I'm looking for an experienced builder thats capable of building a mini passive pre-amp as good or close to the spec of a Townshend Allegri preamp does anyone here have that kind of experience and knowlege of passive pre amps at a budget ?? Must have knowlege and experience of working with Autotransformers !!
Allegri Preamplifier | www.townshendaudio.com
Review http://www.tnt-audio.com/ampli/townshend_allegri_e.html
Target Spec:
Frequency response: 8Hz-100kHz +/- 0.1dB
Maximum signal level: 4V RMS 8Hz; 10V RMS 20Hz
Maximum DC offset : 5mV. (For undistorted 8Hz)
Distortion: Less than 0.01% at 400Hz, 10V (2nd and 3rd harmonic only)
Input impedance is dependent upon the load impedance and gain setting. So, with a power amplifier having 20kohm input impedance (typical)
Impedance: At 0dB, input impedance is 20kohm
At -10dB (normal listening) input impedance is 200k
Inputs: 3x pairs RCA phono sockets (gold plated)
Outputs: 1x pair RCA phono sockets (gold plated) + Subwoofer : 1x pair RCA phono sockets (gold plated)
Dimensions: Size : 150mm/185mm (D) x 92mm (W) x 43mm (H) Approx
Autotransformer has a Four position input selector, a mute switch and a 48 position volume control with intervals chosen to cover a wide range of volume levels in different systems. Autotransformers are wound with Audio Fractal-Wire and laminated with ultra-thin metal laminations for the highest possible resolution.Volume 24 discrete steps, ranging from +4dB to -60 dB.
Well something along these lines ??
Allegri Preamplifier | www.townshendaudio.com
Review http://www.tnt-audio.com/ampli/townshend_allegri_e.html
Target Spec:
Frequency response: 8Hz-100kHz +/- 0.1dB
Maximum signal level: 4V RMS 8Hz; 10V RMS 20Hz
Maximum DC offset : 5mV. (For undistorted 8Hz)
Distortion: Less than 0.01% at 400Hz, 10V (2nd and 3rd harmonic only)
Input impedance is dependent upon the load impedance and gain setting. So, with a power amplifier having 20kohm input impedance (typical)
Impedance: At 0dB, input impedance is 20kohm
At -10dB (normal listening) input impedance is 200k
Inputs: 3x pairs RCA phono sockets (gold plated)
Outputs: 1x pair RCA phono sockets (gold plated) + Subwoofer : 1x pair RCA phono sockets (gold plated)
Dimensions: Size : 150mm/185mm (D) x 92mm (W) x 43mm (H) Approx
Autotransformer has a Four position input selector, a mute switch and a 48 position volume control with intervals chosen to cover a wide range of volume levels in different systems. Autotransformers are wound with Audio Fractal-Wire and laminated with ultra-thin metal laminations for the highest possible resolution.Volume 24 discrete steps, ranging from +4dB to -60 dB.
Well something along these lines ??
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Have you ever wondered what the DIY in DIYaudio stands for?
Waiting 4 hours for a reply might seem tedious when you are paying for consultancy, but on a hobby site where all advice is free it can happen that everyone is busy doing something else.
PS posting the same request in multiple forums is a good way to annoy people and reduce your chances of a good outcome.
Waiting 4 hours for a reply might seem tedious when you are paying for consultancy, but on a hobby site where all advice is free it can happen that everyone is busy doing something else.
PS posting the same request in multiple forums is a good way to annoy people and reduce your chances of a good outcome.
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It's either passive or an amplifier. It can't be both. Rant over.
Only 24 volume steps is a bit mean.
I would be concerned about inter-channel crosstalk which isn't specified. The capacitance between switch poles and between conductors on the ribbon cable could be a problem.
I don't like the inter-board Insulation Displacement Connectors, cheap but in my opinion not good for long term reliability.
Subterranean bass through a transformer is untrue, they dont pass DC.
I have just looked at the price and fallen off my chair.
I would think that something like The Signal Transfer Company: Precision Preamplifier makes more sense.
Only 24 volume steps is a bit mean.
I would be concerned about inter-channel crosstalk which isn't specified. The capacitance between switch poles and between conductors on the ribbon cable could be a problem.
I don't like the inter-board Insulation Displacement Connectors, cheap but in my opinion not good for long term reliability.
Subterranean bass through a transformer is untrue, they dont pass DC.
I have just looked at the price and fallen off my chair.
I would think that something like The Signal Transfer Company: Precision Preamplifier makes more sense.
