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You're good Fjd, nailed it.

I recognized the PCB from the amount of time I spend reading on Shannon Park's site and recognized Justin's choice of chokes. I like what I keep reading about what Justin has done with his amp builds and it sure opens up using tubes to people that may not have considered it before. I keep thinking I should start allocating audio budget $'s to my 'Kenzie headphone amp fund' soon and have some first hand experience.

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I've somwhat moved from the tube amps temporarily to finish a couple of the First Watt clones

 

I really like my F5 clone. Good call.

 

Dave

 

 

 

I've been slowly collecting parts for the Sony VFET schematic that Nelson Pass released to the diy community; however, on that one, I will need to wait until someone has posted more detail about the build and trouble issues. I'm not sure of my exact timing yet, but I would like to start the F5turbo by this fall, if not sooner.

 

This summer travel schedule and personal family issues have continued to present several impediments to my progress; however, I dug up some pictures of the pieces for the F4 clone I picked up (I'm liking it enough paired with my DHT SET amp where I started collecting parts for mono block amps) and my Electra-print single-ended DHT 45 amplifier (I bought one of Jack's prototypes with the partial silver secondary wiring in the output transformers) and the configuration that Nelson Pass suggests. In some respects, it could be a way to capture the 'best of both worlds.'

 

F4 bi-wire.jpg

I know you have already read most of the following, but I figured a re-cap may be useful to some following this thread.

 

The F4 is a Class A "impedance converting" push-pull amplifier that has "current gain" but does not have any voltage gain and does not have any feedback. It 'mates' well with most components that can deliver the voltage gain needed to drive your speakers as it is essentially a very large high-quality buffer. Distortion is a little higher than the F5, but still very much respectable and much lower than my DHT SET amps (although Jack's single-ended DHT 45 amp, comparatively to other DHT amps, has very low distortion numbers), but the noise floor on the F4 is one of the lower that I've seen available. A very quiet amp and only the very narrow-focused F1J & F2J have lower measured specifications.

 

I essentially use my DHT SET amplifier as the "voltage gain stage" directly into the F4 and because the F4 is such a simple Push-Pull circuit with no feedback, a lot of the characteristics of the DHT SET amp that I find very favorable will come through. I think of it kind of like a "SET on steroids" in some ways, but also noting that it looses some of what DHT SET provides in those near-field lower-level listening sessions.

 

Since the F4 is basically a refined power follower, it will essentially push the same voltage out that you send into it, but it will feed much more current through the load than the SET amp, if needed.

 

There are various implementations of "adaptors" out there as the DHT SET output will need to be adapted to the RCA input of the F4. Also, due to the F4's high input impedance (47,000 ohms), a resistor (~ 20 ohm, 5 watt resistor, but some have used anywhere from about 15 ohm - 22 ohm depending on how they like the sound) is needed across the SET outputs since the SET only "sees" the F4 and not the speakers. On DHT SET amps with multiple taps (i.e. 4, 8 or 16 ohm) there seems to be some diversity on which tap sounds best; however, I suspect that is more related to system synergies.

 

Essentially, you have a "component" approach to a quality tube gain-stage followed by a high-end design solid state buffer. I think you see scaled versions of this tube gain stage / solid state buffer concept in headphone amps (I've mentioned one example in my earlier posts) for which the quality implementations seem to be very well-received; therefore, it seems to be a valid higher-end approach to try for speakers.

 

 

Electra-Print Stereo 45 Amplifier Prototype 4.jpg

 

Electra-Print Stereo 45 Amplifier Prototype 5.jpg

 

 

Electra-Print Stereo 45 Amplifier Prototype 1.jpg

 

Electra-Print Stereo 45 Amplifier Prototype 3.jpg

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Edited by Fjd
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As someone who really appreciates point-to-point wiring, thanks for sharing those images. Erik.

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nice looking amps, I like the color scheme of maroon and silver, Jeff Kornef did that for awhile as well

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I like the fact that the RCA's and speaker wiring connectors are on the back and not top.

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I believe that after showing the amp during a few audio shows during 2012, Jack listed the Electra-Print Audio stereo 45 amplifier prototype on eBay with an opening bid that only seemed to cover the cost of the transformers used (looking at his transformer price list).

