. The Monoliths were a little overkill for the PSE 4P1L amplifier.

I also used the interstage transformers LL1692As because they were the best fit for the chosen driver C3g.

In addition the Monoliths and the Lundahl interstage were already broken in for about 600 hours. This made possible to built an amp that reproduces music at highest performance out of the box. What better incentives for the desire to built a new tube amplifier.

From the beginning, I chose a very compact layout design, based on my previous experience with PSE 4P1L. I used the beautiful looking Brazilian cheery wood 6″ wide. This allowed an inside height of about 5″ which was excellent because I was able to fit the power supply on the bottom of the enclosure. The  case design is similar to other amps and preamps: a 1/8″ aluminum top plate where all the components and sub-assemblies are attached to, a wooden enclosure  routed in such a manner that the top plate is sitting nicely on it.

Here are few things about the design:

  • The power supply uses for the high voltage a 300W Lundahl LL1651 with 500V secondary feeding on a hybrid bridge 6CJ3 – SiC schottky, choke input PRC-1 at 5.5H/230mA, followed by CLC ( 200uF-5.5H-200uF). This delivers about 400V @ 180mA. Layout with PRC1 and tubes on top and LL1651 and caps on bottom. The LL1651 provides also AC filament for the two tube rectifiers and for the two drivers. The 300B filaments are powered on DC voltage provided by a Antek 100VA/ 2x9V, raw dc supply and superb Coleman regulators. In order to protect and extend the life of the 300Bs, I used a delayed timer for the high voltage. When the amp is turned on, first the filaments of the 300Bs are powered and the delayed timer starts counting. After about 30 seconds, the relay powers the LL1651 and the tube rectifiers allow a soft start after another 20 seconds or so.
  • The main amplifier has a simple schematics: 300B with 1K/12W-220uF/100V cathode(self) bias, driver C3G with 200ohms – 2200uF Cerafine for cathode bias. The driver feeding the IT that has a CCS( constant current source) from the PSU(power supply unit). CCS is adjusted at 16-18 mA. The 300Bs are running at about 65-68mA and 340V Uak and deliver a maximum of 7Watts per channel.

Shiny Eyes SE 300B features:

  • Custom tube PX300B Genalex Gold Lion
  • Monolith Etude-1, high end output transformers
  • Amazingly linear German made (Siemens) C3g driver
  • Lundahl LL1692A, high end interstage transformers
  • Lundahl main power transformer LL1651
  • Choke input with tube rectifiers
  • MKP high voltage capacitors
  • Coleman filament regulators
  • delayed and soft start
  • Cardas binding posts
  • RCA Neutrik
  • switches to mute the speakers

 

Shiny Eyes SE 300B measurements:

THDTHD FFT

FR

FR at 3W

THD % Output Vrms Output power Wrms
1.22 2.89 1
1.73 4 2
2.18 4.9 3
3 6.11 4.66
3.35 6.52 5.3
4 7.5 7

 

Gain:

x6.52 or 16.3dB

Input sensitivity:

  • 440mVrms for 1W output on 8 ohms resistive
  • 1.15Vrms for 7W output on 8 ohms resistive

Frequency response:

20Hz at +0.5 db to 20kHz at -0.84dB for 3 W output

 

Distortions versus frequency:Harmonics distortion versus frequency

Harmonics distortions Zoomed on lower end.

Harmonics distortion versus frequency-expanded LF

Other pictures:

top closeup

 

The sound of this amp is astounding: very tight bass, extremely sweet and vibrant mids and highs. It makes a very good match for high sensitivity full range drivers. I am using it with the Alpair 12P in small reflex enclosure. This amp is a better match to the 92dB sensitivity speakers compared to the PSE 4P1L.

“Shiny Eyes” 4P1L Gain Stage 19dB on PCB

Here is another 4P1L design. All started when I tried to figure out a gain stage for a First Watt F4. The F4 is a unity gain 25W class A power amp that needs about 14Vrms input in order to deliver max power.

4P1L offers a x9 gain. Therefore, using a 4P1L gain stage is appropriate and the input sensitivity of the hybrid amp will be about 1.55Vrms.

I built my first F4 in a 4U standard ModuShop Dissipante. seen at http://www.modushop.biz/site/index.php?route=product/category&path=66_97_107.

I had to built the 4P1L gain stage so it fits inside this case. The max dimensions were 12″x12″. I built the first one on a garolite FR4 board and attach all components and small PCB to it (see previous built https://simplepleasuretubeamps.files.wordpress.com/2014/12/photo-1-1.jpg). It was a hassle to position and attach each board to the main FR4. This led to the design of a single PCB board. I also wanted to integrate the Coleman regulators and use standard heat sinks such as the Wakefield 657-20ABP. Rod helped me figure out the size of the heatsink.