Yeah very true double the clicks more useful prehaphs and I get your point on the passive amplifier definition and the Allegri are extortionate but the Glastonbury was like £10k that was over the moon by comparison both well out of my budget hence my search for someone more capable than myself of building passives along the lines using a autotransformer preferably someone cable of assembling that to then I could stretch to 48 clicks 
The only way to know the inter-channel crosstalk as I understand is to measure it but I do not have access to an Allegri s no idea but it's a very valid point.
Allegri’s are known for transparency / insight....just wondered why arn't IDC connectors likely to be reliable long term they seem to work in the case of the Allegri has rave reviews
nobody has commented on use of IDC's or Ribbon Cable ?
I looked at the Glasshouse Passive which don't there most simplified kit version I did not like how the attenuator was conected using hookup cable strewn across the casing either - it is ok ish but people are saying that the volume isn't very good on the non TVC model which is better but too expensive for what it is but dose preform as well.
I was also looking at some of these passives below image linked below lets say where the attenuator (48 steps) is set back using a longer shaft which cuts down the travel distance to rear PCB and use of ribbon cable etc
I'm looking for something compact that I can use with a 20/20 Tripath on the desktop other than that I will probably end up with a ifi itube pre-amplifier which like the Allegri is too unnecessary long and will dewarf my little tamp making it feel very short
The Signal Transfer Company Pre-Amp isn't really what I am looking for as it isn't really a passive solution.
The only way to know the inter-channel crosstalk as I understand is to measure it but I do not have access to an Allegri s no idea but it's a very valid point.
Allegri’s are known for transparency / insight....just wondered why arn't IDC connectors likely to be reliable long term they seem to work in the case of the Allegri has rave reviews
nobody has commented on use of IDC's or Ribbon Cable ?
I looked at the Glasshouse Passive which don't there most simplified kit version I did not like how the attenuator was conected using hookup cable strewn across the casing either - it is ok ish but people are saying that the volume isn't very good on the non TVC model which is better but too expensive for what it is but dose preform as well.
I was also looking at some of these passives below image linked below lets say where the attenuator (48 steps) is set back using a longer shaft which cuts down the travel distance to rear PCB and use of ribbon cable etc
I'm looking for something compact that I can use with a 20/20 Tripath on the desktop other than that I will probably end up with a ifi itube pre-amplifier which like the Allegri is too unnecessary long and will dewarf my little tamp making it feel very short
The Signal Transfer Company Pre-Amp isn't really what I am looking for as it isn't really a passive solution.
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There are some other technical issues with the Allegri unit.
Being a 'passive pre-amplifier' the frequency response is going to vary with source impedance, load impedance and attenuation setting. I don't see the measurement conditions specified. I suspect the freqency response specification is only true when the unit is set to unity gain, driven from a low source impedance and driving a high load resistance.
The autotransformer distortion will increase at low frequencies due to the higher flux density in the core. The distortion specification is given at 400 Hz. What is it at 40 Hz (let alone 8 Hz). It does matter because if there is any low fequency energy in the source material it will intermodulate with signals in the audio band.
They are going to be suceptible to external magnetic fields from power supply transformers so expect hum.
Look at the component distributor prices for IDC connectors as used in the Allegri. Also look at the price of Lorlin rotary switches that appear to be used in the other amplifier. They haven't exactly splashed out on quality components.
If you just want a volume control and switches I would go DIY and spend the money saved on the 'amplifier' on some reputable Loudspeakers.
Being a 'passive pre-amplifier' the frequency response is going to vary with source impedance, load impedance and attenuation setting. I don't see the measurement conditions specified. I suspect the freqency response specification is only true when the unit is set to unity gain, driven from a low source impedance and driving a high load resistance.
The autotransformer distortion will increase at low frequencies due to the higher flux density in the core. The distortion specification is given at 400 Hz. What is it at 40 Hz (let alone 8 Hz). It does matter because if there is any low fequency energy in the source material it will intermodulate with signals in the audio band.
They are going to be suceptible to external magnetic fields from power supply transformers so expect hum.
Look at the component distributor prices for IDC connectors as used in the Allegri. Also look at the price of Lorlin rotary switches that appear to be used in the other amplifier. They haven't exactly splashed out on quality components.
If you just want a volume control and switches I would go DIY and spend the money saved on the 'amplifier' on some reputable Loudspeakers.
