Kinda doubt it is Maplin.
In the 70s and 80s there were a whole raft of people making audio equipment for radio stations and such like out of their shed.
Some only lasted for one consignment, others persisted but they were usually good quality items (for the time).
Some where I've got one of those. A phono pre which I bought cheap off ebay because it had XLR outs and I found some info on the net and in the makers opinion the onset of clipping was when THD+N reached -85dB which seemed better than most others I'd seen.
Here we get 80W/ch/4R Mosfet based amps for about 45 quid onwards...
But the build quality could be better.
Anyway, it is your perception that counts, because transformers have become expensive, components and metal too.
And hopefully, when it works, the sound would be a familiar one, from your youth.
Enjoy
But the build quality could be better.
Anyway, it is your perception that counts, because transformers have become expensive, components and metal too.
And hopefully, when it works, the sound would be a familiar one, from your youth.
Enjoy
The transformer is worth $45. The case is worth $45.
With TO220 drivers, the output transistors have to be epitaxial. Which means it doesn't have the high frequency limitations of first generation 2n3055.
TIP41c/42c are too slow for drivers to do high frequency sounds, but can be replaced with MJE15028/29. Lots of oriental transistors are fast enough.
Design of the driver board can be changed as required. This is diyaudio. If split supply, (I see 2 big capacitors) lots of choices. If single supply, AX6 or AX8 come to mind. Double output transistors exceed those designs, but the heat sinks on the drivers eliminate the main power limitation.
Input board has a 8 pin dip, likely an op amp. If it is a hissy or slow one, a dip socket and a 5532 can make huge improvements.
If it lacks guts in the bass, more rail capacitance can help. 4700 uf should be fine, does a PV-4 pretty well.
My favorite test records for high frequency preformance are Peter Nero Young & Warm & Wonderful with solo top octave grand piano on When I Fall in Love. Also Martin Denny Hawaii LST-7488 with lots of jingly percussion. For deep bass test I like ZZ Top Afterburner.
With TO220 drivers, the output transistors have to be epitaxial. Which means it doesn't have the high frequency limitations of first generation 2n3055.
TIP41c/42c are too slow for drivers to do high frequency sounds, but can be replaced with MJE15028/29. Lots of oriental transistors are fast enough.
Design of the driver board can be changed as required. This is diyaudio. If split supply, (I see 2 big capacitors) lots of choices. If single supply, AX6 or AX8 come to mind. Double output transistors exceed those designs, but the heat sinks on the drivers eliminate the main power limitation.
Input board has a 8 pin dip, likely an op amp. If it is a hissy or slow one, a dip socket and a 5532 can make huge improvements.
If it lacks guts in the bass, more rail capacitance can help. 4700 uf should be fine, does a PV-4 pretty well.
My favorite test records for high frequency preformance are Peter Nero Young & Warm & Wonderful with solo top octave grand piano on When I Fall in Love. Also Martin Denny Hawaii LST-7488 with lots of jingly percussion. For deep bass test I like ZZ Top Afterburner.
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Have you heard the Rick Astley version of 'When I Fall in Love'?
You are referring to the Nat King Cole version?
My test tracks are Hotel California, Steve Winwood 'Higher Love' and Asha Bhosle (Hindi) - 'Chura Liya Hai', which has a Spanish sounding Intro.
That is an aside, the above amp is worth so much, let him savour the purchase of a piece of history.
You are referring to the Nat King Cole version?
My test tracks are Hotel California, Steve Winwood 'Higher Love' and Asha Bhosle (Hindi) - 'Chura Liya Hai', which has a Spanish sounding Intro.
That is an aside, the above amp is worth so much, let him savour the purchase of a piece of history.
The use of a test track of solo top octave grand piano, is that one can hear one in person at a local concert hall or church and know what one is supposed to sound like. Such tracks are rare. The top octave quality piano (Steinway, Bechstein, Bosendorfer, 3.2 meter Yamaha only) is particularly difficult to reproduce, which is the source of my criticisms of TIP41c drivers & homotaxial 200 mhz ft 2n3055 output transistors. I had both types at one point , but 2 mhz ft TIP3055 or later & 20-30 mhz drivers like GE D44R4 or ON MJE15028/29 really solve dull lifeless high frequencies. BD139/140 have their followers but the Phillips/Telefunken ones with ft are not sold in the west anymore, the fairchild ones have no Ft spec at all, and the power rating is too small to drive 2 pairs output transistors that this unit has.
I had an original burned dynakit ST120, and the magazine reviews from 1966 leave me with no desire to track down original RCA 2n3055 homotaxials. Tube amps really sounded better than transistors in 1966. A 15 khz + 20 khz IM distortion test of one of those slow transistor originals would have miserable results IMHO.
Fortunate if the OP purchases this, the presence of TO220 & TO92 parts, op amps in dip packages, dates the amp to 1978 or later. Not possible to be from the slow old days, but could have cost cutting tricks like 4558 op amps or TIP41c/42c drivers that limit the sound quality to telephone in warehouse PA service.
