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Author Topic: First Tape Project by Bottlehead RS1500  (Read 8049 times)

Offline docb

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First Tape Project by Bottlehead RS1500
« on: April 16, 2007, 06:07:11 PM »
I am working this month on building some machines that will go to the Home Entertainment Show in New York in May. One of these dedicated playback machines will be available for sale, with delivery to be made after the show.

The machine I am building will include the following:

After an inspection and replacement (if necessary) of any tape path components subject to wear, we carefully align the components in the tape path to get straight and consistent tape travel over the heads and a flat, well centered tape pack on the reels. We take the mechanical improvements a bit further with refinements in the materials and configuration of the fixed tape guides. The end result is a machine that handles tape extremely well and sounds cleaner, with better low level resolution and snap.
Along with the tape path improvements we install improved brake pads that better maintain the factory brake tension specification, replace any necessary springs in the tension roller arm assembly, and carefully adjust the reel servo controlled tape tension to factory specification.

The two track playback head is replaced with a custom extended response head manufactured by Flux Magnetics for optimum performance with 15 ips tapes. Other heads are inspected for wear and refurbished where necessary. Optionally, a dedicated playback only machine can be fitted with long wearing ferrite dummy heads in the record and erase positions. Once the head block is set up as required a careful alignment is done using test tones recorded on our own Ampex ATR duplicating slaves (which have themselves been aligned with MRL test tapes), so you know that your machine is adjusted as closely as possible to those that record your master duplicates.

The output jacks of the machine are rewired to allow the playback head to be connected directly to an outboard reproduction amplifier that has CCIR/IEC1 playback equalization necessary for play of the Tape Project tapes.

The stock power entry panel on the back is replaced with a panel that accommodates high end IEC terminated power cords.

Custom Revox style NAB hub adapters will replace the balky Technics adapters.

The Repro amp

We love the articulate, natural, enveloping sound of tube electronics. Bottlehead has been putting out highly regarded tube gear for 12 years. The Bottlehead tube repro amp is a statement piece that will run with the best of what is out there.

The Repro is designed as a versatile tape head preamp that works well with medium to high inductance playback heads. It can output both single ended signals at the consumer level -10dB and balanced signals at studio level +4dB. CCIR/IEC1 and NAB/IEC2 playback equalization are each available with the turn of a switch

The Repro's circuit is designed to keep the signal as pure and uncolored as possible, while avoiding the harsh and sterile sound that can come from some gear that claims "great detail and speed". EF86 pentodes are used at the input, chosen for their high gain, low noise and sweet sound. The signal passes through a direct coupled passive equalization network to a 6DJ8 type dual triode. From there the signal can be taken at the single ended outputs. To achieve a studio level balanced output the signal passes through a 6CM7 gain stage to a balanced transformer output.

The power supply utilizes a separate hybrid tube/solid state shunt regulator for each channel which tightly regulates the high voltage, giving a sense of bandwidth and separation unparalleled by other means of power supply regulation. Each signal tube is isolated from power supply noise by a Camille Cascode Constant Current Source, giving the sound a black background and bringing the dynamics to an elevated level of realism. Premium quality components are utilized throughout, Schottky diodes, premium Panasonic electrolytic capacitors, high quality coupling capacitors, and a range of premium resistors from tantalum to metal film to carbon composition, each one chosen for optimal performance in the job at hand.

Individual trim pots for level are accessible from the front panel, as is a selector for playback equalization. Tubes and output transformers are socket mounted on the back panel in the tradition of classic studio gear, to allow for quick and easy changes to suit the listener's taste.

The Remote Possibility IR remote receiver

Adding a remote to these machines makes them an absolute joy to operate. Fortunately Panasonic saw fit to incorporate a jack on the rear of the RS 1500 for a wired remote control. In later years they also offered a very limited number of battery powered infrared remote controls. These are so few and far between as to have become collector pieces selling for insane prices.

Bottlehead has come to the rescue with a simple IR remote receiver that complements the classic look of your RS1500, controlling play, stop, fast forward, rewind and pause. The constant tension servo mechanism and updated brakes on the Bottlehead refurbed decks makes cueing, rocking and shuttling possible from your listening chair. A row of positive indicators across the front of the receiver sits conveniently between ten inch reels, flashing the appropriate command indicator as you press the remote.

To incorporate the remote control the obsolete wired remote connector on the back of the RS1500 is replaced with a modern 11 pin relay socket, allowing the remote receiver to be attached and detached at will.

A solid walnut 16U rack cabinet with dovetailed corners will house your refurbished RS1500, the IR remote receiver, the Bottlehead tube repro amplifier.

