anatech said:
Thank you sincerely Mr. Chris for the very valuable opinion.
Actually more "authority" in the bass response is what I am looking for.
With the 545 a piano on my speakers sounds more like an harpsichord, if I can say that.
I ask for more "body", a more solid sound.
Thank you very much.
Kind regards,
beppe
Hi beppe,
Yes, that's the baby!
If the amplifier is properly restored, it's sounds really very good. The proper restoration involves matching all the transistors throughout the amp. There are three adjustments for DC offset. If done properly the amp is stable and amazing.
One of these days I'll do one for myself!
Everyone asks too much for them given how much work should go into them.
-Chris
Yes, that's the baby!
If the amplifier is properly restored, it's sounds really very good. The proper restoration involves matching all the transistors throughout the amp. There are three adjustments for DC offset. If done properly the amp is stable and amazing.
One of these days I'll do one for myself!
Everyone asks too much for them given how much work should go into them.-Chris
anatech said:
My speakers are 4 ohm Dynaudios, 86dB/1W.
Maybe the 545 is current limited because I heard a much better bass with another amp.
I have been told it is not a matter of watts but more of current available from the amp.
The bass is weak and the resulting sound light.
I could provide you with the schematic of the 545 if you want to check for current limiting circuits that I could be bypass.
Thank you sincerely.
Kind regards,
beppe
Hi beppe,
Never, ever mess with the protection circuits of an amplifier. If the amp is current limiting then it's the wrong amp for the load. Having said that, there are times when a manufacturer will "back off" protection in their own design (Nakamichi PA-7 for example). That is not for us to decide. The Nak was overbuilt anyhow.
I can see that for the Dyn's you may want more current capability. They aren't that efficient either so you get it on both ends. You may run into a situation where the bass amp will require it's own electrical circuit depending on the amp and how loud you intend to run it.
Some of the later Carver designs, like a TFM-75 or PT-2400 would be an excellent choice. They have enough power to cause serious damage (read headroom with little limiting). A Lightstar 1 is another overqualified choice.
-Chris
Never, ever mess with the protection circuits of an amplifier. If the amp is current limiting then it's the wrong amp for the load. Having said that, there are times when a manufacturer will "back off" protection in their own design (Nakamichi PA-7 for example). That is not for us to decide. The Nak was overbuilt anyhow.
I can see that for the Dyn's you may want more current capability. They aren't that efficient either so you get it on both ends. You may run into a situation where the bass amp will require it's own electrical circuit depending on the amp and how loud you intend to run it.
Some of the later Carver designs, like a TFM-75 or PT-2400 would be an excellent choice. They have enough power to cause serious damage (read headroom with little limiting). A Lightstar 1 is another overqualified choice.
-Chris
Dear Mr. Chris,
1) thank you very much indeed for helping me to maintain my mental health.
Sometimes I have very strange ideas.
2) your words make me want to replace the speakers at some point.
They are just too demanding and put too much stress on amps.
3) Thank you very much for your valuable suggestions.
I record them for future search.
Kind regards,
beppe
Hi beppe,
I didn't want to give the impression you should replace your speakers. The low efficiency might be due to a shorting strap or ring. This improves linearity but drops efficiency. This is a good thing in a way as you have lower distortion bass. You do have very good speakers. Now you just need to find an amplifier up to the task!
Power is (sort of) cheap. Once you have a good amplifier you will not look back. Now, one of the reasons I suggested Carver is that they should sell for less money. Carver is out of business and there is a feeling that they do not sound good. That's not entirely true. AC power is another matter. That is not changed by any amplifier choice although the Carvers can be a bit more demanding. They take their power immediately in peaks, but run with less heat waste than most other brands.
-Chris
I didn't want to give the impression you should replace your speakers. The low efficiency might be due to a shorting strap or ring. This improves linearity but drops efficiency. This is a good thing in a way as you have lower distortion bass. You do have very good speakers. Now you just need to find an amplifier up to the task!
Power is (sort of) cheap. Once you have a good amplifier you will not look back. Now, one of the reasons I suggested Carver is that they should sell for less money. Carver is out of business and there is a feeling that they do not sound good. That's not entirely true. AC power is another matter. That is not changed by any amplifier choice although the Carvers can be a bit more demanding. They take their power immediately in peaks, but run with less heat waste than most other brands.
-Chris
Hi Beppe:
It seems like me, you too like "more" bass in your music!