Of the test tracks you specify, Eagles Hotel California has guitars modified by guitar amp tricks with no high frequency content. Modified electric guitar sound could have been anything in the studio, there is no standard. My Winwood Higher Love CD was stolen but I believe he was mostly a hammond organ & guitar player, neither of which has any frequency content higher than 7000 hz. Matches the ears of 99.9% of all male listeners, most have no high frequency cilia left after age 20.
I had an original burned dynakit ST120, and the magazine reviews from 1966 leave me with no desire to track down original RCA 2n3055 homotaxials. Tube amps really sounded better than transistors in 1966. A 15 khz + 20 khz IM distortion test of one of those slow transistor originals would have miserable results IMHO.
Fortunate if the OP purchases this, the presence of TO220 & TO92 parts, op amps in dip packages, dates the amp to 1978 or later. Not possible to be from the slow old days, but could have cost cutting tricks like 4558 op amps or TIP41c/42c drivers that limit the sound quality to telephone in warehouse PA service.
Of the test tracks you specify, Eagles Hotel California has guitars modified by guitar amp tricks with no high frequency content. Modified electric guitar sound could have been anything in the studio, there is no standard. My Winwood Higher Love CD was stolen but I believe he was mostly a hammond organ & guitar player, neither of which has any frequency content higher than 7000 hz. Matches the ears of 99.9% of all male listeners, most have no high frequency cilia left after age 20.
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I have 8 kHz ears, tinnitus.
The two English tracks have staccato percussion, which is as nearly a step input as I can get hold of, so tells me how the amp responds.
When I Fall in Love has many performances by many artists, please tell me your version.
The two English tracks have staccato percussion, which is as nearly a step input as I can get hold of, so tells me how the amp responds.
When I Fall in Love has many performances by many artists, please tell me your version.
As for this amp, the choice is to gut it out, or modify it.
I would suggest vertical slots on the external heat sinks, for better circulation, the shape is for air to flow horizontally along the sides.
5532 would be okay, TL072 or OPA 2134? Or a socket to put whatever you want to test.
But let him get it first, if the transformer is blown or there is any other expensive repair, then it will be a long term project.
I offered parts from India to somebody in Israel, as through hole parts are easily available here, and I could find only plastic cased TIP41/47, ST, China.
He was saying those are no good, thermal failure, they run hot, he wanted the old metal cased ones.
I told him to put the next higher rated devices, or maybe really higher.
He was fussing about the authenticity of the restoration.
You mean TIP 41 are not that good in sound reproduction, he was acting like he was an expert, it was all an act?
What transistor would you use to improve those, in the same or similar package?
I would suggest vertical slots on the external heat sinks, for better circulation, the shape is for air to flow horizontally along the sides.
5532 would be okay, TL072 or OPA 2134? Or a socket to put whatever you want to test.
But let him get it first, if the transformer is blown or there is any other expensive repair, then it will be a long term project.
I offered parts from India to somebody in Israel, as through hole parts are easily available here, and I could find only plastic cased TIP41/47, ST, China.
He was saying those are no good, thermal failure, they run hot, he wanted the old metal cased ones.
I told him to put the next higher rated devices, or maybe really higher.
He was fussing about the authenticity of the restoration.
You mean TIP 41 are not that good in sound reproduction, he was acting like he was an expert, it was all an act?
What transistor would you use to improve those, in the same or similar package?
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Peter Nero Young & Warm & Wonderful Album, RCA dynagroove. When I fall in love track has solo grand top octave piano.
I lost 14-20 khz to Army training in 1969, but due to ear plug use, I still have to 14 khz. I was tested in 2008 by employer.
My Peavey SP2 - (2004) speakers do a great job on highs to 17 khz. I can't hear above 14 so the top 17-20 khz doesn't matter. My ST120 was *****y after I first repaired it, but transistor replacement for more Ft got it sounding as good @ 1 to 70 watts as my Peavey CS800s (.03% HD into 8 ohms). The CS800s uses a NJM4560 input stage followed by TO92 predrivers, then MJE15031/32 drivers & MJ15024/25 outputs.
I lost 14-20 khz to Army training in 1969, but due to ear plug use, I still have to 14 khz. I was tested in 2008 by employer.
My Peavey SP2 - (2004) speakers do a great job on highs to 17 khz. I can't hear above 14 so the top 17-20 khz doesn't matter. My ST120 was *****y after I first repaired it, but transistor replacement for more Ft got it sounding as good @ 1 to 70 watts as my Peavey CS800s (.03% HD into 8 ohms). The CS800s uses a NJM4560 input stage followed by TO92 predrivers, then MJE15031/32 drivers & MJ15024/25 outputs.
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I assume you are referring to the Nat King Cole version of When I Fall in Love.
TIP41, which transistors would you choose as replacements if you had to repair or improve an amplifier...same or similar package?
TIP41, which transistors would you choose as replacements if you had to repair or improve an amplifier...same or similar package?