The retail price of a machine we provide, set up like this, will be $5550 plus crating and shipping. I will sell this demo unit for $4725 plus crating and shipping. A $2300 deposit will be required to secure this machine. Give me a call at 360-697-1936 for more info. There are some component upgrades available for the repro amp as well as a very souped up prototype version of the repro amp that I built for myself that I might be talked out of.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline mstcraig

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Re: First Tape Project by Bottlehead RS1500
« Reply #1 on: April 16, 2007, 07:43:13 PM »
"WOW" is all I can say. I can't wait to see and hear this beast in a few weeks. I'll have my camera with me, since the only way I can go home with it is through the world of photography! Who ever buys it, enjoy it for all of us! Craig
Craig Sypnier
(Magnepan, VPI, Sumiko, Shure,
Belles Research, ReVox (A-77 and B-77), Scully 280-B, Teac A-2300SD, Nordost)

Offline xcortes

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Re: First Tape Project by Bottlehead RS1500
« Reply #2 on: April 16, 2007, 08:45:07 PM »
three questions:

it is not clear whether the price is for the deck only or it includes the amp, remote and cabinet.

what are the dimensions and weight (approximate is ok to me) of this puppy?

will the alignment be done also to the 4 track and recording heads?

thanks,

xavier
Xavier Cortes

Offline docb

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Re: First Tape Project by Bottlehead RS1500
« Reply #3 on: April 16, 2007, 10:01:59 PM »
That of course includes everything - tweaked tape deck, repro amp, remote receiver, walnut case, hub adapters, etc. This machine is being set up as a playback only demo machine for the show, so it has a head block on it with a two track extended response head and three ferrite dummy heads. That can be reconfigured pretty easily.

The case dimensions are about 30"H x 20"W x 8"D, with the hubs and guides protruding about another 2". I don't have a weight because it is not yet complete.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline ironbut

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Re: First Tape Project by Bottlehead RS1500
« Reply #4 on: April 16, 2007, 11:06:40 PM »
Yippie!!!!
steve koto
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 HE Audio Jades

Offline classicrecordings

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Re: First Tape Project by Bottlehead RS1500
« Reply #5 on: May 03, 2007, 07:04:35 PM »
Is there enough gain in the output of the head amp to drive power amps without having to go into a line stage?

David
David Stangret
HK Citation 1 Pre-amp, Thorens TD-124, Ortofon 309S arm, SPU cartridges, mono block tube amps, Ars Acoustica LaDiva speakers, and I'm still trying to decide what machine to go with.
http://www.classicrecordings.ca

Offline docb

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Re: First Tape Project by Bottlehead RS1500
« Reply #6 on: May 03, 2007, 08:49:31 PM »
The single ended output of the Tube repro is the -10dB standard for home audio systems and the balanced output is studio standard +4dB. The built in volume trim only affects the balanced output, i.e., there is no built in level control from the single ended output.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline classicrecordings

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Re: First Tape Project by Bottlehead RS1500
« Reply #7 on: May 10, 2007, 07:11:10 PM »
Thank you for the reply, but I read the same information in your previous post; which is why I asked the question.

I am not a technician, but to me, the db ratings are attenuation ratings, but without an output reference point. I would like to know if the head amp will drive my present power amps to full output when connected directly to the head amp. The only way I can figure this out is to know what the voltage output from the tape head amp is.

I hope I am asking this correctly.

Can you tell me:

  • what the rated voltage output of the tape head is in mV?
  • does this signal drive the tape head amp to full output?
  • what is the single ended output in mV of the head amp at that rating?
  • what is the balanced output in mV of the head amp at that rating?

And lastly, can the output trim pots be rewired to operate the single ended outputs?

Thanks in advance for your patience.

David
http://www.classicrecordings.on.ca/
« Last Edit: May 10, 2007, 08:35:41 PM by classicrecordings »
David Stangret
HK Citation 1 Pre-amp, Thorens TD-124, Ortofon 309S arm, SPU cartridges, mono block tube amps, Ars Acoustica LaDiva speakers, and I'm still trying to decide what machine to go with.
http://www.classicrecordings.ca

Offline docb

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Re: First Tape Project by Bottlehead RS1500
« Reply #8 on: May 11, 2007, 09:25:55 AM »
Hi David,

Basically what you are asking is if the tape repro amp can also be used as a control amp (line stage) for consumer gear through the single ended output. The simple answer is, that's not really what it is designed for.

There are indeed reference points for these dB values. The equivalent voltage of +4dBu is 1.23 Vrms into an open load. This is the theoretical ideal output level that you will measure when a VU meter placed across the balanced output would read a signal from tape of 0dB. So of course the preamp will put out a maximum signal even higher than that on a tape with, say, +3dBVU peaks.

The -10dB figure is actually -10dBV rather than dBu. This works out to being 11.8 dB lower than +4dBu, or .316 Vrms. This .316 Vrms would be measured at the single ended output when one would read 0dB on a VU meter which is connected across the +4dBu output. I know, all these different forms of dB units are very confusing!