Yes and the volume control switch in the Allegri looks like a generic far eastern type like this :
http://www.ebay.com/itm/2Pole-23-Step-Rotary-Switch-Attenuator-Volume-Control-Pot-Potentiometer-DIY-New-/251286602182?pt=US_Amplifier_Parts_Components&hash=item3a81d941c6
Hell, can't get that link to work - just search ebay for item 251286602182
The selector switch looks same construction as Lorlin, just different colour, like this:
Make Before Break 2 Pole 6 Way PCB Rotary Switch | Rapid Online
http://www.ebay.com/itm/2Pole-23-Step-Rotary-Switch-Attenuator-Volume-Control-Pot-Potentiometer-DIY-New-/251286602182?pt=US_Amplifier_Parts_Components&hash=item3a81d941c6
Hell, can't get that link to work - just search ebay for item 251286602182
The selector switch looks same construction as Lorlin, just different colour, like this:
Make Before Break 2 Pole 6 Way PCB Rotary Switch | Rapid Online
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PChi are you saying that ''Passive's just wont work period because of varying source/load impedence and anttenuation issues or just the Allegri passive design is flawed, this would be interesting to clarify ??
They claim on their site the following
''Preamps of today do not require gain as all quality source components have an output of about 2 volts with a low output impedance??
Any competent power amplifier will achieve full output with typically 1 volt and have a high input impedance ?? .''.....Is this true ?
I think you are saying this is not true unless in the case that the unit is set to unity gain ?
How do you create unity gain claculations from the source gain and match it to that of the passive create a resistence that matches it ?
I'm not sure you can exactly going by what you said because as you say thier are other variables like the dynamics of the source material but not sure what you meant by intermodulate with the signals in the audio band'' ?
Also why the autotransformer will cause distortion and that will increase at low frequencies ''due to the higher flux density in the core'' ?
''Unlike conventional passive controllers the Townshend Allegri matches the impedance requirements of source and amplifier so that full dynamics are retained.
I completely agree that the unit has little expended on it's actual build probably £60-£100 at most the IDC being the least costly part max....no where anear the asking price. The extrusion is probably just buffered the knobs probably cost second place.
I'd love to try and DIY it almost tempted but apart from buying a pre made autotransformer I would not know how to build the PCB's required for something like and there is no schemeatic.
I do not even know which part of the image represents the Auto Transmitter as I am a total novice with no experience in electronics but I really liked the concept of passives also like the lightspeed and the warp speed.
I was planning to buy some ready made brigeable 2022 Tripaths ready made and use them for mono blocks and needed a pre amplifier that was simple and cost effective to build something to start of using with a 2020 tripath amplifier.
Thanks for pointing out item 251286602182 and it's simalarities with the Lorlin ESSB.
Any links on the the switch and autotransformer would be helpful if there is a wiring diagram I could see would be great.
I was looking at a resister based stepped 48 shunt type attenuator the wiring or hook up diagram I could follow and understand that there is a difference between the shunt type that users resistors and the the wound autotransforner type but not much else.
Any advice ideas or links would be apreciated or a schematic broken down would be helpful if anyone has one purely as a gauge of what a passive like this would need to be built !
Would there be more benefits of using a shunt type 48 shunt type attenuator like this one ?
They claim on their site the following
''Preamps of today do not require gain as all quality source components have an output of about 2 volts with a low output impedance??
Any competent power amplifier will achieve full output with typically 1 volt and have a high input impedance ?? .''.....Is this true ?
I think you are saying this is not true unless in the case that the unit is set to unity gain ?
How do you create unity gain claculations from the source gain and match it to that of the passive create a resistence that matches it ?
I'm not sure you can exactly going by what you said because as you say thier are other variables like the dynamics of the source material but not sure what you meant by intermodulate with the signals in the audio band'' ?
Also why the autotransformer will cause distortion and that will increase at low frequencies ''due to the higher flux density in the core'' ?
''Unlike conventional passive controllers the Townshend Allegri matches the impedance requirements of source and amplifier so that full dynamics are retained.
I completely agree that the unit has little expended on it's actual build probably £60-£100 at most the IDC being the least costly part max....no where anear the asking price. The extrusion is probably just buffered the knobs probably cost second place.
I'd love to try and DIY it almost tempted but apart from buying a pre made autotransformer I would not know how to build the PCB's required for something like and there is no schemeatic.
I do not even know which part of the image represents the Auto Transmitter as I am a total novice with no experience in electronics but I really liked the concept of passives also like the lightspeed and the warp speed.
I was planning to buy some ready made brigeable 2022 Tripaths ready made and use them for mono blocks and needed a pre amplifier that was simple and cost effective to build something to start of using with a 2020 tripath amplifier.
Thanks for pointing out item 251286602182 and it's simalarities with the Lorlin ESSB.
Any links on the the switch and autotransformer would be helpful if there is a wiring diagram I could see would be great.
I was looking at a resister based stepped 48 shunt type attenuator the wiring or hook up diagram I could follow and understand that there is a difference between the shunt type that users resistors and the the wound autotransforner type but not much else.