I have been very happy with the GFA-555 and would not hesitate recommending it to you. The bass is powerful, clean and has character.
To answer your "full range" question, I used 2 of my favourite CDs (Michael Jackson's Thriller and Dire Straits Brothers in Arms), my own ears, my living room and the following eqipment mix/process for you:
1. GFA-555 with 8 ohm Definitive Technology BP2000TL speakers (with built-in two 15" subwoofers): Bass reproduction EXCELLENT.
2. GFA-555 with my modified 6 ohm Radian Research speakers (these have 12" woofers and 12" bass-reflex): Bass reproduction EXCELLENT.
3. GFA-555 with Athena AS-F2.2 8 ohm floor standing speakers (dual 8" woofers): Bass reproduction GOOD.
4. GFA-555 with Infinity Kappa 5.1 6(?) ohm (these have single 8" woofers): Bass reproduction: Very GOOD.
From the above, it seems (obvious?) that bass is significantly better with larger speakers with good sub-woofers or better bass reproducing designs like bass-reflex. Have you considered adding a subwoofer?
I agree with Chris, replacing the current transformer or removing the current limiters in your 545 is not a good idea. Also, moving from 100W to 200W may not give you a big increase. In my den I use a Kenwood KA-3500 to power the Radian Research speakers - the bass reproduction at 35W is awesome.
I would recommend you look around for a good 555.
Good hunting.
Mayank
It seems like me, you too like "more" bass in your music!
I have been very happy with the GFA-555 and would not hesitate recommending it to you. The bass is powerful, clean and has character.
To answer your "full range" question, I used 2 of my favourite CDs (Michael Jackson's Thriller and Dire Straits Brothers in Arms), my own ears, my living room and the following eqipment mix/process for you:
1. GFA-555 with 8 ohm Definitive Technology BP2000TL speakers (with built-in two 15" subwoofers): Bass reproduction EXCELLENT.
2. GFA-555 with my modified 6 ohm Radian Research speakers (these have 12" woofers and 12" bass-reflex): Bass reproduction EXCELLENT.
3. GFA-555 with Athena AS-F2.2 8 ohm floor standing speakers (dual 8" woofers): Bass reproduction GOOD.
4. GFA-555 with Infinity Kappa 5.1 6(?) ohm (these have single 8" woofers): Bass reproduction: Very GOOD.
From the above, it seems (obvious?) that bass is significantly better with larger speakers with good sub-woofers or better bass reproducing designs like bass-reflex. Have you considered adding a subwoofer?
I agree with Chris, replacing the current transformer or removing the current limiters in your 545 is not a good idea. Also, moving from 100W to 200W may not give you a big increase. In my den I use a Kenwood KA-3500 to power the Radian Research speakers - the bass reproduction at 35W is awesome.
I would recommend you look around for a good 555.
Good hunting.
Mayank
Hi Beppe
I use dynaudio speakers with a single GFA-555 and drive the amp into clipping sometimes. I think for more headroom I will consider buying another GFA-555 amp. I will then use both GFA-555 amps in bridge mode (monoblock approach). I think each amp is rated for 800W into 8 ohms (mainly transformer rating). My speakers are close to 6.5 ohm at 80Hz so maybe I will be close to max power to allow something higher than 800W under dynamic conditions.
Since your speakers are closer to 4 ohm you can't use the bridge mode on a GFA-555, but a single GFA-555 can deliver 2x325W into a pair of 4 ohms all day.
I use dynaudio speakers with a single GFA-555 and drive the amp into clipping sometimes. I think for more headroom I will consider buying another GFA-555 amp. I will then use both GFA-555 amps in bridge mode (monoblock approach). I think each amp is rated for 800W into 8 ohms (mainly transformer rating). My speakers are close to 6.5 ohm at 80Hz so maybe I will be close to max power to allow something higher than 800W under dynamic conditions.
Since your speakers are closer to 4 ohm you can't use the bridge mode on a GFA-555, but a single GFA-555 can deliver 2x325W into a pair of 4 ohms all day.
A couple of points please.
The Adcom amps have NO current limiting.
The transformers are too small.
The bass sounds 'muddy'.
If you add bypass caps to a 555 the bass will be 'tight', but you probably won't like it.
Buy an old 555, sell the transformer. Buy two 55-0-55 800VA toroids and stack them(the stock amp has a single 700VA unit). Add the bypass caps.
Buy a preamp with tone controls.