 

I was pleasantly surprised that I was the only bidder and won. This amp has made the list as one of my favorites, not only for sound, but also for versatility. The price was an exciting bonus as Jack now lists the copper output transformer / PVA transformer production 45 amp for $2,495 and the silver output tranformer / PVA transformer production 45 amp for $3,995. The price of silver these days really drives the price up on parts that use the metal.

 

 

http://www.electrafidelity.com/silver-45-se/

 

 

For those that may be interested in the specifications, here are the features and specifications Jack had listed on his auction. The "PVA with volume control" refers to Jack's Passive a Pre-Amplifier that is a nice feature that does not seem to degrade the sound. The "bass control" is another unique feature that allows the user to send a signal to the subwoofer amp.

 

Features:

- Stock 45's and 6SN7's selected for low IMD

- Partial silver output transformers

- Paper in oil coupling caps (American Military type)

- PVA with volume control on the 100 to 600 ohm input

- Bass control to send to another amp

- Algabraic summing

- Low IMD circuit

 

Specifications:

Power Output: 2.72 watts to 8 ohms, to cliping

Bandwidth (American Standard): -1db 29hz to 21khz at 1 Watt

Bandwidth (Sino Standard): -3db 16hz to 32khz at 1 Watt

THD: 0.966% at 1 Watt

IMD: 1.1% at 1 Watt (two tone, 4:1 SMPTE)

Noise Floor: -59.5db from 0db ref. (input shorted)

Loading: 8 ohms to 16 ohms

Choice of Input Impedances: 100 - 600 ohms or 10k ohms

 

 

Edited by Fjd

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Since the F4 is basically a refined power follower, it will essentially push the same voltage out that you send into it, but it will feed much more current through the load than the SET amp, if needed.

 

What are the cases or conditions where this extra current is demanded?

 

 

I'll speculate that maybe it is good for control of the bass and provides the opportunity to use a SET tube amp with a lower efficiency speaker where not possible with SET alone.

 

For me, since the F4 has no gain (0 dB), I have used the F4 in combination with my single-ended DHT 45 amp driving my Klipschorns using the Nelson Pass bi-amp schematic above and I tend to like the bass better than with only using only the single-ended DHT 45 amp by itself.

 

In some respects I guess I may be experiencing what those that bi-amp experience when they use a solid state amp for the bass and a tube amp for high frequencies; however, I believe that with my unusual bi-amp arrangement, I have a good dose of the tube sonic signature driving the bass frequencies and still seem to retain the full bloom of the tube sound from ~ 300Hz up as I cross my Klipschorns at 300Hz.

 

When I run a source direct into the single-ended DHT 45 amplifer, for the bass low end of the audio frequency spectrum, the tube amplifer is providing the "gain" through the F4 in place of a pre amplifer and providing the same gain to the higher frequencies in the audio spectrum directly from the tube amplifer.

 

I've attached the channel schematic of the F4 from the First Watt manual to give you an idea what it consists of and a link to the First Watt manual if you are interested in additional information, but keep in mind that while I can read certain aspects of a schematic, I do not understand everything that goes on and do not know enough to reallly critique a design.

 

 

http://www.firstwatt.com/pdf/prod_f4_man.pdf

 

 

A few F4 specifications taken from the First Watt website:

 

Class A opertion

25 watts (50 watt peak) into 8 ohms

40 watts into 4 ohms

100 watts into 2 ohms as a mono-block with parallel inputs and outputs

40 damping factor

No feedback

47K input ohms

0.05% distortion

distortion is 2nd and 3rd harmonic in charater (rising or declining in proportion to the output power)

direct coupled input and output

-0.5 dB rolloff around 0.1 Hz and 200 KHz and does a clean square wave at 100 KHz

50 noise uV

0.0 dB gain

Mosfet

Push-pull

 

I'm sure that my 300Hz crossover will bother some; therefore, to clarify, ALK built me a custom set of ESN networks for my tractrix horn to crossover at 300Hz and his ESN 5800 network for the mid-range to tweeter crossover point. I use a tractrix mid-horn that I believe was tested and fully loads the horn at ~ 330Hz. The steep slope of the ESNs seem to protect the compression drivers and has them receiving negligible audio signals at about 297Hz and there does not seem to be much, if any, over-excursion of the compression drivers between 300Hz and 330Hz.