The schematic  is simple: The power supply uses 3 transformers ( one of the 187D20 for each filament, and one Antek 50VA 160V for the HT.). Ht supply is filtered by a CLC (470uF-15H-470uF). The raw supply for the filaments uses 1N5822 and CRC 10mF-0.47R-10mF. The Coleman regulators need to be preassembled except the power transistors who are mounted on 2″ Wakefield heatsinks. The 4P1L is biased at about 115V Uak, 35mA and 560mA starved filament. Th headroom in this case is about 7dB. The load for the 4P1L is a cascoded DN2540 CCS. The PCB measures 266mmx274mm. It was much cheaper to order it on 1.6mm thickness and I provided many holes for support. One can use Aluminum stand-offs to make sure that the board stays rigid.

The only concern is how the 4P1L’s socket is attached to the board. I would use neoprene damper sandwich mount, rubber rings and even a dead weight ( in the pictures I just soldered the sockets to the board but I have to remove them and use the dampers..there is a hard to notice noise that comes from the very small vibration of the power transformer and the 4P1L is very sensitive to it).

Distortion levels are very low in the 0.0x % with a predominant 2nd harmonic. The frequency response is as flat as possible in the audio band.

For anyone who wants less gain there are few options. One can use  a step down direct feed line output transformer, such as LL1671/30mA. Another choice would be to use a parafeed line output transformer , such as Jensen JT-10k61-1M.

The sound is very rewarding. The DHT is complementing the solid state push-pull, and the resulting music experience is balanced, with great dynamics and nice sounding harmonics.

overall top overall front viw delay timer top view rear top view coleman regs closeup front closeup

A possible BOM is listed below:

“Shiny Eyes” 4P1L Gain Stage (preamp) 18-19dB
Part name Mouser part# How many Price each Cost total
Toroidal AS-05T160 N/A   Antek transformers part, shipping included 1  $          40.00  $           40.00
Hammond 187D20 546-187D20 2  $          12.82  $           25.64
Thermistor CL-60 527-CL60 3  $            1.78  $             5.34
0.033uF 275V X2 80-PHE840MK5330MK03 1  $            0.36  $             0.36
1N5822 511-1N5822 4  $            0.43  $             1.72
SiC diodes 941-C4D02120A 4  $            2.26  $             9.04
IN4001 512-1N4001 1  $            0.18  $             0.18
IC555 595-NE555P 1  $            0.49  $             0.49
2N3906 610-2N3906 1  $            0.41  $             0.41
IC7805 511-L7805CV 1  $            0.48  $             0.48
DN2540N5 689-DN2540N5-G 4  $            1.42  $             5.68
5V relay 655-RTD14005 1  $            2.04  $             2.04
Trimmer multiturn 200R 72-T93YA-J-200 2  $            1.98  $             3.96
Heatsink Wakefield 2″ 657-20ABPE 4  $            1.83  $             7.32
Heatsink Wakefield 1.5″ 657-15ABPE 2  $            1.16  $             2.32
10mF 16V 598-SLPX103M016A3P3 4  $            1.82  $             7.28
470uF 400V 598-SLPX471M400H7P3 2  $            5.63  $           11.26
0.47 ohms 5W wirewound 588-TWW5JR47E 4  $            0.80  $             3.20
1000uF 16V 647-UVK1C102MPD 2  $            0.26  $             0.52
220uF 16V 598-227CKE016M 1  $            0.10  $             0.10
15 ohms 1/4W 71-RN60D-F-15 2  $            0.11  $             0.22
47 ohms 1/4W 71-RN55D47R0F 4  $            0.17  $             0.68
56 ohms 1/4W 71-RN55D-F-56 2  $            0.16  $             0.32
1ohm 1% CMF551R0000FKEB 2  $            0.88  $             1.76
1kohms 1/4W RN55D1001FRE6 1  $            0.10  $             0.10
1Kohms carbon  composite 588-OD102JE 4  $            0.70  $             2.80
100koms 1/4W RN55D1003FB14 3  $            0.10  $             0.30
1 Mohms 1/4W 71-RN55D-F-1.0M 2  $            0.10  $             0.20
220 ohms 1W 71-CPF1220R00FKE36 2  $            0.45  $             0.90
220 kohms 3W 66-GS3T0220KJ 1  $            1.01  $             1.01
10nF 100V 505-MKP2D021001BJC00 1  $            0.23  $             0.23
0.1uF 100V 505-MKS2.1/100/10 4  $            0.24  $             0.96
1uF 600V min Supreme N/A, from Parts Connection, Sonicraft etc. 2  $          20.00  $           40.00
8 ohms 20W non-inductive Radio shack 2  $            3.00  $             6.00
Loctal Russian sockets  eBay , type    PL3-5-14(or 16) 2  $            6.50  $           13.00
Hammond  158L choke 546-158L 1 23.93 23.93
Bridge rect timer 625-B250C1500G-E4 1  $            0.68  $             0.68
4P1L eBay 2  $          10.00  $           20.00
Total parts on PCB  $         240.43
Total estimated shipping costs  $           25.00
PCB cost ( depending on number ordered and supplier)..cheapest  $           30.00
Other parts ( RCA jacks, IEC main connector, Fuse socket, Mains switch, volume control(s) )…estimated  $           55.00
Enclosure needs to measure at least 12″x12″x4″…rough estimation  $         100.00
Total  $ 445.43