Now you have two rms voltages to work from to determine whether they will drive your amp to maximum output. Next you need to find out what the input sensitivity of your amp is. If it's a solid state consumer type amp with single ended inputs the sensitivity is going to be such that you will get maximum output from the amp at around .316Vrms input level - or probably even lower signal levels than that since a lot of SS amps are crazy sensitive. If it's something like our Bottlehead tube amps the input sensitivity might be a bit less, like max output requiring about .7Vrms input - which would still be quite reasonable connected to a -10dBV source.

If you are using an amp with a balanced input, in theory it should be set up to easily reach maximum output from a +4dBu input signal and everything should match up nicely. In practice you may find that some amps that have both balanced and single ended inputs are super sensitive at the balanced input and would require a fair amount of attenuation of the input signal to keep from overdriving the amp. This can be accomplished with the trim pots on the repro amp, but it would be rather awkward if you play tapes of different levels, as the trimmers are design to be adjusted thru the front panel with a screwdriver so they don't get knocked around once set.

The repro amp circuit is direct coupled between the first two stages that are ahead of the single ended output. So it is not possible to insert an attenuator ahead of the single ended output stage. This leaves the possibility of having an attenuator after that SE output, but ahead of the amp. Because of the relatively high output impedance of the SE stage an attenuator for this output really should be installed at the input of a line amp (or your power amp) end of the interconnecting cable, not at the SE output of the preamp. That interconnect is best kept short, and the impedance of the attenuator should be at least 15K ohms or higher.

Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline PJ

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Re: First Tape Project by Bottlehead RS1500
« Reply #9 on: May 11, 2007, 05:09:15 PM »
Just a quick note here on signal levels, a most confusing subject and a pet peeve of mine.

Conventional wisdom is that magnetic tape has a headroom of about 14dB, which is a factor of five times the voltage. So if a recording actually pushes the limits of the tape, you can expect peaks of five times the nominal, "zero-VU" level. That means about 1.6 volts RMS peaks from the consumer output (RCA jack), and about 6 volts RMS from the balanced XLR output.

(Note that digital media are usually specified relative to a full-scale signal, i.e. with zero dB of headroom. The nominal CD player output of 2.0 volts RMS full-scale is very similar to the peak 1.6 volts RMS mentioned above. I find this difference in references the most frustrating and crazy-making aspect!)

The above assumes the tape is in fact calibrated for this traditional signal level (usually expressed in nanowebers per meter) that corresponds to 14dB headroom, which varies with tape formulation, equalization, and frequency. It also assumes the full 14dB headroom was used in the way the tape was mastered. Perhaps Paul S. will comment on these aspects for the Tape Project tapes?

Bottom line - there is enough level to drive most power amps, but you still need a level control external to the head amp, either a line stage or a power amp with built-in level control.

By the way, I have been working on a white paper on this subject, for Bottlehead. I'd be glad to email a copy of the current draft to anyone interested.
Paul Joppa
Bottlehead R&D

Offline classicrecordings

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Re: First Tape Project by Bottlehead RS1500
« Reply #10 on: May 12, 2007, 10:38:29 AM »
Hi David,

Basically what you are asking is if the tape repro amp can also be used as a control amp (line stage) for consumer gear through the single ended output. The simple answer is, that's not really what it is designed for.

<snip>

Thank you for the very thorough answer. You told me everything that I needed to know.

David
http://www.classicrecordings.on.ca

David Stangret
HK Citation 1 Pre-amp, Thorens TD-124, Ortofon 309S arm, SPU cartridges, mono block tube amps, Ars Acoustica LaDiva speakers, and I'm still trying to decide what machine to go with.
http://www.classicrecordings.ca

Offline classicrecordings

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Re: First Tape Project by Bottlehead RS1500
« Reply #11 on: May 16, 2007, 07:44:43 AM »
Thanks again docb, for your previous answer.

Can you tell me what the rated voltage output of the original Technics tape head, as well as the replacement "Flux Magnetics" head, is in mV. I need to figure out if my Citation1 has enough gain to take either tape head directly into the tape head input.

TIA, David
« Last Edit: May 16, 2007, 11:13:33 AM by classicrecordings »
David Stangret
HK Citation 1 Pre-amp, Thorens TD-124, Ortofon 309S arm, SPU cartridges, mono block tube amps, Ars Acoustica LaDiva speakers, and I'm still trying to decide what machine to go with.
http://www.classicrecordings.ca

Offline classicrecordings

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Re: First Tape Project by Bottlehead RS1500
« Reply #12 on: May 17, 2007, 07:20:17 AM »
No need to answer. I found the information on another page of this forum.

Just in case anyone else misses it: http://www.tapeproject.com/smf/index.php/topic,31.0.html

My apologies, I had looked, but I missed it somehow.

David
David Stangret
HK Citation 1 Pre-amp, Thorens TD-124, Ortofon 309S arm, SPU cartridges, mono block tube amps, Ars Acoustica LaDiva speakers, and I'm still trying to decide what machine to go with.
http://www.classicrecordings.ca