 

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Edited by Fjd

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For those that buy Playboy for the articles. :unsure:

 

 

Richard Schram & John Curl Discuss Amplifiers

 

http://youtu.be/fZwS-oyqc3w

 

 

"Century Stereo is proud to announce that legendary amplifier designer, John Curl, and the Founder and President of Parasound, Richard Schram, will appear together live in our San Jose, CA showroom on the evening of July 17th to give audio enthusiasts some entertaining insights into the history and technology of their combined contributions to high-end audio.

 

The two have partnered for many years producing exceptional gear like the Halo JC1 but they have never partnered for an event like this before. So not only are we excited to have these guys but it will be a true first for attendees.

 

Century Stereo’s Ask the Experts: Amplifiers event will be held on Thursday, July 17th from 6 – 8:30 PM at our showroom in the El Paseo De Saratoga Shopping Center. This intimate event will lead guests through a discussion of what makes a great amplifier and tips for selecting an audio system. Guests are encouraged to ask questions throughout. Richard will also be demoing a full Parasound Halo system, so feel free to bring vinyl or CDs of your choosing. Finally, attendees will also have a chance to win a Parasound Zamp V.3, generously donated by Parasound.

 

So whether you are an audio enthusiast, in the market for a new audio system or just want to talk to John about what it was like to build audio systems for The Grateful Dead & Jefferson Airplane, this is a must attend event."

 

 

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Continuing on the Richard Schram theme and a thank-you to Mustang Guy, I realize that I’ve mostly filled this thread with a lot of my single-ended stuff; however, Mustang Guy [with his big 1970s monster receivers fetish :P ] got me to thinking about my collection of big "Monster Receivers of the 1970s" and, specifically, the big Pacific Stereo (division of CBS at the time) house-brand monster receiver from the 1970s, the Concept 16.5, weighing in at almost 70 lbs, that I now plan to have restored.

 

Some of the older folks that grew up in the 1960s and 1970s on the West Coast may remember the old Pacific Stereo and the Concept house-brand?

 

The Concept receiver was essentially a Richard Schram product since the circuitry was designed by Schram, who went on to greater recognition as the founder of Parasound.  Basically, I believe that Richard earned his amplifier-chops at Pacific Stereo in the 1970s, and then moved on to found Parasound in 1981.  

 

The Concept 16.5 receiver was the TOTL of the Concept series of receivers and was engineered to exceed the performance of expensive component separates of the time.

 

Many here are familiar with the dual-mono power supplies in the Harman Kardon 930 and 730 receivers.  The Concept 16.5 also has fully independent dual-mono power supplies using two oversized Dower transformers and four 10,000uF electrolytic capacitors [i'm sure this is 'chump change' to what could be done today and probably could be doubled easily] to help achieve the monster power output.

 

In addition, the 16.5 uses a 5 gang tuning assembly; and the receiver has two phono inputs.

 

Continuous power output of 165 watts per channel minimum RMS, 20-20,000 Hz, both channels driven into 8 ohms with no more than 0.1% total harmonic distortion (22.2 dBW)

 

Continuous power output of 250 watts per channel minimum RMS, 20-20,000 Hz, both channels driven into 4 ohms with no more than 0.1% total harmonic distortion (24.0 dBW)

 

While some believe that the overall sound quality of the Concept 11 is the best of the receiver line, the 16.5 had a damping factor of 450, which was much higher than practically any other receiver of that time-period, where most were usually rated less than 100.  Some describe this as the "spec" you can really feel.  Other than maybe the Pioneer SX 1250 (I have a restored sample I need to post at some point), not many receivers could drive a 4 ohm speaker load like a Concept 16.5 with its 250 watts per channel.