Any advice ideas or links would be apreciated or a schematic broken down would be helpful if anyone has one purely as a gauge of what a passive like this would need to be built !
Would there be more benefits of using a shunt type 48 shunt type attenuator like this one ?
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Let me get this clear: you want someone to rip off a commercial design for you. You don't know enough to do it yourself. You don't know enough to know why you want that particular designed ripped off for you?
If you like it, then buy it. The original designer should receive his reward.
If you want a home-made box (even if actually done by someone else) why not copy a non-commercial design? There are lots around. Then you can listen to your music with a clear conscience. Better still, DIY!
If you like it, then buy it. The original designer should receive his reward.
If you want a home-made box (even if actually done by someone else) why not copy a non-commercial design? There are lots around. Then you can listen to your music with a clear conscience. Better still, DIY!
Let me make it clearer for you !! I have a clear conscience !
I think you are being slightly rude and judgemental here and it's the second time you have done that in this thread unless you have something constructive to add here that progresses the conversation I will ignore you & your comments totally.
As you see above shunt type control is being evaluated against autotransformers to see which might preform best in a passives design....
Anyone can be influenced or case study anything and learn from that there's nothing morally wrong with that matey.
That's how people learn and develop their own ideas.
The only rip off here is the 2k they charge people for buy something that could be made for under £100 in parts !
I think you are being slightly rude and judgemental here and it's the second time you have done that in this thread unless you have something constructive to add here that progresses the conversation I will ignore you & your comments totally.
As you see above shunt type control is being evaluated against autotransformers to see which might preform best in a passives design....
Anyone can be influenced or case study anything and learn from that there's nothing morally wrong with that matey.
That's how people learn and develop their own ideas.
The only rip off here is the 2k they charge people for buy something that could be made for under £100 in parts !
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PChi are you saying that ''Passive's just wont work period because of varying source/load impedence and anttenuation issues or just the Allegri passive design is flawed, this would be interesting to clarify ??
They claim on their site the following
''Preamps of today do not require gain as all quality source components have an output of about 2 volts with a low output impedance??
Any competent power amplifier will achieve full output with typically 1 volt and have a high input impedance ?? .''.....Is this true ?
I think you are saying this is not true unless in the case that the unit is set to unity gain ?
How do you create unity gain claculations from the source gain and match it to that of the passive create a resistence that matches it ?
I'm not sure you can exactly going by what you said because as you say thier are other variables like the dynamics of the source material but not sure what you meant by intermodulate with the signals in the audio band'' ?
Also why the autotransformer will cause distortion and that will increase at low frequencies ''due to the higher flux density in the core'' ?
''Unlike conventional passive controllers the Townshend Allegri matches the impedance requirements of source and amplifier so that full dynamics are retained.
I completely agree that the unit has little expended on it's actual build probably £60-£100 at most the IDC being the least costly part max....no where anear the asking price. The extrusion is probably just buffered the knobs probably cost second place.
I'd love to try and DIY it almost tempted but apart from buying a pre made autotransformer I would not know how to build the PCB's required for something like and there is no schemeatic.
I do not even know which part of the image represents the Auto Transmitter as I am a total novice with no experience in electronics but I really liked the concept of passives also like the lightspeed and the warp speed.
I was planning to buy some ready made brigeable 2022 Tripaths ready made and use them for mono blocks and needed a pre amplifier that was simple and cost effective to build something to start of using with a 2020 tripath amplifier.
Thanks for pointing out item 251286602182 and it's simalarities with the Lorlin ESSB.
Any links on the the switch and autotransformer would be helpful if there is a wiring diagram I could see would be great.
I was looking at a resister based stepped 48 shunt type attenuator the wiring or hook up diagram I could follow and understand that there is a difference between the shunt type that users resistors and the the wound autotransforner type but not much else.
Any advice ideas or links would be apreciated or a schematic broken down would be helpful if anyone has one purely as a gauge of what a passive like this would need to be built !
Would there be more benefits of using a shunt type 48 shunt type attenuator like this one ?
I am not disputing all of the claims about the Allegri. No need to use bold text.
Power amplifiers do have a high input input resistance but can have some input capacitance because they might expect to be driven from a low source impedance. Another factor is the interconnecting cable capacitance which causes the impedance to fall with increasing frequency.
Intermodulation distortion is described at Intermodulation - Wikipedia, the free encyclopedia
Making wideband transformers isn't easy. An example is at SOWTER ATTENUATOR TRANSFORMERS TVC VOLUME CONTROL.
Ah ha! the beast as arisen (arose? awakened... hmm...) or the genie is here, take your pick! Wishing you good luck and success in selling your products!
I have done that, and many other things. Depending on how you'd like this done I might be interested in building your thing.
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