The Adcom amps have NO current limiting.
The transformers are too small.
The bass sounds 'muddy'.
If you add bypass caps to a 555 the bass will be 'tight', but you probably won't like it.
Buy an old 555, sell the transformer. Buy two 55-0-55 800VA toroids and stack them(the stock amp has a single 700VA unit). Add the bypass caps.
Buy a preamp with tone controls.
djk said:
Dear Mr. Djk,
thank you very much for your kind and precious explanations
1) Very important information. I did not know this.
So the circuit is not a "bottle-neck" for current.
2) Actually in my 545 the single toroid looks quite humble.
I have even thought about replacing it with two 500VA from Nuvotem Talema, available in my city.
What do you think?
3) I like tight bass but also powerful and deep. Anyway I do not find the bass particularly loose even now.
4) Before buying a 555 I would be very interested in your opinion about modifying a 545.
It should have a 120W/8ohm. I think that what is lacking is indeed the current, because I had the opportunity to try a 50Watter/8ohm with high current and the bass had much more "authority".
I did not think about stacking them.
Very interesting idea also because free space inside is usually limited.
Could you give me some practical advice about stacking toroids?
I mean, what kind of material should I put between them and the case ? and also between one toroid and the other.
5) I am sorry but this is against my precepts (eh, eh, eh).
Thank you sincerely for your extremely kind and very valuable advice.
Now I understand that Adcom amps have some potential for good sound.
Thanks a lot again.
Kind regards,
beppe
Dear Mr. Djk,
In my present application of a single GFA-555, clipping was caused by limit of voltage on the rails not the current rating of the transformer. My understanding of the transformer in the 555 is that it's a 800VA toroid with independant windings for each channel. So for bridging it seems under rated as you pointed out. The dual transformer would help in bridge mode only. Then I fear for the 16 TO-3 transistors SOA ratings in the case of bridging into 4 (6) ohms.
No current limiting is a good thing in most cases for a robust amplifier design yes? I like the way my GFA-555 sounds in stock condition for bi amp for LF drivers. IMO any modifications would be minor to sonic performance but my ears are not that good anymore.
Have you had good results with extra transformer/bypass cap modifications to the old 555? I am aware of most modifcations to this amp in other threads in this forum with Mr. Pass's participation.
I also use a GFA-535 with dual transformers and it uses the same PCB as a GFA-545 minus a pair of output transistors. Very nice as well.
In my present application of a single GFA-555, clipping was caused by limit of voltage on the rails not the current rating of the transformer. My understanding of the transformer in the 555 is that it's a 800VA toroid with independant windings for each channel. So for bridging it seems under rated as you pointed out. The dual transformer would help in bridge mode only. Then I fear for the 16 TO-3 transistors SOA ratings in the case of bridging into 4 (6) ohms.
No current limiting is a good thing in most cases for a robust amplifier design yes? I like the way my GFA-555 sounds in stock condition for bi amp for LF drivers. IMO any modifications would be minor to sonic performance but my ears are not that good anymore.
Have you had good results with extra transformer/bypass cap modifications to the old 555? I am aware of most modifcations to this amp in other threads in this forum with Mr. Pass's participation.
I also use a GFA-535 with dual transformers and it uses the same PCB as a GFA-545 minus a pair of output transistors. Very nice as well.
Hi djk,
The 555 uses 0R82 emitter resistors. The voltage drop across those becomes high at peak currents. So no current limiting in a normal sense.
Driving this amp harder will blow the outputs in bridged mode. They will "see" a 2 ohm load. I seldom saw blown 555's unless there was a load fault or they were driving 4 ohms in bridge. There are driver transistor issues in these at high powers as well. If you are going to push it to the limit, you'd best choose another amplifier.
Now the 555II uses 0R22 emitter resistors and no current limiting. That amplifier may do a better job with a 4 ohm load.
-Chris
The 555 uses 0R82 emitter resistors. The voltage drop across those becomes high at peak currents. So no current limiting in a normal sense.
Driving this amp harder will blow the outputs in bridged mode. They will "see" a 2 ohm load. I seldom saw blown 555's unless there was a load fault or they were driving 4 ohms in bridge. There are driver transistor issues in these at high powers as well. If you are going to push it to the limit, you'd best choose another amplifier.
Now the 555II uses 0R22 emitter resistors and no current limiting. That amplifier may do a better job with a 4 ohm load.
-Chris
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