 

 

Concept 16.5 receiver inside 2.jpg

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Edited by Fjd

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:) 

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Edited by A1UC

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You need to show them 'nekkid' so we can all see those Jupiter caps. :P

 

 

 

:) 

 

VRD1.JPG

 

Edited by Fjd

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Continuing on the Richard Schram theme and a thank-you to Mustang Guy, I realize that I’ve mostly filled this thread with a lot of my single-ended stuff; however, Mustang Guy [with his big 1970s monster receivers fetish :P ] got me to thinking about my collection of big "Monster Receivers of the 1970s" and, specifically, the big Pacific Stereo (division of CBS at the time) house-brand monster receiver from the 1970s, the Concept 16.5, weighing in at almost 70 lbs, that I now plan to have restored.

 

Some of the older folks that grew up in the 1960s and 1970s on the West Coast may remember the old Pacific Stereo and the Concept house-brand?

 

The Concept receiver was essentially a Richard Schram product since the circuitry was designed by Schram, who went on to greater recognition as the founder of Parasound.  Basically, I believe that Richard earned his amplifier-chops at Pacific Stereo in the 1970s, and then moved on to found Parasound in 1981.  

 

The Concept 16.5 receiver was the TOTL of the Concept series of receivers and was engineered to exceed the performance of expensive component separates of the time.

 

Many here are familiar with the dual-mono power supplies in the Harman Kardon 930 and 730 receivers.  The Concept 16.5 also has fully independent dual-mono power supplies using two oversized Dower transformers and four 10,000uF electrolytic capacitors [i'm sure this is 'chump change' to what could be done today and probably could be doubled easily] to help achieve the monster power output.

 

In addition, the 16.5 uses a 5 gang tuning assembly; and the receiver has two phono inputs.

 

Continuous power output of 165 watts per channel minimum RMS, 20-20,000 Hz, both channels driven into 8 ohms with no more than 0.1% total harmonic distortion (22.2 dBW)

 

Continuous power output of 250 watts per channel minimum RMS, 20-20,000 Hz, both channels driven into 4 ohms with no more than 0.1% total harmonic distortion (24.0 dBW)

 

While some believe that the overall sound quality of the Concept 11 is the best of the receiver line, the 16.5 had a damping factor of 450, which was much higher than practically any other receiver of that time-period, where most were usually rated less than 100.  Some describe this as the "spec" you can really feel.  Other than maybe the Pioneer SX 1250 (I have a restored sample I need to post at some point), not many receivers could drive a 4 ohm speaker load like a Concept 16.5 with its 250 watts per channel.

 

Yes, my latest fetish. Monster receivers from the 70's. The muscle cars of the electronics world.

 

That's a beauty!

 

I went and checked the specs on my big Technics, and the damping factor is 60. It has about the same power specs as the 16.5 otherwise. There are two 22uF caps and one power supply. 165w at 8ohms and 205 at 4ohms. Once I get sick of listening to it, I will be moving on to something different. I will be adding your 16.5 to my searches...

Edited by mustang guy

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Nice on the Jupiter copper capacitors!  :emotion-21:  I included a few pictures below of my stereo VRD amplifer.  I currently have Mojo Dijon capacitors; however, I keep thinking of sending it to Craig for a checkup and cap and resistor upgrade. :emotion-29:  :emotion-29:  :emotion-29:

 

 

 

:) 

 

photo 1.JPG

 

 

 

 

The famous Mojo Dijon capacitors!

 

 

 

 

vrd stereo amp inside.jpg

 

 

vrd stereo outside.jpg

 

 

VRD stereo amp.jpg

Edited by Fjd

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Felt this material was relevant to the thread.

 

John Bedini describes and briefly demos one of his earlier generation amplifier designs:

 

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John Bedini describes and briefly demos one of his earlier generation amplifier designs:

 

Nice. I enjoyed the description and visual of John Bedini's amp.

 

 

Here is a look at my original Electra-print 300b/6A3 DRD mono blocks. I believe these amplifiers were built by Jack Elliano long before the Welborne version, before his Electra-Fidelity website operation and before Bill Gaw reviewed the next version of the 300b DRDs for "Enjoy the Music."