Peter Nero & Nat King Cole are different people. Nat King Cole mostly recorded in the era when RCA was still using ribbon mikes, which did not do high frequencies well. The voice frequencies were fine. Peter Nero version has no lyrics, only piano & orchestra.
TIP41c/42c have Ft of 6 mhz. They sounded poor compared to the surviving pair of RCA 2n5320 2n5322 in my ST120. Those had 50 mhz Ft. My original replacements were NTE49/50, sounded rather poor. TIP41c/42c were no better. MJE15028/29 sounded great, as good as the channel with 2n5320/5322. MJE15028/29 are 20 mhz parts.
TIP41c/42c have Ft of 6 mhz. They sounded poor compared to the surviving pair of RCA 2n5320 2n5322 in my ST120. Those had 50 mhz Ft. My original replacements were NTE49/50, sounded rather poor. TIP41c/42c were no better. MJE15028/29 sounded great, as good as the channel with 2n5320/5322. MJE15028/29 are 20 mhz parts.
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Playing the Peter Nero version, now.
Nice.
So this Israeli guy was talking nonsense, he should have put the better parts...He has a website and all, very impressive. Does restorations for Arcam, NAD, B&O etc. Claims customers from USA too.
And mostly hot air it seems.
Thank You for the information.
Nice.
So this Israeli guy was talking nonsense, he should have put the better parts...He has a website and all, very impressive. Does restorations for Arcam, NAD, B&O etc. Claims customers from USA too.
And mostly hot air it seems.
Thank You for the information.
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Well guys thanks for your insights in this amp, its underway, and I will give it a listen first before upgrading of butchering it.
Pleasant day.
Pleasant day.
Steve Winwood's "Higher Love" is a typical 80s track, plenty of synth, good percussion on it too
Check it out visually and with a series bulb first.
Treat it as an unknown, measure DC on the speakers and so on...
Treat it as an unknown, measure DC on the speakers and so on...
Rings many bells.
I have made and sold over 10000 such amplifiers from early 70´s to mid 2000s, in my case within Guitar/Bass amps but same power amp: 2N3055 or equivalent TO3 output, TIP drivers, I even recognize the VI short protection in one picture.
Nominal "+/- 40V" rails, som 70W into 8 (per channel), up ton 100/4 .
As classic/standard as a car with 4 wheels.
The circuit must be not too far from this venerable UK amp.
So classic it was used by Pink Foyd, The Who, etc. as PA amp:
Search for "RCA 70W amplifier" , originals used RCA40411 transistors which *everybody* substituted by something else.
I have made and sold over 10000 such amplifiers from early 70´s to mid 2000s, in my case within Guitar/Bass amps but same power amp: 2N3055 or equivalent TO3 output, TIP drivers, I even recognize the VI short protection in one picture.
Nominal "+/- 40V" rails, som 70W into 8 (per channel), up ton 100/4 .
As classic/standard as a car with 4 wheels.
The circuit must be not too far from this venerable UK amp.
So classic it was used by Pink Foyd, The Who, etc. as PA amp:
Search for "RCA 70W amplifier" , originals used RCA40411 transistors which *everybody* substituted by something else.
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As a PA amp....
As a music amp, how would it stand in comparison to other amps?
Any changes you would recommend to make it sound better, as in improved frequency and tonal response?.
Also, if possible, a clearer picture of the schematic would be appreciated.
Thanks for the search line.
As a music amp, how would it stand in comparison to other amps?
Any changes you would recommend to make it sound better, as in improved frequency and tonal response?.
Also, if possible, a clearer picture of the schematic would be appreciated.
Thanks for the search line.
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Yes, as said, its a medium power stereo PA amplifier, plain and simple. It will be built down to the lowest possible price so it's not going to be Hifi but the power amplifiers likely could be replaced by clone kits that can at least use better TO3 power transistors on the same heatsinks. The XLR inputs can still be used too (plenty of DIYs think they they look cool and they're usually much better quality than RCA connectors and binding posts )
The offer covers the most expensive parts of a finished amp so $45 US is a real bargain for anyone who wants to experiment but doesn't have the workspace, tools or cash for the metalwork, heatsinks, transformer etc.(s).
The offer covers the most expensive parts of a finished amp so $45 US is a real bargain for anyone who wants to experiment but doesn't have the workspace, tools or cash for the metalwork, heatsinks, transformer etc.(s).
I wonder how much old Japanese amps go for in the UK, in working condition, enough power - 20W/ch - for a listening room in the house.
Indianajo has suggested replacement options for the transistors, maybe an op amp upgrade...can be done in an afternoon if all the material is at hand.
Yes, with all the parts in place, and if is working, maybe it is a good price.
Some of the TO-3 may be better than 3055, and maybe the 3055 can be used somewhere else...
Indianajo has suggested replacement options for the transistors, maybe an op amp upgrade...can be done in an afternoon if all the material is at hand.
Yes, with all the parts in place, and if is working, maybe it is a good price.
Some of the TO-3 may be better than 3055, and maybe the 3055 can be used somewhere else...