 

 

 

Electra-print 300b DRD 2 bias resistor.jpg

 

 

Electra-print 300b DRD 1.jpg

 

 

 

The "Enjoy the Music review was a two-part article that can be found in the links below.

 

http://www.enjoythem...aachapter27.htm

 

http://www.enjoythem...aachapter28.htm

 

http://www.electra-p...com/300bdrd.php

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Yes, my latest fetish. Monster receivers from the 70's. The muscle cars of the electronics world.

 

 

 

I would have to agree.  :emotion-21: Here is a list of some of the most powerful (mfg 8 ohm ratings) pre-1990 vintage receivers of all time.  Many are from the 1970s; however, there are a few after that period that seemed to deserve recognition in this list.  I almost picked up a Rotel RX-1603 for a nice price; however, it was sold before I got around to it.

 

 

1. Technics SA-1000           - 330 WPC

2. Marantz 2600                 - 300 WPC

3. Sansui G-33000               - 300 WPC

4. Pioneer SX-1980             - 270 WPC

5. Marantz 2500                  - 250 WPC

6. Sansui G-22000               - 220 WPC

7. Sansui G-9700                  - 200 WPC

8. Kenwood KR-9050          - 200 WPC

9. Hitachi SR-2004               - 200 WPC

10. Marantz 2385                - 185 WPC

11. Pioneer SX-1280            - 185 WPC

12. Technics SA-5770          - 185 WPC

13. Rotel RX-1603                - 180 WPC

14. Nikko NR-1415              - 175 WPC

15. Fisher RS-1080               - 170 WPC

16. Yamaha CR-3020           - 170 WPC

17. Concept 16.5                  - 165 WPC

18. Technics SA-5760          - 165 WPC

19. Kenwood KR-9600        - 160 WPC

20. Luxman R-117                - 160 WPC

21. Onkyo TX-8500 MkII     - 160 WPC

22. Pioneer SX-1250            - 160 WPC

23. Sansui G-8700                - 160 WPC

24. Sansui G-9000/901        - 160 WPC

25. Sansui 9900Z                   - 160 WPC

 

 

These didn't make the list as they are 'only' 125 WPC; however, I think they look great.

 

 

Marantz 2325.png

 

 

Marantz 4400 scope 2.png

Edited by Fjd

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Man, those tubes look so big they actually look like light bulbs!

You want to see big tubes look at the EML 45's!!!

 

 

 

Here is a "scale" photo with a 12 oz can for a reference to the size of the EML 45 tubes.

 

 

EML 45 tube scale with 12 oz coke can.jpg

 

 

 

 

EML 45 mesh plate tube.jpg

Edited by Fjd

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Here are a couple of examples of the 6B4G get*set*go amplifiers based on the circuit engineered by Shannon Parks of diy-tube fame.  Shannon has a stereo design PCB and a parts list that is based on easy-to-find transformers and parts, including inexpensive power tubes that sound similar to the 2A3 tube as the 6B4G is essentially a 6.3 volt 2A3 tube.

 

The get*set*go uses one 6SL7 driver tube, a 6AX5GT rectifier tube, and two 6B4G power tubes operating in single-ended Class A with no feedback.

 

While it can be one of those topics of contention,the 6B4G tubes operate using DC filaments instead of AC for quiet operation (no hum pots needed).

 

 

6B4G tube Get-Set-Go amp 03.jpg

 

 

6B4G tube Get-Set-Go amp 02.jpg

 

 

6B4G tube Get-Set-Go amp 01.jpg

 

 

6B4G tube Get-Set-Go amp 06.jpg

 

 

6B4G tube Get-Set-Go amp 05.jpg

 

 

6B4G tube Get-Set-Go amp 04.jpg

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Edited by Fjd

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Ahhhhh yes, there it is....vintage Tripath. The original. Circa 2002.

 

This is the guts of an old Blaupunkt PA2100. Sure, it's a mobile audio power amp, but underneath it ain't built like most. A four pound chunk of densely-populated circuit board. No fans....and would you check out the size of that IC!  :blink:

 

150 watts of some of the cleanest digital power in the palm of the hand.   B)

 

Under the hood:

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Lifting up the skirt:

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The power plant:

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Edited by Quiet_Hollow

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